Experimental study of RO membrane organic fouling for wastewater reclamation

EXPERIMENTAL STUDY OF RO MEMBRANE ORGANIC FOULING FOR WASTEWATER RECLAMATION ZHAO YAN NATIONAL UNIVERSITY OF SINGAPORE 2009 EXPERIMENTAL STUDY OF RO MEMBRANE ORGANIC FOULING FOR WASTEWATER RECLAMATION ZHAO YAN (M.E., Harbin Institute of Technology, Harbin, P.R. China) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CIVIL ENGINEERING FACULTY OF ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2009 ACKNOWLEGEMENT ACKNOWLEDGEMENT I would like to take this opportunity to acknowledge and thank all those who have helped me along the way. First and foremost, I would like to express sincere gratitude to my supervisor, Professor Say Leong ONG and co-supervisor Associate Professor Lianfa SONG, for their patient guidance and critical comments throughout the course of this study. Without their encouragement and support, the work would not have been completed. I would also like to thank my thesis committee members Associate Professor Jiangyong HU and Assistant Professor How Yong NG for their valuable advice and time to serve in my committee. I owe my special thanks to the staff in Center of Water Research, Mr. Tan Eng Hin, Michael, and Mr. S.G. Chandrasegaran, Ms. Lee Leng Leng and Ms. Tan Xiaolan for their kind assistance and help in handling miscellaneous laboratory matters. Appreciation also goes to Mr Chua Seng Chye and Mr Lee Siew Chor for their kind coordination during sample collection at Bedok NEWater Plant. Thank all the former and current members of our research group for their invaluable discussions, help, and friendship. And also thank Quek Li Wen and Tan Chye Leong for their assistance in part of this work during their Final Year Project. I wish to express my special appreciation to National University of Singapore for providing me the Ph.D scholarship and many opportunities towards my academic and professional pursuit. i ACKNOWLEGEMENT Last but not the least, I extend my heartfelt gratitude to my family and my fiancé, for their everlasting love and support throughout these years. Without them, I would not have been here today. ii TABLE OF CONTENTS TABLE OF CONTENTS ACKNOWLEDGEMENT . i SUMMARY vi TABLE OF CONTENTS iii LIST OF TABLES . iii LIST OF FIGURES x LIST OF ABBREVIATIONS vii CHAPTER ONE INTRODUCTION 1.1 Need for advanced municipal wastewater reclamation technologies 1.2 Limitations of RO membrane process for wastewater reclamation . 1.3 Research needs . 10 1.4 Research objectives 17 1.5 Organization of thesis 18 CHAPTER TWO LITERATURE REVIEW . 20 2.1 Application of RO membrane process for wastewater reclamation 20 2.2 Advantages of RO Process for wastewater reclamation . 26 2.3 Fouling of RO process for wastewater reclamation 28 2.3.1 Definition of fouling 29 2.3.2 Major types of foulants and associated fouling mechanisms . 30 2.3.2.1 Colloidal fouling . 30 2.3.2.2 Scaling . 34 2.3.2.3 Biofouling . 35 2.3.2.4 Organic fouling . 39 2.3.3 Fouling potential assessment and foulant characterization 39 2.4 Organic fouling of RO process used in wastewater reclamation . 48 2.4.1 Effect of composition and characteristics of EfOM . 49 2.4.1.1 Composition and characteristics of NOM . 49 2.4.1.2 Composition and characteristics of SMP or EPS 55 2.4.2 Effect of membrane structure and surface properties 63 2.4.3 Effect of hydrodynamic parameters . 66 2.4.4 Effect of solution chemistry . 68 2.5 Fouling control strategies and associated costs . 71 iii TABLE OF CONTENTS CHAPTER THREE MATERIALS AND METHODS 77 3.1 Materials . 77 3.1.1 Feed water 77 3.1.2 RO membrane 80 3.2 Isolation and fractionation of EfOM 80 3.3 EPS extraction 83 3.4 EfOM characterization . 84 3.4.1 Apparent MWD . 84 3.4.2 Non-purgable organic carbon and specific ultraviolet absorbance measurement . 84 3.4.3 Polysaccharide and protein concentration measurement . 85 3.5 Laboratory-scale cross-flow membrane filtration unit 87 3.6 Experimental protocols of RO fouling experiments . 88 3.6.1 Phase I: Fouling behavior observation and foulant characterization . 88 3.6.2 Phase II: Fouling potential investigation of individual EfOM fractions . 90 3.6.3 Assessment of clean water flux reversibility . 91 3.6.4 Feed water fouling potential assessment 90 3.7 Membrane foulant characterization . 93 3.7.1 Membrane morphology and elemental composition analysis 93 3.7.2 Foulant organic ratio quantification . 93 3.7.3 Foulant organic functional group analysis . 94 3.7.4 Foulant inorganic composition analysis . 95 3.8 Membrane surface chemistry characterization 95 3.8.1 Membrane surface charge measurement 95 3.8.2 Membrane contact angle measurement 96 CHAPTER FOUR RESULTS AND DISCUSSIONS 97 4.1 Part – Fouling behavior and foulant characteristics of RO membranes for treated secondary effluent reclamation 97 4.1.1 Feed water characteristics 98 4.1.2 Fouling behavior with increasing permeate recovery 100 4.1.3 Fouling layer characteristics 106 4.1.3.1 Organic composition of fouling layer . 106 4.1.3.2 Inorganic Composition of Fouling Layer 110 iv TABLE OF CONTENTS 4.1.3.3 Changes in membrane surface morphology 113 4.1.3.4 Changes in membrane surface chemistry 115 4.1.4 Fouling Potential with Increasing Recovery 116 4.1.5 Summary – Part . 118 4.2 Part – Fouling of RO membranes by EfOM: relating major components of EfOM to their characteristic fouling behaviors . 119 4.2.1 Distribution, composition and characteristics of EfOM fractions . 120 4.2.2 Membrane fouling by various EfOM fractions 125 4.2.2.1 Flux decline rate and extent 125 4.2.1.2 The influence of calcium ions . 128 4.2.3 Mass of fouling layer deposited . 130 4.2.4 Affinity of fouling layer with the membrane . 132 4.2.5 Summary – Part . 134 CHAPTER FIVE CONCLUSIONS AND RECOMMENDATIONS . 136 5.1 Conclusions 136 5.2 Recommendations for future studies 138 REFERENCES 142 Appendix A Publications and conference papers from this project 157 v SUMMARY SUMMARY Despite considerable research effort undertaken by the scientific community, membrane fouling still remains as a major technical hurdle that needs to be addressed to enhance the cost-effectiveness of reverse osmosis (RO) systems for wastewater reclamation. The residual organic matter in treated secondary effluent, known as effluent organic matter (EfOM), has been implicated as an important RO foulant. However, our current understanding of this category of foulant is still very limited towards its efficient control. This study first investigated the fouling behaviors of wastewater reclamation RO membranes fed with ultrafiltration (UF) prefiltered secondary effluent from a tropical area wastewater reclamation plant at two operationally important permeate recovery levels. The associated fouling mechanisms were delineated with the aid of microscopic analysis of the fouling layer characteristics. There was a remarkable correlation between the different fouling behaviors observed and the characteristics of fouling layers developed. Organic fouling by carbohydrates and protein-like matters was found to be primarily responsible for the flux loss observed at the first-stage RO operating with a recovery of 55%. At the second-stage RO with a higher recovery of 70%, the greatly enhanced deposition of organic foulants together with inorganic precipitation led to the formation of a thicker and irreversible composite fouling layer. Calcium phosphate and calcium carbonate were found to be the major precipitates at this recovery. The enhanced organic vi SUMMARY deposition along with increasing permeate recovery was also corroborated by the significantly increasing organic fouling potential measured after inhibition of scaling. This study clearly demonstrated the need for more effective organic fouling control at the second-stage RO. As EfOM is a mixture of structurally complex poorly-defined organic compounds, this study further investigated the interactions between fractional components of EfOM and RO membranes and attempted to identify the most influential fraction(s) or physico-chemical properties governing the fouling process. Organic fouling behavior of EfOM was observed to closely correlate to the composition and physico-chemical properties of its components. Both hydrophilic in nature and strongly negatively-charged, the hydrophilic acid fraction resulted in minimal flux decline. Regardless of the presence of calcium ions, the hydrophilic neutral fraction, mainly composed of small size carbohydrates, resulted in the highest flux decline and exhibited highest affinity towards the membrane. EPS biopolymers, to which great importance has been associated with regard to causing RO organic fouling, resulted in less fouling than hydrophilic carbohydrates. Although EPS biopolymers tended to accumulate on the membrane in much higher quantities, the cake layer formed was found to constitute a much lower resistance towards filtration and have a much lower membrane affinity, probably due to their large molecular sizes. Therefore, it should be expected to impose a weaker fouling threat for longterm RO operation. Overall, this study suggested that fouling phenomenon of RO membranes vii SUMMARY treating wastewater might be mitigated by reducing the concentrations of small hydrophilic neutral organics. The required changes in the composition or physico-chemical properties of EfOM might be accomplished by implementing pertinent pretreatment or modifying operational conditions of the preceding biological treatment. viii REFERENCES REFERENCES Abdel-Jawad, M., S. Ebrahim, M. A1-Tabtabaei, and S. Al-Shammari (1999) Advanced technologies for municipal wastewater purification: technical and economic assessment. Desalination, 124, 251-261. Abdessemed, D., G. Nezzal, and R. Ben Aim (2000) Coagulation-adsorptionultrafiltration for wastewater treatment and reuse. Desalination, 131, 307-314. Afonso, M.D., G. Hagmeyer and R. Gimbel (2001) Streaming potential measurements to assess the variation of nanofiltration membranes surface charge with the concentration of salt solutions. Sep. Purif. Technol., 22-23, 529-541. Aiken, G.R. (1984) Evaluation of ultrafiltration for determining molecular weight of fulvic acid. Environ. Sci. Technol., 18, 978-981. Aiken, G.R. and R.L. Malcolm (1987) Molecular weight of aquatic fulvic acids by vapor pressure osmometry. Geochim. Cosmochim. Acta., 51, 21772184. Aiken, G.R., D.M. McKnight, K.A. Thorn and E.M. Thurman (1992) Isolation of hydrophilic organic acids from water using nonionic macroporous resins. Org. Geochem., 18(4), 567-573. Alexander, K., S. Alt, E. Owens, M. Patel and L. McGovern (2003) Low fouling reverse osmosis membranes evidence to the contrary on microfiltered secondary effluent. In Proc. 2003 AWWA Memb. Technology Conf., Atlanta, GA. Al-Malack, M.H. and G. K. Anderson (1996) Coagulation-crossflow microfiltration of domestic wastewater. J. Membr. Sci., 121, 59-65. Aloson, E., A. Santos, G.J. Solis and P. Riesco (1998) On the feasibility of urban wastewater tertiary treatment by membranes; A comparative assessment. Desalination, 117, 49-60. Altman, M., R. Semiat and D. Hasson (1999) Removal of organic foulants from feed waters by dynamic membranes. Desalination, 125, 65-75. Amy, G.L., C.W.J. Bryant and M. Belyani (1987) Molecular weight distributions of soluble organic matter in various secondary and tertiary effluents. Water Sci. Technol., 19, 529-538. Ang, W.S. and M. Elimelech (2008) Fatty acid fouling of reverse osmosis membranes: implications for wastewater reclamation. Wat. Res., 42, 43934403. Ang, W.S. and M. Elimelech (2007) Protein (BSA) Fouling of Reverse Osmosis Membranes: implications for Wastewater Reclamation. J. Membr. Sci., 296, 83-92. 142 REFERENCES Ang, W.S., S. Lee and M. Elimelech (2006) Chemical and physical aspects of cleaning of organic-fouled reverse osmosis membranes. J. Membr. Sci., 272, 198-210. Aoki, S., Y. Fuse, E. Yamada (2004) Determination of humic substances and other dissolved organic matter and their effects on the increase of COD in Lake Biwa. Anal. Sci., 20, 159-164. Arora, M.L. (1983) Fouling of RO membranes in wastewater applications. Desalination. 48, 299-319. AWWA Membrane Technology Research Committee (2005) Committee report: recent advances and research in membrane fouling. J. Am. Water Works Assoc., 97 (8), 79-89. Bailey, D.A., K. Jones and C. Mitchell (1974) The reclamation of water from sewage effluents by reverse osmosis. Wat. Pollut. Control., 73, 353-364. Barker, D.J. and D.C. Stuckey (1999) A review of soluble microbial products (SMP) in wastewater treatment systems. Water Res., 33, 3063-3082. Barker, D.J., S.M.L. Salvi, A.A.M. Langenhoff, and D.C. Stuckey (2000) Soluble microbial products in ABR treating low-strength wastewater. J. Env. Eng., 126, 239-249. Bartels, C.R., M. Wilf, K. Andes and J. Iong (2005) Design consideration for wastewater treatment by reverse osmosis. Water Sci. Technol., 51, 473-482. Beckett, R., Z. Jue and J.C. Giddings (1987) Determination of molecular weight distribution of fulvic and humic acids using flow field-flow fractionation. Environ. Sci. Technol., 21, 289-295. Bender M.E., Matson W.R. and R.A. Jordan (1970) On the significance of metal complexing agents in secondary sewage effluents. Environ. Sci. Technol., 4(6), 520-521. Bitton, G.L. (1994) Wastewater Microbiology. Weily-Liss. New York. Boerlage, S.F.E., M.D. Kennedey, G.J. Witkamp, J.P. van der Hoek and J.C. Schippers (1997) Prediction of BaSO4 solubility in reverse osmosis systems. In Proc. AWWA Membrane Technology Conference, New Orleans, 1997. Boerlage, S.F.E., M.D. Kennedy, M.R. Dickson, D.E.Y. El-Hodali and J.C. Schippers (2002) The modified fouling index using ultrafiltration membranes (MFI-UF): characterization, filtration mechanisms and proposed reference membrane, J. Membr. Sci., 197, 1-21. Bourgeous, K.N., J.L. Darby and G. Jacangelo (2001) Ultrafiltration of wastewater: effects of particles, mode of operation, and backwash effectiveness, Wat. Res., 35, 77-79. Braghetta, A., F.A. DiGiano and W.P. Ball (1998) NOM accumulation at NF membrane surface: impact of chemistry and shear. J. Environ. Eng. ASCE, 124, 1087-1098. Brown, M.J. and J.N. Lester (1980) Comparison of bacterial extracellular polymer extraction methods, Appl. Environ. Microbiol., 40, 179-185. 143 REFERENCES Buffle, J., P. Deladoey and W. Haerdi (1988) The use of ultrafiltraion for the speration and fractionation of organic ligands in freshwaters. Anal. Chim. Acta, 101, 339-357. Carroll, T., S. King, S.R. Gray, B.A. Bolto, and N.A. Booker (2000) The fouling of microfiltration membranes by NOM after coagulation treatment. Water Res., 34, 2861–2868. Chang, T.C., S.J. You and S.H. Chuang (2007) Evaluation for the Reclamation Potential of High-Tech Industrial Wastewater Effluent Treated with Different Membrane Processes. Environ. Eng. Sci., 24, 762-768. Chapman, H., S. Vigneswaran, H.H. Ngo, S. Dyer, and R. Ben Aim (2002) Pre-flocculation of secondary treated wastewater in enhancing the performance of microfiltration. Desalination, 146, 367-372. Chellam, S., J.G. Jacangelo, and T.P. Bonacquisti (1998) Modeling and experimental verification of pilot plant scale hollow fiber, direct flow microfiltration with periodic backwashing, Environ. Sci & Techno., 32, 75-81. Childress, A.E. and M. Elimelech (1996) Effect of solution chemistry on the surface charge of polymeric reverse osmosis and nanofiltration membranes. J. Membr. Sci., 119, 253-268. Childress, A.E. and M. Elimelech (2000) Relating nanofiltration membrane performance to membrane charge (electrokinetic) characteristics. Environ. Sci. Technol., 34, 3710-3716. Chin, Y.P., G. Aiken and E. Oloughlin (1994) Molecular weight, polydispersity, and spectroscopic properties of aquatic humic substances. Environ. Sci. Technol., 28, 11, 1853-1858. Cho, J.; Amy, G.; Pellegrino, J. and Yoon, Y. (1998) Characterization of clean and natural organic matter (NOM) fouled NF and UF membranes, and foulants characterization. Desalination, 118, 101-108. Cho, J., G.L. Amy and J. Pellegrino (1999) Membrane filtration of natural organic matter: initial comparison of rejection and flux decline characteristics with ultrafiltration and nanofiltration membranes. Water Res., 33, 2517-2526. Chudoba, J. (1985) Inhibitory effect of refractory organic compounds produced by activated sludge microorganisms on microbial activity and flocculation. Wat. Res., 19, 197-200. Clarke, R. (1999) Global Environment Outlook 2000. UNEP, Earthscan Publications. Crozes, G., C. Anselme, and J. Mallevialle (1993) Effect of adsorption of organic matter on fouling ultrafiltration membranes. J. Membr. Sci., 84, 61-77. Crozes, G.F., J.G. Jacangelo, C. Anselme and J.M. Laine (1997) Impact of ultrafiltration operating conditions on membrane irreversible fouling. J. Membr. Sci., 124, 63-76. Daigger, G.T. and Grady C.P.L.J. (1977) A model for the bio-oxidation process based on product formation concepts. Wat. Res., 11, 1049-1057. 144 REFERENCES Darton, T., U. Annunziata, F. del Vigo Pisano and S. Gallego (2004) Membrane autopsy helps to provide solutions to operational problems. Desalination, 167, 239-245. Decarolis, J. S. Hong and J. Taylor (2001) Fouling behavior of a pilot scale inside-out hollow fiber UF membrane during dead-end filtration of tertiary wastewater. J. Membr. Sci., 191, 165-178. del Pino, M.P. and B. Durham (1999) Wastewater reuse through dualmembrane processes: opportunities for sustainable water resources. Desalination, 124, 271-277. Dignac, M.F., P. Ginestet, D. Rybacki, A. Bruchet, V. Urbain and P. Scribe (2000) Fate of wastewater organic pollution during activated sludge treatment: nature of residual organic matter. Wat. Res., 34, 4185-4194. Ding, W.H., Y. Fujita, R. Aeschimann and M. Reinhard (1996) Identification of organic residues in tertiary effluents by GC/EI-MS, GC/CI-MS and GC/TSQ-MS. Fresenius J Anal. Chem., 354, 48-55. Drewes, J.E. and P. Fox (2000) Effect of drinking water sources on reclaimed water quality in water reuse systems. Water Environ. Res., 72, 353-362. Drewes, J.E., M. Reinhard and P. Fox (2003) Comparing microfiltrationreverse osmosis and soil-aquifer treatment for indirect potable reuse of water. Water Res., 37, 3612-3621. Dudley, L., F. Vigo Pisano and M. Fazel. (2000) Optimizing membrane performance – practical experiences. Membr. Technol., 12, 5-8. Duois, M., K.A. Gilles, J.K. Hamilton, P.A. Rebers and F. Smith (1956) Calorimetric method for determination of sugars and related substances. Anal. Chem., 28, 350-356. Durham, B. (1997) Membrane pretreatment of reverse osmosis- Long time experience on difficult waters. Desalination, 110, 49-58. Durham, B., M.M. Bourbigot and T. Pankratz (2001) Membranes as pretreatment to desalination in wastewater reuse: operating experience in the municipal and industrial sectors. Desalination, 138, 83-90. Durham, B., M.M. Bourbigot and T. Pankratz. (2002) Membranes as pretreatment to desalination in wastewater reuse. Membr. Technol., 2002(3), 8-12. Everest, W.R., I.C. Watson and D. Maclain (1998) Groundwater reclamation by innovative desalting in Orange County, California. Desalination, 117, 197202. Fan, L.H., J.L. Harris, F.A. Rodick and N.A. Booker (2001) Influence of the characteristics of natural organic matter on the fouling of microfiltration membranes. Wat. Res., 18, 4455-4463. Fane, A.G. and S.A. Fane (2005) The role of membrane technology in sustainable decentralized wastewater systems. Water Sci. Technol., 51(10), 317-325. 145 REFERENCES Flemming, H.C., G. Schaule, T. Griebe, J. Schmitt and A. Tamachkiarowa (1997) Biofouling- the Achilles heel of membrane processes. Desalination, 113, 215-225. Flemming, H.C., G. Schaule and H.F. Ridgway (2003) Living with biofilms elements of an integrated anti-fouling strategy. In Proc. of International Membrane Science and Technology Conference (IMSTEC’03), Sydney, Australia Frolund, B., T. Griebe and P.H. Nielsen (1995) Enzymatic activity in the activated-sludge floc matrix. Appl. Microbiol. Biotechnol., 43, 755-761. Gabelich, C.J., K.P. Ishida, F.W. Gerringer, R. Evangelista, M. Kalyan and I.H. Suffet (2006) Control of residual aluminum from conventional treatment to improve reverse osmosis performance. Desalination, 190, 147-160. Gabelich, C.J., T.I. Yun, J.F. Green, I.H. Suffet and W.R. Chen (2002) Evaluation of precipitative fouling for Colorado River water desalination using reverse osmosis. U.S. Department of the Interior, Bureau of Reclamation, Water Treatment Engineering and Research Group. Gander, M., B. Jefferson and S. Judd (2000a) Aerobic MBRs for domestic wastewater treatment: a review with cost considerations. Sep. Purif. Technol., 18, 119-130. Gander, M.A., B. Jefferson and S.J. Judd (2000b) Membrane bioreactors for use in small wastewater treatment plants: Membrane materials and effluent quality. Water Sci. Technol., 41(1), 205-211. Gaudy, Jr. A.F. and T.R. Blachly (1985) A study of the biodegradability of residual COD. J. WPCF, 57(4), 332-338. Gillerman, L., A. Bick, N. Buriakovsky and G. Oron. (2006) Secondary wastewater polishing with ultrafiltration membranes for unrestricted reuse: fouling and flushing model. Environ. Sci. Technol., 40, 6830-6836. Golomb A. and F. Besik (1970) Reverse osmosis – a review of its application to waste treatment. Wat. Sewage Wks., 117, 81-89. Griebe, T. and H. C. Flemming (1998) Biocide-free antifouling strategy to protect RO membranes from biofouling. Desalination, 118, 153-156. Gwon, E.M., M.J. Yu, H.K. Oh and Y. H. Ylee (2003) Fouling characteristics of NF and RO operated for removal of dissolved matter from groundwater. Water Res., 37, 2989-2997. Hejzlar, J. and J. Chudoba (1986) Microbial polymers in the aquatic environment-II Isolation from biologically non-purified and purified municipal waste water and analysis. Wat. Res. 10, 1217-1221. Her, N., G, Amy and C. Jarusutthirak (2000) Seasonal variations of nanofiltration foulants: identification and control. Desalination, 132, 143-160. Her, N., G. Amy, H.R. Park, and M. Song (2004) Characterizing algogenic organic matter (AOM) and evaluating associated NF membrane fouling. Water Res., 38, 1427-1438. Hinrichsen, D. (2007) Freshwater: lifeblood of the planet. http://www.peopleandplanet.net/ 146 REFERENCES Hinrichsen, D., B. Robey and U.D. Upadhyay (1998) Solutions for a watershort world. http://www.infoforhealth.org/pr/m14/m14print.shtml Hong, S. and M. Elimelech (1997) Chemical and physical aspects of natural organic matter (NOM) fouling of nanofiltration membranes. J. Membr. Sci., 132, 159-181. Howe, K.J. and M.M. Clark (2002) Fouling of microfiltration and ultrafiltration membranes by natural waters. Environ. Sci. Technol., 36, 35713576. Howell, J.A. (1995) Sub-critical flux operation. J. Membr. Sci. 107, 165-171. Imai, A., T. Fukushima, K. Matsushige, Y.H. Kim and K. Choi (2002) Characterization of dissolved organic matter in effluents from wastewater treatment plants. Wat. Res. 36, 859-870. Into, M., A.S. Jonsson and G. Lengden (2004) Reuse of industrial wastewater following treatment with reverse osmosis. J. Membrane Sci., 242, 21-25. Jacangelo, J.G., S.S. Adham and J.M. Laine (1995) Mechanisms of Cryptosporidium, Giardia, and MS2 virus removal by MF and UF. J.AWWA, 87, 107-121. Jarusutthirak, C., G. Amy and J.P. Croue (2002) Fouling characteristics of wastewater effluent organic matter (EfOM) isolates on NF and UF membranes. Desalination, 145, 247-255. Jarusutthirak, C., G. Amy and J.P. Croue (2006) Role of soluble microbial products (SMP) in membrane fouling and flux decline. Environ. Sci. Technol., 40 (3), 969-974. Jermann, D., W. Pronk, S. Meylan and M. Boller (2007) Interplay of different NOM fouling mechanisms during ultrafiltration for drinking water production. Wat. Res., 41, 1713-1722. Jones, K.L. and C.R. O’Melia (2000) Protein and humic acid adsorption onto hydrophilic membrane surfaces: effects of pH and ionic strength. J. Membr. Sci., 165, 31-46. Jucker, C. and M.M. Clark (1994) Adsorption of aquatic humic substances on hydrophobic ultrafiltration membranes. J. Membr. Sci., 97, 37-52. Kaiya, Y., Y. Itoh, K. Fujita and S. Takizawa (1996) Study on fouling materials in the membrane treatment processes for potable water, Desalination, 106, 71-77. Khirani, S., R.B. Aim and M.H. Manero (2006) Improving the measurement of the modified fouling index using nanofiltration membranes (NF-MFI), Desalination, 191, 1-7. Kim, S.H., S.Y. Moon, C.H. Yoon, S.K. Yim and J.W. Cho (2005) Role of coagulation in membrane filtration of wastewater for reuse. Desalination, 173, 301-307. Kimura, K., G. Amy, J.E. Drewes, T. Heberer, T. Kim and Y. Watanabe (2003) Rejection of organic micropollutants (disinfection by-products, endocrine disrupting compounds, and pharmaceutically active compounds) by NF/RO membranes. J. Membr. Sci., 227, 113-121. 147 REFERENCES Kimura, K., Y. Hane, Y. Watanabe, G. Amy and N. Ohkuma (2004) Irreversible membrane fouling during ultrafiltration of surface water. Water Res., 38, 3431-3441. Kimura, K., N.Yamato, H. Yamamura and Y. Watanabe (2005) Membrane fouling in pilot-scale membrane bioreactors (MBRs) treating municipal wastewater. Environ. Sci. Technol., 39 (16), 6293-6299. Kohl, H.R., D.E. Bedford, R.A. Bergman and J.C. Lozier (1992) Innovative reverse osmosis pretreatment processes for wastewater reclamation. In Proc. of American Water Works Association Annual Conference, Vancouver, BC. Kohl, H.R., J. Lozier, D. Bedford and B. Fulgham (1993) Evaluating reverse osmosis membrane performance on secondary effluent pretreated by membrane microfilters, In Proc. of American Water Works Association Annual Conference, San Antonio, TX. Kulovaara, M., S. Metsamuuronen and M. Nystrom (1999) Effects of aquatic humic substances on a hydrophobic ultrafiltration membrane. Chemosphere, 38, 3485-3496. Kuo, W.C. and G.F. Parkin (1996) Characterization of soluble microbial products from anaerobic treatment by molecular weight distribution and nickel-chelating properties. Water Res., 30(4), 915-922. Laine, J.M., J.P. Jagstrom, M.M. Clark and J. Mallevialle (1989) Effects of ultrafiltration membrane composition. J. AWWA, 11, 61-67. Laspidou, C.S. and B.E. Rittmann (2002) A unified theory for extracellular polymeric substances, soluble microbial products, and active and inert biomass. Wat. Res., 36 2711-2720. Lawrence, P., S. Adham and L. Barrott (2002) Ensuring water re-use projects succeed-institutional and technical issues for treated water re-use. Desalination, 152, 291-298. Lazarova, V., B. Levine, J. Sack, G. Cirelli, P. Jeffrey, H. Muntau, M. Salgot and F. Brissaud (2001) Role of water reuse for enhancing integrated water management in Europe and Mediterranean countries. Water Sci. Technol., 43(10), 25-33. Le Gouellec, Y.A. and M. Elimelech (2002) Calcium sulfate (gypsum) scaling in nanofiltration of agricultural drainage water, J. Membr. Sci., 205, 279-291. Lee, S. and M. Elimelech (2006) Relating organic fouling of reverse osmosis membranes to intermolecular adhesion forces. Environ. Sci. Technol., 40, 980987. Lee, S., W.S. Ang and M. Elimelech (2006) Fouling of reverse osmosis membranes by hydrophilic organic matter: implications for water reuse. Desalination, 187, 313-321. Lee, W. S. Kang and H. Shin (2003) Sludge characteristics and their contribution to microfiltration in submerged membrane bioreactors, J. Membr. Sci., 216, 217-227. 148 REFERENCES Leenheer, J.A. (1981) Comprehensive approach to the preparative isolation and fractionation of dissolved organic carbon from natural waters and wastewaters. Environ. Sci. Technol., 15, 578-587. Leenheer, J.A., E.R. Colleen, L.B. Barber, R.A. Schroeder, R. Anders and M.L. Davisson (2001) Nature and Chlorine Reactivity of Organic Constituents from Reclaimed Water in Groundwater, Los Angeles County, California. Environ. Sci. Technol., 35, 3869-3876. Leenheer, J.A. and J.P. Croue (2003) Characterizing aquatic dissolved organic matter. Environ. Sci. Technol., 37, 18A-26A. Leslie, G.L., W.R. Dunivin, P. Gabillet, S.R. Conklin, W. Mills, and R.G. Sudak (1996) Pilot testing of microfiltration and ultrafiltration upstream of reverse osmosis during reclamation of municipal wastewater. In Proc. of American Desalting Association 1996 Biennial Conference, Monterey, CA. Li, Q.L. and M. Elimelech (2004) Organic fouling and chemical cleaning of nanofiltration membranes: measurements and mechanisms, Environ. Sci. Technol., 38, 4683-4693. Lin, C.F., S.H. Liu, and O.J. Hao (2000) Effect of functional groups of humic substances on UF performance. Wat. Res. 35, 2395-2402. Lin, C.F., T.Y. Lin, and O.J. Hao (1999) Ultrafiltration processes for removing humic substances: effect of molecular weight fractions and PAC pretreatment. Water Res., 33, 1252-1264. Lin, C.F., T.Y. Lin, and O.J. Hao (2000) Effects of humic substance characteristics on UF performance. Water Res. 34, 1097-1106. Lindau, J. and A.S. Jonsson (1994) Cleaning of ultrafiltratio membranes after treatment of oily waste water. J. Membr. Sci., 87, 71-78. Lodge, B. S.J. Judd and A.J. Smith (2004) Characterization of dead-end ultrafiltration of biotreated domestic wastewater. J. Membr. Sci. 231, 91-98. Logan, B.E. and Q. Jiang (1990) Molecular size distributions of dissolved organic matter. J. Environ. Eng. ASCE, 116(6), 1046-1062. Lopez-Ramirez, J.A., S. Sahuquillo, D. Sales and J.M. Quiroga (2003) Pretreatment optimization studies for secondary effluent reclamation with reverse osmosis. Water Res. 37, 1177-1184. Lovins, W.A., J.S. Taylor and S.K. Hong (2002) Microorganisms rejection by membrane systems. Environ. Eng. Sci., 19, 453-465. Lowry, O.H., N.J. Rosebrough, A.L. Farr and R.J. Randall (1951) Protein measurement with folin-phenol reagent. J. Biol. Chem., 193, 265-275. Lozier, J. and A. Fernandez (2001) Using a membrane bioreactor/reverse osmosis system for indirect potable reuse. Water Supply, 5–6 (1), 303-313. Maartens A., P. Swart and E.P. Jacobs (1999) Feed-water pretreatment: methods to reduce membrane fouling by natural organic matter. J. Membr. Sci., 163, 51-62. Madaeni S.S., Mohamamdi T. and M.K. Moghadam (2001) Chemical cleaning of reverse osmosis membranes. Desalination, 134, 77-82. 149 REFERENCES Madireddi, K., R.W. Babcock, B. Levine, T.L. Huo, E. Khan, Q.F. Ye, J.B. Neethling, I.H. Suffet and M.K. Stenstrom (1997) Pilot scale wastewater reclamation at Lake Arrowhead, California: An overview. Wat. Environ. Res., 69, 350-362. Mallevialle, J., C. Anselme and O. Marsigny (1989) Effects of humic substances on membrane processes. In: I.H. Suffet, P. MacCarthy (Eds.), Aquatic Humic Substances, Influence on Fate and Treatment of Pollutants, American Chemical Society, Washington, DC, 749-767. Mallevialle, J., P.E. Odendaal and M.R. Wiesner (1996) Water treatment membrane processes. McGraw-Hill, New York. Manka, J. and M. Rebhun (1982) Organic groups and molecular weight distribution in tertiary effluents and renovated waters. Wat. Res., 16, 399-403. Mash, H., P.K. Westerhoff, L.A. Baker, R.A. Nieman and M.L. Nguyen (2004) Dissolved organic matter in Arizona reservoirs: assessment of carbonaceous sources carbonaceous sources. Organic Geochemistry, 35, 831-843. McCuthan, J.W. and J.S. Johnson (1970) Reverse osmosis at Coalinga, California. J. AWWA., 62, 346-353. Mickley, M. (2004) Review of Concentrate Management Options, Mickley & Associates. Mohammadi, T., S.S. Madaeni and M.K. Moghadam (2002) Investigation of membrane fouling. Desalination, 153, 155-160. Moritz, T., S. Benferb, P. Arkib and G. Tomandlb (2001) Investigation of ceramic membrane materials by streaming potential measurements. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 195, 25-33. Namkung, E and B.E. Rittmann (1986) Soluble microbial products (SMP) formation kinetics by biofilms. Wat. Res., 20, 795-806. Namour, Ph. and M.C. Muller (1998) Fractionation of organic matter from wastewater treatment plants before and after a 21-day biodegradation test: a physical-chemical method for measurement of the refractory part of effluents. Water Res., 32, 2224-2231. National Research Council. (1998) Issues in Potable Reuse: The Viability of Augmenting Drinking Water Supplies with Reclaimed Water. National Academy Press, Washington D. C. Neis, U. and A. Tiehm (1997) Particle size analysis in primary and secondary wastewater effluents, Water Sci. Technol., 36(4), 151-158. Ng, H.Y., T.W. Tan and S.L. Ong (2006) Membrane fouling of submerged membrane bioreactors: impact of mean cell retention time and the contributing factors. Envrion. Sci. Technol., 40, 2706-2713. Nghiem, D.L. and A.I. Schäfer (2002) Adsorption and transport of trace contaminant estrone in NF/RO membranes. Environ. Eng. Sci., 19, 441-451. Nghiem, L.D., A.I. Schaefer and M. Elimelech (2004) Removal of natural hormones by nanofiltration membranes: measurement, modeling, and mechanisms, Environ. Sci. Technol., 38, 1888–1896. 150 REFERENCES Nilson, J. A. and F.A. DiGiano (1996) Influence of NOM composition on nanofiltration. J. AWWA, 88 (5), 53-66. Noguera, D.R., N. Araki and B.E. Rittmann (1994) Soluble microbial products (SMP) in anaerobic chemostats, Biotech. Bioeng. 44, 1040-1047. Nystrom, M., K. Ruohomaki and L. Kaipia (1996) Humic acid as a fouling agent in filtration. Desalination, 106, 79-87. Owen, D.M., G.L. Amy, Z.K. Chowdhury, R. Paode, G. McCoy and K. Viscosil (1995) NOM characterization and treatability. J. AWWA, 87(1), 46-63. Ozaki, H. and H. Li (2002) Rejection of organics compounds by ultra-low pressure reverse osmosis membrane. Water Res. 36, 123–130. Park, C., H. Kim, S. Hong and S. Choi. (2006) Variation and prediction of membrane fouling index under various feed water characteristics. J. Membr. Sci., 284, 248-254. Park, N., B. Kwon, I.S. Kim and J. Cho (2005) Biofouling potential of various NF membranes with respect to bacteria and their soluble microbial products (SMP): characterizations, flux decline, and transport parameters. J. Membr. Sci., 258, 279-291. Park, N., B. Kwon, S.D. Kim and J. Cho (2006) Characterizations of the colloidal and microbial organic matters with respect to membrane foulants. J. Membr. Sci., 275, 29-36. Parker, J.A. and J.L. Darby (1995) Particle-associated coliform in secondary effluent: Shielding from ultraviolet light disinfection. Wat. Environ. Res., 67, 1065-1075. Parker, J.A., C. Reith and B. Birkenhead (1998) Membranes enabling the affordable and cost effective reuse of wastewater as an alternative water source. Desalination, 117, 203-210. Patel, R., A.C. Penisson, R.D. Hill and M.R. Wiesner, Membrane microfiltration of secondary wastewater effluent, in: Chemical Water and Wastewater Treatment III, R. Klute and H.H. Hahn, eds., Springer-Verlag, Berlin, 1994, pp. 29-36. Pihlajamäki, A., P. Väisänen and M. Nyström (1998) Characterization of clean and fouled polymeric ultrafiltration membranes by Fourier transform IR spectroscopy-attenuated total reflection. Colloids Surf. A Physicochem. Eng. Aspects, 138, 323-333. Pinjing, H.; L. Phan and G. Guowei, (2001) Reclaimed municipal wastewater a potential water resource in China. Wat. Sci. Techno., 43(10), 17-23. Pontie, M., S. Rapenne, A. Thekkedath, J. Duchesne, V. Jacquemet, J. Leparc and H. Suty (2005) Tools for membrane autopsies and antifouling strategies in seawater feeds: a review. Desalination, 181, 75-90. Post, J. (2006) Wastewater treatment and reuse in the eastern and Mediterranean region. Water 21, 6, 36-41. Potts, D.E., R.C. Ahlert and S.S. Wang (1981) A critical review of fouling of reverse osmosis membranes. Desalination, 36, 235-264. 151 REFERENCES Qin, J.J., K.A. Kekre, G. Tao, M.H.Oo, M.N. Wai , T.C. Lee, B. Viswanath and H. Seah (2006) New option of MBR-RO process for production of NEWater from domestic sewage. J. Membr. Sci., 272, 70-77. Qin, J.J., M.H. Oo, M.N. Wai, C.M. Ang, F.S. Wong and H. Lee (2003) A dual membrane UF/RO process for reclamation of spent rinses from a nickelplating operation-a case study. Water Res., 37, 3269-3278. Qin, J.J., M.H. Oo, M.N. Wai, H.W. Lee, S.P. Hong, J.E. Kim, Y.J. Xing and M.C. Zhang (2005) Pilot study for reclamation of secondary treated sewage effluent. Desalination, 171, 299-305. Qin, J.J., M.H. Oo., L.W. Hsiao and K. Rob (2004) Dead-end ultrafiltration for pretreatment of RO in reclamation of municipal wastewater effluent. J. Membr. Sci., 243, 107-113. Qualls, R.G. and B.L. Haines (1991) Geochemistry of dissolved organic nutrients in water percolating through a forest ecosystem. Soil Sci. Soc. Am. J., 55, 1112-1123. Reardon, R., F. DiGiano, M. Aitken, S. Paranjape, J.H. Kim and S.Y. Chang (2006) Membrane treatment of secondary effluent for subsequent reuse. Water Environment Research Foundation Report, IWA Publishing. Rebhun, M. and J. Manka (1971) Classification of organics in secondary effluents Environ. Sci. Technol., 6, 606-609. Redondo, J. A. and I. Lomax (1997). Experiences with the pretreatment of raw water with high fouling potential for reverse osmosis plant using FILMTEC membranes. Desalination, 110, 167-182. Ridgway, H.F. and H.C. Flemming (1996) Membrane biofouling. In Water Treatment Membrane Processes. Ed. by Mallevialle et al. McGraw Hill, New York. Ridgway, H.F., A. Kelly, C. Justice, and B.H. Olson (1983) Microbial fouling of reverse-osmosis membranes used in advanced wastewater treatment technology: chemical, bacteriological, and ultrastructural analyses. Appl. Environ. Microbiol., 45, 1066-1084. Rittmann, B.E. and M.J. Semmens (1992) Committee report: membrane processes in potable water treatment. J. Am. Water Works Assn., 84(1), 59-67. Rittmann, B.E., Bae W., Namkung E. and C.J. Lu (1987) A critical evaluation of microbial product formation in biological processes. Water Sci. Technol., 19, 517-528. Roorda, J.H. (2004) Filtration characteristics in dead-end ultrafiltration of wttp-effluent. Ph.D Dissertation, Delft University of Technology. Sagle, A.C., D.L. Gin, M. Sharma and B.D. Freeman (2005) Chlorine Resistance Studies on Membranes. Polymeric Materials: Science & Engineering, 93, 732-733. Salerno, M.B., S. Rothstein, C. Nwachukwu, H. Shelbi, D. Velegol and B.E. Logan (2005) Differences between chemisorbed and physisorbed biomolecules on particle deposition to hydrophobic surfaces. Environ. Sci. Technol., 39, 6371-6377. 152 REFERENCES Samson, P. and B. Charrier (1997) International Freshwater Conflict: Issues and Prevention Strategies. Green Cross International. Saunders, F.M. and R.I. Dick (1981) Effect of mean-cell residence time on organic composition of activated sludge effluents. J. WPCF, 53(2), 201-215. Schaefer, J. (2001) Reliable water supply by reusing wastewater after membrane treatment. Desalination, 138, 91. Schafer, A.I., U. Schwicker, M.M. Fischer, A.G. Fane and T.D. Waite (2000) Microfiltration of colloids and natural organic matter. J. Membr. Sci., 171, 151-172. Schafer, A.I., Natural Organic Matter Removal using Membranes: Principles, Performance and Cost, CRC Press, Boca Raton, USA, 2001. Schiener, P., S. Nachaiyasit and D.C. Stuckey (1998) Production of soluble microbial products (SMP) in an anaerobic baffled reactor: composition, biodegradability and the effect of process parameters. Environ. Techno. 19, 391-400. Schneider, R.P., L.M. Ferreira, P. Binder and J.R. Ramos (2005) Analysis of foulant layer in all elements of an RO train. J. Membrane Sci., 261, 152-162. Seidel, A. and M. Elimelech (2002) Coupling between chemical and physical interactions in natural organic matter (NOM) fouling of nanofiltration membranes: implications for fouling control. J. Membrane Sci., 203, 245-255. Shahalam, A.M., A. Al-Harthy, and A. Al-zawhry (2002) Feed water pretreatment in RO systems: unit processes in the Middle East. Desalination. 150, 235-245. Shon, H.K., S. Vigneswaran, I.S. Kim, J. Cho and H.H. Ngo (2004) The effect of pretreatment to ultrafiltration of biologically treated sewage effluent: a detailed effluent organic matter (EfOM) characterization. Water Res., 38, 1933-1939. Shon, H.K., S. Vigneswaran, R.B. Aim, I.S. Kim, J. Cho and H.H. Ngo (2006) Fouling of ultrafiltration membrane by effluent organic matter: a detailed characterization using different organic fractions in wastewater. J. Membr. Sci., 278, 232-238. Singh, G. and L. Song (2005) Quantifying the effect of ionic strength on colloidal fouling potential in membrane filtration, J. Colloid Interface Sci., 284, 630-638. Soltanieh, M. and W.N. Gill (1981) Review of reverse osmosis membranes and transport models. Chem. Eng. Commun., 12, 279-363. Song, L., K.L. Chen, S.L. Ong and W.J. Ng (2004) A new normalization method for determination of colloidal fouling potential in membrane processes. J. Colloid Interface Sci., 271, 426-433. Speth, T.F., R.S. Summers and A.M. Gusses (1998) Nanofiltration foulants from treated surface water, Environ. Sci. Technol., 32, 3612-3617. Steve, L. (2003) Water and war. http://www.unep.org/OurPlanet/imgversn/154/lonergan.html 153 REFERENCES Stevenson, F.J. (1982) Humus chemistry. John Wiley & Sons, New York. Sundstrom G. (2006) Reuse: Alternate water sources benefit industries and communities. Industrial WaterWorld. January. Tang, C.Y., Y.N. Kwon and J.O. Leckie (2007) Characterization of humic acid fouled reverse osmosis and nanofiltration membranes by transmission electron microscopy and streaming potential measurements, Environ. Sci. Technol., 41, 942-949. Tarabara, V.V., F. Pierrisnard, C. Parron, J.Y. Bottero and M.R. Wiesner (2002) Morphology of deposits formed from chemically heterogeneous suspensions: application to membrane filtration. J. Colloid. & Interface Sci., 256, 367-377. Taylor, J.S. and M. Wiesner (1999) Membranes, in Water Quality and Treatment, fifth ed., Am. Water Works Assoc. McGraw-Hill, New York, 11, 171. Tchobanoglous, G., J. Darby, K. Bourgeous, J. Mcardle, P. Genest and M. Tylla (1998) Ultrafiltration as an advanced tertiary treatment process for municipal wastewater. Desalination,119, 315-322. Thurman E.M. (1985) Organic geochemistry of natural waters. Martinus Nijhoff/Dr W. Junk Publishers, Dordrecht. Till, S.W., S.J. Judd and B. Mcloughlin. (1998) Reduction of faecal coliform bacteria in sewage effluents using a microporous polymeric membrane, Wat. Res., 32, 1417-1422. Vaknin, S. (2005) The Emerging Water Wars. http://www.progress.org/2005/water27.htm van der Hoek, J.P., J.A.M.H. Hofman, P.A.C. Bonne, M.M. Nederlof and H.S. Vrouwenvelder (2000) RO treatment: selection of a pretreatment scheme based on fouling characteristics and operating conditions based on environmental impact. Desalination, 107, 89-101. Van Houtte, E., J. Verbauwhede, F. Vanlerberghe, S. Demunter, and J. Cabooter (1998) Treating different types of raw water with micro- and ultrafiltration for further desalination using reverse osmosis. Desalination, 117, 49-60. Vidal, J. (2006) Cost of water shortage: civil unrest, mass migration and economic collapse. http://www.guardian.co.uk/water/story/0,,1851712,00.html Vigneswaran, S., D.S. Chaudhary, H.H. Ngo, W.G. Shim and H. Moon (2003) Application of a PAC-membrane hybrid system for removal of organics from secondary sewage effluent: experiments and modelling, Separat. Sci. Technol., 38, 2183-2199. Walton, N.R.G. (1988) The significance of colour changes in some reverse osmosis permeators. Desalination, 68, 29-33. Water Environment Federation (2006) Membrane Systems for Wastewater Treatment. WEF Press Inc., New York. 154 REFERENCES Weis, A., M.R. Bird and M.J. Nystrom (2003) The chemical cleaning of polymeric UF membranes fouled with spent sulphite liquor over multiple operational cycles. J. Membr. Sci., 216, 67-79. Wend, C.F., P.S. Stewart, W. Jones and A.K. Camper (2003) Pretreatment for membrane water treatment systems: a laboratory study. Water Res., 37, 33673378. Wiesner, M.R., S. Veerapaneni and D. Brejchova (1992) Improvements in membrane microfiltration using coagulation pretreatment, in: R. Klute and H. Hahn, eds., Chemical Water and Wastewater Treatment II, Springer-Verlag, Berlin, 281-296. Wilf, M. and S. Alt (1999) Desalination Research and Development Report No.42, US Department of Interior, Bureau of Reclamation. Wilf, M., L. Awerbuch, C. Bartels, M. Mickley, G. Pearce and N. Voutchkov (2007) The guidebook to membrane desalination technology: reverse osmosis, nanofiltration and hybrid systems process, design, applications and economics, Balaban Publishers. Winfield, B.A. (1979) A study of the factors affecting the rate of fouling of reverse osmosis membranes treating secondary sewage effluents. Water Res., 13, 565-569. Xie, R.J., M.J. Gomez, Y.J. Xing and P.S. Klose (2004) Fouling assessment in a municipal water reclamation reverse osmosis system as related to concentration factor. J. Environ. Eng. Sci., 3, 61–72. Yamagiwa, K., H. Kobayashi, A. Ohkawa and M. Onodera (1993) Membrane fouling in ultrafiltration of hydrophobic nonionic surfactant, J. Chem. Eng. Jpn., 26(1), 13-18. Yuan, W. and A.L. Zydney (1999) Humic acid fouling during microfiltration. J. Membrane Sci., 157, 1-12. Yuan, W. and A.L. Zydney (2000). Humic acid fouling during ultrafiltration. Environ. Sci. Technol., 34, 5043-5050. Yuan, W., A. Kocic, and A.L. Zydney (2002) Analysis of humic acid fouling during microfiltration using a pore blockage-cake filtration model. J. Membrane Sci., 198, 51-62. Zhang, M.M., C. Li, M.M. Benjamin and Y.J. Chang (2003) Fouling and natural organic matter removal in adsorbent/membrane systems for drinking water treatment. Environ. Sci. Technol., 37, 1663-1669. Zhang, X.Q, P.L. Bishop and M.J. Kupferle (1998) Measurement of polysaccharides and proteins in biofilm extracellular polymers. Wat. Sci. Tech., 37, 345-348. Zhao, Y., J. Taylor and S. Hong (2005) Combined influence of membrane surface properties and feed water qualities on RO/NF mass transfer, a pilot study. Water Res., 39, 1233-1244. Zhou, Q.H. S.E. Cabaniss, and P.A. Maurice (2000) Considerations in the use of high-pressure size exclusion chromatography (HPSEC) for determining molecular weights of aquatic humic substances. Water Res., 34, 3505-3514. 155 REFERENCES Zhu, H. and M. Nyström (1998) Cleaning results characterized by flux, streaming potential and FTIR measurements, Colloids Surf. A Physicochem. Eng. Aspects, 138 309-321. Zhu, X. and M. Elimelech (1995) Fouling of reverse osmosis membranes by aluminium oxide colloids. J. Environ. Eng. ASCE., 121, 884-893. Zhu, X. and M. Elimelech (1997) Colloidal fouling of reverse osmosis membranes: measurement and fouling mechanisms. Environ. Sci. Technol., 31 (12), 3654-3662. 156 APPENDIX A Appendix A Publications and conference papers from this project A.1 Journal publications 1. Liang S., Zhao Y., Liu C. and Song L. (2007). “Effect of solution chemistry on the fouling potential of dissolved organic matter in membrane bioreactor systems”. J. Membr. Sci., 310 (1-2), pp. 503-511. 2. Zhao Y., Song L. and Ong S.L. (Submitted). “Fouling Behavior and Foulant Characteristics of Reverse Osmosis Membranes for Treated Secondary Effluent Reclamation”. J. Membr. Sci. 3. Zhao Y., Song L. and Ong S.L. (Submitted). “Fouling of RO membranes by effluent organic matter (EfOM): relating major components of EfOM to their characteristic fouling behaviors”. J. Membr. Sci. A.2 Conference papers 1. Zhao Y. and Song L. (2007). “Organic fouling potential characterization of secondary effluent as feed water to RO membranes”. The 18th North American Membrane Society Annual Meeting, 12-16 May 2007, Orlando, Florida, USA. 2. Zhao Y. and Song L. (2006). “Characterization of foulants on RO membrane treating secondary effluent after UF pretreatment”. The 17th North American Membrane Society Annual Meeting, 12-17 May 2006, Chicago, Illinois, USA. 157 [...]... TWO LITERATURE REVIEW 2.1 Application of RO membrane process for wastewater reclamation The application of membrane processes for wastewater reclamation has been initially developed with RO process In view of the superior rejection capabilities of RO membranes and high loadings of impurities present in treated effluent fed to RO, effective control of membrane fouling has long been considered critical... operation of membrane systems used for wastewater reclamation varies for specific reuse applications and will be determined by the level of treatment required (Water Environment Federation, 2006) 1.2 Limitations of RO membrane process for wastewater reclamation The two important performance indicators for membrane processes are: the quality of product water, which is related to the rejection efficiency of. .. the fouling of RO membranes caused by EfOM, the biggest challenge lies in a lack of understanding in terms of composition and characteristics of EfOM and its associated fouling mechanisms EfOM represents a large group of structurally complex, heterogeneous and poorly defined organic compounds derived from both raw wastewater and microbial metabolic activities Although a myriad of compounds such as proteins,... underlying fouling mechanisms on RO membranes treating highfouling treated effluent is needed The information obtained could facilitate the formulation of effective fouling prevention or mitigation strategies through practical and economic approaches 1.4 Research objectives The overall objective of this study is to develop an improved understanding of EfOM fouling behavior and underlying mechanisms on RO membranes... composition of new and fouled membrane surface by SEM-EDX…………………………………………………………….…….116 Table 4.5 Inorganic composition of physically stripped fouling layer…………………………………………………………….………… 110 Table 4.6 Surface chemistry of fouled membranes as compared to the clean membrane ………………………………….…………………… 113 ix LIST OF FIGURES LIST OF FIGURES Figure 2.1 Overview of schemes of using RO membrane systems for wastewater reclamation. .. EPS, particularly the hydrophilic colloids and macromolecules, have recently been observed as major foulants of NF /RO membranes used for wastewater reclamation (Jarusutthirak et al., 2002; 2006) However, systematic fouling characterization studies of RO membranes receiving MF/UF pretreated 11 CHAPTER ONE INTRODUCTION secondary effluent for reclamation have yet to be conducted Most fouling characterization... sites for sparingly soluble salts leading to irreversible membrane fouling (Schneider et al., 2005) As readily available microbial nutrients, they could also be assimilated by “opportunistic” microorganisms and thereby encourage membrane biofouling the “Achilles heels” of RO membrane processes (Ridgway et al., 1996; Flemming et al., 1997) 7 CHAPTER ONE INTRODUCTION To hinder the occurrence of fouling, ... provide a comprehensive review on previous theoretical and experimental studies on fouling of RO membrane processes used in wastewater reclamation applications with critical technical issues and research gaps being identified This includes an overview of the key types of foulants and their fouling characteristics, with a specific emphasis on EfOM and the resulting organic fouling pertinent to this study. .. emerging micropollutants (Kimura et al., 2004) However, the efficiency of RO membranes in rejecting these organic contaminants has not been fully proven Fouling occurrence during wastewater reclamation might influence the rejection efficiency of membranes towards these organic contaminants and compromise 9 CHAPTER ONE INTRODUCTION the reclaimed water quality It has been reported colloidal fouling could... of operating conditions for membrane systems is also kept far from optimum A higher initial flux will result in a faster decline in specific flux and a much higher cleaning frequency, and the net effect is often far less cumulative water production (Chellam et al., 1998) Fouling phenomenon also set the upper limit of permeate recovery attained by a RO membrane process For MF and UF membranes used for . RO membrane process for wastewater reclamation 20 2.2 Advantages of RO Process for wastewater reclamation 26 2.3 Fouling of RO process for wastewater reclamation 28 2.3.1 Definition of fouling. EXPERIMENTAL STUDY OF RO MEMBRANE ORGANIC FOULING FOR WASTEWATER RECLAMATION ZHAO YAN NATIONAL UNIVERSITY OF SINGAPORE 2009 EXPERIMENTAL STUDY OF RO. control. This study first investigated the fouling behaviors of wastewater reclamation RO membranes fed with ultrafiltration (UF) prefiltered secondary effluent from a tropical area wastewater