2018, IWA, IWA Felllow　　　　　　　　　　　　　　　
KIMURA Katsuki

2017, 最優秀論文賞、Frontiers International Conference on Wastewater Treatment, Palermo.　　　　　　　　　　　　　　　
木村 克輝

2011, 日本水環境学会論文賞　　　　　　　　　　　　　　　
木村 克輝

2010, クリタ水・環境科学研究優秀賞　　　　　　　　　　　　　　　
木村 克輝

2004, 土木学会年次学術講演会優秀講演者　　　　　　　　　　　　　　　
木村 克輝

2003, 土木学会年次学術講演会優秀講演者　　　　　　　　　　　　　　　
木村 克輝

2001, 水環境学会論文奨励賞(廣瀬賞)　　　　　　　　　　　　　　　
Japan

2001, 土木学会年次学術講演会優秀講演者　　　　　　　　　　　　　　　
Japan

Characterization of biopolymers isolated from a pilot-scale membrane bioreactor treating municipal wastewater
Takayuki Kakuda, Ayana Suzuki, Rin Naito, Kanta Tominaga, Akira Hafuka, Hiroshi Yamamura, Katsuki Kimura
International Biodeterioration & Biodegradation, 198, 106010, 106010, Elsevier BV, Feb. 2025
Scientific journal

Effective reset of fouling in a high-rate MBR by in-situ, air-exposed and chemically enhanced backwash: A cautionary tale for granular scouring use
Michael J. Rocco, Hitoshi Makizuka, Akira Hafuka, Toru Tsuchiya, Katsuki Kimura
Journal of Water Process Engineering, 68, 106495, 106495, Elsevier BV, Dec. 2024
Scientific journal

Synergistic effects of nanobubbles and chemicals on backwashing for submerged MBRs treating municipal wastewater
Helmano Fernandes, Soichiro Kiuchi, Takayuki Kakuda, Akira Hafuka, Toru Tsuchiya, Yoshihiko Matsui, Katsuki Kimura
Journal of Water Process Engineering, 63, 105541, 105541, Elsevier BV, Jun. 2024, [Peer-reviewed], [Last author, Corresponding author]
Scientific journal

Innovative receiving phase for Chemcatcher® passive sampler for phosphorus in the water environment: Calibration of sampling rate by water temperature and pH
Akira Hafuka, Yuma Okuda, Kazuto Sano, Jumpei Ueda, Katsuki Kimura
Water Research, 120412, 120412, Elsevier BV, Jul. 2023, [Peer-reviewed], [Last author]
Scientific journal

Fouling mitigation in membrane bioreactors by nanobubble-assisted backwashing
Helmano Fernandes, Soichiro Kiuchi, Takayuki Kakuda, Akira Hafuka, Toru Tsuchiya, Yoshihiko Matsui, Katsuki Kimura
Journal of Water Process Engineering, 53, 103860, 103860, Elsevier BV, Jul. 2023, [Peer-reviewed], [Last author, Corresponding author]
Scientific journal

Efficient Recovery of Organic Matter from Municipal Wastewater by a High-Rate Membrane Bioreactor Equipped with Flat-Sheet Ceramic Membranes
Michael Joseph Rocco, Akira Hafuka, Toru Tsuchiya, Katsuki Kimura
Membranes, 03 Mar. 2023, [Peer-reviewed], [Last author, Corresponding author]
Scientific journal

Quantitative and qualitative variations of biopolymers in a pilot-scale membrane bioreactor treating municipal wastewater throughout 3 years of operation
Takayuki Kakuda, Rin Naito, Ayana Suzuki, Akira Hafuka, Katsuki Kimura
Journal of Environmental Management, 328, 116863, 116863, Elsevier {BV}, Feb. 2023, [Peer-reviewed], [Last author]
English, Scientific journal

EFFICIENT CONTROL OF FOULING IN A HIGH-RATE MEMBRANE BIOREACTOR (HR-MBR) FOR CARBON RECOVERY FROM MUNICIPAL WASTEWATER
槇塚仁志, ROCCO Michael Joseph, 羽深昭, 木村克輝
土木学会論文集(Web), 79, 25, 2023, [Peer-reviewed], [Last author, Corresponding author]

Fouling potentials of biopolymers isolated from surface water and supernatants of a membrane bioreactor
水落望乃香, 山本祐士朗, 小野順也, 羽深昭, 木村克輝
土木学会論文集(Web), 79, 25, 2023, [Peer-reviewed], [Last author, Corresponding author]

Intensive routine cleaning for mitigation of fouling in flat-sheet ceramic membranes used for drinking water production: Unique characteristics of resulting foulants
Hideki Sakamoto, Akira Hafuka, Toru Tsuchiya, Katsuki Kimura
Separation and Purification Technology, 301, 121950, 121950, Elsevier {BV}, Nov. 2022, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal

Isolation of LC-OCD-quantified biopolymers from surface water: Significant differences between real biopolymers and model biopolymers
Kanta Tominaga, Rina Nagai, Akira Hafuka, Wenzheng Yu, Katsuki Kimura
Journal of Membrane Science, 658, 120714, 120714, Elsevier {BV}, Sep. 2022, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal

Efficient direct membrane filtration (DMF) of municipal wastewater for carbon recovery: Application of a simple pretreatment and selection of an appropriate membrane pore size
Toru Sugiyama, Yui Ito, Akira Hafuka, Katsuki Kimura
Water Research, 118810, 118810, Elsevier {BV}, Aug. 2022, [Peer-reviewed], [Last author, Corresponding author]
Scientific journal

In-situ biogas upgrading with H2 addition in an anaerobic membrane bioreactor (AnMBR) digesting waste activated sludge
Akira Hafuka, Sota Fujino, Katsuki Kimura, Kazuyuki Oshita, Naoya Konakahara, Shigetoshi Takahashi
Science of The Total Environment, 828, 154573, 154573, Elsevier BV, Mar. 2022, [Peer-reviewed]
Scientific journal

Phosphorus Recovery by Adsorption from the Membrane Permeate of an Anaerobic Membrane Bioreactor Digesting Waste-Activated Sludge
Akira Hafuka, Katsuki Kimura
Membranes, 12, 1, 99, Jan. 2022, [Peer-reviewed]
Scientific journal

Characterization of Biopolymers in Water Based on their Enzymatic Degradability
YAMAMOTO Yushiro, ONO Junya, NAGAI Rina, HAFUKA Akira, KIMURA Katsuki
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 78, 7, III_177, III_184, Japan Society of Civil Engineers, 2022, [Peer-reviewed], [Last author, Corresponding author]
Japanese, Although water/wastewater treatment using membrane technology has various advantages over conventional methods, membrane fouling still impedes wide-spread use of the technology. Recent studies have demonstrated that high-molecular-weight hydrophilic organic matters (i.e., biopolymers) play an important role in the evolution of membrane fouling. However, detailed information on biopolymers such as molecular composition and structure is still unknown. In this study, biopolymers were collected and isolated from surface water and municipal wastewater, and their degradability by enzymes was investigated. Enzymes that could degrade specific structures of polysaccharides and proteins (α-amylase, cellulase, protease, and lysozyme) were used in this study. LC-OCD analysis could detect degradation of biopolymers (i.e., shift of molecular weight distribution) caused by enzymes, which cannot be detected by common analytical methods. Biopolymers isolated from surface water were degraded by α-amylase and cellulase, whereas biopolymers isolated from municipal wastewater were degraded by lysozyme. These results clearly indicate that the two biopolymer samples examined in this study had different structures and properties, which has not been clearly shown so far. Use of various combinations of biopolymers and enzymes in the method established in this study may deepen understanding of the structure of biopolymers.

Optimization of Nanobubble Assisted Backwashing of Membranes
NAKAGAWA Hayato, KIUCHI Soichiro, FERNANDES Helmano, HAHUKA Akira, KIMURA Katsuki
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 78, 7, III_143, III_148, Japan Society of Civil Engineers, 2022, [Peer-reviewed], [Last author, Corresponding author]
Japanese, Membrane bioreactor (MBR) has many advantages over the conventional activated sludge systems, but occurence of membrane fouling is a problem. Our research group found that backwashing utilizing nanobubbles can effectively alleviate membrane fouling in MBRs, but there is plenty of room for the optimization of backwashing using nanobubbles. In this study, we prepared ceramic membranes fouled by sodium alginate, which is often used as model foulant of MBR and investigated factors which can enhance the cleaning efficiency. It was confirmed in this study that cleaning efficiency of backwashing was enhanced by using nanobubbles. Contribution of hydroxyl radical generated from nanobubbles to the enhancement of cleaning efficiency would be limited. Instead, it was suggested that nanobubbles intruded into the fouling layer during backwashing and loosened the structure of it, which led to increase in cleaning efficiency of hydraulic cleaning.

Passive sampling of low concentration of orthophosphate in a river and a lake
Sano Kazuto, Okuda Yuma, Hafuka Akira, Kimura Katsuki
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 78, 7, III_359, III_368, Japan Society of Civil Engineers, 2022, [Peer-reviewed], [Last author]
Japanese, Monitoring of orthophosphate (PO_4-P) concentrations in rivers and lakes is important to conserve water environment. Grab sampling followed by general instrumental analysis cannot provide representative concentration of PO_4-P exists in low concentration range in water environment. In this study, passive sampling of orthophosphate was conducted in Sakusyukotoni River and Lake Barato to obtain time-averaged concentration of PO_4-P. As a result, obtained time-averaged concentration of PO_4-P with passive sampling in Sakusyukotoni River coincided with concentrations of dissolved phosphorus in samples obtained by grab sampling. In Lake Barato, vertical profiles of time-averaged concentration of PO_4-P were obtained using passive sampling.

Effect of SRT on digestibility of polysaccharides, proteins, and lipids in waste activated sludge using an anaerobic membrane bioreactor (AnMBR) and analysis of membrane foulant
KANUMA Shunsuke, FUJINO Sota, HAFUKA Akira, KIMURA Katsuki
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 78, 7, III_33, III_41, Japan Society of Civil Engineers, 2022, [Peer-reviewed], [Last author]
Japanese, Effects of SRT and HRT on digestibility of polysaccharides, proteins, and lipids in waste activated sludge were investigated in an anerobic membrane bioreactor (AnMBR). The AnMBR was operated in six different phases. Degradation efficiencies of polysaccharides, proteins, and lipids were increased with prolonged SRT from 30 days to 90 days. Shortening of HRT from 30 days to 15 days lead to increase of organic loading rate, which further increased biogas production rate. Trans-membrane pressure reached to 41 kPa during 154-days continuous membrane filtration of digested sludge. Inorganic irreversible fouling was dominant in the used membrane and Ca, P, and Mg were extracted.

EFFECT OF MEMBRANE PORE SIZE AND MATERIALS ON MEMBRANE FOULING IN MBRS
Takumi NAKAMURA, Takayuki KAKUDA, Akira HAFUKA, Masatsugu ONO, Katsuki KIMURA
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 78, 7, III_135, III_142, Japan Society of Civil Engineers, 2022, [Peer-reviewed], [Last author, Corresponding author]
Japanese, Scientific journal, Membrane properties affect membrane fouling in MBRs. Although many previous studies have investigated the relationship between membrane properties and membrane fouling, there are few studies in which specific membrane properties of interest were varied intentionally and independently. In this study, membranes with the same material and different pore sizes, and membranes with the same structure and different materials were fabricated and used in a bench-scale MBR treating municipal wastewater. In the experiments in which UF and MF membranes made from CPVC were compared, there was almost no difference in fouling between the two membranes. This result implies that effects of pore sizes on fouling in MBRs are limited as long as a local flux imposed on membranes is fixed. In the experiments in which CPVC UF and PVDF UF membranes with the same structure were compared, fouling in the CPVC membrane was faster than that in the PVDF membrane. With the tested flux range of 0.72-0.90 m/d, it was suggested that PVDF is a better membrane material than CPVC in terms of prevention of membrane fouling.

Phosphorus compounds in the dissolved and particulate phases in urban rivers and a downstream eutrophic lake as analyzed using 31P NMR
Akira Hafuka, Yoichi Tsubokawa, Ryuichiro Shinohara, Katsuki Kimura
Environmental Pollution, 288, 117732, Elsevier {BV}, Nov. 2021, [Peer-reviewed], [Last author]
English, Scientific journal, Phosphorus (P) discharges from human activities result in eutrophication of lakes. We investigated whether the forms of phosphorus (P) in rivers with high effluent loads flowing through urban areas of Sapporo, Japan, were transformed when transported downstream into a eutrophic lake, namely Lake Barato. We hypothesized that the inorganic P supplied from the rivers might be transformed to organic forms in the lake. The results showed that soluble reactive phosphorus (SRP) and particulate inorganic phosphorus (PIP) dominated in the river discharge to the lake. Suspended solids in the rivers were rich in iron (Fe) so PIP was associated with Fe. A comparison of the concentrations at the river mouth and 4.5 km downstream showed that the concentrations of SRP and PIP were lower at 4.5 km downstream than at the river mouth, whereas the concentrations of organic P (i.e., dissolved organic phosphorus and particulate organic phosphorus) were similar. The results from solution 31P nuclear magnetic resonance spectroscopy of lake water showed that pyrophosphate was only present in the particulate fraction, while orthophosphate diesters (DNA-P) were only present in the dissolved fraction. Riverine samples contained orthophosphate (ortho-P) only, while lake samples contained ortho-P, orthophosphate monoesters, and DNA-P. The results suggest that the P forms, particularly those of dissolved P, shifted from inorganic to organic forms as the water was discharged from the river to the lake.

Direct membrane filtration (DMF) for recovery of organic matter in municipal wastewater using small amounts of chemicals and energy
Katsuki Kimura, Mutsumi Yamakawa, Akira Hafuka
Chemosphere, 277, Aug. 2021, [Peer-reviewed], [Lead author, Corresponding author]
Scientific journal, The recovery and utilization of organic matter in municipal wastewater are essential for the establishment of a sustainable society, such that these factors have drawn significant recent attention. The up-concentration of organic matter via direct membrane filtration (DMF), followed by anaerobic digestion, is advantageous over the treatment of the entire wastewater by an anaerobic process, such as an anaerobic membrane bioreactor (AnMBR). However, the occurrence of severe membrane fouling in the DMF is a problem. In this study, DMF was carried out at an existing wastewater treatment plant to attempt long-term operation. A combination of vibration of membrane modules, short-term aeration, and chemically enhanced backwash (CEB), with multiple chemicals (i.e., the alternative use of citric acid and NaClO), was found to be effective for the mitigation of membrane fouling in DMF. Furthermore, switching the feed from influents to effluents in the primary sedimentation basin significantly mitigated membrane fouling. In this study, in which microfiltration membrane, with a nominal pore size of 0.1 μm, was used, ∼75% of the organic matter in raw wastewater was recovered, with the volumetric concentration of wastewater by 50- or 150-fold. Organic matter recovered by DMF had significantly higher potentials for biogas production than the excess sludge generated from the same wastewater treatment plant. An analysis of the energy balance (i.e., the energy used for DMF and recovered by DMF) suggests that the proposed DMF can produce a net-positive amount of electricity of ∼0.3 kWh from 1 m3 of raw wastewater with a typical strength (chemical oxygen demand of 500 mg/L).

Intensive monitoring of sludge filterability of a pilot-scale membrane bioreactor treating municipal wastewater for better interpretation of fouling
Takayuki Kakuda, Hiroyuki Iwasaki, Xia Huang, Katsuki Kimura
Journal of Water Process Engineering, 40, Apr. 2021, [Peer-reviewed], [Last author, Corresponding author]
Scientific journal, In this study, a pilot-scale membrane bioreactor (MBR) treating municipal wastewater was operated over 600 d. Intensive monitoring of sludge filterability with high frequency, which is rarely reported in previous studies, was performed. Detailed information on sludge filterability obtained in this study makes the advanced interpretation of membrane fouling possible and allows to take effective countermeasures. Two methods (batch membrane filtration and measurement of capillary suction time (CST)) were used to assess sludge filterability, which significantly varies during the long-term operation. Although these two methods generated similar data, the CST measurement is easier than batch-filtration and is therefore recommended for intensive monitoring of sludge filterability in MBRs. Using the data obtained in this study, the evolution of reversible and irreversible fouling was distinguished. The importance of separately assessing the impact of colloidal matter on sludge filterability was also demonstrated: colloidal matter caused the deterioration of sludge filterability. To detect such impacts, the frequency of the assessment should be sufficiently high. A new method (modification of CST measurement) proposed in this study could be used for such frequent assessments. Temperature in the reactor and ion balance in raw wastewater were identified as key factors in the deterioration of sludge filterability. A specific fraction of polysaccharides (lipopolysaccharides) exhibited a significant correlation with the deterioration of sludge filterability. This study can provide important information for the operation and maintenance of large-scale MBRs treating municipal wastewater.

NUTRIENTS RECOVERY COMBINED WITH DIRECT MEMBRANE FILTRATION (DMF) OF MUNICIPAL WASTEWATER FOR RECOVERY OF ORGANIC MATTER
ITO Yui, SUGIYAMA Toru, TAKAHASHI Taketsugu, HAHUKA Akira, KIMURA Katsuki
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 77, 7, III_339, III_345, Japan Society of Civil Engineers, 2021, [Peer-reviewed], [Last author, Corresponding author]
Japanese, Organic matter and nutrients in municipal wastewater are important resources to be recovered. Direct membrane filtration (DMF) can efficiently recover and concentrate organic matter in municipal wastewater. In most of the previous studies investigating DMF, recovery of nutrients in the treated water (permeate) was not considered. In this study, phosphate ion adsorption was attempted in the pretreatment of DMF in which microbial carriers with zirconium-based phosphate ion adsorbent were placed. As for recovery of ammonium ions in the permeate, use of poly(sodium acrylate) was examined. Experiments were conducted with real municipal wastewater and the results showed that 75% of the phosphate ion and 80% of the ammonium ions could be recovered. The recovery of ammonium ions could be further improved by using nanofiltration that could eliminate the effect of coexisting multivalent ions.

ASSESMENT OF FOULING POTENTIAL OF BIOPOLYMERS ISOLATED FROM SURFACE WATER USING QUARTZ CRYSTAL MICROBALANCE WITH DISSIPATION MONITORING（QCM-D）
ONO Junya, NAGAI Rina, Tominaga Kanta, HAFUKA Akira, KIMURA Katsuki
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 77, 7, III_321, III_328, Japan Society of Civil Engineers, 2021, [Peer-reviewed], [Last author, Corresponding author]
Japanese, While water purification using membranes has many advantages over conventional treatment, membrane fouling is still a major problem. Recent studies have suggested that high-molecular-weight hydrophilic organic matters called biopolymers play an important role in the evolution of membrane fouling. In this study, biopolymers were collected and isolated from several drinking water sources with different characteristics, and the properties of the isolated biopolymers were investigated. Degrees of membrane fouling caused by the biopolymers were clearly different depending on the sources, indicating that the characteristics of biopolymers varied with the source. Differences in biopolymers were evident in those molecular weight distribution measurements using LC-OCD and infrared spectra. It was also postulated that biopolymers mainly composed of polysaccharides tended to cause severe irreversible fouling. Analysis of the biopolymers using quartz crystal microbalance with dissipation monitoring(QCM-D) demonstrated an interesting result; the order of affinity of each isolated biopolymers to the membrane material (i.e. PVDF) was consistent with the order of degrees of membrane fouling observed in the membrane filtration test. In addition, viscoelasticity of the biopolymers assessed by QCM-D may explain reversibility of membrane fouling.

High-flux operation of MBRs with ceramic flat-sheet membranes made possible by intensive membrane cleaning: Tests with real domestic wastewater under low-temperature conditions
Yusuke Ninomiya, Katsuki Kimura, Tsubasa Sato, Takayuki Kakuda, Masashi Kaneda, Akira Hafuka, Toru Tsuchiya
Water Research, 181, 115881, 115881, 115881, Elsevier BV, Aug. 2020, [Peer-reviewed], [Corresponding author]
English, Scientific journal

Anaerobic digestibility of up-concentrated organic matter obtained from direct membrane filtration of municipal wastewater
Akira Hafuka, Taketsugu Takahashi, Katsuki Kimura
Biochemical Engineering Journal, 107692, 107692, Elsevier BV, Jun. 2020, [Peer-reviewed], [Last author]
Scientific journal

Irreversible fouling in hollow-fiber PVDF MF/UF membranes filtering surface water: Effects of precoagulation and identification of the foulant
Katsuki Kimura, Keita Kume
Journal of Membrane Science, 602, 117975, 117975, Elsevier BV, May 2020, [Peer-reviewed], [Lead author, Corresponding author]
Scientific journal

Fouling potential of lipopolysaccharides released at low temperatures in MBRs
T. Kakuda, H. Iwasaki, K. Kimura
Water Science and Technology, 81, 3, 529, 534, IWA Publishing, 01 Feb. 2020, [Peer-reviewed], [Last author, Corresponding author]
Scientific journal,
Sludge filterability in membrane bioreactors (MBRs) fluctuates and affects membrane fouling. Therefore, understanding the reasons for the fluctuations of sludge filterability is important for the efficient operation of MBRs. In this study, a pilot-scale MBR treating municipal wastewater was operated for about 600 days and the variations in sludge filterability were continuously monitored by batch-filtration experiments using the same membranes as in the MBR. To investigate the reasons for the deterioration of sludge filterability, constituents in sludge supernatant were intensively monitored, and the correlations with sludge filterability were determined. The concentration of lipopolysaccharides (LPS) in sludge supernatant exhibited significantly higher correlation with sludge filterability than did conventional indexes (i.e. polysaccharides and proteins). Size fractions affecting MBR sludge filterability were also investigated, and it was suggested that colloidal LPS deteriorated MBR sludge filterability. Based on the long-term operation of the MBR, increase in colloidal LPS under low temperatures of the mixed liquor suspension was a key factor in the deterioration of sludge filterability. The impact of LPS increasing under low temperatures should be investigated by operating bench-scale MBRs fed with synthetic wastewater in controlled conditions.

DIRECT MEMBRANE FILTRATION (DMF) OF MUNICIPAL WASTEWATER USING A BIOFILM PROCESS AS A PRE-TREATMENT
SUGIYAMA Toru, YAMAKAWA Mutsumi, TAKAHASHI Taketsugu, HAFUKA Akira, KIMURA Katsuki
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 76, 7, III_227, III_234, Japan Society of Civil Engineers, 2020, [Peer-reviewed], [Last author, Corresponding author]
Japanese, Organic matter in municipal wastewater should be regarded as a resource for energy production in future wastewater management. Concentration of organic matter in municipal wastewater is necessary for application of anaerobic digestion. Direct membrane filtration (DMF) of municipal wastewater using microfiltration can easily concentrate organic matter in municipal wastewater. However, severe membrane fouling and high concentration of organic matter in treated water have been identified as problems to be solved. In this study, a biofilm process using sponge carriers was used as a pre-treatment, aiming for mitigating membrane fouling and reducing concentration of organic matter in the permeate. The pretreatment worked efficiently when water temperature was low: membrane fouling could be mitigated while recovery of organic matter was maintained. However, when water temperature was high, the pre-treatment accelerated membrane fouling in the subsequent membrane process. It was probably due to production of biopolymers in the pre-treatment process. To control the fouling caused by such biopolymers, use of chemical cleaning by oxidants (e.g., NaClO) would be effective. When the water temperature was high, the BOD concentration in the DMF permeate was reduced to 7 mg/L, which is almost same the level as that in conventional activated sludge process.

TRACKING CHANGES OF SLUDGE COMPONENTS INVOLVED IN SLUDGE FILTERABILITY IN MBR
NAITO Rin, KAKUDA Takayuki, HAFUKA Akira, KIMURA Katsuki
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 76, 7, III_165, III_171, Japan Society of Civil Engineers, 2020, [Peer-reviewed], [Last author, Corresponding author]
Japanese, In this study, changes of sludge components involved in membrane fouling were continuously monitored (>300 days) at a pilot-scale MBR treating real municipal wastewater. It was found that concentrations of colloidal TOC, dissolved lipopolysaccharides (LPS) and biopolymers in the sludge supernatant are strongly correlated with sludge filterability. Size fractions affecting membrane fouling were also investigated, and the results suggested that colloidal matter ranging 0.45-1.0 m, and 5.0-11 µm has significant impact on MBR fouling. Futhermore, isolation of biopolymers from the MBR sludge supernatant was conducted, and their characteristics were compared with sodium alginate which is commonly used as a model biopolymer. Isolated biopolymers caused more severe membrane fouling than did sodium alginate. It was suggested that biopolymers in MBR supernatant have higher fouling potential than that previously estimated by sodium alginate.

CLEANING OF FOULED MEMBRANES USED FOR MBRS BY USING MICROBUBLLES AND NANOBULLES
KIUCHI Soichiro, FERNANDES Helmano, HAHUKA Akira, KIMURA Katsuki
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 76, 7, III_149, III_155, Japan Society of Civil Engineers, 2020, [Peer-reviewed], [Last author, Corresponding author]
Japanese, Membrane bioreactor (MBR) has some advantages over the activated sludge method, but the membrane fouling that occurs during MBR operation is a big problem. Microbubbles and nanobubbles, which have been reported to have cleaning effects on various types of stains, may be able to efficiently clean fouled membranes. In this study, we conducted a basic study on the membrane cleaning effect of microbubbles and nanobubbles using bench-scale MBR. A large cleaning effect was confirmed in the immersion cleaning using microbubbles. Although nanobubbles did not exhibit a sufficient cleaning effect in the immersion cleaning, it was confirmed that the cleaning effect equal to or higher than that of the backwashing using chemicals was confirmed by mixing the nanobubbles in the backwashing water together with the granular carrier. It was shown that nanobubbles have a small adverse effect on MBR sludge. Membrane cleaning using microbubbles and nanobubbles may be able to solve various problems associated with membrane cleaning using chemicals.

Distinction between polymeric and ceramic membrane in AnMBR treating municipal wastewater: In terms of irremovable fouling
Z. Liu, Xianzheng Zhu, Peng Liang, Xiaoyuan Zhang, Katsuki Kimura, Xia Huang
Journal of Membrane Science (IF: ), 588, Oct. 2019, [Peer-reviewed]
© 2019 Elsevier B.V. Polymeric flat-sheet membrane (FS) and ceramic flat-tubular membrane (CM) are the most widely-used membranes in anaerobic membrane bioreactor (AnMBR). However, fouling mechanism on FS and CM were rarely compared before and needed to be deeply illuminated. In this work, distinction of irremovable fouling formed on polyvinylidene fluoride FS and Al2O3 CM in AnMBR treating municipal wastewater was studied. Lab-scale AnMBR operation showed that FS presented severer irremovable fouling and faster fouling rate. Foulants characterization revealed that irremovable fouling of FS was composed of more organics (FS = 0.91, CM = 0.35 g-TOC/m2-membrane) and biomass (FS = 47.3, CM = 8.65 × 1010 cell/m2-membrane), leading to gel layer loosely structured. Conversely, irremovable fouling of CM contained more inorganics (FS = 0.08, CM = 0.55 g/m2-membrane), facilitating dense gel layer with larger specific filtration resistance. Membrane cleaning tests found that gel layer on FS was efficiently removed by NaClO, while gel layer on CM was loosened by NaClO but destructed by citric acid. NaClO/NaOH both reduced resident bacteria, whereas increased the proportion of live cells. Irreversible fouling on FS involved more organics while more inorganics on CM. Irreversible biofouling could utilize citric acid as substrate for metabolism and proliferation. This study not only helps to probe fouling mechanism with different membrane materials, but also aids to develop differentiated effective cleaning strategy to corresponding membrane modules.

Energy consumption in a baffled membrane bioreactor (B-MBR): estimation based on long-term continuous operation
T. Miyoshi, T. P. Nguyen, T. Tsumuraya, K. Kimura, Y. Watanabe
Water Science and Technology, 80, 6, 1011, 1021, IWA Publishing, 15 Sep. 2019, [Peer-reviewed]
Scientific journal,
We investigated the operating conditions of a baffled membrane bioreactor (B-MBR) under which long-term stable operation can be achieved through the continuous operation of a pilot-scale B-MBR. Under appropriate operating conditions, the B-MBR was capable of achieving excellent treated water quality in terms of biochemical oxygen demand and concentration of total nitrogen. Excellent removal of total phosphorus was also achieved. In addition, the degree of membrane fouling was acceptable, indicating that stable continuous operation of a B-MBR is possible under the operating conditions adopted in the present study. Estimation of the specific energy consumption in hypothetical full-scale B-MBRs operated under the conditions recommended by the findings was also performed in this study. The results suggest that energy consumption in full-scale B-MBRs would be in the range of 0.20–0.22 kWh/m3. These results strongly suggest that energy consumption in MBR operation can be significantly reduced by applying the concept of a B-MBR.

Membrane fouling caused by lipopolysaccharides: A suggestion for alternative model polysaccharides for MBR fouling research
Katsuki Kimura, Takayuki Kakuda, Hiroyuki Iwasaki
Separation and Purification Technology, 223, 224, 233, Elsevier BV, Sep. 2019, [Peer-reviewed], [Lead author, Corresponding author]
Scientific journal, © 2019 Polysaccharides were identified as key foulants in membrane bioreactors (MBRs) in previous studies. Polysaccharides used for MBR fouling research should represent real foulants, and alginate and dextran have often been used as model polysaccharides. However, their properties are not necessarily similar to those of polysaccharides that actually cause membrane fouling in MBRs. In recent studies, it was shown that polysaccharides causing membrane fouling in MBRs had the structures of lipopolysaccharides (LPSs), which are components of the cell wall of gram-negative bacteria. In the present study, therefore, membrane fouling caused by commercially available LPSs was investigated and was compared with that caused by model polysaccharides. In a series of batch filtration tests using four different microfiltration (MF) and ultrafiltration (UF) membranes, regardless of the membrane used, LPSs caused more severe membrane fouling than did alginate or dextran when they were filtered under the condition of the same organic carbon concentration. The properties of LPSs were found to be considerably different from those of alginate and dextran. In particular, affinity of LPS to PVDF polymer assessed by quartz crystal microbalance (QCM) mass measurement was remarkably high, and it would account for the severe fouling caused by LPSs. In experiments with filtering of mixtures of the model polysaccharides and a biomass suspension collected from a pilot-scale MBR, which were conducted to mimic the sudden increase in dissolved polysaccharides in real MBRs, LPS induced significant irreversible fouling, while alginate and dextran did not. The results obtained in this study clearly demonstrated high fouling potential of LPSs. Use of LPSs in future MBR fouling studies is therefore recommended.

Anaerobic digestion performance of concentrated municipal sewage by forward osmosis membrane: Focus on the impact of salt and ammonia nitrogen
Yue Gao, Zhou Fang, Peng Liang, Xiaoyuan Zhang, Yong Qiu, Katsuki Kimura, Xia Huang
Bioresource Technology, 204, 210, Mar. 2019, [Peer-reviewed]
© 2019 Elsevier Ltd Sewage can become a valuable source if its treatment is re-oriented. Forward osmosis (FO) is an effective pre-treatment for concentrating solutions. A laboratory-scale anaerobic digestion (AD) bioreactor was setup for the treatment of concentrated real sewage by FO membrane to investigate the removal of chemical oxygen demand (COD) and biogas production. Inhibitory batch tests were carried out for the impact of NaCl and NH 4+ -N. Results showed that the concentrated sewage could be purified with 80% COD removal, and energy recovery could be achieved. But the process was inhibited. The results of inhibitory batch test showed that (i) when the NH 4+ -N concentration was lower (<200 mg/L), the biogas production was promoted, when it went high, the inhibition appeared; (ii) single existence of NaCl had negative influence on methane production; (iii) the inhibition was more severe with co-existence of NaCl and NH 4+ -N. The AD performance could be recovered via sludge acclimation.

Intensive membrane cleaning for MBRs equipped with flat-sheet ceramic membranes: Controlling negative effects of chemical reagents used for membrane cleaning
Katsuki Kimura, Hiroki Uchida
Water Research, 21, 28, Mar. 2019, [Peer-reviewed]
© 2018 Intensive membrane cleaning can be used with ceramic membranes since they are physically/chemically robust. It might therefore be possible for membrane bioreactors (MBRs) to be operated under the condition of a high membrane flux when ceramic membranes are used with such intensive membrane cleaning. In this study, bench-scale MBRs equipped with flat-sheet ceramic membranes were operated for long periods. Circulation of granular materials (cylindrical polyurethane) in the tank and frequent chemically enhanced backwash (CEB) were used as intensive physical cleaning and chemical cleaning in this study, respectively. Experiments were carried out with synthetic wastewater. The use of granular materials, which can cause significant damage to polymeric membranes (Kurita et al., 2015), was effective for controlling the formation of cake (deposition of microbial flocs) on the surface of the ceramic membranes. When both mechanical cleaning using the granular materials and CEB with 1000 ppm of sodium hypochlorite (NaClO) were applied, contrary to an expectation, evolution of reversible fouling (formation of a transparent gel layer on the membrane surface) became uncontrollable, whereas irreversible fouling was effectively controlled. The use of NaClO induced release of organic macromolecules via biomass decay, leading to the evolution of reversible fouling. When the intensity of CEB with NaClO was adequately lowered, with the aid of the mechanical cleaning using the granules, the bench-scale MBR could be operated stably under an elevated membrane flux for a long period (>70 days). It was postulated that the adjustment of CEB intensity preferably altered properties of organic macromolecules released from biomass: the structure of the gel layer was porous when the CEB intensity was lowered. When CEB is used in MBRs, it is thus important to balance cleaning efficiency and its harmful effect on biomass. When adequate CEB is used with intensive mechanical cleaning, MBRs with ceramic membranes can be operated under high flux conditions.

Estimation of Dissolved Organic Foulant during Direct Treatment of Sewage by Forward Osmosis
Youhei NOMURA, Taro MIYOSHI, Tomoya NISHIUCHI, Katsuki KIMURA, Taku FUJIWARA
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 75, 7, III_359, III_365, Japan Society of Civil Engineers, 2019, [Peer-reviewed]
Japanese, Scientific journal, Direct treatment of sewage by forward osmosis (FO) using polyamide FO membrane was examined, and the dissolved organic foulant in the sewage was estimated. Filtrated sewage and 3 M sodium chloride solution were used as feed solution (FS) and draw solution, respectively. The permeate flux decreased from 18.7 L/m²/h to 9.9 L/m²/h during 14 h of FO treatment owing to the membrane fouling, whereas the FO membrane rejected 98 % of dissolved organic carbon in FS. The dissolved orgnic matter was partially accumulated in the fouling layer. Analysis using liquid chromatography–organic carbon detection revealed that biopolymer fraction was dominant organic matter in the fouing layer. Although the accumulation of fraction of humic substances, building blocks, and low-molecular weight acids was only 1–2 %, that of biopolymer fraction was above 15 %. The biopolymer fraction is therefore estimated as a key dissolved organic foulant.

Effects of recirculation and separation times on nitrogen removal in baffled membrane bioreactor (B-MBR)
T. Miyoshi, T. Tsumuraya, T. P. Nguyen, K. Kimura, Y. Watanabe
Water Science and Technology, 77, 2803, 2811, Aug. 2018, [Peer-reviewed]
© IWA Publishing 2018. In this study, we investigated the effects of recirculation and separation times on removals of organic matter, nitrogen, and phosphorus in a baffled membrane bioreactor (B-MBR) treating real municipal wastewater. A pilot-scale B-MBR experimental apparatus was operated under two different sets of recirculation and separation times. The results revealed that, irrespective of operating conditions, the biochemical oxygen demand (BOD) and concentration of total nitrogen (T-N) in the treated water can be lowered to less than 3 and 5 mg/L, respectively. Although T-N was effectively removed in the two different operating conditions, increase in the fraction of recirculation time results in tiny deterioration of nitrogen removal efficiency in the B-MBR. Phosphorus removal efficiency was also slightly decreased as the fraction of recirculation time (ratio between recirculation and separation times) was increased. The results of the measurement of dissolved oxygen (DO) profiles at different points of the B-MBR apparatus indicate that the increase in DO concentration in the anoxic zone of the B-MBR becomes much more pronounced by increasing recirculation intensity. On the basis of the results obtained in this study, it can be concluded that efficient removal of BOD, T-N, and total phosphorus can be achieved by the B-MBR as long as appropriate recirculation intensity is selected.

Surface water biopolymer fractionation for fouling mitigation in low-pressure membranes
Katsuki Kimura, Koki Shikato, Yasumitsu Oki, Keita Kume, Stefan A. Huber
Journal of Membrane Science, 554, 83, 89, Elsevier B.V., 15 May 2018, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal, With the widespread application of liquid chromatography with organic carbon detection (LC-OCD) to investigate membrane fouling in low-pressure membranes such as microfiltration (MF) and ultrafiltration (UF), membrane fouling by macromolecular hydrophilic biopolymer fraction has been recognized. In this study, a drinking water source was intensively investigated over 16 months. Membrane filtration using hollow-fiber MF membranes was carried out in constant flux mode with periodic backwashing, and two pretreatments (aluminum coagulation and anion exchange) were examined in terms of biopolymer removal and fouling mitigation. Higher biopolymer removal rates achieved by anion exchange than coagulation did not cause better control of membrane fouling in MF. Coagulation and anion exchange removed different types of biopolymers, which implied diversity in the biopolymer fraction. A modified set-up of LC-OCD analysis in which two different columns were sequentially connected was examined. It was demonstrated that the biopolymer fraction detected as a single peak with molecular weight of >
10,000 Da with the conventional LC-OCD set-up comprised of molecules with a variety of molecular weights including >
1,000,000 Da. It was found that coagulation removed large-size biopolymers with higher fouling potentials
while anion exchange preferentially removed small-size biopolymers with lower fouling potential. Concentration of large-size biopolymers in the feed water collected on different dates correlated with the degree of membrane fouling. In an attempt to generalize the conclusion drawn from the experiments using the specific drinking water source, batch MF tests filtering biopolymers isolated from different drinking water sources were also carried out. Importance of the large-size biopolymer fraction in the evolution of membrane fouling was also suggested with different drinking water sources.

Effective physical cleaning and adequate membrane flux for direct membrane filtration (DMF) of municipal wastewater: Up-concentration of organic matter for efficient energy recovery
Katsuki Kimura, Daisuke Honoki, Taku Sato
SEPARATION AND PURIFICATION TECHNOLOGY, 181, 37, 43, ELSEVIER SCIENCE BV, Jun. 2017, [Peer-reviewed]
English, Scientific journal, Organic matter in municipal wastewater should be regarded as a resource for energy production in the future. Direct application of anaerobic digestion to municipal wastewater is easy if the concentration of organic matter is increased. Although microfiltration membranes can concentrate organic matter in raw municipal wastewater, severe membrane fouling is likely to occur. In this study, efficient physical cleaning methods for direct membrane filtration (DMF) of municipal wastewater were investigated. Agitation of the tank, vibration of membrane modules, and use of granular materials were examined. Aeration was not tested because it leads to microbial degradation of organic matter (loss of recoverable energy). No single cleaning method worked well for DMF. However, a combination of membrane vibration and agitation of the tank was found to be effective. When the effective physical cleaning was performed with chemically enhanced backwash using citric acid and an adequate membrane flux, DMF of real municipal wastewater could be continued for almost one month without conducting any off-line membrane cleaning. The increase in transmembrane pressure was almost perfectly controlled in the long-term operation, during which 75% of organic matter was successfully recovered and 50-fold concentration (based on volume) of wastewater was continuously achieved with hydraulic retention time of 3.1 h. (C) 2017 Published by Elsevier B.V.

Efficient control of membrane fouling in MF by removal of biopolymers: Comparison of various pretreatments
Katsuki Kimura, Yasumitsu Oki
WATER RESEARCH, 115, 172, 179, PERGAMON-ELSEVIER SCIENCE LTD, May 2017, [Peer-reviewed]
English, Scientific journal, In recent studies on membrane fouling in microfiltration (MF) and ultrafiltration (UF) for drinking water production, hydrophilic macromolecular organics referred to as biopolymers have been shown to be major players in the fouling. In this study, various pretreatments were compared to maximize removal of biopolymers and to control membrane fouling efficiently. Multiple water samples were collected from different drinking water sources and were used in this study. Coagulation using polyaluminum chloride (PACl) was carried out under conditions of different dosages and different pHs and was also carried out in combination with the use of powdered activated carbon (PAC) or magnetic ion exchange (MIEX (R)) resin. The efficiency of removal of biopolymers was highest by the combination of MIEX (R) and coagulation regardless of the type of sample. Efficient removal of biopolymers achieved by the combination of MIEX (R) and coagulation led to efficient control of membrane fouling in MF, which was confirmed by bench-scale filtration tests conducted under a constant flux of 62.5 LMH using commercially available hollow-fiber membranes. Enhanced coagulation with increased coagulant dosage or acidic coagulation (pH = 6) also exhibited good removal of biopolymers in some cases and led to control of fouling. In contrast, the combination of PAC and coagulation sometimes caused more rapid evolution of fouling by forming cake layers on the membrane surface. Results of bench-scale tests showed that the concentration of biopolymers in the feed water correlated well with the degree of physically irreversible fouling, which was dominant in this study. The strong correlation was shown with multiple water samples treated by various pretreatments, demonstrating that biopolymer concentration in feed water is a good index for fouling studies. (C) 2017 Elsevier Ltd. All rights reserved.

Influence of different biofilm carriers on the operation and membrane fouling of submerged membrane bioreactors
Tokihiro Kurita, Takuma Mogi, Katsuki Kimura
SEPARATION AND PURIFICATION TECHNOLOGY, 169, 43, 49, ELSEVIER SCIENCE BV, Sep. 2016, [Peer-reviewed]
English, Scientific journal, It has been reported that the combination process of biofilm and submerged membrane bioreactors (MBRs) can mitigate membrane fouling. In this study, the influence of using three different biofilm carriers (fixed rope carrier, moving granular carrier and moving sponge carrier) on the operation and membrane fouling of MBRs was investigated. Using rope or sponge carriers with MBR processes improved the removal efficiency of nitrogen via the creation of an anoxic part inside the carriers. However, membrane fouling became very severe when rope carriers were used. Using granular or sponge carriers effectively mitigated membrane fouling because they mechanically cleaned the membrane surface. The cake/gel layer on the membrane surface was perfectly removed by granular or sponge carriers. However, the deterioration of the filterability of the mixed liquor suspensions was significant with granular carriers, leading to the evolution of physically irreversible fouling, whereas such deterioration was insignificant with the sponge carrier. The characteristics of the soluble microbial products (SMP) significantly varied depending on the types of carriers used, which could influence the filterability of mixed liquor suspensions and the development of irreversible membrane fouling. (C) 2016 Elsevier B.V. All rights reserved.

Maximizing biopolymer removal by coagulation for mitigation of fouling in the following membrane process
Katsuki Kimura, Nalco Ando
SEPARATION AND PURIFICATION TECHNOLOGY, 163, 8, 14, ELSEVIER SCIENCE BV, May 2016, [Peer-reviewed]
English, Scientific journal, In recent studies dealing with membrane fouling in microfiltration (MF)/ultrafiltration (UF) processes for drinking water production, biopolymers, which are hydrophilic macromolecules, have been identified as the key foulants. However, removal of biopolymers from water has been rarely focused on in previous studies. In this study, removal of biopolymers by coagulation, which is the most common pretreatment for MF/UF in existing full-scale facilities, was investigated. Surface water samples from three rivers used as raw water for drinking water production were examined in this study. Sampling was repeated in different seasons to examine a wide range of water quality. It was demonstrated that dosages commonly used in existing facilities were insufficient to maximize biopolymer removal by coagulation conducted at neutral pH. It was shown that an extremely high dosage of the coagulant was necessary to maximize biopolymer removal. A new dosage index, aluminum (Al, mg/L)/biopolymer (Bp, mu g/L), was used in this study. Al/Bp of about 20 was found to be necessary at pH 7 to almost maximize biopolymer removal by coagulation regardless of the water tested. Maximized biopolymer removal brought about least evolution of membrane fouling, which was separately verified in bench-scale filtration tests. Efficiency of coagulation for biopolymer removal varied depending on the season: samples collected in the cold season exhibited poor removal of biopolymers. Detailed examinations of biopolymers in each sample suggested that properties of the biopolymers changed seasonally. (C) 2016 Elsevier B.V. All rights reserved.

Importance of the co-presence of silica and organic matter in membrane fouling for RO filtering MBR effluent
Katsuki Kimura, Saaya Okazaki, Takeya Ohashi, Yoshimasa Watanabe
JOURNAL OF MEMBRANE SCIENCE, 501, 60, 67, ELSEVIER SCIENCE BV, Mar. 2016, [Peer-reviewed]
English, Scientific journal, Reverse osmosis (RO) is an important technique for potable water reuse. However, the problem of membrane fouling in RO must be addressed for its widespread use. In this study, fouling in RO was investigated with 2540 membrane elements fed with effluents from a membrane bioreactor (MBR) treating municipal wastewater. The results of chemical cleaning, elemental analysis for a cross section of the fouled membrane and microwave digestion of the fouled membrane suggested that silica was a major player in the membrane fouling. Also, organic matter present in the MBR effluent (mainly composed of soluble microbial products) was found to play an important role in the evolution of membrane fouling. A unique experimental setup enabled investigation of the interaction between silica and organic matter in the membrane fouling in RO: concentrations of silica and organic matter in the feedwater were manipulated. Remarkable membrane fouling occurred only when feedwater containing both silica and organic matter was filtered. It was found that silica or organic matter alone did not cause severe membrane fouling in the RO. The co -presence of silica and organic matter seems to have synergetic effects that cause severe membrane fouling in RO. (C) 2015 Elsevier B.V. All rights reserved.

INFLUENCE OF SIZE OF BIOPOLYMERS IN SURFACE WATER AND PORE SIZE OF MF/UF MEMBRANES ON EVOLUTION OF MEMBRANE FOULING
KIMURA Katsuki, OKI Yasumitsu
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 72, 7, III_535, III_541, Japan Society of Civil Engineers, 2016
Japanese, Membrane fouling caused by natural organic matter (NOM) hinders widespread application of microfiltration (MF) and ultrafiltration (UF) to water treatment. In this study, we focused on biopolymers, which are hydrophilic organic matter with large molecular weights and have been reported as primary foulants in recent studies. Influence of size of biopolymers and pore sizes of MF/UF membranes on evolution of membrane fouling was investigated. It was found that coagulation by polyaluminum chloride and anion exchange removed different fractions of biopolymers: coagulation removed biopolymers with large molecular weights (>1,000,000 Da) whereas anion exchange removed biopolymers with small molecular weights (<100,000 Da). Fouling in MF was significantly mitigated when the feed water was treated by coagulation, indicating that biopolymers with large molecular weight were the primary foulants in MF. Pretreatment by anion exchange followed by coagulation substantially removed biopolymers, leading to efficient control of membrane fouling in MF. The high removal of biopolymers by anion exchange followed by coagulation could be attributed to the fact that humic substances were significantly removed by anion exchange: more amounts of coagulant became available to react with biopolymers as a result of elimination of humics. When UF membrane was examined, evolution of irreversible fouling hardly occurred. This could be explained by the size of biopolymers. They could not intrude into pores of the UF membrane. However, small particles rejected by the UF membrane could cause reversible fouling.

Tracking inorganic foulants irreversibly accumulated on low-pressure membranes for treating surface water
Hiroshi Yamamura, Katsuki Kimura, Kumiko Higuchi, Yoshimasa Watanabe, Qing Ding, Akira Hafuka
WATER RESEARCH, 87, 218, 224, PERGAMON-ELSEVIER SCIENCE LTD, Dec. 2015, [Peer-reviewed]
English, Scientific journal, While low-pressure membrane filtration processes (i.e., microfiltration and ultrafiltration) can offer precise filtration than sand filtration, they pose the problem of reduced efficiency due to membrane fouling. Although many studies have examined membrane fouling by organic substances, there is still not enough data available concerning membrane fouling by inorganic substances. The present research investigated changes in the amounts of inorganic components deposited on the surface of membrane filters over time using membrane specimens sampled thirteen times at arbitrary time intervals during pilot testing in order to determine the mechanism by which irreversible fouling by inorganic substances progresses. The experiments showed that the inorganic components that primarily contribute to irreversible fouling vary as filtration continues. It was discovered that, in the initial stage of operation, the main membrane-fouling substance was iron, whereas the primary membrane-fouling substances when operation finished were manganese, calcium, and silica. The amount of iron accumulated on the membrane increased up to the thirtieth day of operation, after which it reached a steady state. After the accumulation of iron became static, subsequent accumulation of manganese was observed. The fact that the removal rates of these inorganic components also increased gradually shows that the size of the exclusion pores of the membrane filter narrows as operation continues. Studying particle size distributions of inorganic components contained in source water revealed that while many iron particles are approximately the same size as membrane pores, the fraction of manganese particles slightly smaller than the pores in diameter was large. From these results, it is surmised that iron particles approximately the same size as the pores block them soon after the start of operation, and as the membrane pores narrow with the development of fouling, they become further blocked by manganese particles approximately the same size as the narrowed pores. Calcium and silica are assumed to accumulate on the membrane due to their cross-linking action and/or complex formation with organic substances such as humic compounds. The present research is the first to clearly show that the inorganic components that contribute to membrane fouling differ according to the stage of membrane fouling progression; the information obtained by this research should enable chemical cleaning or operational control in accordance with the stage of membrane fouling progression. (C) 2015 Elsevier Ltd. All rights reserved.

Application of glyco-blotting for identification of structures of polysaccharides causing membrane fouling in a pilot-scale membrane bioreactor treating municipal wastewater
Katsuki Kimura, Shin-Ichiro Nishimura, Risho Miyoshi, Asiful Hoque, Taro Miyoshi, Yoshimasa Watanabe
BIORESOURCE TECHNOLOGY, 179, 180, 186, ELSEVIER SCI LTD, Mar. 2015, [Peer-reviewed]
English, Scientific journal, A new approach for the analysis of polysaccharides in membrane bioreactor (MBR) is proposed in this study. Enrichment of polysaccharides by glyco-blotting, in which polysaccharides are specifically collected via interactions between the aldehydes in the polysaccharides and aminooxy groups on glycoblotting beads, enabled MALDI-TOF/MS analysis at a high resolution. Structures of polysaccharides extracted from fouled membranes used in a pilot-scale MBR treating municipal wastewater and those in the supernatant of the mixed liquor suspension in the MBR were investigated. It was found that the overlap between polysaccharides found in the supernatants and those extracted from the fouled membrane was rather limited, suggesting that polysaccharides that dominate in supernatants may not be important in membrane fouling in MBRs. Analysis using a bacterial carbohydrate database suggested that capsular polysaccharides (CPS) and/or lipo-polysaccharides (LPS) produced by gram-negative bacteria are key players in the evolution of membrane fouling in MBRs. (C) 2014 Elsevier Ltd. All rights reserved.

Transition of major components in irreversible fouling of MBRs treating municipal wastewater
Katsuki Kimura, Rie Ogyu, Taro Miyoshi, Yoshimasa Watanabe
SEPARATION AND PURIFICATION TECHNOLOGY, 142, 326, 331, ELSEVIER SCIENCE BV, Mar. 2015, [Peer-reviewed]
English, Scientific journal, Evolution of irreversible fouling in pilot-scale membrane bioreactors (MBRs) treating municipal wastewater was studied. Three membrane modules were sacrificed to analyze foulants after they had been used for different durations (1 day, 8 days, 24 days). The module used for 1 day reflected fouling occurring at the initial stage, whereas the module used for 24 days reflected the later stage of fouling. After each module had been used for the predetermined period, it was disassembled and subjected to powerful chemical analysis such as Fourier transform infrared (FTIR) analysis. It was clearly shown that components involved in evolution of irreversible fouling gradually changed depending on the duration. The initial fouling (conditioning of membrane) was caused by humics, whereas later fouling was mainly caused by polysaccharides. A model for evolution of irreversible fouling in MBRs and implications for fouling control are discussed. (C) 2015 Elsevier B.V. All rights reserved.

Energy saving in the operation of submerged MBRs by the insertion of baffles and the introduction of granular materials
Tokihiro Kurita, Katsuki Kimura, Yoshimasa Watanabe
SEPARATION AND PURIFICATION TECHNOLOGY, 141, 207, 213, ELSEVIER SCIENCE BV, Feb. 2015, [Peer-reviewed]
English, Scientific journal, A membrane bioreactor (MBR) is not a mainstream wastewater treatment technology, mainly because the energy consumption in an MR operation is high. This study investigated the mitigation of membrane fouling and the reduction in aeration through the introduction of granules into a pilot-scale baffled membrane bioreactor (BMBR) used to treat municipal wastewater. With granular materials, the BMBR could be stably operated, even when the filterability of the mixed liquor suspensions was considerably low due to low temperatures. The aeration rate could be reduced by more than 50% with the help of granules. However, it was found that the introduction of granules damaged parts of the membrane surface. The damage might be avoided by adjusting the contact intensity of the granules and the membrane surface. (C) 2014 Elsevier B.V. All rights reserved.

Mitigation of Membrane Fouling in MBRs by Biomass Carriers
Kimura Katsuki
membrane, 40, 6, 327, 331, THE MEMBRANE SOCIETY OF JAPAN, 2015
Japanese, It is necessary to reduce costs in operation of membrane bioreactors (MBRs) for widespread use of the technology. Aeration used for prevention of attachment of biomass on the membrane surface accounts for the largest portion of the total energy consumption in MBRs and therefore should be focused on. Placing biomass carriers in submerged MBRs has been examined and been reported to be effective in mitigation of membrane fouling. In our bench–scale experiments in which a submerged flat–sheet MBR was operated with cylindrical carriers made from PEG, it was estimated that aeration rate in MBRs could be reduced by 50%. This estimation was verified in a pilot–scale MBR treating municipal wastewater. In that pilot–scale experiment, however, it was found that the carriers introduced caused damages on a part of membrane structures. Observations with a high–speed digital camera revealed that carriers moved much more rapidly in the pilot–scale MBR than in the bench–scale MBR. Also, the carriers moved randomly in the pilot–scale MBR whereas they steadily moved up almost perpendicularly in the bench–scale MBR. These differences in the manner of movement of the carriers in the MBRs seemed to explain the difference in the damage of the membrane in the two MBRs. Modification of aeration in the pilot–scale MBR is likely to avoid the damage on the membrane and is now being examined in our laboratory.

Proteins causing membrane fouling in membrane bioreactors
Taro Miyoshi, Yuhei Nagai, Tomoyasu Aizawa, Katsuki Kimura, Yoshimasa Watanabe
WATER SCIENCE AND TECHNOLOGY, 72, 6, 844, 849, IWA PUBLISHING, 2015, [Peer-reviewed]
English, Scientific journal, In this study, the details of proteins causing membrane fouling in membrane bioreactors (MBRs) treating real municipal wastewater were investigated. Two separate pilot-scale MBRs were continuously operated under significantly different operating conditions; one MBR was a submerged type whereas the other was a side-stream type. The submerged and side-stream MBRs were operated for 20 and 10 days, respectively. At the end of continuous operation, the foulants were extracted from the fouled membranes. The proteins contained in the extracted foulants were enriched by using the combination of crude concentration with an ultrafiltration membrane and trichloroacetic acid precipitation, and then separated by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). The N-terminal amino acid sequencing analysis of the proteins which formed intensive spots on the 2D-PAGE gels allowed us to partially identify one protein (OmpA family protein originated from genus Brevundimonas or Riemerella anatipestifer) from the foulant obtained from the submerged MBR, and two proteins (OprD and OprF originated from genus Pseudomonas) from that obtained from the side-stream MBR. Despite the significant difference in operating conditions of the two MBRs, all proteins identified in this study belong to beta-barrel protein. These findings strongly suggest the importance of beta-barrel proteins in developing membrane fouling in MBRs.

Confirmation of the correlation between membrane fouling in microfiltration and biopolymer concentrations in various Japanese surface waters
K. Kimura, K. Tanaka, Y. Watanabe
WATER SCIENCE AND TECHNOLOGY-WATER SUPPLY, 15, 2, 288, 293, IWA PUBLISHING, 2015, [Peer-reviewed]
English, Scientific journal, A variety of surface waters used for drinking water sources were collected from different parts of Japan to investigate a correlation between the concentration of hydrophilic biopolymer (e.g. proteins and polysaccharides) in the feed water and membrane fouling in microfiltration. Hollow-fiber membranes made from polyvinylidene fluoride with a nominal pore size of 0.1 mu m were used in the series of experiments involving the constant-flow mode of operation with automatic periodical backwashing. Easily available indexes of water quality, such as dissolved organic carbon, UV absorbance, Ca concentration and turbidity could not explain the degree of fouling encountered in the filtration tests. In contrast, a clear correlation between the concentrations of biopolymers determined by liquid chromatography with organic carbon detection (LC-OCD) and membrane fouling was confirmed in this study. The concentrations of humics exhibited a weak correlation. The impacts of seasonal variation of feed water and coagulant dosage on membrane fouling were also explained well by biopolymer concentrations. Concentrations of biopolymers can be a useful indicator of the fouling potential of feed water in microfiltration.

The influence of granular materials on the operation and membrane fouling characteristics of submerged MBRsh
Tokihiro Kurita, Katsuki Kimura, Yoshimasa Watanabe
JOURNAL OF MEMBRANE SCIENCE, 469, 292, 299, ELSEVIER SCIENCE BV, Nov. 2014, [Peer-reviewed]
English, Scientific journal, Aeration to mitigate membrane fouling accounts for the largest fraction of energy consumed in membrane bioreactors (MBRs). To reduce the energy consumed during MBR operation, alternative methods must be developed to control membrane fouling. Granules should be introduced into submerged MBRs to mitigate membrane fouling due to their mechanical cleaning effect On the membrane surface. This study assessed the possible reduction in aeration for submerged MBRs through introducing granules and investigated membrane fouling characteristics from using granules. Two bench-scale MBRs operated in parallel with synthetic wastewater, and granules were introduced into one MBR. The MBR with granules operated stably even after aeration was reduced by 50%. Reversible fouling was almost entirely controlled through the introduction of granules. However, the granules promoted irreversible fouling due to cake elimination, which acted as a dynamic filter. The overall benefit from granules was apparent; although, reversible fouling dominated in the absence of granules. The foulant characteristics differed with granule use. These characteristic changes were also explained by the absence of the dynamic filtration effect. (C) 2014 Elsevier B.V. All rights reserved.

Rising behaviour of single bubbles in narrow rectangular channels in Newtonian and non-Newtonian liquids
Lutz Boehm, Tokihiro Kurita, Katsuki Kimura, Matthias Kraume
INTERNATIONAL JOURNAL OF MULTIPHASE FLOW, 65, 11, 23, PERGAMON-ELSEVIER SCIENCE LTD, Oct. 2014, [Peer-reviewed]
English, Scientific journal, A phenomenological investigation of single bubbles ascending in a confined geometry with a rectangular cross section was done. Motivated by the goal to get a deeper understanding of the bubble behaviour in flat sheet membrane modules used in membrane bioreactors, the parameters channel depth (=spacing, 5-7 mm), bubble size (3-9 mm), superimposed liquid velocity (0-23.5 cm/s) and rheology of the continuous phase (Newtonian, shear-thinning) were varied. The shear-thinning liquid was used to simulate the rheological behaviour of activated sludge apparent in membrane bioreactors. The analysed properties included the rising paths, bubble shape, absolute and relative terminal rise velocities, friction factors and oscillation frequencies and amplitudes of the bubble.
As expected, a significant influence of the rheology of the continuous phase was found on the rising behaviour. In the shear-thinning liquid, the bubbles followed mostly a straight rising path with negligible oscillations. The variation of the channel depth mainly had an influence on the terminal rise velocity of the bubbles ascending in the shear-thinning liquid with higher values in the channel with the larger channel depth. Increasing the bubble size led to higher rising velocities and to enhanced oscillations. (C) 2014 Elsevier Ltd. All rights reserved.

Membrane cleaning in membrane bioreactors: A review
Zhiwei Wang, Jinxing Ma, Chuyang Y. Tang, Katsuki Kimura, Qiaoying Wang, Xiaomeng Han
JOURNAL OF MEMBRANE SCIENCE, 468, 276, 307, ELSEVIER SCIENCE BV, Oct. 2014, [Peer-reviewed]
English, Membrane bioreactors (MBRs) have been widely used in wastewater treatment and reclamation. Membrane cleaning is an essential part during the operation of MBRs since membrane fouling is an unavoidable problem. In past decades, with the in-depth understanding on membrane fouling, significant advances in membrane cleaning have been achieved. However, a comprehensive review on membrane cleaning in MBRs is still lacking. This paper attempts to critically review the recent developments of membrane cleaning. Firstly, the fouling and cleaning fundamentals are addressed, and then a comprehensive review on physical, chemical, and biological/biochemical cleaning is presented. The procedures of determining proper cleaning protocols for MBR systems are also proposed. Finally, the existing challenges and future research efforts are discussed in order to ensure the development of membrane cleaning toward a more effective and sustainable way in MBRs. (C) 2014 Elsevier B.V. All rights reserved.

Seasonal variation of effective chemical solution for cleaning of ultrafiltration membrane treating a surface water
Hiroshi Yamamura, Katsuki Kimura, Yoshimasa Watanabe
SEPARATION AND PURIFICATION TECHNOLOGY, 132, 110, 114, ELSEVIER SCIENCE BV, Aug. 2014, [Peer-reviewed]
English, Scientific journal, Water treatment using ultrafiltration (UF) membranes is gaining popularity world-wide, but the problem of membrane fouling needs to be addressed. We investigated the characteristics of membrane foulants by conducting two long-term filtration experiments using surface water from the Chitose River. The membrane was made of polyacrylonitrile and had a molecular weight cut-off of 100 kDa. The experiments were conducted in February 2004 Winter operation (Run 1) and October 2005 Summer operation (Run 2), when feed water characteristics were considerably different. Despite this, rates of physically irreversible fouling were similar. By measuring pure water permeability before and after chemical cleaning, we found that acidic or chelate solutions were most effective for cleaning the membrane from Run 1, whereas an alkaline solution was more effective for that from Run 2. Analysis of the chemical solutions that effective worked for canceling the fouling revealed that acidic cleaning in Run 1 extracted iron, carbohydrate and humic acid, while alkaline cleaning in Run 2 extracted carbohydrates. These results indicates that the iron, carbohydrates and humic acid caused the physically irreversible fouling in Run I, and carbohydrates were mainly responsible in Run 2. Based on the findings obtained in this study, it was suggested that the most important foulants and the most effective chemical cleaning agents may differ substantially between seasons. (C) 2014 Elsevier B.V. All rights reserved.

Hydrophilic fraction of natural organic matter causing irreversible fouling of microfiltration and ultrafiltration membranes
Hiroshi Yamamura, Kenji Okimoto, Katsuki Kimura, Yoshimasa Watanabe
WATER RESEARCH, 54, 123, 136, PERGAMON-ELSEVIER SCIENCE LTD, May 2014, [Peer-reviewed]
English, Scientific journal, Although membrane filtration is a promising technology in the field of drinking water treatment, persistent membrane fouling remains a major disadvantage. For more efficient operation, causative agents of membrane fouling need to be identified. Membrane fouling can be classified into physically reversible and irreversible fouling on basis of the removability of the foulants by physical cleaning. Four types of natural organic matter (NOM) in river water used as a source of drinking water were fractionated into hydrophobic and hydrophilic fractions, and their potential to develop irreversible membrane fouling was evaluated by a bench-scale filtration experiment together with spectroscopic and chromatographic analyses. In this study, only dissolved NOM was investigated without consideration of interactions of NOM fractions with particulate matter. Results demonstrated that despite identical total organic carbon (TOC), fouling development trends were significantly different between hydrophilic and hydrophobic fractions. The hydrophobic fractions did not increase membrane resistance, while the hydrophilic fractions caused severe loss of membrane permeability. These results were identical with the case when the calcium was added to hydrophobic and hydrophilic fractions. The largest difference in NOM characteristics between hydrophobic and hydrophilic fractions was the presence or absence of macromolecules; the primary constituent causing irreversible fouling was inferred to be "biopolymers", including carbohydrates and proteins. In addition, the results demonstrated that the extent of irreversible fouling was considerably different depending on the combination of membrane materials and NOM characteristics. Despite identical nominal pore size (0.1 mu m), a polyvinylidene fluoride (PVDF) membrane was found to be more rapidly fouled than a PE membrane. This is probably explained by the generation of strong hydrogen bonding between hydroxyl groups of biopolymers and fluorine of the PVDF membrane. On the basis of these findings, it was suggested that the higher fouling potential of the hydrophilic fraction of the dissolved NOMs from various natural water sources are mainly attributed to macromolecules, or biopolymers. (C) 2014 Elsevier Ltd. All rights reserved.

Toxicity assessment of chlorinated wastewater effluents by using transcriptome-based bioassays and Fourier transform mass spectrometry (FT-MS) analysis
Toshikazu Fukushima, Hiroe Hara-Yamamura, Makoto Urai, Ikuro Kasuga, Futoshi Kurisu, Taro Miyoshi, Katsuki Kimura, Yoshimasa Watanabe, Satoshi Okabe
WATER RESEARCH, 52, 73, 82, PERGAMON-ELSEVIER SCIENCE LTD, Apr. 2014, [Peer-reviewed]
English, Scientific journal, Effects of chlorination on the toxicity of wastewater effluents treated by activated sludge (AS) and submerged membrane bioreactor (S-MBRB) systems to HepG2 human hepatoblastoma cells were investigated. In addition to the cytotoxicity and genotoxicity assays, the DNA microarray-based transcriptome analysis was performed to evaluate the change in types of biological impacts on HepG2 cells of the effluents by chlorination. Effluent organic matter (EfOM) and disinfection by-products (DBPs) were also characterized by using Fourier transform mass spectrometry (FT-MS). Although no significant induction of genotoxicity was observed by chlorination for both effluents, the chlorination elevated the cytotoxicity of AS effluent but reduced that of S-MBRB effluent. The FT-MS analyses revealed that more DBPs including nitrogenated DBPs (N-DBPs) were formed in the AS effluent than in the S-MBRB effluent by chlorination, supporting the increased cytotoxicity of AS effluent. The lower O/C ratio of S-MBRB EfOM suggests that a large number of organic molecules were detoxified by chlorination, which consequently decreased the cytotoxicity of S-MBRB effluent. Integration of all the results highlights that both cytotoxicity and biological impacts of chlorinated wastewater effluents were clearly dependent on the EfOM characteristics such as DBPs and O/C ratio, namely, on types of treatment systems. (C) 2014 Elsevier Ltd. All rights reserved.

Microfiltration of different surface waters with/without coagulation: Clear correlations between membrane fouling and hydrophilic biopolymers
Katsuki Kimura, Ken Tanaka, Yoshimasa Watanabe
WATER RESEARCH, 49, 434, 443, PERGAMON-ELSEVIER SCIENCE LTD, Feb. 2014, [Peer-reviewed]
English, Scientific journal, Although low-pressure membranes (microfiltration (MF) or ultrafiltration (UF)) have become viable options for drinking water treatment, problems caused by membrane fouling must still be addressed. The objective of this study was to compare five different surface waters and to identify a relevant index of water quality that can be used for prediction of the fouling potential of the water. Bench-scale filtration tests were carried out with commercially available hollow-fiber MF membranes. Fairly long-term (a few days) filtrations in the constant-flow mode were carried out with automatic backwash. Membrane fouling in this study was shown to be irreversible as a result of the periodic backwash carried out throughout of the operation. Easily accessible indexes of water quality including dissolved organic carbon (Doc), uv absorbance, Ca concentration and turbidity could not explain the degree of fouling encountered in the filtration tests. Fluorescence excitation-emission matrix (EEM) could provide information on the presence of protein-like substances in water, and peaks for protein showed some correlation with the membrane fouling. Biopolymer (characterized by high molecular weights and insensitivity to UV light absorption) concentrations in the five waters determined by liquid chromatography with organic carbon detection (LC-OCD) exhibited an excellent correlation with the fouling rates. Coagulation with polyaluminum chloride could mitigate membrane fouling in all cases. The extent of fouling seen with coagulated waters was also correlated with biopolymer concentrations. The relationship between biopolymer concentrations and the fouling rates established for the raw waters could also be applied to the coagulated waters. These results suggested that the contribution of biopolymers to membrane fouling in the present study was significant, an observation that was supported by the analysis of foulants extracted at the termination of each test. Biopolymer concentrations determined by LC-OCD might be used as a key indicator of fouling potential of water for low-pressure membranes. (C) 2013 Elsevier Ltd. All rights reserved.

Evaluation of whole wastewater effluent impacts on HepG2 using DNA microarray-based transcriptome analysis
Hiroe Hara-Yamamura, Koji Nakashima, Asiful Hoque, Taro Miyoshi, Katsuki Kimura, Yoshimasa Watanabe, Satoshi Okabe
Environmental Science and Technology, 47, 10, 5425, 5432, 21 May 2013, [Peer-reviewed]
English, Scientific journal, DNA microarray-based transcriptome analysis with human hepatoma HepG2 cells was applied to evaluate the impacts of whole wastewater effluents from the membrane bioreactors (MBRs) and the activated sludge process (AS). In addition, the conventional bioassays (i.e., cytotoxicity tests and bioluminescence inhibition test), which were well-established for the evaluation of the overall effluent toxicity, were also performed for the same samples. Transcriptome analysis revealed that 2 to 926 genes, which were categorized to 0 to 225 biological processes, were differentially expressed after exposure to the effluents and the raw wastewater. Among the tested effluents, the effluent from a MBR operated at a relatively long solid retention time (i.e., 40 days) and small membrane pore size (i.e., 0.03 μm) showed the least impacts on the HepG2 even at the level comparable to tap water. The observed gene expression responses were in good agreement with the results of cytotoxicity tests, and provided additional molecular mechanistic information on adverse effects occurred in the sublethal region. Furthermore, the genes related to "lipid metabolism", "response to endogenous stimulus", and "response to inorganic substance" were selected as potential genetic markers, and their expression levels were quantified to evaluate the cellular impacts and treatability of wastewater effluents. Although the harmful impacts and innocuous impacts could not be distinguished at present, the results demonstrated that the DNA microarray-based transcriptome analysis with human HepG2 cells was a powerful tool to rapidly and comprehensively evaluate impacts of whole wastewater effluents. © 2013 American Chemical Society.

Direct membrane filtration of municipal wastewater with chemically enhanced backwash for recovery of organic matter
Shaik Khaja Lateef, Bing Zheng Soh, Katsuki Kimura
Bioresource Technology, 150, 149, 155, Elsevier Ltd, 2013, [Peer-reviewed]
English, Scientific journal, Direct membrane filtration (DMF) of municipal wastewater using a microfiltration membrane was investigated to capture organic matter. In contrast to the expectation that membrane fouling cannot be controlled in DMF of domestic wastewater, it was possible to stably continue membrane filtration with relatively high membrane fluxes (~20. LMH) for >
200. h by applying chemically enhanced backwash (CEB), whereas approximately 75% of the organic matter in wastewater could be recovered. Off-line chemical membrane cleaning could completely restore membrane permeability, indicating the possibility of a much longer operation of DMF. Selection of chemical reagents used for CEB was found to influence the amount of organic matter recovered by DMF. Based on the experimental results, feasibility of DMF was discussed by a comparison with a conventional wastewater treatment plant treating the same wastewater as studied in this study. © 2013 The Authors.

Permeability decline in nanofiltration/reverse osmosis membranes fed with municipal wastewater treated by a membrane bioreactor
Katsuki Kimura, Naoko Ogawa, Yoshimasa Watanabe
Water Science and Technology, 67, 9, 1994, 1999, 2013, [Peer-reviewed]
English, Scientific journal, Decline in the permeability in nanofiltration (NF)/reverse osmosis (RO) membranes that filtered effluents from a membrane bioreactor (MBR) treating municipal wastewater was investigated in this study. Four different 2-inch spiral-wound NF/RO membrane elements were continuously operated for 40 days. The results showed that the amount of deposits on the membrane surface did not affect the degree of permeability decline. Laboratory-scale filtration tests with coupons obtained from the fouled membranes also revealed that the contribution of the gel/cake layer to total filtration resistance was minor. Rather, constituents that were strongly bound to the membranes were mainly responsible for permeability decline. Chemical cleaning of the fouled membranes carried out after removal of the cake showed that silica played an important role in the decline in permeability. A considerable amount of organic matter which was mainly composed of carbohydrates and proteins was also desorbed from the fouled membranes. © IWA Publishing 2013.

Membrane fouling caused by sub-micron particles in a mixed liquor suspension of an MBR
K. Kimura, R. Ogyu, T. Miyoshi, T. Naruse, T. Tsuyuhara, Y. Watanabe
WATER SCIENCE AND TECHNOLOGY, 67, 11, 2602, 2607, IWA PUBLISHING, 2013, [Peer-reviewed]
English, Scientific journal, Membrane fouling needs to be mitigated for widespread use of membrane bioreactors (MBRs). It has been pointed out that particles with small sizes found in supernatants (sub-micron particles) of mixed liquor suspensions of MBRs are important in the evolution of membrane fouling of this technology. However, information on characteristics of sub-micron particles in MBRs is still insufficient. In this study, a pilot-scale MBR treating municipal wastewater was used to investigate and characterize sub-micron particles in an MBR and to identify the size fraction(s) responsible for irreversible fouling in an MBR. It was clearly shown that characteristics of sub-micron particles in the MBR varied considerably depending on their sizes. Results of Fourier transform infrared (FTIR) analysis and monosaccharide analysis suggested that irreversible fouling in this study was mainly caused by the specific size fraction of 0.1-0.45 mu m, which was close to the size of micropores of the membrane used. Pore plugging might explain this to some extent.

Further examination of polysaccharides causing membrane fouling in membrane bioreactors (MBRs): Application of lectin affinity chromatography and MALDI-TOF/MS
Katsuki Kimura, Ippei Tanaka, Shin-Ichiro Nishimura, Risho Miyoshi, Taro Miyoshi, Yoshimasa Watanabe
WATER RESEARCH, 46, 17, 5725, 5734, PERGAMON-ELSEVIER SCIENCE LTD, Nov. 2012, [Peer-reviewed]
English, Scientific journal, Membrane fouling remains a major obstacle for wider application of membrane bioreactors (MBRs) to wastewater treatment. Polysaccharides in mixed liquor suspensions in the reactors are thought to be mainly responsible for the evolution of membrane fouling in MBRs. However, details of polysaccharides causing membrane fouling in MBRs are still unknown. In this study, polysaccharides in a mixed liquor suspension of a pilot-scale MBR treating municipal wastewater were fractionated by using lectins, special proteins that bind to specific polysaccharides depending on their properties. Fouling potentials of the fractionated polysaccharides were assessed by bench-scale dead-end filtration tests. It was clearly shown that the degrees of fouling caused by fractionated polysaccharides were significantly different. The amounts of polysaccharides in each fraction could not explain the variations in the fouling, indicating the presence of polysaccharides with high specific fouling potentials. To investigate structures and origins of the polysaccharides with high fouling potentials, matrix-assisted laser desorption/ionization (MALDI)-time of flight (TOF)/mass spectrometry (MS) analysis was applied to the fractionated polysaccharides after partial hydrolysis. Several mass peaks obtained could be assigned to fragments of structures of polysaccharides (i.e., oligosaccharides) reported in a database/literature. This is the first report showing the plausible structures of polysaccharides in MBRs based on MS. A deeper understanding and effective control of membrane fouling in MBRs could be achieved with information obtained by the approach used in this study. (C) 2012 Elsevier Ltd. All rights reserved.

Identification of proteins involved in membrane fouling in membrane bioreactors (MBRs) treating municipal wastewater
Taro Miyoshi, Tomoyasu Aizawa, Katsuki Kimura, Yoshimasa Watanabe
INTERNATIONAL BIODETERIORATION & BIODEGRADATION, 75, 15, 22, ELSEVIER SCI LTD, Nov. 2012, [Peer-reviewed]
English, Scientific journal, The proteins that caused membrane fouling in a continuous operation of membrane bioreactors (MBRs) treating real municipal wastewater were investigated in detail. We continuously operated two identical pilot-scale MBRs under different solid retention times (SRTs) and extracted the foulants at the end of the operation. Regardless of the operating conditions, proteins were dominant components in the foulants extracted from the fouled membranes. The extracted proteins were subjected to the separation with two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and the identification through the N-terminal amino acid sequencing analysis. The proteins concentrated by the combination of the crude concentration using an ultra-filtration (UF) membrane and trichloroacetic acid (TCA) precipitation were separated and visualized well on 2D-PAGE gels. The results of 2D-PAGE analysis indicated that the compositions of proteins that caused membrane fouling significantly differed depending on the SRT, although such differences cannot be seen in the amino acid composition analysis. Analyzing selected 2D-PAGE spots by N-terminal amino acid sequencing analysis led to the identification of two well-characterized outer membrane proteins originating from Pseudomonas genus, namely OprF and OprD. To our knowledge, this is the first successful identification of proteins that have caused membrane fouling in continuous operations of MBRs treating real wastewater. (C) 2012 Elsevier Ltd. All rights reserved.

Polysaccharides and Proteins Causing Membrane Fouling
KIMURA Katsuki
MEMBRANE, 37, 5, 230, 234, THE MEMBRANE SOCIETY OF JAPAN, 01 Sep. 2012
Japanese, Application of membrane technology to water purification and wastewater treatment is being accelerated. The main obstacle for wider use of membrane technology is membrane fouling, which can be divided into two types depending on its reversibility: reversible (mostly cake layer) fouling and irreversible fouling. The former type of fouling can be cancelled by physical cleaning such as backwashing or air-souring, whereas the latter needs chemical cleaning to be cancelled. Most of full-scale membrane filtration units are operated with routine physical cleaning and control of irreversible fouling is therefore important. We have focused on characteristics of foulants causing irreversible fouling in membrane processes and have conducted many pilot-scale experiments using real drinking water source and municipal wastewater. Foulants extracted from the fouled membranes were subject to various analysis to investigate the characteristics of foulants. Analysis using Fourier transform infrared (FTIR) and 13C nuclear magnetic resonance (NMR) spectrum revealed that foulants that were responsible for irreversible fouling were mainly composed of polysaccharides and proteins regardless of type of application. It was also found that monosaccharide composition and amino acid composition in the foulants significantly varied depending on operational conditions of membrane processes. Detailed information on the foulants that cause irreversible fouling including their structures and origins is being revealed by advanced analytical techniques such as MALDI-TOF/MS. Once the structures of the foulants have been fully identified, it will be possible to specifically monitor the important foulants or microorganisms that produce them, which might enable effective control of membrane fouling. Also, extensive investigation of interactions between the important foulants and various membrane materials/structures should lead to the development of new anti-fouling membranes.

Characteristics of foulants in air-sparged side-stream tubular. membranes used in a municipal wastewater membrane bioreactor
Asiful Hoque, Katsuki Kimura, Taro Miyoshi, Nobuhiro Yamato, Yoshimasa Watanabe
SEPARATION AND PURIFICATION TECHNOLOGY, 93, 83, 91, ELSEVIER SCIENCE BV, Jun. 2012, [Peer-reviewed]
English, Scientific journal, Membrane bioreactors (MBRs) have become very attractive during the past decade owing to their advantages, although MBR operation has not been optimized yet. Recently, air-sparged side-stream MBRs (ASMBRs) have received much attention because they can overcome the drawbacks of submerged MBRs such as the difficulty of cleaning membrane modules. Widespread application of MBRs has been limited by problems associated with membrane fouling, and ASMBRs are not exceptions. Hydraulic conditions on the membrane surface used in an ASMBR are different from those in a submerged MBR, and this difference affects the characteristics of foulants. The aim of this study was to determine foulant characteristics in a pilot-scale ASMBR operated at an existing municipal wastewater treatment plant. Cylindrical membrane modules holding about 100 membrane tubes each were installed vertically in the ASMBR. Differences of foulants depending on tube positions in the horizontal cross section were investigated in the first experiment. There were no significant differences in the foulant characteristics regardless of the tube positions in the membrane module. This first experiment also showed that humic substances were dominant in the foulants extracted from the tubular membranes used in the ASMBR, whereas hydrophilic substances such as polysaccharides/proteins were reportedly dominant in foulants in the case of submerged MBRs. In the following experiment, a tiny hollow-fiber membrane module was submerged in the ASMBR's reaction tank to filter the shared biomass suspension and enable direct comparison of foulant characteristics in different MBR configurations (i.e., air-sparged side-stream versus submerged). Humic substances were again found to be dominant in foulants extracted from the ASMBR's tubular membranes, whereas hydrophilic organic matter was dominant in foulants extracted from the submerged hollow-fiber membranes. We hypothesize that different hydraulic conditions in the two configurations brought about the difference in foulants. The results obtained in this study suggest that effective measures to address membrane fouling will differ depending on the MBR configuration. (C) 2012 Elsevier B.V. All rights reserved.

Performance of Membrane Bio-Reactor Equipped with Air-Sparged Side-Stream Tubular Membrane: Treatment Efficiency and Membrane Fouling
A. Hoque, T. Miyoshi, K. Kimura, Y. Watanabe
SEPARATION SCIENCE AND TECHNOLOGY, 47, 10, 1455, 1463, TAYLOR & FRANCIS INC, 2012, [Peer-reviewed]
English, Scientific journal, We conducted a high-load operation of a baffled bio-reactor equipped with air-sparged side-stream tubular membrane modules for treating actual municipal wastewater at two different periods (high-and low-temperature). Although nitrogen removal efficiency slightly decreased at the low-temperature period, this baffled bio-reactor showed excellent nitrogen and phosphorus removal efficiencies. We also investigated the developments of both physically reversible and irreversible fouling during operation with two-phase flow (mixed-liquor and gas) at various gas velocities and the mixed-liquor velocity was fixed at 0.50 m/s. The membrane flux was fixed at 80 L/m(2)/hour throughout the experiments. Regardless of the difference in temperature, the trends in the development of these two types of membrane fouling caused by the difference in gas velocity were similar. For physically reversible fouling, an optimum gas velocity, in which the development of this type of fouling was minimized, was found to be around 0.42 m/s (corresponding void fraction was 0.45). A further increase in gas velocity resulted in more reversible fouling. On the other hand, the degree of physically irreversible fouling decreased as gas velocity increased. The results obtained in this study indicated the effect of gas velocity on fouling control differs depending on the type of membrane fouling.

Characteristics of proteins involved in membrane fouling in membrane bioreactors (MBRs) treating municipal wastewater: the application of metaproteomic analyses
Taro Miyoshi, Tomoyasu Aizawa, Katsuki Kimura, Yoshimasa Watanabe
DESALINATION AND WATER TREATMENT, 34, 1-3, 150, 155, DESALINATION PUBL, Oct. 2011
English, Scientific journal, We investigated the relationship between the nature of proteins and their fouling propensities in pilot-scale membrane bioreactors (MBRs) treating real municipal wastewater with two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). In 2D-PAGE, proteins are separated based on their isoelectric points and molecular weights, and therefore, information can be obtained on the nature of the proteins. Foulants extracted from fouled membranes at the end of continuous operation and organic matter contained in mixed liquor suspension were analyzed by 2D-PAGE, and the results were compared. This analysis was performed for two identical MBRs operated under different solid retention times (SRT) to investigate the effect of the operating condition on the types of proteins with high fouling propensities. In the MBR operated with a long SRT, the presence of proteins that appeared in the neutral pH range was more pronounced in the extracted foulant. Because the pH of the mixed liquor suspension was in the range of 6-7 throughout the continuous operation, the difference in protein profiles between the extracted foulant and the organic matter contained in the mixed liquor suspension in the MBR operated with a long SRT can be explained by a decrease in solubility of a protein at its isoelectric point. In contrast, in the MBR operated with a short SRT, the presence of proteins that appeared in the acidic region (pH 3-5) was more prominent in the extracted foulant compared with the organic matter contained in the mixed liquor suspension. The results obtained in this study imply that dominant fouling mechanisms differed depending on the operating condition.

Characteristics of proteins involved in membrane fouling in membrane bioreactors (MBRs) treating municipal wastewater: the application of metaproteomic analyses
Taro Miyoshi, Tomoyasu Aizawa, Katsuki Kimura, Yoshimasa Watanabe
DESALINATION AND WATER TREATMENT, 34, 1-3, 150, 155, DESALINATION PUBL, Oct. 2011, [Peer-reviewed]
English, Scientific journal, We investigated the relationship between the nature of proteins and their fouling propensities in pilot-scale membrane bioreactors (MBRs) treating real municipal wastewater with two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). In 2D-PAGE, proteins are separated based on their isoelectric points and molecular weights, and therefore, information can be obtained on the nature of the proteins. Foulants extracted from fouled membranes at the end of continuous operation and organic matter contained in mixed liquor suspension were analyzed by 2D-PAGE, and the results were compared. This analysis was performed for two identical MBRs operated under different solid retention times (SRT) to investigate the effect of the operating condition on the types of proteins with high fouling propensities. In the MBR operated with a long SRT, the presence of proteins that appeared in the neutral pH range was more pronounced in the extracted foulant. Because the pH of the mixed liquor suspension was in the range of 6-7 throughout the continuous operation, the difference in protein profiles between the extracted foulant and the organic matter contained in the mixed liquor suspension in the MBR operated with a long SRT can be explained by a decrease in solubility of a protein at its isoelectric point. In contrast, in the MBR operated with a short SRT, the presence of proteins that appeared in the acidic region (pH 3-5) was more prominent in the extracted foulant compared with the organic matter contained in the mixed liquor suspension. The results obtained in this study imply that dominant fouling mechanisms differed depending on the operating condition.

Characteristics of proteins involved in membrane fouling in membrane bioreactors (MBRs) treating municipal wastewater: The application of metaproteomic analyses
Taro Miyoshi, Tomoyasu Aizawa, Katsuki Kimura, Yoshimasa Watanabe
Desalination and Water Treatment, 34, 150, 155, Jan. 2011, [Peer-reviewed]
We investigated the relationship between the nature of proteins and their fouling propensities in pilot-scale membrane bioreactors (MBRs) treating real municipal wastewater with two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). In 2D-PAGE, proteins are separated based on their isoelectric points and molecular weights, and therefore, information can be obtained on the nature of the proteins. Foulants extracted from fouled membranes at the end of continuous operation and organic matter contained in mixed liquor suspension were analyzed by 2D-PAGE, and the results were compared. This analysis was performed for two identical MBRs operated under different solid retention times (SRT) to investigate the effect of the operating condition on the types of proteins with high fouling propensities. In the MBR operated with a long SRT, the presence of proteins that appeared in the neutral pH range was more pronounced in the extracted foulant. Because the pH of the mixed liquor suspension was in the range of 6-7 throughout the continuous operation, the difference in protein profiles between the extracted foulant and the organic matter contained in the mixed liquor suspension in the MBR operated with a long SRT can be explained by a decrease in solubility of a protein at its isoelectric point. In contrast, in the MBR operated with a short SRT, the presence of proteins that appeared in the acidic region (pH 3-5) was more prominent in the extracted foulant compared with the organic matter contained in the mixed liquor suspension. The results obtained in this study imply that dominant fouling mechanisms differed depending on the operating condition. © 2011 Desalination Publications. All rights reserved.

Membrane fouling in nanofiltration/reverse osmosis membranes coupled with a membrane bioreactor used for municipal wastewater treatment
Naoko Ogawa, Katsuki Kimura, Yoshimasa Watanabe
DESALINATION AND WATER TREATMENT, 18, 1-3, 292, 296, DESALINATION PUBL, Jun. 2010, [Peer-reviewed]
English, Scientific journal, Securing a new water resource is becoming an important issue as severe shortage of water is seen throughout the world. Reuse of highly treated wastewater can be a viable option to address this issue. In this study, an advanced wastewater treatment system comprised of a membrane bioreactor followed by nanofiltration (NF) and reverse osmosis (RO) membranes was examined at pilot-scale with real wastewater. Treatment performance of the system was evaluated on the basis of 40 days continuous operation. At the end of the operation, membrane fouling in NF/RO membranes was investigated by disassembling the membrane modules. Although there was no significant difference in water qualities of the permeates between the NF and the RO membranes, membrane fouling was more significant in the NF membrane than in the RO membrane. After disassembling the membrane modules, a portion of the fouled membranes was cleaned stepwise and pure water permeabilities of the membrane specimen at each cleaning step were determined with a bench-scale cross-flow filtration unit. It was revealed that contribution of the cake/gel layers to the total filtration resistance was limited in both NF and RO membranes. It was found that inorganic matter, particularly silica, was main foulant in the NF membrane whereas organic matter mainly caused fouling in the RO membrane.

Journal of Water Supply: Research and Technology - AQUA. Preface
Stefan Panglisch, Katsuki Kimura, Gary Amy
Journal of Water Supply: Research and Technology - AQUA, 59, 2-3, 79, 80, 2010
English, Scientific journal

Influence of membrane properties on physically reversible and irreversible fouling in membrane bioreactors
T. Tsuyuhara, Y. Hanamoto, T. Miyoshi, K. Kimura, Y. Watanabe
WATER SCIENCE AND TECHNOLOGY, 61, 9, 2235, 2240, IWA PUBLISHING, 2010, [Peer-reviewed]
English, Scientific journal, This study aimed to examine the impact of membrane properties on membrane fouling in membrane bioreactor (MBR). Membrane fouling was divided into two categories: physically reversible and irreversible fouling. Membrane properties related to each type of membrane fouling were investigated separately. Five microfiltration (MF) and one ultrafiltration (UF) membranes with different properties (pore size, contact angle, roughness, zeta potential, and pure water permeability) were examined with a laboratory-scale MBR, fed with synthetic wastewater. Two separate experiments were conducted: the first to examine physically reversible fouling, and the second to examine physically irreversible fouling. The correlation between the degree of each type of fouling and membrane properties was studied. High correlation was observed between the degree of physically reversible fouling and roughness (R(2) = 0.96). In contrast, with regard to physically irreversible fouling, strong correlation between roughness and degree of membrane fouling can only be found in the case of MF membranes. Except for the membrane with the highest roughness, the degree of physically irreversible fouling can be well correlated with pure water permeability (lower pure water permeability results in higher degree of physically irreversible fouling) including UF membrane. On the basis of the results obtained in this study, it can be concluded that roughness is an important factor in determination of physically reversible fouling regardless of the types of membrane (i.e. MF or UF membranes) and evolutions of physically irreversible fouling can be mitigated when an MBR is operated with membranes with smooth surface and high pure water permeability.

Fouling potentials of polysaccharides in membrane bioreactors (MBRs) assessed by lectin affinity chromatography
T. Miyoshi, I. Tanaka, T. Tsuyuhara, E. Watanabe, T. Aizawa, K. Kimura, Y. Watanabe
WATER SCIENCE AND TECHNOLOGY, 61, 7, 1787, 1792, IWA PUBLISHING, 2010, [Peer-reviewed]
English, Scientific journal, In this study, the fouling potentials of polysaccharides contained in mixed liquor suspension in a membrane bioreactor (MBR) treating municipal wastewater were investigated using lectin affinity chromatography. This investigation was carried out with different membranes to assess the effects of membrane materials on fouling potentials of polysaccharides. In lectin affinity chromatography, some polysaccharides with high affinity to the lectin in the column can be retained in the column. The fouling potentials of the retained polysaccharides were evaluated by dead-end filtration test. Degree of reduction in fouling potential differed considerably when different lectins were used in affinity chromatography indicating that fouling potentials of polysaccharide differed depending on types of polysaccharide. Trends in the reduction of fouling potential were different depending on membrane materials. Characteristics of the organic matter associated with polysaccharides removed by lectins were investigated by means of excitation-emission matrices (EEM). The results of EEM analysis indicate that the characteristics of the organic matter eluted from different lectins were different as long as elution reagents for the lectin were different. Characteristics of the organic matter eluted from the lectins which have the same elution reagent were similar in terms of shapes of EEM fluorescence spectra. However, the trends in reduction of fouling potentials could not be explained by the characteristics of organic matter assessed by EEM analysis. On the basis of the results obtained in this study, it can be concluded that characteristics of membrane and structures or properties of sugar chain would play an important role in determining fouling potentials.

Elimination of selected pharmaceuticals by biosolids from municipal wastewater treatment plants: importance of modest pH change and degree of mineralization
K. Kimura, H. Hara, Y. Watanabe
WATER SCIENCE AND TECHNOLOGY, 62, 5, 1084, 1089, IWA PUBLISHING, 2010, [Peer-reviewed]
English, Scientific journal, Lab-scale batch experiments with biosolids collected from a full-scale activated sludge system (AS) and a pilot-scale membrane bioreactor (MBR) were carried out to investigate the mechanisms of elimination of 5 acidic pharmaceuticals and 2 neutral pharmaceuticals. Batch elimination experiments were conducted under the conditions of pH of 6 and 7, and a great impact of pH on elimination of pharmaceuticals was shown by the significant differences in elimination rates under different pH conditions: elimination of pharmaceuticals was enhanced under the condition of lower pH regardless of the type of biosolid. Degree of mineralization of ibuprofen was also investigated in this study by using (14)C-labeled compounds. Although ibuprofen has been considered to be a readily biodegradable pharmaceutical in previous studies, the results obtained in this study demonstrated that the degree of mineralization of ibuprofen would be limited in biological wastewater treatment including MBRs. The results obtained in this study imply that a large portion of pharmaceuticals that have been considered "biodegradable", such as ibuprofen, entering into wastewater treatment plants will eventually be discharged into natural water bodies as intermediates, although concentrations of them may look reduced on the basis of common analytical methods (i.e. GC/MS or LC/MS/MS).

Seasonal variation in membrane fouling in membrane bioreactors (MBRs) treating municipal wastewater
Taro Miyoshi, Tomoo Tsuyuhara, Rie Ogyu, Katsuki Kimura, Yoshimasa Watanabe
WATER RESEARCH, 43, 20, 5109, 5118, PERGAMON-ELSEVIER SCIENCE LTD, Dec. 2009, [Peer-reviewed]
English, Scientific journal, We investigated seasonal variation in membrane fouling in membrane bioreactors (MBRs) treating municipal wastewater regarding the difference between physically reversible and irreversible fouling. Two separate MBRs with different solid retention times (SRTs) operated in parallel for about 200 days including high-and low-temperature periods to evaluate the effect of operating conditions on seasonal variation of membrane fouling. Seasonal variations of both types of membrane fouling (i.e., physically reversible and irreversible fouling) were observed for the MBR with short SRT (13 days). However, in the MBR with long SRT (50 days), there were no significant seasonal variations in both types of membrane fouling. In the MBR with short SRT, the trends in the seasonal variation in the development rates of physically reversible and irreversible fouling were different. Physically reversible fouling was more significant in the low-temperature period, while physically irreversible fouling developed more rapidly in the high-temperature period. The development rates of physically reversible fouling can be related to the concentration of dissolved organic matter in the mixed liquor suspension of MBRs; whereas those of physically irreversible fouling could not be explained by the concentration of dissolved organic matter. The characteristics of dissolved organic matter differed depending on the temperature period, and the trends of dissolved organic matter variation in mixed liquor were similar with those of foulants that caused physically irreversible fouling. The results obtained in this study indicated that seasonal variation in physically reversible and irreversible fouling is related to changes in quantity and quality of organic matter, respectively. (C) 2009 Elsevier Ltd. All rights reserved.

Influence of residual organic macromolecules produced in biological wastewater treatment processes on removal of pharmaceuticals by NF/RO membranes
Katsuki Kimura, Tomonori Iwase, Shusuke Kita, Yoshimasa Watanabe
WATER RESEARCH, 43, 15, 3751, 3758, PERGAMON-ELSEVIER SCIENCE LTD, Aug. 2009, [Peer-reviewed]
English, Scientific journal, Increasing attention has been given to pollution of the water environment by pharmaceutical compounds discharged from wastewater treatment plants. High-pressure driven membranes such as a nanofiltration (NF) membrane and a reverse osmosis (RO) membrane are considered to be effective for control of pharmaceuticals in wastewater treatment. In practical applications of NF/RO membranes to municipal wastewater treatment, feed water for the membranes always contains organic macromolecules at concentrations of up to 10 mg-TOC/L, which are mainly composed of soluble microbial products (SMPs) produced during biological wastewater treatment such as an activated sludge process. In this study, influence of these organic macromolecules on removal of six pharmaceuticals by NF/RO membranes (UTC-60 and LF10) was investigated. Two types of biological treatment (conventional activated sludge process followed by media filtration (i.e., tertiary treatment) and treatment with a membrane bioreactor (MBR)) were examined as pretreatments for NF/RO membranes in this study. In the filtration tests with wastewater effluents, removal of the pharmaceuticals was higher than that seen with deionized pure water spiked with the pharmaceuticals. The increase was significant in the case of the NF membrane. Both alteration of membrane surface properties due to membrane fouling and association of the pharmaceuticals with organic macromolecules contributed to the increase in removal of pharmaceuticals by the membranes. Characteristics of the organic macromolecules contained in the wastewater effluents differed depending on the type of treatment, implying that removal of pharmaceuticals by NF/RO membranes is influenced by the type of pretreatment employed. (C) 2009 Elsevier Ltd. All rights reserved.

Changes in characteristics of soluble microbial products in membrane bioreactors associated with different solid retention times: Relation to membrane fouling
Katsuki Kimura, Takuro Naruse, Yoshimasa Watanabe
WATER RESEARCH, 43, 4, 1033, 1039, PERGAMON-ELSEVIER SCIENCE LTD, Mar. 2009, [Peer-reviewed]
English, Scientific journal, A membrane bioreactor (MBR) is a promising wastewater treatment technology, but there is a need for efficient control of membrane fouling, which increases operational and maintenance costs. Soluble microbial products (SMP) have been reported to act as major foulants; in the operation of MBRs used for wastewater treatment. In this study, SMP in MBRs operated with different sludge retention times (SRTs) were investigated by means of various analytical techniques and their relations to the evolution of membrane fouling were considered. Bench-scale filtration experiments were carried out in a laboratory with synthetic wastewater to eliminate fluctuations that would occur with the use of real wastewater and that would lead to fluctuations in compositions of SMP. Three identical submerged MBRs were operated for about 50 days under the same conditions except for SRT (17, 51 and 102 days). Accumulation of SMP in the MBRs estimated by conventional analytical methods (i.e., the phenol-sulfuric acid method and the Lowry method) was significant in the cases of short SRTs. However, the degrees of membrane fouling in the MBRs were not directly related to the concentrations of SMP in the reactors estimated by the conventional analytical methods. Non-conventional analytical methods such as excitation-emission matrix (EEM) fluorescence spectroscopy revealed that characteristics of SMP in the three reactors considerably differed depending on SRT. Foulants were extracted from the fouled membranes at the end of the operation and were compared with SMP in each MBR. It was clearly shown that characteristics of the foulants were different depending on SRT, and similarities between SMP and the extracted foulants were recognized in each MBR on the basis of results of EEM measurements. However, such similarities were not found on the basis of results obtained by using the conventional methods for analysis of SMP. The results of this study suggest that the use of conventional methods for analysis of SMP is not appropriate for investigation of membrane fouling in MBRs. (C) 2008 Elsevier Ltd. All rights reserved.

The difference in characteristics of foulants in submerged MBRs caused by the difference in the membrane flux
Katsuki Kimura, Taro Miyoshi, Takuro Naruse, Nobuhiro Yamato, Rie Ogyu, Yoshimasa Watanabe
DESALINATION, 231, 1-3, 268, 275, ELSEVIER SCIENCE BV, Oct. 2008, [Peer-reviewed]
English, Scientific journal, The main obstacle for a wider use of membrane bioreactors (MBRs) for wastewater treatment is membrane fouling, which increases operating costs. Fora more efficient control of membrane fouling in MBRs, an understanding of the mechanisms of membrane fouling is important. We conducted two separate pilot-scale experiments using real municipal wastewater to investigate the influence of the membrane flux in MBRs on the characteristics of foulants, which were analyzed by Fourier transform infrared (FTIR) spectra, (13)C nuclear magnetic resonance (NMR) spectra, monosaccharide composition and amino acid analyses. In each experiment, two identical membrane modules were submerged in the same MBR tank and were operated under different membrane fluxes. The results obtained in this study indicated that the membrane filtration flux significantly influenced membrane fouling in MBRs. Membrane fouling in the module operated with the higher flux was much greater than that of the other on the basis of the volume of filtered mixed liquor suspension. Analyses of the foulants desorbed from the fouled membranes revealed that the nature of the foulants significantly differed depending on the membrane flux despite the fact that the two modules filtered the same mixed liquor suspension at the same time. The difference in characteristics of the foulants caused by the difference in the membrane flux was similar in the two separate experiments, indicating that reproducibility of the data was sufficient. It was thought that different fractions of the mixed liquor suspension were transported to the surfaces of the membranes depending on the membrane flux and subsequently caused membrane fouling to different extents. The foulant desorbed from the membrane operated with a higher flux seemed to cause severer fouling than the foulant desorbed from the other membrane.

Affinity of functional groups for membrane surfaces: Implications for physically irreversible fouling
Hiroshi Yamamura, Katsuki Kimura, Takaharu Okajima, Hiroshi Tokumoto, Yoshimasa Watanabe
ENVIRONMENTAL SCIENCE & TECHNOLOGY, 42, 14, 5310, 5315, AMER CHEMICAL SOC, Jul. 2008, [Peer-reviewed]
English, Scientific journal, Fouling in membranes used for water treatment has been attributed to the presence of natural organic matter (NOM) in water. There have been reports recently on the contribution of hydrophilic fractions of NOM(e.g., carbohydrate-like substances) to fouling, but there is still little information about the physicochemical interactions between membranes and carbohydrate-like substances. In this study, the affinity of carbohydrate-like substances to two different microfiltration (MF) membranes was investigated by using atomic force microscopy (AFM) and functionally modified microspheres. Microspheres were attached to the tip of the cantilever in an AFM apparatus and the adhesion forces working between the microspheres and the membranes were determined. The microspheres used in this study were coated with either hydroxyl groups or carboxyl groups to be used as surrogates of carbohydrate-like substances or humic acid, respectively. Measurements of adhesion force were carried out at pH of 6.8 and the experimental results demonstrated that the adhesion force to membranes was strong in the case of hydroxyl groups but weak in the case of carboxyl groups. The strong adhesion between the hydroxyl group and the membrane surface is explained by the strong hydrogen bond generated. It was also found that the affinity of the hydroxyl group to a polyvinylidenefluoride (PVDF) membrane was much higher than that to a polyethylene (PE) membrane, possibly due to the high electronegative nature of the PVDF polymer. The time course of changes in the affinity of hydroxyl group to a membrane used in a practical condition was investigated by repeatedly carrying out AFM force measurements with PE membrane specimens sampled from a pilot plant operated at an existing water treatment plant. Microspheres exhibited strong affinity to the membrane at the initial stage of operation (within 5 days), but subsequently exponential reduction of the affinity was seen until the end of operation, as a result of fouling development. However, the magnitude of affinity of hydroxyl-modified microspheres was much higher than that of carboxyl-modified microspheres even after the significant reduction of affinity of hydroxyl-modified microspheres to the membranes was seen. The results obtained in this study partially explain why hydrophilic NOM dominated over humic substances in foulants of membranes used for water treatment in recent studies on fouling.

Irreversible membrane fouling in microfiltration membranes filtering coagulated surface water
Katsuki Kimura, Tomohiro Maeda, Hiroshi Yamamura, Yoshimasa Watanabe
JOURNAL OF MEMBRANE SCIENCE, 320, 1-2, 356, 362, ELSEVIER SCIENCE BV, Jul. 2008, [Peer-reviewed]
English, Scientific journal, Chemical coagulation has been widely used as a method to mitigate membrane fouling in MF/UF membranes used for drinking water treatment. Optimization of coagulation as pre-treatment of membrane processes has not been achieved yet: the optimum condition of coagulation for conventional treatment systems is not necessarily applicable to membrane-based treatment systems. This study investigated (physically) irreversible membrane fouling in an MF membrane used with pre-coagulation by aluminum salt. In a series of bench-scale filtration tests, feed water containing commercially available humic acid or organic matter isolated from surface water was coagulated with polyaluminum chloride (PACl) under various conditions and subsequently filtered with an MF membrane with the nominal pore size of 0.1 mu m. It was found that coagulation conditions had great impacts on the degree of physically irreversible fouling. Acidic conditions improved the quality of treated water but generally caused greater physically irreversible fouling than did neutral or alkaline conditions. Also, dosage of coagulant was found to be influential on the degree of membrane fouling: high dosage of coagulant frequently caused more severe irreversible fouling. Sizes of flocs seemed to become small under acidic conditions in this study, which was indicated by high concentrations of aluminum in the permeate under acidic conditions. It is thought that small flocs produced under acidic conditions could migrate into micropores of the membrane and caused physically irreversible fouling by plugging or adsorption. These findings obtained in the bench-scale tests were verified in a long-term pilot-scale test. (C) 2008 Elsevier B.V. All rights reserved.

Baffled membrane bioreactor (BMBR) for efficient nutrient removal from municipal wastewater
Katsuki Kimura, Rie Nishisako, Taro Miyoshi, Ryusuke Shimada, Yoshimasa Watanabe
WATER RESEARCH, 42, 3, 625, 632, PERGAMON-ELSEVIER SCIENCE LTD, Feb. 2008, [Peer-reviewed]
English, Scientific journal, Submerged membrane bioreactors (MBRs) are now widely used for various types of wastewater treatment. One drawback of submerged MBRs is the difficulty in removing nitrogen because intensive aeration is usually carried out in the tank and the MBRs must therefore be operated under aerobic conditions. In this study, the feasibility of treating municipal wastewater by a baffled membrane bioreactor (BMBR), particularly in terms of nitrogen removal, was examined. Simultaneous nitrification/denitrification in a single and small reaction tank was possible by inserting baffles into a normal submerged MBR as long as wastewater was fed in the appropriate way. To examine the applicability of the BMBR, pilot-scale experiments were carried out using real municipal wastewater. Although neither external carbon addition nor mixed liquor circulation was carried out in the operation of the BMBR, average removal rates of total organic carbon (TOC), total phosphorus (T-P) and total nitrogen (T-N) reached 85%, 97% and 77%, respectively, with the hydraulic retention time (HRT) of 4.7h. Permeability of the membrane could be maintained at a high level throughout the operation. It was found that denitrification was the limiting step in removal of nitrogen in the BMBR in this study. Various types of monitoring carried out in the BMBR also demonstrated the possibility of further improvements in its performance. (c) 2007 Elsevier Ltd. All rights reserved.

Mechanism involved in the evolution of physically irreversible fouling in microfiltration and ultrafiltration membranes used for drinking water treatment
Hiroshi Yamamura, Katsuki Kimura, Yoshimasa Watanabe
ENVIRONMENTAL SCIENCE & TECHNOLOGY, 41, 19, 6789, 6794, AMER CHEMICAL SOC, Oct. 2007, [Peer-reviewed]
English, Scientific journal, Control of membrane fouling is important for more efficient use of membranes in water treatment. Control of physically irreversible fouling, which is defined as fouling that requires chemical cleaning to be cancelled, is particularly important for reduction of operation cost in a membrane process. In this study, a long-term filtration experiment using three different types of MF and UF membranes was carried out at an existing water purification plant, and the evolution of physically irreversible fouling was investigated. The experimental results demonstrated that the extent of physically irreversible fouling differed significantly depending on the membrane type. Cleaning of the fouled membranes with various chemical reagents demonstrated that organic matter was mainly responsible for physically irreversible fouling. Organic matter that had caused physically irreversible fouling in the long-term operation was desorbed from the fouled membranes and was subjected to Fourier transform infrared and C-13 nuclear magnetic resonance analyses. These analyses revealed that carbohydrates were dominant in the membrane foulant regardless of the type of membrane. Based on measurements of molecular weight distribution of organic matter in the feedwater and the permeates from the membranes, a two-step fouling mechanism is proposed to explain the dominance of carbohydrates in the foulant: hydrophobic (humic-like) components with small molecular weight are first adsorbed on the membrane and, consequently, narrow the size of micro-pores of membranes, and then hydrophilic (carbohydrate-like) compounds with larger molecular weight plug the narrowed pores or the hydrophilic compounds are adsorbed onto the membrane surface conditioned by the hydrophobic components.

Influence of calcium on the evolution of irreversible fouling in microfiltration/ultrafiltration membranes
Hiroshi Yamamura, Kenji Okimoto, Katsuki Kimura, Yoshimasa Watanabe
JOURNAL OF WATER SUPPLY RESEARCH AND TECHNOLOGY-AQUA, 56, 6-7, 425, 434, I W A PUBLISHING, Sep. 2007, [Peer-reviewed]
English, Scientific journal, Water treatment using microfiltration (MF)/ultrafiltration (UF) membranes is gaining in popularity all over in this study the influence of problem of membrane fouling needs to be addressed the world but the, calcium on irreversible fouling in MF/UF membrane filtering natural organic matter (NOM) was investigated on the basis of a series of bench-scale filtration tests. Two types of feed water, solution of commercially available humic acid and surface water used for drinking water source, were filtered with four different MF/UF membranes. It was found that the influence of calcium on the evolution of irreversible fouling would differ depending on the feed water characteristics. Calcium facilitated the aggregation of small molecules with hydrophobic nature contained in commercially available humic acid and the aggregate probably plugged the micropores, resulting in severe irreversible fouling. The effect of calcium was not obvious in the case of the surface water used in this study. This result implies that the use of commercial humic acid for the examination of membrane fouling would be inappropriate.

Transition in fouling mechanism in microfiltration of a surface water
Hiroshi Yamamura, Soryong Chae, Katsuki Kimura, Yoshimasa Watanabe
WATER RESEARCH, 41, 17, 3812, 3822, PERGAMON-ELSEVIER SCIENCE LTD, Sep. 2007, [Peer-reviewed]
English, Scientific journal, The main disadvantage of membrane filtration is membrane fouling, which remains as the major obstacle for more efficient use of this technology. Information about the constituents that cause fouling is indispensable for more efficient operation. We examined the changes in both foulant characteristics and membrane morphology by performing the pilot-scale filtration test using one microfiltration membrane. During the operation, we cut the membrane fibers three times, and the components that caused irreversible fouling were extracted by acid or alkaline solution. We found that the characteristic of inorganic matter extracted by acid solution completely differed depending on the filtration period. A large amount of iron was extracted in the second chemical cleaning, while manganese was the dominant component of the extracted inorganic matter in the third chemical cleaning. The analysis of Fourier transform infrared (FTIR) and cross polarization magic angle spinning carbon-13 (CPMAS C-13) nuclear magnetic resonance (NMR) demonstrated that the contribution of humic substances and carbohydrate in the organic foulant had increased as fouling developed. The changes in the major foulant have no relation with the fluctuation in feed water. The analysis of membrane morphology illustrated that the cake layer started to build up after the blockage of membrane pores. Based on the above results, we hypothesized the following fouling mechanism: the pores were covered or narrowed with relatively large particles such as iron, carbohydrate or protein; small particles such as manganese or humic substances blocked the narrowed pores; and finally an irreversible cake layer started to build up on the membrane surface. (c) 2007 Elsevier Ltd. All rights reserved.

Elimination of selected acidic pharmaceuticals from municipal wastewater by an activated sludge system and membrane bioreactors
Katsuki Kimura, Hiroe Hara, Yoshimasa Watanabe
ENVIRONMENTAL SCIENCE & TECHNOLOGY, 41, 10, 3708, 3714, AMER CHEMICAL SOC, May 2007, [Peer-reviewed]
English, Scientific journal, The elimination of six acidic pharmaceuticals (clofibric acid, diclofenac, ibuprofen, ketoprofen, mefenamic acid, and naproxen) in a real wastewater treatment plant (WWTP) using an activated sludge system and membrane bioreactors (MBRs) was investigated by using a gas chromatography/mass spectrometry (GC/MS) system for measurement of the compounds. Limited information is available for some of the tested pharmaceuticals at present. Solid retention times (SRTs) of the WWTP and the two MBRs were 7, 15, and 65 days, respectively. The elimination rates varied from compound to compound. The MBRs exhibited greater elimination rates for the examined pharmaceuticals than did the real plant. Dependency of the elimination rates of the pharmaceuticals on SRTs was obvious; the MBR operated with a longer SRT of 65 days clearly showed better performance than did the MBR with a shorter SRT of 15 days. The difference between the two MBRs was particularly significant in terms of elimination of ketoprofen and diclofenac. Measurements of the amounts of adsorbed pharmaceuticals on the sludge and aerobic batch elimination experiments were carried out to investigate the elimination pathways of the pharmaceuticals. Results of the batch elimination tests revealed that the sludges in the MBRs had large specific sorption capacities mainly due to their large specific surface areas. Despite the sorption capacities of sludges, the main mechanism of elimination of the pharmaceuticals in the investigated processes was found to be biodegradation. Biodegradation of diclofenac, which has been believed to be refractory to biodegradation, seemed to occur very slowly.

Modification of submerged membrane bioreactors (MBRs) by inserting baffles: pilot scale study
K. Kimura, M. Enomoto, Y. Watanabe
WATER SCIENCE AND TECHNOLOGY, 55, 7, 119, 126, IWA PUBLISHING, 2007, [Peer-reviewed]
English, Scientific journal, Submerged membrane bioreactors (MBRs) have been gaining in popularity in various types of wastewater treatment. One drawback of submerged MBRs is difficulty in removing nitrogen as they are accompanied with intensive aeration inside the reactor and therefore principally operated under aerobic conditions. In order to address this problem, a simple modification for submerged MBRs, insertion of baffles to create alternative aerobic/anoxic conditions, was proposed. In this study, the performance of the proposed baffled membrane bioreactor (BMBR) was investigated based on a pilot-scale experiment using a real municipal wastewater. With appropriate operating conditions, the BMBR could remove more than 70% of total nitrogen contained in the feed water without any external carbon source. The BMBR demonstrated a good treatment performance in terms of TOC and phosphorus removal as well. Increase of trans-membrane pressure difference was subtle, which might be attributed to the alternative creation of aerobic/anoxic conditions.

Difference in membrane fouling in membrane bioreactors (MBRs) caused by membrane polymer materials
Nobuhiro Yamato, Katsuki Kimura, Taro Miyoshi, Yoshimasa Watanabe
JOURNAL OF MEMBRANE SCIENCE, 280, 1-2, 911, 919, ELSEVIER SCIENCE BV, Sep. 2006, [Peer-reviewed]
English, Scientific journal, There is a need for efficient control of membrane fouling in membrane bioreactors (MBRs), but there is still an insufficient understanding of the phenomena of membrane fouling and little is known about the influence of polymeric membrane materials on membrane fouling in MBRs. In this study, the influence of polymeric membrane materials on membrane fouling in MBRs was investigated on the basis of results of a pilot-scale experiment using real municipal wastewater. Two different polymers, polyethylene (PE) and polyvinylidene fluoride (PVDF), were examined side by side and the degree of fouling in each membrane was monitored. Also, analysis of the foulants in both membranes was carried out. The results obtained in this study demonstrated that PVDF is superior to PE in terms of prevention of irreversible fouling in MBRs used for treatment of municipal wastewater. Dissolved matter was mainly responsible for the irreversible fouling. Reversible fouling in the PVDF membrane might be related to an increase in sub-micron-sized organic matter that was mainly composed of carbohydrate. Composition of the foulants causing irreversible fouling differed considerably depending on the membrane polymeric materials. The results suggested that some fractions in organic matter in the mixed liquor have higher affinities with the membrane than do other fractions and consequently cause greater irreversible fouling. (c) 2006 Elsevier B.V. All rights reserved.

Influence of dissolved organic carbon and suspension viscosity on membrane fouling in submerged membrane bioreactor
Y Watanabe, K Kimura, T Itonaga
SEPARATION SCIENCE AND TECHNOLOGY, 41, 7, 1371, 1382, TAYLOR & FRANCIS INC, 2006, [Peer-reviewed]
English, Scientific journal, This paper deals with the membrane fouling in membrane bioreactor (MBR). Based on the experimental data obtained in the MBR pilot plant study, the influence of F/M ratio on the irreversible and reversible fouling was discussed in the wide range of MLSS concentration. In the case of lower MLSS concentration (2,000-3,000 mg/L), irreversible fouling rate of membrane increased with increasing F/M ratio because of the accumulation of DOC in the mixed liquor. It seems that soluble microbial products with the similar size of the membrane pore will be most responsible for the irreversible fouling. In the case of higher MLSS concentration (8,000-12,000 mg/L), reversible fouling rate of membrane increased with increasing F/M ratio because of the increased suspension viscosity caused by the increased activated sludge size or volume even in the same MLSS concentration.

Irreversible fouling in MF/UF membranes caused by natural organic matters (NOMs) isolated from different origins
Katsuki Kimura, Hiroshi Yamamura, Yoshimasa Watanabe
SEPARATION SCIENCE AND TECHNOLOGY, 41, 7, 1331, 1344, TAYLOR & FRANCIS INC, 2006, [Peer-reviewed]
English, Scientific journal, For more efficient use of membrane technology in water treatment, it is essential to understand more about the fouling that requires chemical cleaning to be eliminated (i.e., irreversible fouling). In this study, five different MF/UF membranes and four types of organic matter collected from different origins were examined in terms of the degree of irreversible membrane fouling. Experimental results demonstrated that the extent of irreversible fouling differed significantly depending on the properties of both the membrane and organic matter. Among the tested membranes, UF membranes made of polyacrylonitrile (PAN) exhibited the best performance in terms of prevention of irreversible fouling. In contrast, MF membranes, especially one made of polyvinylidenefluoride (PVDF), suffered significant irreversible fouling. Conventional methods for characterization of organic matter such as specific ultraviolet absorption (SUVA), XAD fractionation, and excitation-emission matrix (EEM) were found to be inadequate for prediction of the degree of irreversible fouling. This is because these analytical methods represent an average property of bulk organic matter, while the fouling was actually caused by some specific fractions. It was revealed that hydrophilic fraction of the organic matter was responsible for the irreversible fouling regardless of the type of membranes or organic matter.

Membrane fouling in pilot-scale membrane Bioreactors (MBRs) treating municipal wastewater
K Kimura, N Yamato, H Yamamura, Y Watanabe
ENVIRONMENTAL SCIENCE & TECHNOLOGY, 39, 16, 6293, 6299, AMER CHEMICAL SOC, Aug. 2005, [Peer-reviewed]
English, Scientific journal, The main obstacle for wider use of membrane bioreactors (MBRs) for wastewater treatment is membrane fouling (i.e., deterioration of membrane permeability), which increases operating costs. For more efficient control of membrane fouling in MBRs, an understanding of the mechanisms of membrane fouling is important. However, there is a lack of information on membrane fouling in MBRs, especially information on features of components that are responsible for the fouling. We conducted a pilot-scale experiment using real municipal wastewater with three identical MBRs under different operating conditions. The results obtained in this study suggested that the food-microorganisms ratio (F/M) and membrane filtration flux were the important operating parameters that significantly influenced membrane fouling in MBRs. Neither concentrations of dissolved organic matter in the reactors nor viscosity of mixed liquor, which have been thought to have influences on fouling in MBRs, showed clear relationships with membrane fouling in this study. Organic substances that had caused the membrane fouling were desorbed from fouled membranes of the MBRs at the termination of the operation and were subjected to Fourier transform infrared (FTIR) and C-13 nuclear magnetic resonance (NMR) analyses. These analyses revealed that the nature of the membrane foulant changes depending on F/M. It was shown that high F/M would make the foulant more proteinaceous. Carbohydrates were dominant in membrane foulants in this study, while features of humic substances were not apparent.

Removal of pharmaceutical compounds by submerged membrane bioreactors (MBRs)
K Kimura, H Hara, Y Watanabe
DESALINATION, 178, 1-3, 135, 140, ELSEVIER SCIENCE BV, Jul. 2005, [Peer-reviewed]
English, Scientific journal, Unintentional indirect potable water reuse, where wastewater effluent is used as a part of a downstream drinking water source, has become a great concern. In this case, a variety of organic micro-pollutants contained in wastewater effluent could create problems. Membrane bioreactors (MBRs) have gained significant popularity as an advanced wastewater treatment technology and might be effective in removing such organic micro-pollutants. Available information on the performance of MBRs regarding removal of micro-pollutants, however, is currently limited. This study examined the ability of submerged MBRs to remove pharmaceutically active compounds (PhACs). Experiments were conducted at an existing municipal wastewater treatment facility, and the performance of the MBRs was compared with that of the conventional activated sludge (CAS) process. Six acidic PhACs (clofibric acid, diclofenac, ibuprofen, ketoprofen, mefenamic acid, naproxen) and one acidic herbicide (dichloprop) were investigated. Compared with CAS, MBRs exhibited much better removal regarding ketoprofen and naproxen. With respect to the other compounds, comparable removal was observed between the two types of treatment. Removal efficiencies of the PhACs were found to be dependent on their molecular structure such as number of aromatic rings or inclusion of chlorine.

Effect of pre-coagulation on mitigating irreversible fouling during ultrafiltration of a surface water
K Kimura, Y Hane, Y Watanabe
WATER SCIENCE AND TECHNOLOGY, 51, 6-7, 93, 100, I W A PUBLISHING, 2005, [Peer-reviewed]
English, Scientific journal, Membrane fouling can be divided into two types: reversible fouling and irreversible fouling. The former can be easily canceled by physical cleaning (e.g., backwashing) while the latter needs chemical cleaning to be mitigated. For more efficient use of membranes, the control of irreversible membrane fouling is of importance. In this study, the effectiveness of pre-coagulation/sedimentation on irreversible membrane fouling was investigated, based on the pilot-scale operation of the membrane unit installed at an existing water purification plant. The membrane employed was a low-pressure ultrafiltration (UF) membrane made of polysulfone and having a molecular weight cut-off of 750,000 daltons. Although pre-coagulation/ sedimentation significantly mitigated membrane fouling mainly through the reduction of reversible membrane fouling, the degree of irreversible fouling was not reduced by the pre-treatment. This was because the irreversible fouling observed during this study was mainly attributed to polysaccharides/protein like fractions of organic substances that cannot be efficiently removed by coagulation/sedimentation. Aluminium used as coagulant was thought to cause irreversible fouling to some extent but did not in the pilot operation, which could probable be explained by the fact that coagulation was conducted at relatively high pH (7.0) in this study.

Baffled membrane bioreactor (BMBR) for advanced wastewater treatment: Easy modification of existing MBRS for efficient nutrient removal
K Kimura, Y Watanabe
WATER SCIENCE AND TECHNOLOGY, 52, 10-11, 427, 434, I W A PUBLISHING, 2005, [Peer-reviewed]
English, Scientific journal, In this study, a novel membrane bioreactor (MBR) in which nitrification and denitrification simultaneously proceed in a single reaction chamber is proposed for advanced municipal wastewater treatment. Anoxic/aerobic environments are alternatively created in the proposed MBR by inserting baffles 14 inside the membrane chamber. The performance of the proposed baffled membrane bioreactor (BMBR) was examined at an existing municipal wastewater treatment facility based on long-term operation. Although the procedure was simple, insertion of the baffles actually created the alternative anoxic/aerobic environments in the chamber at a constant interval and showed a great improvement in the nutrient removal. The insertion did not cause any adverse effect on membrane permeability. In this study, almost complete elimination of NH4+-N was observed while around 8 mg/L of NO(3)(-)center dot N was detected in the treated water. The modification proposed in this study can immediately be applied to most existing MBRs and is highly recommended for more efficient wastewater treatment.

Rejection of neutral endocrine disrupting compounds (EDCs) and pharmaceutical active compounds (PhACs) by RO membranes
K Kimura, S Toshima, G Amy, Y Watanabe
JOURNAL OF MEMBRANE SCIENCE, 245, 1-2, 71, 78, ELSEVIER SCIENCE BV, Dec. 2004, [Peer-reviewed]
English, Scientific journal, As high quality drinking water becomes scarcer, unintentional indirect potable water reuse, where wastewater effluent is used as a part of a downstream drinking water source, has become a great concern throughout the world. In this case, a variety of organic micro-pollutants contained in wastewater effluent Could create problems. High pressure-driven membranes such as nanofiltration (NF) or reverse osmosis (RO) might be a powerful option to deal with such micro-pollutants, however, a lack of information on their performance is apparent. This study examined the ability of RO membranes to retain neutral (uncharged) endocrine disrupting compounds (EDCs) and pharmaceutically active compounds (PhACs). A total of 11 compounds were chosen so that a certain range of molecular weights and octanol-water distribution coefficients (K-ow) could be studied. With respect to membranes, two different materials (polyamide and cellulose acetate) were examined. Generally, the polyamide membrane exhibited a better performance in terms of the rejection of the selected compounds but the retention was not complete (57-91%). It was found that salt rejection or molecular weight cut-off (MWCO) that are often used to characterize membrane rejection properties did not provide quantitative information in terms of EDCs/PhACs rejection by NF/RO membranes. Molecular weight of the tested compounds could generally indicate the tendency of rejection for the polyamide membranes (size exclusion dominated the retention by the polyamide membrane) while polarity was better able to describe the retention trend of the tested compounds by the cellulose acetate membrane. The results obtained in this study imply that each membrane polymer material for NF/RO membranes, including ones that will be newly developed in the future, Would exhibit different trends in terms of rejection of organic micro-pollutants, which is determined by physico-chemical properties of the compounds. (C) 2004 Elsevier B.V All rights reserved.

起源を異にする溶存有機物による不可逆的膜ファウリング
山村寛, 木村克輝, 渡辺義公
環境工学研究論文集, 41, 257, 267, Japan Society of Civil Engineers, 25 Nov. 2004
Japanese, Membrane filtration has been gaining popularity in the various field. However, membrane fouling is an obstacle for wider application of this technology. Especially, the control of irreversible membrane fouling, which can be defined as fouling requiring chemical reagents to be mitigated, is of importance. The aims of this study were (i) to investigate the degree of irreversible fouling caused by different organic matters and (ii) to characterize the faulants that caused irreversible fouling. In this study, four different organic matters (commercially available humic acid, organic matters isolated from two drinking water sources and a wastewater treatment effluent) and membranes (two microfiltration (ME) membranes and two ultrafiltration (UF) membranes) were used. It was observed that the permeate flux did not decline in the UF membranes while there was a large flux decline in the MF membranes. Especially, a rapid flux decline was observed with the polyvinylidene fluoride (PVDF) membrane. The extents of fouling in the MF membranes were strongly depended on both the types of organic matters and membrane materials. A series of chemical analyses such as fluorescence excitation-emission matrix (EEM), specific UV adsorbance (SUVA) and ion chromatography (IC) were applied to elucidate which fractions of organic matter caused the irreversible fouling. SUVA of faulants was significantly lower than was determined for the feed water. This implies that the faulants had hydrophilic features. The results with EEM and IC also confirmed that a variety of hydrophilic compounds such as polysaccharide or protein-like compounds contributed to the formation of the irreversible fouling observed in this study.

Irreversible membrane fouling during ultrafiltration of surface water
K Kimura, Y Hane, Y Watanabe, G Amy, N Ohkuma
WATER RESEARCH, 38, 14-15, 3431, 3441, PERGAMON-ELSEVIER SCIENCE LTD, Aug. 2004, [Peer-reviewed]
English, Scientific journal, For more efficient use of membranes, the control of irreversible membrane fouling, which can be defined as fouling requiring chemical reagents to be mitigated, is of importance. In this study, irreversible fouling caused by constituents in surface water was investigated, based on a long-term pilot scale study. The membrane employed was a low-pressure hydrophobic ultrafiltration (UF) membrane made of polysulfone and having a molecular weight cutoff of 750,000 Da. Various chemical reagents were examined to overcome the irreversible fouling that had developed through 5 months of continuous filtration. Among the tested cleaning reagents, alkaline (NaOH) and oxidizing reagent (NaClO) showed good performance in the restoration of membrane permeability, which implied that organic matter played an important role in the development of the irreversible fouling in this study. Chemical analysis, adsorptive fractionation methods, fluorescence excitation-emission matrix (EEM) and Fourie-transformed infra-red (FTIR) spectra analysis were applied to elucidate which fraction of organic matter caused the irreversible fouling. All of the analysis indicated that polysaccharide-like organic matter was responsible for the evolution of the irreversible fouling. In addition to organic matter, presumably iron and manganese also contributed to the irreversible fouling to some extent. (C) 2004 Elsevier Ltd. All rights reserved.

Influence of suspension viscosity and colloidal particles on permeability of membrane used in membrane bioreactor (MBR)
T Itonaga, K Kimura, Y Watanabe
WATER SCIENCE AND TECHNOLOGY, 50, 12, 301, 309, I W A PUBLISHING, 2004, [Peer-reviewed]
English, Scientific journal, In this study, pilot scale experiments were carried out to examine membrane fouling occurring in membrane bioreactors (MBR) with or without pre-treatment (coagulation/sedimentation). Especially, the influence of suspension viscosity and dissolved organic matter (DOM) on membrane fouling was investigated. The pre-coagulation/sedimentation process improved the performance of a MBR in terms of membrane permeability by controlling irreversible fouling and formation of thick cake layer. The upper limit of MLSS concentration for an efficient operation in MBR without pre-treatment was suggested to be around 10 g/L based on the measurement of suspension viscosity. In-this study, it was difficult to directly relate membrane fouling to DOM detected in the membrane chamber. A series of laboratory scale dead-end filtration experiments was carried out to investigate which fractions in biomass suspension would be the most influential in the deterioration of membrane permeability. Based on the dead-end tests, it was shown that the deterioration of membrane permeability was mainly caused by the colloidal particle fraction in the biomass suspension.

Rejection of organic micropollutants (disinfection by-products, endocrine disrupting compounds, and pharmaceutically active compounds) by NF/RO membranes
K Kimura, G Amy, JE Drewes, T Heberer, TU Kim, Y Watanabe
JOURNAL OF MEMBRANE SCIENCE, 227, 1-2, 113, 121, ELSEVIER SCIENCE BV, Dec. 2003, [Peer-reviewed]
English, Scientific journal, The growing demand on water resources has increased interest in wastewater reclamation for potable reuse, in which rejection of organic micropollutants such as disinfection by-products (DBPs), endocrine disrupting compounds (EDCs), and pharmaceutically active compounds (PhACs) is of great concern. The objective of this study was to investigate the rejection of DBPs, EDCs, and PhACs by nanofiltration (NF) and reverse osmosis (RO) membranes as a function of their physico-chemical properties and initial feed water concentration. Experimental results indicated that negatively charged compounds could be rejected very effectively (i.e., >90%) regardless of other physico-chemical properties of the tested compounds due to electrostatic exclusion. No time-dependency was observed for rejection of charged compounds. In contrast, rejection of non-charged compounds was generally lower (<90% except for one case) and influenced mainly by the molecular size of the compounds. A clear time-dependency was observed for rejection of non-charged compounds, attributable to compound adsorption on the membrane. It was demonstrated that feed water concentration influenced rejection efficiency of the membrane. Experiments conducted at a low ng/l concentration range resulted in lower rejection efficiency as compared to experiments conducted at a mug/l range, suggesting the need to conduct experiments at the relevant concentration of interest. (C) 2003 Elsevier B.V. All rights reserved.

Adsorption of hydrophobic compounds onto NF/RO membranes: an artifact leading to overestimation of rejection
K Kimura, G Amy, J Drewes, Y Watanabe
JOURNAL OF MEMBRANE SCIENCE, 221, 1-2, 89, 101, ELSEVIER SCIENCE BV, Aug. 2003, [Peer-reviewed]
English, Scientific journal, This study addresses the adsorption of hydrophobic compounds at low concentration (similar to100 ppb) onto NF/RO membranes. In this study, three surrogate compounds and three NF/RO membranes were tested under cross-flow conditions. Experimental results showed that the adsorption of hydrophobic compounds was significant for neutral compounds and ionizable compounds when electrostatically neutral. Also, operating conditions such as the permeate flow rate (flux) had a significant effect on the degree of compound adsorption. A comparison of the adsorption observed in dynamic filtration tests with that in static batch adsorption tests suggests that more adsorption sites are accessible for molecules during membrane filtration due to the pressurized advective flow. It was observed that the concentration of the tested compounds changed during filtration tests due to adsorption. Therefore, an accurate evaluation of a given membrane in terms of the rejection of a hydrophobic compound is not possible until saturation of the membrane with the compound of interest is accomplished. The experimental results demonstrated that a relatively large amount of the feed water needed to be filtered to reach saturation conditions. (C) 2003 Elsevier B.V. All rights reserved.

Nitrate removal by a combination of elemental sulfur-based denitrification and membrane filtration
K Kimura, M Nakamura, Y Watanabe
WATER RESEARCH, 36, 7, 1758, 1766, PERGAMON-ELSEVIER SCIENCE LTD, Apr. 2002, [Peer-reviewed]
English, Scientific journal, In this paper, a new method for removal of nitrate from groundwater, in which elemental sulfur-based denitrification (autotrophic denitrification) and membrane separation are combined, is proposed. By using a membrane, autotrophic denitrifiers, whose growth rate is considerably low, can be kept at a high concentration. The performance of the proposed process was examined through a long-term experiment in the laboratory using synthetic feed water. A rotating membrane disk module equipped with UF membrane (750.000Da) was used in this study. Complete removal of nitrate (25mg N/L) was achieved under the conditions of a biomass concentration of about 1000 mg protein/L and HRT of 160min. Dissolved oxygen concentration and sulfur/biomass ratio in the membrane chamber were found to be the key factors in maintenance of high-process performance, Deterioration in membrane permeability was insignificant. It was found that membrane filtration could be continued with a water flux of 0.5 m(3)/m(2)/day for about 100 days without any chemical membrane cleaning. The proposed process, however, caused a slight increase in assimilable organic carbon. Sulfide was not detected in the denitrified water. (C) 2002 Elsevier Science Ltd. All rights reserved.

膜濾過と生物膜を組み合わせた高度浄水処理プロセスに関する研究　　　　　　　　　　　　　　　
水道協会雑誌, 81(4), 10, 2002, [Peer-reviewed]

Performance and membrane foulant in the pilot operation of a novel biofilm-membrane reactor
K Kimura, Y Watanabe
2ND WORLD WATER CONGRESS: DRINKING WATER TREATMENT, 2, 2, 177, 183, I W A PUBLISHING, 2002, [Peer-reviewed]
English, International conference proceedings, We have developed a novel biofilm-membrane reactor (BMR) in which a nitrifying biofilm is fixed on the surface of a rotating membrane disk. With this reactor, both strict solid-liquid separation and oxidation of ammonia nitrogen can be simultaneously performed. Based on the results obtained in previous bench-scale experiments, a pilot-scale study was conducted using river water at a water purification plant. The results obtained in the pilot study can be summarized as follows. (1) By implementation of pre-treatment (coagulation and sedimentation) and simple membrane cleaning (sponge cleaning), the filter run could be continued for 17 months without any chemical washing. (2) Sufficient nitrification was observed when water temperature was high. Deterioration in nitrification efficiency during winter was reduced by the addition of phosphorus. (3) In addition to nitrification, biological oxidation of AOC and manganese can be expected with the BMR. In this study, both AOC and manganese concentration in the permeate decreased to a level less than 10 mug/L. (4) Irreversible membrane fouling, which was thought to be mainly caused by manganese, became significant as the operation period became longer.

A novel biofilm-membrane reactor for advanced drinking water treatment - pilot scale study
K Kimura, Y Watanabe, N Ohkuma
MEMBRANES IN DRINKING AND INDUSTRIAL WATER PRODUCTION II, 1, 5-6, 157, 168, IWA PUBLISHING, 2001, [Peer-reviewed]
English, International conference proceedings, The authors have proposed a novel biofilm-membrane reactor (BMR) in which nitrifying biofilm is fixed on the surface of the rotating membrane disk. With this reactor, both strict solid-liquid separation and oxidation of ammonia nitrogen can be simultaneously performed. Based on the knowledge obtained in the previous experiments with the bench-scale equipment, a pilot scale study was conducted using river water at a water purification plant. The results obtained in the pilot study can be summarized as follows: (1) A pilot scale BMR worked successfully even with the water from an actual drinking water source. By implementation of pre-treatment (coagulation and sedimentation), the filter run could be continued for more than 8 months without any chemical washing. (2) The sponge cleaning developed in this study was found to be very effective. This indicates that the accumulated cake resistance is dominant in the practical situation. (3) Sufficient nitrification was observed when water temperature was high. (4) In addition to the nitrification, biological oxidation of AOC and manganese can be expected with the BMR. In this study, both AOC and manganese concentration in the permeate decreased to a level less than 10 mug/L.

Kinetic analysis of nitrifying biofilm growing on the rotating membrane disk
K Kimura, Y Watanabe, S Okabe, H Satoh
WATER SCIENCE & TECHNOLOGY: WATER SUPPLY, VOL 1, NO 4, 1(4), 111, 4, 111, 118, I W A PUBLISHING, 2001, [Peer-reviewed]
English, International conference proceedings, The authors have proposed a novel water treatment process in which nitrifying bacteria are fixed on the surface of rotating membrane disks. This biofilm-membrane process can perform strict solid-liquid separation and oxidation of ammonia nitrogen simultaneously. In this research, applicability of the conventional biofilm model (assuming the biofilm structure to be flat, homogeneous and continuous) to analysis of the biofilm developing in the proposed process was examined. A long-term operation for culturing the active nitrifying biofilm was carried out prior to kinetic investigation. By cryosectioning of the biofilm and image analysis, the thickness of the biofilm was determined to be 87 pm. From this biofilm thickness and the result of the batch ammonia consumption test, the intrinsic zero-order ammonia consumption rate of the biofilm was estimated precisely to be 930 g/m(3)/h. Using these parameters, the ammonia concentration profile in the biofilm was calculated by the conventional model, and the applicability of the model was examined by comparing the calculated profile with the ones measured with a microelectrode. The calculated profile was very close to the measured ones, which indicated feasibility of the conventional model to the analysis of the biofilm grown in the proposed process. The studied biofilm actually had a simple, i.e. flat, homogeneous and continuous, structure due to membrane filtration. This was the reason why the conventional model could still be employed. In the analysis of the data dealing with low concentrations of ammonia, however, first-order kinetics should be used. The first-order ammonia consumption rate constant of the studied biofilm was estimated to be 808 h(-1).

Filtration resistance and efficient cleaning methods of the membrane with fixed nitrifiers
K Kimura, Y Watanabe, N Ohkuma
WATER RESEARCH, 34, 11, 2895, 2904, PERGAMON-ELSEVIER SCIENCE LTD, Aug. 2000, [Peer-reviewed]
English, Scientific journal, The authors have proposed a novel membrane process where nitrifying bacteria are fixed on the surface of the rotating membrane disks. With this proposed membrane process, the simultaneous performance of the strict solid liquid separation and the oxidation of ammonia is enabled. In this study, three long-term experiments were carried out and the distribution of the filtration resistance and the efficient cleaning method of the proposed membrane process were investigated. The membrane Aux was fixed at 0.8 m(3)/m(2)/d and the feed ammonia concentration was controlled within the range of 0.1-1.0 mg-N/l. in the proposed membrane process, the filtration resistance caused by the accumulated cake was dominant. The shear-stress induced by the increased disk's rotational speed was found to be efficient for removing the accumulated cake, However, this cleaning method did not work well when feed water contained suspended particles at 10 of turbidity unit. In order to increase the cleaning efficiency, a small quantity of sponge particles were introduced into the membrane chamber and the disk's rotational speed was increased. This membrane cleaning method using sponge particles proved so effective that the filtration resistance due to the accumulated cake was completely cancelled. Membrane filtration could be continued for more than 3000 h due to the implementation of this cleaning method utilizing sponge particles once every 1000-1500 h. For the maintenance of the ammonia oxidation rate, however, a part of the detached nitrifiers had to be returned to the membrane chamber after the membrane cleaning. (C) 2000 Elsevier Science Ltd. All rights reserved.

Membrane application to water purification process in Japan - development of hybrid membrane system
Y Watanabe, K Kimura, T Suzuki
WATER SCIENCE AND TECHNOLOGY, 41, 10-11, 9, 16, I W A PUBLISHING, 2000, [Peer-reviewed]
English, Scientific journal, This paper deals with two recent developments made by the authors about the hybrid membrane systems applicable to the water purification. The performance of a hybrid MF membrane system with circulating powdered activated carbon and condensed sludge has been studied using a pilot plant. The powdered activated carbon was intermittently dosed to the system for adsorbing mainly the humic substances. Manganese ions and ammonia nitrogen were biologically oxidized by the iron-oxidizing bacteria and ammonia oxidizing bacteria inhibiting the condensed sludge. In the hybrid MF membrane system, decreasing rate of the permeability was much less than that of a conventional MF membrane process. This may result from the reduced organic loading to the membrane due to the adsorption of humic substances onto the powdered activated carbons. A novel UF membrane process was also developed, where the nitrifying bacteria are fixed on the surface of the rotating disk membranes. With this membrane process. the simultaneous performance of the strict solid-liquid separation and the biological ammonia oxidation are possible. In order to increase the washing efficiency, a small quantity of the sponge particles were introduced into the membrane chamber and then the disk rotational speed was increased. This membrane washing method using sponge particles was so effective that the filtration resistance due to the accumulated cake was completely cancelled.

Membrane filtration resistance caused by nitrifiers oxidizing low concentrations of ammonia.
KIMURA Katsuki, WATANABE Yoshimasa
ENVIRONMENTAL ENGINEERING RESEARCH, 36, 287, 294, Japan Society of Civil Engineers, 1999
Japanese, The authors have proposed a novel membrane process for drinking water treatment in which nitrifiers are fixed on the membrane surface. With this proposed membrane process, strict solid-liquid separation by membrane filtration and oxidation of ammonia can be performed simultaneously. Fixed nitrifiers are supposed to cause membrane filtration resistance to some extent. The magnitude of the filtration resistance caused by the fixed nitrifiers for oxidizing low concentrations of ammonia was evaluated in this study. Experimental results showed that the fixation of the nitrifiers on the membrane surface had a little influence on the increase of the filtration resistance. Most of the resistance was caused by trace inorganic and organic substances contained in the feed water (tap water). The filtration resistance was divided into the cake resistance and the irreversible fouling resistance. The nitrifiers for the oxidation of low concentrations of ammonia seemed to increase the cake resistance a little and hardly cause the irreversible fouling.

A study on filtration resistance in the membrane process where ammonia oxidizers are fixed on the membrane surface.
Katsuki Kimura, Yoshimasa Watanabe, Naoki Ohkuma
Journal of Environmental Systems and Engineering, 608, 608, 87, 95, Japan Society of Civil Engineers, 1998, [Peer-reviewed]
Japanese, The authors have developed a novel membrane process in which ammonia oxidizers are fixed on the membrane disk. In this study, the characteristics of the membrane filtration resistance was investigated. The results derived from this study were summarized as follows: (1) The magnitude of the filtration resistance was strongly affected by the initial inoculation. (2) The filtration resistance due to the accumulated cake was found to be dominant. (3) Increasing the disk rotational speed was found to be efficient for removing cake. About 3000 hours of the operation could be continued by only implementing this simple cleaning method every 500 hours. (4) Filtration resistance excluding the cake resistance seemed to be caused by humic substances and extracellular polymeric substance produced by biomass.

Filtration resistance induced by ammonia oxidizers accumulating on the rotating membrane disk
K Kimura, Y Watanabe, N Ohkuma
WATER SCIENCE AND TECHNOLOGY, 38, 4-5, 443, 452, PERGAMON-ELSEVIER SCIENCE LTD, 1998, [Peer-reviewed]
English, Scientific journal, Membrane filtration and oxidation of ammonia were simultaneously performed by using a rotating membrane disk module. Nitrification performance, composition of the accumulated cakes on the membrana and the filtration resistances were investigated under five different operating conditions. The filtration resistance due to the accumulated cake on the membrane was found to be dominant in this treatment method, compared to the resistance due to the micropore plugging or irreversible adherence. The cake consisted mainly of iron, humic substances and bacteria. The possibility that extracellular polymeric substances were related to the cake resistance was also shown. The composition of the cake depended on the length and the condition of operation. Accumulation of ammonia oxidizers caused by oxidation of low concentrations of ammonia (less than 1 mg/l) did not increase transmembrane pressure significantly. Therefore, the application of this treatment method for drinking water treatment is feasible. Filtration resistance due to the micropore plugging or irreversible adherence to the membrane was caused by organic substances. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.

A novel biofilm-membrane reactor for ammonia oxidation at low concentrations
Y Watanabe, K Kimura, S Okabe, G Ozawa, N Ohkuma
WATER SCIENCE AND TECHNOLOGY, 36, 1, 51, 60, PERGAMON-ELSEVIER SCIENCE LTD, 1997, [Peer-reviewed]
English, For the oxidation of low concentrations of NH4+-N, conventional biofilm reactors such as a rotating biological contactor encounter difficulty due to mass transport limitation of NH4+-N. Therefore, the authors have developed a novel biofilm-membrane reactor, in which biomass is fixed on the surface of rotating membrane disks to enhance NH4+-N transport into the biofilm. Three long-term bench-scale experiments were carried out and sufficient nitrification efficiency was obtained even at low levels of NH4+-N. The experimental results were evaluated in comparison with model simulation. (C) 1997 IAWQ. Published by Elsevier Science Ltd.

NITRIFICATION PERFORMANCE OF THE BIOFILMS FIXED ON THE ROTARY DISK MEMBRANE FOR LOW NH_4^+-N CONCENTRATIONS
KIMURA Katsuki, WATANABE Yoshimasa, OHKUMA Naoki
Doboku Gakkai Ronbunshu, 552, 552, 43, 52, Japan Society of Civil Engineers, 1996, [Peer-reviewed]
Japanese, For the oxidation of low concentrations of NH₄⁺-N, the authers have developed a novel biofilm-membrane reactor, in which biomass is fixed on the surface of rotating membrane disks. The results obtained from this study were summarized as follows: (1) The NH₄⁺-N oxidation efficiency of the biofilm-membrane rector is much higher than that of conventional biofilm reactors. This is explained by the two major reasons, i. e., increasing NH₄⁺-N flux to the biofilm by advection and high rotational speed, and obtaining the treated water from the bottom of the biofilm. (2) Bacterial extracellular polymers seem to have severe influences on the membrane clogging. By adjusting the quantity of fixed biomass, however, the operation could be continued as long as 1000 hours without any cleaning.

膜を利用した水処理技術に関する近年の動向
山村寛, 大和信大, 保科克行, 茂木拓真, 戸田光, 木村克輝, 大熊那夫紀, 水環境学会誌, 47(A), 12, 2024

膜分離活性汚泥法(MBR)における膜ファウリングの制御—Control of Membrane Fouling Occurring in Membrane Bioreactors (MBRs)—特集 水処理技術における混相流
木村 克輝, 混相流 = Japanese journal of multiphase flow, 36, 2, 180, 186, Jun. 2022
日本混相流学会, Japanese

バッチ式反応器での異なる水素添加量に対するBiological Biogas Upgradingの応答—第34回環境システム計測制御学会(EICA)研究発表会
新田 大知, 大下 和徹, 高岡 昌輝, 日下部 武敏, 伊藤 竜生, 佐藤 夏紀, 水野 志穂, 木村 克輝, 羽深 昭, EICA : journal of EICA : 環境システム計測制御学会誌 / 学会誌「EICA」編集委員会 編, 27, 2・3, 119, 124, 2022
環境システム計測制御学会, Japanese

大型実証プラントにおける仕切板挿入型MBRの処理性,運転性及び省エネ性の検証
グェン タンフォン, 田村尚也, 円谷輝美, 張亮, 前島崇, 大熊健治, 木村克輝, 山村寛, 渡辺義公, 下水道研究発表会講演集, 59th, 2022

都市下水処理MBRから回収したバイオポリマーの膜ファウリング発生ポテンシャル
角田貴之, 内藤りん, 鈴木綾菜, 羽深昭, 山村寛, 木村克輝, 膜シンポジウム(CD-ROM), 34, 2022

バッチ式反応器による水素添加メタン発酵の検討—Hydrogen-supplemented methane fermentation in batch reactor—京都大学環境衛生工学研究会 第43回 シンポジウム講演論文集
新田 大知, 大下 和徹, 高岡 昌輝, 日下部 武敏, 髙橋 滋敏, 小中原 亨, 水野 志穂, 木村 克輝, 羽深 昭, 環境衛生工学研究 = Environmental & sanitary engineering research : 京都大学環境衛生工学研究会機関誌, 35, 3, 100, 102, Jul. 2021
京都大学環境衛生工学研究会, Japanese

Development of a High Phosphate Ion Selective-Passive Sampler
奥田雄眞, 羽深昭, 木村克輝, 高津文人, 日本水環境学会年会講演集, 55th, 2021

Fouling Control in Concentration of Municipal Wastewater for Recovery of Organic Matter with Flat-sheet Ceramic Membranes
高橋威胤, 杉山徹, 伊藤結衣, 羽深昭, 木村克輝, 日本水環境学会年会講演集, 55th, 2021

Methane fermentation of sewage sludge by an anaerobic membrane bioreactor and phosphate adsorption from filtrate
稲垣誠吾, 羽深昭, 木村克輝, 日本水環境学会年会講演集, 55th, 2021

Impact of Low Temperature Shock on Changes in MBR Sludge Components and Sludge Filterability
角田貴之, 内藤りん, 鈴木綾菜, 羽深昭, 木村克輝, 日本水環境学会年会講演集, 55th, 2021

Quantitative Analysis of Pathogenic and Indicator Viruses at a Wastewater Treatment Plant with Pilot-scale MBR
石崎知依, 木村克輝, 岡部聡, 北島正章, 日本水環境学会年会講演集, 55th, 2021

Isolation and Characterization of Biopolymers in Drinking Water Sources
冨永勘太, 永井梨奈, 羽深昭, 木村克輝, 日本水環境学会年会講演集, 55th, 2021

大型実証プラントにおける仕切板挿入型MBRの運転性と膜ファウリング進行
田村尚也, グェン タンフォン, 円谷輝美, 張亮, 前島崇, 木村克輝, 渡辺義公, 下水道研究発表会講演集, 58th, 2021

大型実証プラントにおける仕切板挿入型MBRの省エネルギー効果の検証
グェン タンフォン, 田村尚也, 円谷輝美, 張亮, 前島崇, 木村克輝, 渡辺義公, 下水道研究発表会講演集, 58th, 2021

下水中有機物回収を行う高負荷MBRにおけるファウリング抑制
佐賀サムエル旗生, ロコ マイケル, 羽深昭, 木村克輝, 下水道研究発表会講演集, 58th, 2021

都市下水の直接膜ろ過に組み込み可能な栄養塩回収方法の開発
伊藤結衣, 杉山徹, 高橋威胤, 羽深昭, 木村克輝, 下水道研究発表会講演集, 58th, 2021

環境技術思想-持続可能な社会に向かって 第13講 下水道を創エネルギーインフラへ転換する膜処理技術
木村克輝, 月刊下水道, 44, 8, 65, 69, 2021
環境新聞社, Japanese

Hydrogen-supplemented methane fermentation in batch reactor
新田大知, 大下和徹, 高岡昌輝, 日下部武敏, 高橋滋敏, 小中原亨, 水野志穂, 木村克輝, 羽深昭, 環境衛生工学研究, 35, 3, 2021

サイズ分画した表流水中バイオポリマーの膜ファウリングポテンシャル評価
永井梨奈, 冨永勘太, 木村克輝, 全国会議(水道研究発表会)講演集, 2020, 2020

セラミック平膜を用いた浄水処理における膜ファウリングの抑制
坂本秀樹, 久米啓大, 土屋達, 木村克輝, 全国会議(水道研究発表会)講演集, 2020, 2020

Baffled membrane bioreactor: Efficient nutrient removal, operational energy reduction, and modeling
Katsuki Kimura, Usman Rehman, Current Developments in Biotechnology and Bioengineering, 59, 73, 2020, [Invited]
Elsevier, Introduction other

凝集処理のUF膜ファウリング抑制効果:MF膜との比較
久米啓太, 鹿戸皇希, 木村克輝, 全国会議(水道研究発表会)講演集, 2018, 2018

膜分離活性汚泥法(MBR)の効率化に向けて
三好太郎, 円谷輝美, PHONG Nguyen Thanh, 木村克輝, 渡辺義公, 日本水環境学会シンポジウム講演集, 20th, 281‐282, 26 Sep. 2017
Japanese

仕切板挿入型MBRにおいて汚泥越流/分断時間比が窒素除去に及ぼす影響
三好太郎, 円谷輝美, グェン タンフォン, 木村克輝, 渡辺義公, 下水道研究発表会講演集, 54th, 203‐205, 03 Jul. 2017
Japanese

Performance of a baffled membrane bioreactor (BMBR) operated with sponge biomass carriers: Substantial reduction in operational energy
K. Kimura, S. Yamamoto, Lecture Notes in Civil Engineering, 4, 153, 158, 01 Jan. 2017
© Springer International Publishing AG 2017. The authors have proposed a baffled membrane bioreactor (BMBR) that can eliminate the energy needed for the mixed liquor circulation. A combination of the BMBR concept and use of biomass carriers is promising, and a substantial reduction in energy consumption should be possible. In this study, a pilot-scale BMBR treating municipal wastewater was operated with sponge biomass carriers and its performance was investigated in terms of treated water quality and energy consumption (aeration intensity). Long-term operation of the BMBR revealed that aeration demand for the BMBR was substantially reduced with minimal membrane fouling and excellent nitrogen removal being achieved. The expected energy consumption (aeration intensity) in a full-scale BMBR operated with sponge carriers is very low, definitely lower than the values in “normal” MBRs. With the proposed modification of the MBR, processes using MBRs will no longer be considered to be energy-intensive processes.

粒状担体の投入と散気装置の改良による浸漬型MBRの曝気量削減
栗田宗大, 山本昌平, 飯田稔彦, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 50th, 58, 10 Mar. 2016
Japanese

担体投入型BMBRにおける曝気量削減が膜ファウリング及び処理水質に与える影響
山本昌平, 栗田宗大, 飯田稔彦, 木村克輝, 下水道研究発表会講演集, 53rd, 2016

精密ろ過膜の表面に蓄積したフミン酸,多糖類,タンパク質の質及び量の経時変化
山村寛, 木村克輝, 渡辺義公, 全国会議(水道研究発表会)講演集, 2015, 184, 185, 18 Sep. 2015
Japanese

浸漬型MBR槽内における粒状担体の流動性と膜洗浄効果の評価
栗田宗大, 木村克輝, 渡辺義公, 下水道研究発表会講演集, 52nd, 227, 229, 01 Jul. 2015
日本下水道協会, Japanese

スポンジ担体の投入による浸漬型MBRにおける膜ファウリングの制御
内田大貴, 栗田宗大, 木村克輝, 下水道研究発表会講演集, 52nd, 2015

下水処理を行うフルスケールMBRより採取した閉塞膜の詳細分析
栗田宗大, 木村克輝, 日本水環境学会年会講演集, 49th, 2015

MBR汚泥性状が粒状担体の膜ファウリング抑制効果に及ぼす影響
栗田宗大, 茂木拓真, 安彦健斗, 中島貴史, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 48th, 276, 17 Mar. 2014
Japanese

膜ろ過の凝集前処理において撹拌強度がナノ粒子の挙動に及ぼす影響
大木康充, 安藤菜子, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 48th, 90, 17 Mar. 2014
Japanese

膜ファウリングの発生と水道原水中バイオポリマー濃度の相関
田中健, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 48th, 89, 17 Mar. 2014
Japanese

異なる微生物担体による浸漬型MBRの膜ファウリング抑制効果
茂木拓真, 栗田宗大, 木村克輝, 日本水環境学会年会講演集, 48th, 2014

Current Research in Drinking Water Treatment with Membrane Technology
山村 寛, 木村 克輝, 水環境学会誌, 36, 12, 430, 438, Dec. 2013
日本水環境学会 ; 1992-, Japanese

遺伝子発現解析に基づく再生水中残留医薬品の毒性評価
中島弘司, 原(山村)宏江, 木村克輝, 岡部聡, 三好太郎, 渡辺義公, 日本水環境学会年会講演集, 47th, 412, 11 Mar. 2013
Japanese

ヒト由来培養細胞を用いた塩素消毒下水処理水の毒性評価
福島寿和, 木村克輝, 岡部聡, 三好太郎, 渡辺義公, 日本水環境学会年会講演集, 47th, 516, 11 Mar. 2013
Japanese

膜分離活性汚泥法において膜ファウリングに関与しているタンパク質の解析
三好太郎, 相沢智康, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 47th, 265, 11 Mar. 2013
Japanese

細胞応答に基づいた膜処理再生水中の毒性画分の探索―粒径に着目して
原(山村)宏江, HOQUE Asiful, 木村克輝, 岡部聡, 三好太郎, 渡辺義公, 日本水環境学会年会講演集, 47th, 517, 11 Mar. 2013
Japanese

粒状担体の投入がMBRの運転効率および膜ファウリング特性に与える影響 (第50回下水道研究発表会講演集)
栗田 宗大, 木村 克輝, 渡辺 義公, 下水道研究発表会講演集, 50, 331, 333, 2013
日本下水道協会, Japanese

槽外型MBRにおいて膜ファウリングに関与しているタンパク質の解析
三好太郎, 永井悠平, 相沢智康, 木村克輝, 渡辺義公, 環境工学研究フォーラム講演集, 49th, 93, 95, 28 Nov. 2012
Japanese

NF膜による微量有機成分の除去機構
吉本みどり, LATEEF Shaik khaja, 木村克輝, 渡辺義公, 環境工学研究フォーラム講演集, 49th, 119, 120, 28 Nov. 2012
Japanese

槽外型MBRに装着したセラミック膜における膜ファウリング原因物質の分析
安井信人, 木村克輝, 大和信大, 三好太郎, 渡辺義公, 日本水環境学会年会講演集, 46th, 356, 14 Mar. 2012
Japanese

トキシコゲノミクス的アプローチを用いた再生水の水質評価~残留医薬品の影響~
中島弘司, 原宏江, HOQUE Asiful, 木村克輝, 岡部聡, 三好太郎, 渡辺義公, 日本水環境学会年会講演集, 46th, 93, 14 Mar. 2012
Japanese

トキシコゲノミクス的アプローチを用いた膜処理再生水の水質評価の試み
原(山村)宏江, HOQUE Asiful, 木村克輝, 岡部聡, 中島弘司, 三好太郎, 渡辺義公, 日本水環境学会年会講演集, 46th, 74, 14 Mar. 2012
Japanese

MBR膜ファウリング多糖のMALDI‐TOFMS分析における試料調製条件の検討
田村尚也, 木村克輝, 三好太郎, 渡辺義公, 日本水環境学会年会講演集, 46th, 353, 14 Mar. 2012
Japanese

運転条件の異なる膜分離活性汚泥法における膜透過水fluxと曝気風量の関連
三好太郎, 工藤憲三, 渡辺義公, 木村克輝, 相沢智康, 日本水環境学会年会講演集, 46th, 345, 14 Mar. 2012
Japanese

担体投入に伴うMBRの運転効率の改善
栗田宗大, 木村克輝, 渡辺義公, 衛生工学シンポジウム論文集, 20th, 2012

担体投入が浸漬型MBRにおける膜ファウリングの発生に及ぼす影響
栗田宗大, 木村克輝, 三好太郎, 渡辺義公, 日本水環境学会年会講演集, 46th, 2012

槽外型セラミック膜に装着したセラミック膜における膜ファウリング
安井信人, 三好太郎, 大和信大, 木村克輝, 渡辺義公, 環境工学研究フォーラム講演集, 48th, 94, 96, 25 Nov. 2011
Japanese

Changes in characteristics of soluble microbial products in membrane bioreactors associated with different solid retention times : Relation to membrane fouling
木村 克輝, 水環境学会誌 = Journal of Japan Society on Water Environment, 34, 8, 244, 244, 10 Aug. 2011
Japanese

膜分離活性汚泥法において膜ファウリングを引き起こしているタンパク質のメタプロテオーム解析
三好太郎, 相沢智康, 木村克輝, 渡辺義公, 土木学会年次学術講演会講演概要集(CD-ROM), 66th, ROMBUNNO.VII-067, 05 Aug. 2011
Japanese

MBRの化学薬品洗浄における薬液使用順序および洗浄方法が洗浄効率に与える影響
渡辺江梨, 木村克輝, 三好太郎, 渡辺義公, 日本水環境学会年会講演集, 45th, 229, 18 Mar. 2011
Japanese

逆洗を行う中空糸膜における膜長さ方向の膜ファウリング進行度の分布
笹口真幹, 木村克輝, 山村寛, 渡辺義公, 日本水環境学会年会講演集, 45th, 224, 18 Mar. 2011
Japanese

膜分離活性汚泥法において膜ファウリングに関与しているタンパク質の構造解析を通じた膜ファウリング発生機構の検討
三好太郎, 渡辺義公, 相沢智康, 木村克輝, 日本水環境学会年会講演集, 45th, 227, 18 Mar. 2011
Japanese

槽外型MBRに装着したセラミック膜における膜ファウリング
安井信人, 木村克輝, 三好太郎, 渡辺義公, 日本水環境学会年会講演集, 45th, 230, 18 Mar. 2011
Japanese

都市下水再生処理を行うNF/RO膜におけるファウリング物質蓄積状況の経時追跡
大橋威哉, 木村克輝, 三好太郎, 渡辺義公, 日本水環境学会年会講演集, 45th, 232, 18 Mar. 2011
Japanese

担体投入に伴うMBRの運転効率の改善
栗田宗大, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 45th, 2011

担体投入に伴うMBRの運転効率の改善
栗田宗大, 三好太郎, 木村克輝, 渡辺義公, 環境工学研究フォーラム講演集, 48th, 2011

膜分離活性汚泥法において膜ファウリングに関与しているタンパク質の構造解析
三好太郎, 相沢智康, 木村克輝, 渡辺義公, 環境工学研究フォーラム講演集, 47th, 118, 120, 12 Nov. 2010
Japanese

前処理にMBRを用いたNF/RO膜のファウリング物質
小川菜穂子, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 44th, 520, 15 Mar. 2010
Japanese

レクチンを用いたMBR内溶存態糖類のファウリングポテンシャルの評価
田中一平, 三好太郎, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 44th, 521, 15 Mar. 2010
Japanese

膜分離活性汚泥法(MBR)において膜ファウリングに関与しているタンパク質のプロテオーム解析
三好太郎, 木村克輝, 相沢智康, 渡辺義公, 日本水環境学会年会講演集, 44th, 95, 15 Mar. 2010
Japanese

Membrane Filtration in Water and Wastewater Treatment
Y. Watanabe, K. Kimura, Treatise on Water Science, 4, 23, 61, 01 Jan. 2010
This chapter describes the membrane fouling for water and wastewater-treatment application. In surface water treatment, hydrophilic fraction of the natural organic matter, especially carbohydrate-like substances, seems to be the main foulant for the physically irreversible fouling. In membrane bioreceptors, carbohydrate-like substances produced in the biological oxidation may be the main foulant. However, more detail of the characteristics of the carbohydrate substances must be investigated to understand the fouling mechanism in membrane filtration process., Elsevier, English

健全な水環境と水循環の創造のための膜技術
木村 克輝, 水環境学会誌 = Journal of Japan Society on Water Environment, 31, 12, 738, 10 Dec. 2008
Japanese

都市下水処理を行うNF/RO膜における膜ファウリング
小川菜穂子, 木村克輝, 渡辺義公, 環境工学研究フォーラム講演集, 45th, 32, 34, 28 Nov. 2008
Japanese

MF/UF膜ろ過における物理的に不可逆的な膜ファウリングの原因物質及び発生機構に関する研究
山村寛, 木村克輝, 渡辺義公, 日本水環境学会シンポジウム講演集, 11th, 231, 236, 17 Sep. 2008
Japanese

Origin of Foulants in Membrane Bioreactors (MBRs) Treating Municipal Wastewater
三好太郎, 成瀬拓朗, 大給理江, 木村克輝, 渡辺義公, 水環境学会誌, 31, 9, 541, 548, 10 Sep. 2008
The origin of foulants that causes physically irreversible fouling in pilot-scale membrane bioreactors (MBRs) treating real municipal wastewater was investigated. Utilization-associated products (UAP), biomass-associated products (BAP), and organic matter contained in the raw wastewater could be considered as potential sources of foulants in MBRs. Organic matter contained in the raw wastewater and BAP were characterized to assess their contributions to the evolution of physically irreversible fouling. Fourier transform infrared (FTIR) analysis, fluorescence excitation-emission matrices (EEM), and monosaccharide/amino acid composition analysis were used to characterize the organic matter. The results revealed that the organic matter contained in the raw wastewater was minor among the foulants regardless of the SRT. The characteristics of the foulant of the MBR operated with a long SRT were relatively similar to those of BAP, while no obvious similarity was observed between the characteristics of BAP and that of the foulant in the MBR operated with a short SRT. It was suggested that the contribution of UAP to the physically irreversible fouling increases as the SRT is shortened. The foulant of the MBR operated with a short SRT exhibited a higher specific filtration resistance than that of the MBR operated with long SRT. UAP causes severe physically irreversible fouling and it is important to minimize the accumulation of UAP in the mixed liquor of MBRs., Japan Society on Water Environment, Japanese

Caによるファウリング促進機構に関する研究
山村寛, 木村克輝, 沖本賢司, 渡辺義公, 全国水道研究発表会講演集, 59th, 168, 169, 01 May 2008
Japanese

河川水のMF膜ろ過において膜ファウリングを発生させるNOM画分
木村克輝, 上原敏裕, 山村寛, 渡辺義公, 全国水道研究発表会講演集, 59th, 164, 165, 01 May 2008
Japanese

高度下水処理中に残存する有機物がNF/RO膜処理における医薬品除去に与える影響
岩瀬智典, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 42nd, 409, 19 Mar. 2008
Japanese

MBRの活性汚泥混合液中に含まれるサブミクロン粒径画分の特性
大給理江, 三好太郎, 露原智央, 成瀬拓朗, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 42nd, 172, 19 Mar. 2008
Japanese

河川水のMF膜ろ過においてファウリングに関与するNOMの粒径画分
上原敏裕, 山村寛, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 42nd, 58, 19 Mar. 2008
Japanese

原子間力顕微鏡を用いたMF膜表面における多糖類様成分の付着力の測定
山村寛, 木村克輝, 岡嶋孝治, 渡辺義公, 日本水環境学会年会講演集, 42nd, 56, 19 Mar. 2008
Japanese

様々な表流水有機物中の親水性画分による膜ファウリング
沖本賢司, 山村寛, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 42nd, 60, 19 Mar. 2008
Japanese

MF膜を用いた河川水ろ過におけるファウリング原因物質の変化
樋口久美子, 山村寛, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 42nd, 57, 19 Mar. 2008
Japanese

Control of physically irreversible fouling in microfiltration by pre-coagulation
山村寛, 前田智宏, 木村克輝, 渡辺義公, 環境工学研究論文集, 44, 135, 141, 16 Nov. 2007
A long-term filtration experiment with a microfiltration membrane was carried out at an existing water purification plant and the influence of pre-coagulation on the evolution of physically irreversible fouling was investigated. Coagulation carried out at pH 7 mitigated the evolution of physically irreversible fouling. It was found that the degree of physically reversible fouling increased as a result of coagulation. Chemical analysis of the foulant desorbed by NaOH or HCl solution showed that pre-coagulation could prevent the fouling caused by iron, but could not control the fouling caused by organic matters. Particle size distribution of iron in the feed water implied that physically irreversible fouling was caused by the iron of size close to the micro-pores of the membrane (around 0.1μm) when coagulationwas not carried out. The pre-coagulation enlarged the size of iron particles, and would prevent the evolution of physically irreversible fouling. Based on the results obtained in this study, for the control of physically irreversible fouling, the optimum condition of coagulation is determined as follows: the one that can enlarge particles in the feed water with the size that is close to opening of membrane micro-pores., Japan Society of Civil Engineers, Japanese

MBR‐NF/RO膜処理を用いた都市下水からの中性医薬品の除去
岩瀬智典, 喜多修介, 木村克輝, 渡辺義公, 土木学会年次学術講演会講演概要集(CD-ROM), 62nd, Disk 2, ROMBUNNO.7-246, 01 Sep. 2007
Japanese

MF膜の不可逆的膜ファウリングに寄与するNOM画分
山村寛, 沖本賢司, 木村克輝, 渡辺義公, 土木学会年次学術講演会講演概要集(CD-ROM), 62nd, Disk 2, ROMBUNNO.7-244, 01 Sep. 2007
Japanese

都市下水のMBR処理におけるF/M比と膜ファウリング物質特性の関連性
大給理江, 三好太郎, 成瀬拓朗, 木村克輝, 渡辺義公, 土木学会年次学術講演会講演概要集(CD-ROM), 62nd, Disk 2, ROMBUNNO.7-191, 01 Sep. 2007
Japanese

仕切板挿入型MBRを用いた都市下水からの栄養塩除去
木村克輝, 西迫里恵, 渡辺義公, 下水道研究発表会講演集, 44th, 151, 153, 29 Jun. 2007
日本下水道協会, Japanese

河川水のUF膜濾過におけるファウリング物質の特性
山村寛, CHAE Soryong, 木村克輝, 渡辺義公, 全国水道研究発表会講演集, 58th, 200, 201, 25 Apr. 2007
Japanese

前凝集条件がMF膜濾過の処理水質および膜ファウリングに及ぼす影響
木村克輝, 前田智宏, 渡辺義公, 全国水道研究発表会講演集, 58th, 202, 203, 25 Apr. 2007
Japanese

MBRにおいて逆洗方法の差異が膜ファウリングに及ぼす影響
成瀬拓朗, 三好太郎, 山村寛, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 41st, 230, 15 Mar. 2007
Japanese

膜分離活性汚泥法と標準活性汚泥法における医薬品の除去機構
原宏江, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 41st, 365, 15 Mar. 2007
Japanese

NF/RO膜を用いた医薬品除去における共存有機物マトリックスの影響
岩瀬智典, 原宏江, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 41st, 35, 15 Mar. 2007
Japanese

Membrane Bioreactorにおける膜ファウリングの進行に関与する有機物の特性解析
三好太郎, 成瀬拓朗, 大給理江, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 41st, 226, 15 Mar. 2007
Japanese

MF膜を用いた河川水ろ過におけるファウリング機構の経時変化
山村寛, CHAE Soryong, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 41st, 449, 15 Mar. 2007
Japanese

原水水質変動に起因するUF膜ファウリング原因物質の変化
山村寛, 蔡小龍, 木村克輝, 渡辺義公, 土木学会年次学術講演会講演概要集(CD-ROM), 61st, Disk 2, ROMBUNNO.7-003, 01 Sep. 2006
Japanese

MBR‐NF/RO膜処理を用いた都市下水からの医薬品の除去
岩瀬智典, 原宏江, 木村克輝, 渡辺義公, 土木学会年次学術講演会講演概要集(CD-ROM), 61st, Disk 2, ROMBUNNO.7-061, 01 Sep. 2006
Japanese

MF膜におけるファウリングの原因物質に関する研究―膜の材質の違いによる閉塞成分の差異―
山村寛, 木村克輝, 渡辺義公, 全国水道研究発表会講演集, 57th, 218, 219, 25 Apr. 2006
Japanese

MBRを用いた都市下水処理における槽内水組成と膜ファウリングの関係
大和信大, 三好太郎, 成瀬拓朗, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 40th, 360, 15 Mar. 2006
Japanese

都市下水処理を行うMBRにおける膜ファウリング物質の特性解析―膜材質の影響―
三好太郎, 大和信大, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 40th, 358, 15 Mar. 2006
Japanese

膜分離活性汚泥法と標準活性汚泥法における医薬品除去性の比較
原宏江, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 40th, 354, 15 Mar. 2006
Japanese

仕切板挿入型MBRによる都市下水高度処理に関する研究
島田隆右, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 40th, 361, 15 Mar. 2006
Japanese

Hybrid membrane bioreactor for water recycling and phosphorus recovery
Y Watanabe, K Kimura, WATER SCIENCE AND TECHNOLOGY, 53, 7, 17, 24, 2006
This paper deals with the performance of hybrid membrane bioreactor (MBR) combining the precoagulation/sedimentation and membrane bioreactor. The hybrid MBR not only produces the treated water with excellent permeate quality but also shows much lower membrane fouling than the conventional MBR. It may come from its extremely low F/M ratio to maintain the low viscosity even in the high MLSS concentration range of about 20,000 mg/L. Some results of microbial community analysis in MBRs was conducted to demonstrate the other reason for its lower membrane fouling. Hybrid MBR has a high potential to be used for the recycling use of the municipal wastewater. Coagulated sludge produced in the hybrid MBR is a promising phosphorus resource. This paper also contains a recent progress of phosphorus recovery technology, which uses a new phosphoric acids absorbent, i.e. the hexagonal mesostructured zirconium sulfate (ZS). The ZS has the extremely high adsorption capacity of phosphoric acids through anion exchange. The adsorbed phosphoric acids are released from the ZS in a high pH range of about 13., I W A PUBLISHING, English, Book review

前凝集/ＭＦ膜処理において凝集条件が膜ファウリングに及ぼす影響
前田 智宏, 木村 克輝, 渡辺 義公, 衛生工学シンポジウム論文集, 13, 235, 238, 16 Nov. 2005
北海道大学衛生工学会, Japanese

都市下水処理を行うMBRにおいて発現する膜ファウリングに関する研究
三好 太郎, 大和 信大, 木村 克輝, 渡辺 義公, 衛生工学シンポジウム論文集, 13, 231, 234, 16 Nov. 2005
北海道大学衛生工学会, Japanese

河川水UF膜ろ過における不可逆的膜ファウリングの原因物質
山村 寛, 木村 克輝, 渡辺 義公, 衛生工学シンポジウム論文集, 13, 227, 230, 16 Nov. 2005
北海道大学衛生工学会, Japanese

Influence of Operating Condition and Suspension Characteristics on Membrane Fouling in Membrane Bioreactors
大和信大, 木村克輝, 渡辺義公, 水環境学会誌, 28, 11, 663, 669, 10 Nov. 2005
In this study, the influence of the food-to-microorganism ratio (F/M) and permeate flux on membrane fouling was investigated using pilot-scale membrane bioreactors (MBRs) fed with actual municipal wastewater. Membrane fouling rate was affected by both F/M and permeate flux. It was shown that the influence of permeate flux on the membrane fouling rate was more significant than that of F/M. Batch filtration experiments were conducted to evaluate the degree of irreversible fouling caused by different fractions (suspended solids, colloids, soluble matter) in the mixed liquor of MBRs. From the results of the batch experiments, it was revealed that (a) irreversible fouling was caused mainly by the soluble fraction, and (b) irreversible fouling became significant when the MBR operated with a high F/M and a short solid retention time. There was a relationship between the fouling rate and the concentration of dissolved organic carbon (DOC) particles in the mixed liquor, whose size was between 0.2 μm and 0.5 μm. The concentration of organic matter with an apparent molecular weight of around 1MDa was also correlated with the fouling rate. These two constituents in the mixed liquor suspension seemed to affect membrane fouling., Japan Society on Water Environment, Japanese

Membrane Bioreactorにおける膜材質の差異が膜ファウリング進行に及ぼす影響
三好太郎, 大和信大, 木村克輝, 渡辺義公, 土木学会年次学術講演会講演概要集(CD-ROM), 60th, Disk 2, ROMBUNNO.7-035, 20 Aug. 2005
Japanese

前凝集/MF膜処理において凝集条件が膜閉塞及び処理水質に及ぼす影響
前田智宏, 木村克輝, 渡辺義公, 土木学会年次学術講演会講演概要集(CD-ROM), 60th, Disk 2, ROMBUNNO.7-020, 20 Aug. 2005
Japanese

膜を用いた高度下水処理による医薬品除去
原宏江, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 39th, 42, 17 Mar. 2005
Japanese

Membrane Bioreactorを用いた都市下水処理における膜ファウリングに関する研究
大和信大, 木村克輝, 渡辺義公, 環境工学研究論文集, 41, 269, 278, 25 Nov. 2004
This study examined the influence of operating conditions on membrane fouling in membrane bioreactors (MBRs) used for municipal wastewater treatment. Also, the mechanism of fouling evolution was investigated based on both pilot-scale and lab-scale experiments. Three pilot-scale MBRs were operated for about 100 daysat an existing municipal wastewater treatment facility. In the long-term operation, probably because aeration intensitywas enough to avoid formation of cake layer on the membrane surface, reversible fouling was not significant (i. e., irreversibletype of fouling dominated). The lab-scale experiments demonstrated that dissolved organic matter (DOM) accumulating in the reactors was likely to be responsible for the irreversible fouling. DOM loading on the membrane surface was found to influence the degree of total filtration resistance. It was revealed that changes in the composition of DOM (e. g., decrease in specific UV absorbance) in the reactors were also related to the irreversible fouling. Especially, dissolved sugar and dissolved protein contained in the mixed liquor played an important role in the development of the irreversible fouling., Japan Society of Civil Engineers, Japanese

下水処理水中に含まれる有機物によるMF膜ファウリング
山村寛, 木村克輝, 渡辺義公, 土木学会年次学術講演会講演概要集(CD-ROM), 59th, Disk 2, 7, 072, 01 Sep. 2004
Japanese

逆浸透膜を用いた非荷電EDCs/PhACsの除去
木村克輝, 戸島志保, 渡辺義公, 土木学会年次学術講演会講演概要集(CD-ROM), 59th, Disk 2, 7, 070, 01 Sep. 2004
Japanese

MBR(Membrane Bioreactor)を用いた都市下水処理システムにおける女性ホルモン様物質の挙動に関する研究
久保広明, 渡辺義公, 岡部聡, 木村克輝, 日本水環境学会年会講演集, 38th, 363, 17 Mar. 2004
Japanese

溶存有機物特性が中空糸膜ファウリングの進行に及ぼす影響
山村寛, 木村克輝, 渡辺義公, 日本水環境学会年会講演集, 38th, 318, 17 Mar. 2004
Japanese

Developing the new leachate treatment system using membrane bioreactor of anaerobic ammonia oxidation type and establishing the safety evaluation method of treated water using DNA chip.
渡辺義公, 岡部聡, 木村克輝, 第4回廃棄物対策研究発表会成果発表抄録集 平成16年度廃棄物対策研究推進事業, I.35-I.37, 2004
Japanese

Advanced municipal wastewater treatment by a novel membrane bioreactor: simultaneous nitrification and denitrification in a single reaction chamber
糸永貴範, 笹川学, 木村克輝, 渡辺義公, 環境工学研究論文集, 40, 1, 10, 14 Nov. 2003
In this study, a novel membrane bioreactor (MBR) in which nitrification and denitrification simultaneously proceed in a single reaction chamber is proposed for advanced municipal wastewater treatment. Anoxic/aerobic conditions are separately created in the proposed MBR by inserting baffles inside of the membrane chamber and consequently simultaneous nitrification/denitrification can be carried out The technology established in this study can easily be applied to almost all of existing MBRs. Pilot-scale experiment to examine performance of the proposed MBR was carried out at an existing municipal wastewater treatment plant In this paper, experimental results obtained in the pilot study are shown. Inserting baffles inside the membrane chamber actually increased removal of nitrogen by 30%. Coagulation and sedimentation were carried out in the pilot study for pre-treatment of the MBR. Removal efficiency in terms of total organic carbon, total phosphorus, and total nitrogen determined for whole treatment system (i. e., coagulation/sedimentation/the proposed MBR) was attained to 91.5%, 97.2%, and 66.2%, respectively. Increase in transmembrane pressure difference was minimal in the pilot operation. It was demonstrated that high quality effluent and mitigation of membrane fouling could simultaneously be achieved by the proposed MBR., Japan Society of Civil Engineers, Japanese

MBR(Membrane Bioreactor)を用いた下水処理水の安全性評価およびMicropollutantsの挙動に関する研究
久保広明, 岡部聡, 木村克輝, 渡辺義公, 土木学会年次学術講演会講演概要集(CD-ROM), 58th, Disk 2, VII-085, 01 Sep. 2003
Japanese

都市下水のMBR処理における不可逆的膜ファウリング削減に関する研究
三浦佑己, 糸永貴範, 木村克輝, 渡辺義公, 土木学会年次学術講演会講演概要集(CD-ROM), 58th, Disk 2, VII-128, 01 Sep. 2003
Japanese

河川水UF膜ろ過における不可逆的膜ファウリングに及ぼす前凝集沈殿の影響
木村克輝, 羽根康史, 渡辺義公, 土木学会年次学術講演会講演概要集(CD-ROM), 58th, Disk 2, VII-126, 01 Sep. 2003
Japanese

疎水性低分子量有機物のNF/RO膜への吸着
木村克輝, 渡辺義公, AMY G, 日本水環境学会年会講演集, 37th, 44, 04 Mar. 2003
Japanese

河川水UF膜ろ過における不可逆的膜ファウリングに関する検討
羽根康史, 木村克輝, 渡辺義公, AMY G, 日本水環境学会年会講演集, 37th, 489, 04 Mar. 2003
Japanese

前凝集・膜分離活性汚泥法における膜ファウリング要因についての検討
久保広明, 松宮知, 木村克輝, 渡辺義公, 土木学会年次学術講演会講演概要集(CD-ROM), 57th, VII-153, 01 Sep. 2002
Japanese

Advanced Drinking Water Treatment by the Membrane with Fixed Biofilm　　　　　　　　　　　　　　　
Journal of Japan Water Works Association, 71(4), 10, 2002

前凝集沈殿・膜分離活性汚泥法による都市下水の高度処理
田辺 耕平, 木村 克輝, 松宮 知, 渡辺 義公, 衛生工学シンポジウム論文集, 9, 203, 208, 01 Nov. 2001
北海道大学衛生工学会, Japanese

生物膜と分離膜を組み合わせた高度浄水処理プロセス
羽根 康史, 木村 克輝, 渡辺 義公, 大熊 那夫紀, 衛生工学シンポジウム論文集, 9, 197, 202, 01 Nov. 2001
北海道大学衛生工学会, Japanese

高度浄水処理における低水温時リン添加の影響
羽根康史, 木村克輝, 渡辺義公, 土木学会年次学術講演会講演概要集 第7部, 56th, 384, 385, 01 Sep. 2001
Japanese

膜分離活性汚泥法における蓄積溶解性有機成分と膜透過性能の関係
松宮知, 田辺耕平, 木村克輝, 渡辺義公, 土木学会年次学術講演会講演概要集 第7部, 56th, 376, 377, 01 Sep. 2001
Japanese

前凝集と膜分離活性汚泥法を組み合わせた都市下水処理における栄養塩除去性の向上に関する研究
田辺耕平, 木村克輝, 渡辺義公, 土木学会年次学術講演会講演概要集 第7部, 56th, 442, 443, 01 Sep. 2001
Japanese

単体硫黄を利用した独立栄養性脱窒と膜分離の組み合わせによる硝酸性窒素の除去
木村克輝, 中村公彦, 渡辺義公, 全国水道研究発表会講演集, 52nd, 312, 313, 27 Apr. 2001
Japanese

配水過程における生物膜生成能に及ぼす異なる浄水処理プロセスの影響
小鍛冶利彦, 岡部聡, 渡辺義公, 木村克輝, 全国水道研究発表会講演集, 52nd, 278, 279, 27 Apr. 2001
Japanese

回転平膜モジュールのスポンジ洗浄に関する基礎検討
照井茂樹, 吉川慎一, 大西真人, 木村克輝, 渡辺義公, 環境工学研究フォーラム講演集, 37th, 22, 24, 13 Nov. 2000
Japanese

前凝集・膜分離活性汚泥法を用いた都市下水の高度処理
木村克輝, 鈴木秀孝, 渡辺義公, 土木学会年次学術講演会講演概要集 第7部, 55th, 84, 85, 31 Aug. 2000
Japanese

Simultaneous processing of nitrification and denitrification with sulfur using a membrane bioreactor.
中村公彦, 木村克輝, 渡辺義公, 環境工学研究フォーラム講演集, 36th, 37, 39, 15 Nov. 1999
Japanese

Kinetic analysis of biofilm attached to surface of separation membrane.
木村克輝, 渡辺義公, 岡部聡, 佐藤久, 土木学会年次学術講演会講演概要集 第7部, 54th, 430, 431, 01 Aug. 1999
Japanese

Membrane filtration resistance caused by nitrifiers oxidizing low concentrations of ammonia
Environmental Engineering Research, 36, 287, 1999

Simultaneous removal of suspended matter and ammonia using the rotating flat membrane process.
木村克輝, 渡辺義公, 大熊那夫紀, 土木学会年次学術講演会講演概要集 第7部, 53rd, 184, 185, Oct. 1998
Japanese

Removal of manganese and arsenic using dipping type MF.
渡辺義公, 木村克輝, 大和信大, 笠原伸介, 土木学会年次学術講演会講演概要集 第7部, 53rd, 242, 243, Oct. 1998
Japanese

Filtration resistance of biofilm clinged to rotary flat film surface.
木村克輝, 渡辺義公, 大熊那夫紀, 土木学会年次学術講演会講演概要集 第7部, 52nd, 370, 371, Sep. 1997
Japanese

Integration of separation membrane and biofilm using rotating flat plate membrane module.(II).
木村克輝, 渡辺義公, 大熊那夫紀, 土木学会年次学術講演会講演概要集 第7部, 51st, 184, 185, Aug. 1996
Japanese

Nitrification performance of biofilms fixed on the rotating membrane disk.　　　　　　　　　　　　　　　
Journal of Environmental Systems and Engineering, 552, 43, 1996

分離膜・生物膜一体型リアクターの開発
木村 克輝, 渡辺 義公, 大熊 那夫紀, 衛生工学シンポジウム論文集, 3, 1, 6, 01 Nov. 1995
北海道大学衛生工学会, Japanese

回転平膜モジュールを用いた分離膜と生物膜の一体化
木村克輝, 土木学会第50回年次学術講演会講演集2B論文集, 1076, 1077, 1995

2014 - Present
日本膜学会　　　　　　　　　　　　　　　

細菌及び藻類より回収したバイオポリマーの特性及び膜閉塞抑制手法の解明
科学研究費助成事業
01 Apr. 2022 - 31 Mar. 2025
三好 太郎, 木村 克輝
日本学術振興会, 基盤研究(C), 国立保健医療科学院, 22K04389

進化型MBRによる下水からの有機物回収：下水道の創エネルギーインフラへの転換
科学研究費助成事業 基盤研究(A)
05 Apr. 2021 - 31 Mar. 2025
木村 克輝, 西村 紳一郎, 羽深 昭
ベンチスケールのMBR実験システムを構築し、実下水処理場に実験装置を設置して連続ろ過実験を繰り返し実施した。本研究で提案・確立を行うエネルギー回収型MBRでは深刻な膜ファウリングの発生が確実に起こるため、これに対処するための担体を用いた機械的洗浄と薬品併用逆洗（CEB）を実施しながら連続ろ過運転を行った。HRT、SRT、DOを様々に変化させて実験を行い、有機物回収率、膜ファウリング発生度、処理水水質のそれぞれが高いレベルで調和するような運転条件の探索を試みた。HRTを極短の1.5-2時間、SRTも極短の0.5日とすることで、有機物回収率（初沈流入水に対して）は70％を超過する結果が得られた。実下水を用いた実験であったことからDOを一定範囲に制御することが難しく、MBR内のDO濃度は大きく変動した（1-7 mg/L）。処理水中のCOD濃度は20 mg/L程度となり、高い有機物回収率と処理水中の有機物濃度低減を同時に達成可能であることを実証した。膜ファウリングの発生については、CEBに用いる次亜塩素酸の濃度が洗浄効果に大きな影響を及ぼすことを観察した。本年度の研究では50-1000 ppmの範囲でCEBに用いる次亜塩素酸の濃度を変化させたが、最も安定したMBRの運転が可能になったのは次亜塩素酸の濃度を50 ppmに設定した時であった。過度に高い薬品濃度は微生物からの有機物放出を誘引し、MBR内の汚泥ろ過性を低下させるものと考えられた。CEBに用いる次亜塩素酸濃度を50 ppm とし、正味の膜透過水フラックスを20 LMHに設定した実験では５日間程度はほとんど膜ファウリングが発生しない状況を繰り返し観察した。
日本学術振興会, 基盤研究(A), 北海道大学, 21H04569

Concentration of organic matter in municipal wastewater by membrane processes with extremely intensive membrane cleaning: sewage systems can be transformed into energy generating infrastructures
Grants-in-Aid for Scientific Research
29 Jun. 2018 - 31 Mar. 2021
Kimura Katsuki
Organic matter in municipal wastewater can be recovered and concentrated by using direct membrane filtration (DMF) adequately, which leads to net-generation of energy from wastewater. Flat-sheet ceramic membranes are physically and chemically robust, and therefore intensive membrane cleanings that cannot be used with polymeric membranes can be used. In this study, DMF of municipal wastewater by flat-sheet ceramic membranes was investigated. With the aid of intensive physical and chemical cleaning, long-term operations under high membrane fluxes were possible. In addition, switching the feed from of the influent of the primary sedimentation basin to the effluent, very short-period aeration, alternative use of acid and oxidant in chemically enhanced backwash were found to be effective for mitigation of membrane fouling in DMF.
Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Research (Pioneering), Hokkaido University, 20K20351

Fundamental control of membrane fouling based on detailed information on biopolymers in surface water
Grants-in-Aid for Scientific Research
01 Apr. 2018 - 31 Mar. 2021
Kimura Katsuki
In previous studies, the importance of biopolymers (hydrophilic organic macro-molecules) in evolution of fouling of membranes filtering surface water was pointed out. In this study, a new method for isolation of biopolymers from surface water was established. It was found that the new method provided significantly high rates of recovery and purity of biopolymers. Physical-chemical properties and fouling potentials of the biopolymers isolated from various drinking water sources were investigated. It turned out that the properties isolated from natural water were considerably different from those of model biopolymers (e.g., alginate) used often in previous researches. Fouling potentials of the isolated biopolymers were assessed by using QCM. Information obtained by this assessment could be used for efficient selection of materials for new anti-fouling membranes.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, 18H03789

Micro algae production system using purified municipal wasterwater by membrane bioreactor
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
01 Apr. 2016 - 31 Mar. 2019
Watanabe Yoshimasa
Treated municipal wastrwater by MBR was reused for the cultivation of microalgae. Microalgae can be use as the source of protein for theaquaculture. The results obtained in the research can be summarized as follows:
1) MBR: Buffled MBR can be operated by controlling the cycle time in bMBR and ORP in the inner part of buffles to maintain the optomum nitrogen oncentration for the microalgae cultivation. Operation nerg of bMBR was reduced to 0.2 kwh/m3 by using the long (3 m) and high density PTFE membrane module, 2)MIcroalgare:P. Ellipoidea was selected which has the optimum growth pH of 3.0. Protein content of about 18% was obtained, which is almost the same as a sardine.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Chuo University, 16H04440

Control of membrane fouling by specific removal of polysaccharides using glycoblotting
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
01 Apr. 2015 - 31 Mar. 2018
Kimura Katsuki
Biopolymers, defined as hydrophilic organic macromolecules in natural water, have been identified as major players in membrane fouling. In this study, glycoblotting, which was developed to specifically capture oligosaccharides in the field of medical science, was applied for establishing a new pre-pretreatment for membrane processes in water treatment. Removal of biopolymers was limited under a normal temperature. However, use of catalysts such as aniline or oxidants enabled to remove biopolymers via glycoblotting under a normal temperature. It was suggested that biopolymers detected by the conventional method should be further fractionated to investigate membrane fouling caused by biopolymers. Modified liquid chromatography with organic carbon detection (LC-OCD) analysis enabled the further fractionation of biopolymers.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 15H04063

New approach to control gastroenteritis viruses in wastewater reclamation and reuse by taking advantage of glycomics information
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
01 Apr. 2014 - 31 Mar. 2017
Sano Daisuke
This study aims to find a new approach to control gastroenteritis viruses in wastewater treatment processes by taking advantage of glycan-recognition of viruses. Firstly, glycans that can be captured by norovirus particles were identified by glycan microarray. Based on the glycan microarray results, GD1a positive bacteria were isolated from environmental water samples. Microfiltration of norovirus in the presence of HBGA-positive bacteria was then performed. HBGA-producing genes were identified to track HBGA-positive bacteria in wastewater treatment processes. Finally, the removal of rotavirus HAL1166, which and recognize HBGA, with microfiltration membrane was investigated.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, 26249075

Development of Membrane Bioreactor with less nergy consumption and multi^function
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
21 Oct. 2013 - 31 Mar. 2016
watanabe yoshimasa, KIMURA Katsuki, YAMAMURA Hiroshi, SATOH Hisashi, HAFUKA Akira
A pilot plant study of the buffled MBR with PTFE membranes of 3 m long ,which can achieve simultaneous removal of BOD, T-N and T-P in a single reacto, was carried out. As the results, stabler removal of BOD, T-N and T-P was observed, and the electric power consumption rate of 0.35 kWh/m3 was obtained. It is very low compared with the existing MBR.We developted a nove PTFE hollow fiber MF membrane module with intensive air diffuser. A series of small pilot plant experiment showed a quite low electric power consumption is possible in the MBR with the novel module. P recovery from the MBR exess sludge was possible when the effluent from the MBR was treated through the column filled with zirconia mezo-structured paricles. Anaerobic MBR with a MF hollowfiber membrane incoorated with zirukonium mes- structured particles has a high potential for the phosphate recovery from the excess sludge.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Chuo University, 25249073

Control of membrane fouling based on structures of polysaccharides revealed by application of glyco-blotting
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
01 Apr. 2012 - 31 Mar. 2015
KIMURA Katsuki, HINOU Hiroshi, AIZAWA Tomoyasu
Enrichment of polysaccharides by glyco-blotting, in which polysaccharides are specifically purified via interactions between the aldehydes in the polysaccharides and aminooxy groups on glycoblotting beads, enabled MALDI-TOF/MS analysis at a high resolution. Structures of polysaccharides extracted from fouled membranes used in a pilot-scale MBR and those in the supernatant of the mixed liquor suspension in the MBR were investigated. It was demonstrated that the overlap between polysaccharides found in the supernatants and those extracted from the fouled membrane was limited, implying that polysaccharides that dominate in supernatants may not be important in membrane fouling in MBRs. Analysis using a bacterial carbohydrate database suggested that capsular polysaccharides (CPS) and/or lipo-polysaccharides (LPS) play an important role in the evolution of membrane fouling in MBRs.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 24360212

Development of Resources Oriented Sanitation System Based on the Concept "Don't Mix" and "Don't Collect" Wastewater
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (S)
11 May 2009 - 31 Mar. 2014
FUNAMIZU NAOYUKI, TAKAHASHI Masahiro, OHTAKI Masahiro, ISODA Hiroko, USHIJIMA Ken, KIMURA Katsuki, ITO Ryusei, GUIZANI Mokhtar, HAN Junkyu, KAKIMOTO Takashi, ONODA Yu
The new resources oriented sanitation system based on the concept "Don't mix" and "Don't collect" wastewater is proposed in this study. The newly developed element technologies for the resource oriented systems for three situations (rural area and urban slum area in developing countries and a rural area in Japan) include 1) composting type toilet; 2) urine volume reduction ; 3) Nitrogen and Phosphorus recovery from urine; 4) farming technologies for wise reuse recovered urine and compost; 5) gray water reclamation; 6) bio-assay system for toxicity assessment of reclaimed water and 7) assessment method for evaluating inactivation level of pathogens in composting.
Material flow analysis on Nitrogen, Phosphorus and water has shown the feasibility of the newly developed system at the rural area in Burkina Faso and the urban slum in Indonesia.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (S), Hokkaido University, 21226013

Control of membrane fouling in MBRs on the basis of proteome analysis and measurements of atomic force
Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (A)
2009 - 2011
KIMURA Katsuki
In this study, structure of proteins that were involved in membrane fouling in membrane bioreactors(MBRs) was investigated. Proteins causing membrane fouling were obtained from fouled membranes used in an MBR treating municipal wastewater. Modification of sample pre-treatment enabled application of two-dimensional gel electrophoresis and the protein causing membrane fouling could be separated on the basis of molecular weights and isoelectric points. The separated proteins were subjected to amino acid sequence analysis. It was shown that outer membrane proteins of bacteria belonging to the genus Pseudomonas played an important role in the evolution of membrane fouling in MBRs.
Japan Society for the Promotion of Science, Grant-in-Aid for Young Scientists (A), Hokkaido University, 21686050

ナノ構造物を表面に固定した新規機能性膜の開発
科学研究費助成事業 挑戦的萌芽研究
2008 - 2009
木村 克輝, 定金 正洋
水処理各方面で様々な種類の分離膜が導入され始めているが、未だに主流技術とはなりえていない。その主な原因は膜ファウリングに伴う運転コストの増加および溶解性低分子量成分の除去性である。本研究は、ナノスケールでの規則的かつ立体的な構造制御が可能となっているカーボンナノファイバーを分離膜表面に固定することで、従来は考えられなかった新機能を有する分離膜創生を行い、上述した問題の解決を目指すものである。21年度は、平膜状アルミナ多孔体上にカーボンナノファイバーを固定化する条件の最適化を検討し、以下の条件を確立した。平膜状アルミナ多孔体(WhatmanアルミナフィルターAnodisc 25)を0.3M硝酸ニッケルのエタノール溶液に浸し、超音波バス中で10分間超音波処理を行った。そめ後、硝酸ニッケル溶液から平板状アルミナ多孔体を取り出し、この硝酸ニッケル溶液の染み込んだ平板状アルミナ多孔体を300度に加熱している焼成炉に1時間入れ、アルミナ多孔体中の硝酸ニッケルを酸化ニッケルに変換した。その後、この酸化ニッケルを担持した平板状アルミナ多孔体をメタンガス流通下(毎分20ml)、550度で2時間反応させることにより、カーボンナノファイバーを生成させた。この方法により平板状アルミナ多孔体上全てにカーボンナノファイバーを生成させることが出来ることが確認できた
日本学術振興会, 挑戦的萌芽研究, 北海道大学, 20656083

Optimization of advanced wastewater treatment systems using membrane technology on the basis of behavior of pharmaceutical compounds
Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (A)
2006 - 2008
KIMURA Katsuki
従来型の下水処理技術では除去が難しい医薬品類による水環境及び水道水源の汚染が顕在化している。本研究では、次世代の下水処理技術として注目されている膜処理を用いた場合の医薬品除去性について検討した。膜分離活性汚泥法やナノろ過、逆浸透処理による医薬品の除去性は従来型下水処理と比較して大幅に高くなる。生物処理部の操作条件はシステム全体における医薬品除去性に大きな影響を及ぼすことが明らかとなった。また、下水処理過程において医薬品は完全に分解されるわけではなく、構造が特定されない中間生成物として放流されるものがあることを示した。
Japan Society for the Promotion of Science, Grant-in-Aid for Young Scientists (A), Hokkaido University, 18686043

Identification and quantification of fecal pollutions by using genetic and chemical markers
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
2003 - 2004
OKABE Satoshi, KIMURA Katsuki
Identification and quantification of microbial contaminants of fecal origin are major priority in the control of drinking and recreational water qualities. In this study, we proposed a new PCR-based approach using 16S rRNA gene markers of enteric anaerobes, Bacteroides-Prevotella spp for discriminating human, cow, and pig fecal contamination in environmental waters without culturing indicator organisms. One human-, three cow-, and two pig-specific Bacteroides-Prevotella 16S rRNA genetic markers were identified based on 16S rRNA gene clone libraries constructed from each fecal samples, respectively. Host-specific markers suggested that there are species composition differences in Bacteroides-Prevotella community in feces of each host species. Additionally, all host-specific genetic markers were detected in river water collected from area frequently contaminated with fecal pollution. We further developed a real-time polymerase chain reaction (qPCR) assay to quantify each host-specific genetic marker in fecal and environmental water samples. First we designed host-specific primers for the real-time PCR assay and validated their specificity on human, cow, and pig fecal samples. The real-time PCR detection of serially diluted DNA extracted DNA from pure cultured B.fragilis and plasmid DNAs was linear ranging from 4.0 to 4.0×10^5 copies/PCR and 6.0×10^1 to 6.0×10^8 copies/PCR, respectively. Using a simple filtration method, the quantification limit of newly developed qPCR assay was 10-70 genetic marker copies/100mL. Second, we applied this qPCR assay with each host-specific primer set to ratural river for over one year and confirmed that our qPCR assay could discriminate human, cow, and pig sources of fecal contamination with high specificity. These results implied that the qPCR assay described here should be widely applicable for monitoring spatial and temporal fluctuations in specific fecal contaminations in natural environments.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), HOKKAIDO UNIVERSITY, 15360283

EDCs/PhACsの水中有機成分との結合及び膜処理による除去に関する研究
科学研究費助成事業 若手研究(B)
2003 - 2004
木村 克輝
本年度は、膜分離活性汚泥法(Membrane bioreactor, MBR)による医薬品由来化合物(PhACs)除去性の検討を行った。MBRは膜を用いた次世代の下水処理技術として注目されている技術であるが、PhACsのMBRによる除去性に関する検討例は現時点でほとんど存在していない。実験は、実都市下水処理場に設置したパイロットスケールのMBRを用いて行った。標準活性汚泥法を採用している実都市下水処理場最終沈殿池流出水中のPhACs濃度とMBR処理水中のPhACs濃度を比較することにより、MBRのPhACs除去性について評価した。検討の対象としたPhACsのうち、clofibric acid、ibuprofen、ketoprofen、naproxen、fenoprofen、mefenamic acid、diclofenac、primidone、carbamazepineの9種類のPhACsが流入下水から検出された。今回検討の対象としたPhACsは、各処理プロセスにおける除去性によって3つのグループに分けることができた。ibuprofenはMBRと活性汚泥法の両方において良好に除去されていたが、diclofenacはどちらの処理法によっても顕著な除去は観察されなかった。また、ketoprofen、mefenamic acid、naproxen、fenoprofen、clofibric acidは活性汚泥法よりもMBRにおいて効果的に除去されていた。これらのPhACs除去性とPhACsの構造との関連性に着目すると、PhACsの構造に含まれるベンゼン環数が除去性に大きな影響を及ぼしているようであった。構造中のベンゼン環数が1つのibuprofenについては、MBRと活性汚泥法は同程度の除去性を示したが、ベンゼン環数が2つのketoprofen、mefenamic acid、naproxen、fenoprofenについては活性汚泥法よりもMBRにおいて良好な除去が達成された。ベンゼン環とハロゲン基をそれぞれ2つ有するdiclofenacはMBR/活性汚泥法の双方において顕著な除去は観察されなかった。PhACsの構造中にベンゼン環やハロゲン基が多く存在する物質ほど生物処理による除去が困難になるものと推測される。MBR/活性汚泥法間におけるPhACs除去性の差異は、両プロセスにおけるSRTの長短によるものであったと考えられる。MBRではSRTを極めて長く設定できるため、増殖速度の遅い微生物種が増殖できることに加え、元々存在していた微生物がPhACsに対して代謝活性を獲得する可能性がある。
日本学術振興会, 若手研究(B), 北海道大学, 15760404

Hybrid municipal wastewater treatment system for recovering the reclaimed water and phosphorous resource
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
2002 - 2004
WATANABE Yoshimasa, OKABE Satoshi, KIMURA Katsuki
A novel membrane Bioreactor(MBR) in which nitrification and denitrification simultaneously proceed in a single reaction chamber has been proposed for advanced municipal wastewater treatment. Anoxia/aerobic conditions are separately created in the proposed MBR by inserting baffles inside of the membrane chamber and consequently simultaneous nitrification/denitriication can be carried out. The technology established in this study can easily be applied to almost all of existing MBR's. Pilot-scale experiment to examine performance of the proposed MBR was carried out at an existing municipal wastewater treatment plant. Inserting baffles inside the membrane chamber actually increased removal of nitrogen by 30%.
In order to evaluate the reclaimed water quality, new method for detecting the indicator microorganisms. Molecular microbiological procedures such as T-RFLP and Real-Time PCR areused to detect the both bacteria. We can distinguish their original among human, cow and pig. We have successfully applied the new method in Toyohira River basin. Ortho-phosphate ion in aqueous solution could be effectively trapped in the zirconium sulfate-surfactant micelle mesostructure (ZS). The reaction proceeded through anion exchange between HSO_4-and OH-in ZS and HPO_3-. Maximum sorption capacity of ZS for HPO3-was330 μmol/gZS. This value is 1.6 times higher than the existing best sorbent. The microbial community structure of a pilot-scale conventional membrane bioreactor (CMBR), hybrid MBR (HMBR) and a full-scale activated sludge (AS) process, treating the same municipal wastewater, were analyzed by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and fluorescence in situ hybridization (FISH) techniques. Both techniques demonstrated that the HMBR supported a significantly different microbial community structure comparing with the CMBR and with that of a full-scale AS process. FISH analysis revealed also that the population of Chloroflexi bacteria (formerly known as green nonsulfur bacteria), in the CMBR was four times greater than the HMBR and two times greater than the AS process.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), HOKKAIDO UNIVERSITY, 14205077

水中溶存有機物の分画・評価　　　　　　　　　　　　　　　
科学研究費補助金
2000 - 2004
Competitive research funding

膜ファウリング機構に関する研究　　　　　　　　　　　　　　　
科学研究費補助金
2000 - 2004
Competitive research funding

Characterization of dissolved natural organic matter　　　　　　　　　　　　　　　
Grant-in-Aid for Scientific Research
2000 - 2004
Competitive research funding

A study on membrane fouling mechanism　　　　　　　　　　　　　　　
Grant-in-Aid for Scientific Research
2000 - 2004
Competitive research funding

Development of Effective Cleaning and Pre-treatment for Membrane Filtration
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
2000 - 2001
WATANABE Yoshimasa, KIMURA Katsuki
Effects of coagulation/sedimentation as a pretreatment on the dead-end ultafiltration(UF) membrane was studied in terms of membrane fouling and removal efficiency of natural dissolved organic carbon, using Chitose River water. Two types of experimental runs were carried out. One was bench scale membrane filtration with Jar-test and the other was continuous membrane filtration equipped with jet mixed separator as a unit of coagulation/sedimentation. In the bench scale experiment, effects of coagulant dosage, pH and operating pressure on membrane fouling and removal efficiency of natural dissolved organic matter were investigated. In the continuous membrane filtration experiment, we also investigated the reduction of membrane fouling and the removal efficiency of natural dissolved organic matter. Coagulation/sedimentation prior to membrane filtration process increased the removal efficiency of natural dissolved organic matter and improved the membrane filterability.
We investigated the effects of physical cleaning on the UF membrane fouling in dead-end and outside-inside mode operation under a constant flux. By the air-scrubbing combined with the back washing, the irreversible cake resistance was drastically decreased, comparing with the back washing only. By monitoring the increase in trans-membrane pressure and analyzing the quality of wastewater caused by physical cleaning, it may be explained that the high molecular weight humic substances and suspended particles removed by membrane were effectively lifted and sheared by air-scrubbing. From the experimental results using physical cleaning with different times of air-scrubbing and back washing, and air-scrubbing intensity, it was found that the longer the air-scrubbing and back washing and the stronger the air-scrubbing, the higher the cleaning effect. But there exists the optimum condition of physical cleaning.
For the control of membrane fouling and improvement of water quality, ozoneation process was used as a pretreatment of microfiltration(MF). Effect of ozone dosage and residual ozone in MF permeate were investigated in terms of membrane fouling and removal efficiency of organic and inorganic matter. Removal efficiency of humic substances in case of pre-ozonation was 1.5-2.0 times higher compared to the case of direct filtration of Chitose river water. But, the removal of TOC in the case of pre-ozonation was somewhat lower than the case of direct filtration of Chitose river water. In case of ozone oxidation followed by air-scrubbing and ozonation alone, removal efficiency of manganese are about 90 %, 50 %, respectively. AOC in case of pre-ozonation was 2.5-8.2 times higher compared with the case of direct filtration of Chitose river water. Pre-ozonation improved the membrane filterability. Especially, when residual ozone exists in permeate, high permeate flux and low operation pressure were achieved in constant pressure mode and constant flux mode., respectively. The reasons of improved of membrane filterabilty by using pre-ozonation may be considered as follows : Firstly, degradation of high molecular weight organic matter, mainly humic substances. Secondly, the improvement of physical cleaning effect against organic and inorganic matter accumulated in the membrane.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 12450210

原水水質に対応した合理的膜選択による膜閉塞制御に関する研究
科学研究費助成事業 奨励研究(A)
2000 - 2001
木村 克輝
本年度は、有機物濃度の高い水道水源(江別市千歳川表流水)および有機物濃度の低い水道水源(札幌市豊平川表流水)を対象として、三次元励起・蛍光スペクトル(EEMs)、各種樹脂を用いるLeenheerの方法による溶存有機物のキャラクタリゼーションを行い、両者の関係を考察した。この結果、比較的短時間で得ることのできるEEMsから、Leenheerの方法による有機物の分画結果を予測しうることがわかった。並行して千歳川表流水、豊平川表流水それぞれを用いたパイロットスケール膜ろ過実験を実浄水場において行い、長期間にわたり実験を継続することによって膜を閉塞させた。これらの膜の一部分を採取し、膜を閉塞させた有機成分を酸・アルカリなどの各種薬品により抽出するとともに、抽出前後の膜透過性能の変化を小型膜ろ過モジュールによって評価した。薬品によって抽出された成分のEEMsを検討することによって、溶存有機物中のどのような画分が膜閉塞、特に不可逆的な膜閉塞に深く関与しているかを検討した。この結果、不可逆的な膜閉塞は主に疎水的酸性成分によって引き起こされていることが示唆された。強アルカリを用いて有機成分の抽出を行う際には、膜本体からの親水性成分の漏出が無視できない量となった、この部分の影響をどのように除去しうるかが課題として残されている。今後はより広範な範囲の水・膜の組み合わせについて本研究で開発した膜閉塞成分検討法を適用してゆくことで、原水水質に対応した合理的膜選択手法の確立に近づくことができるものと考えられる。
日本学術振興会, 奨励研究(A), 北海道大学, 12750489

メンブレンバイオリアクターの最適化　　　　　　　　　　　　　　　
ＪＳＴ戦略的創造研究推進制度（研究チーム型） （戦略的基礎研究推進事業：ＣＲＥＳＴ）
1997 - 2001
Competitive research funding

Optimization of membrane bioreactor　　　　　　　　　　　　　　　
JST Basic Research Programs (Core Research for Evolutional Science and Technology :CREST)
1997 - 2001
Competitive research funding

Hybrid Wastewater Treatment System for Water Reuse and P Recovery
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
1996 - 1998
WATANABE Yoshimasa, KIMURA Katsuki, OKABE Satoshi, TADANO Toshiaki
1) This research dealt with the coagulation characteristics of polysilicato-iron (PSI), a new inorganic polymer coagulant, when it was applied to coagulate algae and municipal wastewater. The experimental results obtained with jar tests indicate that PSI was more effective than PAC and AS in coagulating and separating Microcystis sp. and Stephanodiscus sp. When the jet mixed separator (JMS) was used as a unit of simultaneous flocculation and sedimentation, PSI had almost the same effect as PAC at the same dosage of 5 mg/l Al or Fe in coagulating municipal wastewater.
2) This research has developed a novel membrane process in which ammonia oxidizers are fixed en the membrane disk. In this study, the characteristics of the membrane filtration resistance was investigated The results derived from this study were summarized as follows : (1) The magnitude of the filtration resistance was strongly affected by the initial inoculation. (2) The filtration resistance due to the accumulate cake was found to be dominant. (3) Increasing the disk rotational speed was found to be efficient for removing cake. About 3000 hours of the operation could be continued by only implementing this simple cleaning method every 500 hours. (4) Filtration resistance excluding the cake resistance seemed to be caused by humic substances and extracellular polymeric substance produced by biomass.
3) The density of ammonia-oxidizers which formed dense cell cluster was about 5 times higher in the innermost biofilm than in the middle and surface of the biofilm. Due to the presence of ammonia-oxidizers throughout the biofilm, ammonium oxidation zone was expanded with increasing in oxygen penetration depth, which consequently resulted in an increase of the overall ammonium flux into the biofilm. Specific ammonium oxidation rate was dependent upon the density of ammonia-oxidizers.
4) Phosphorus deficiency induces the synthesis of acid phosphatases in roots of lupin and other plant species. In this study we examined the induction of secretory acid phosphatase (S-Apase) at both the molecular and cellular levels. Lupin plants had increased levels of total acid phosphatase activity within two to five days after P was withered and levels approximately doubled by 15 days. Lateral roots and not main taproots were responsible for this increase in acid phosphatase activity. Immunoblot analysis using antibodies raised against a purified S-Apase showed that the synthesis of this protein was induced as early as 2 days in the P deficient treatment and that levels dramatically increased by 15 days. In contrast, no immunoreactive polypeptide was evident from crude extracts prepared from root tissues of-P treated plants.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), HOKKAIDO UNIVERSITY, 08458160

膜を用いた新しい用廃水処理システムの開発　　　　　　　　　　　　　　　
Competitive research funding

医薬品の水処理過程中における動態　　　　　　　　　　　　　　　
Competitive research funding

Development of a novel water /wastewater system using membrane technology　　　　　　　　　　　　　　　
Competitive research funding