LONG-TERM EFFECTS OF ZINC OXIDE NANOPARTICLES ON WASTEWATER TREATMENT IN A MEMBRANE BIOREACTOR (MBR) PROCESS TAN SIEW YEN, MAGDALENE (B.Eng.(Hons.), NUS A THESIS SUBMITTED FOR THE DEGREE OF MASTER OF ENGINEERING DEPARTMENT OF CHEMICAL AND BIOMOLECULAR ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2015 i i ACKNOWLEDGEMENTS I would hereby like to express my deepest gratitude to my Project Supervisor, Associate Professor Ting Yen Peng for his invaluable advice and guidance throughout the course of this project Special thanks are also extended to Dr Qiu Guang Lei who did his utmost in supervising and guiding me throughout the project I am truly grateful by his support and assistance offered in the course of this project I would also like to express appreciate to all my laboratory mates, namely Divya Shankari Srinivasa Ragha, Shruti Vyas, Subhabrata Das, Thulasya Ramanathan and Gayathri Natarajan, and laboratory officer, Sylvia Wan, for their constant help and support while conducting the study in the laboratory Lastly, I would like to express my sincere gratitude to my family and friends for their constant support and encouragement ii This page is intentionally left blank iii TABLE OF CONTENTS DECLARATION i ACKNOWLEDGEMENTS ii TABLE OF CONTENTS iv SUMMARY vii LIST OF TABLES ix LIST OF FIGURES x NOMENCLATURE xii INTRODUCTION 1.1 Nanoparticles 1.2 Zinc oxide nanoparticles 1.3 Membrane bioreactors 1.4 Objectives of research 1.5 Scope of research 1.6 Schedule of various experimental phases LITERATURE REVIEW 2.1 Zinc oxide nanoparticles 10 11 11 2.1.1 Environment relevant concentrations 12 2.1.2 Stability of zinc oxide nanoparticles in aqueous environment 17 2.2 Ecotoxicity effects of zinc oxide nanoparticles 19 2.2.1 Mechanisms of zinc oxide nanoparticles 21 2.2.2 Effects of zinc oxide nanoparticles on bacteria 23 2.2.3 Effects of zinc oxide nanoparticles on wastewater treatment 25 2.3 Membrane bioreactors 29 iv 2.3.1 Introduction 29 2.3.2 ZnO nanoparticles in MBRs 34 2.3.3 Membrane fouling 39 2.3.4 Membrane fouling control 44 MATERIALS AND METHODS 47 3.1 Experimental setup 47 3.2 Operating conditions in the MBR system 49 3.3 Synthetic municipal wastewater feed 50 3.4 Analytical methods 51 3.4.1 Wastewater characteristics 52 3.4.2 Sludge characteristics 54 3.4.3 Membrane fouling rate 55 3.4.4 Zinc phosphate precipitate in mixed liquor 55 3.4.5 Soluble Microbial Products (SMP) and Extracellular Polymeric Substances (EPS) 56 3.4.6 Bacterial community dynamics 57 3.4.7 Zn content in wastewater and activated sludge 59 RESULTS AND DISCUSSION 60 4.1 Standard curves 60 4.2 Effect of ZnO nanoparticles on wastewater treatment 60 4.2.1 Wastewater characteristics 61 4.2.2 Sludge characteristics 71 4.2.2.1 MLSS, MLVSS, SVI and Sludge morphology 71 4.2.2.2 Soluble microbial substances (SMP) and Extracellular polymeric substances (EPS) 78 4.3 Fate of ZnO nanoparticles 4.3.1 Solubility of ZnO NPs 88 88 v 4.3.2 Removal behaviour of ZnO NPs 89 4.3.3 Mass balance of Zn 92 4.4 ZnO nanoparticles effect on bacterial community 96 CONCLUSIONS 100 5.1 Effects of ZnO NPs on removal efficiencies 100 5.2 Effects of ZnO NPs on sludge characteristics 101 5.3 Effects of ZnO NPs on bacteria community in MBR 101 5.4 Fate of ZnO NPs in MBR 102 FURTHER STUDIES 103 6.1 Effect of ZnO NPs in MBR using municipal wastewater 103 6.2 Transformation of ZnO NPs in MBR system 104 6.3 Impact of ZnO NPs on MBR bacterial community 105 6.4 Effect of ZnO NPs on physiochemical stability of MBR activated sludge flocs 105 6.5 Impact of ZnO NPs on membrane fouling 106 REFERENCES 107 APPENDIX 123 Appendix A1: Standard Curves 123 Appendix A2: EDX Analysis 127 vi SUMMARY In recent years, the growing release of zinc oxide nanoparticles (ZnO NPs) from consumer-products in various sectors into sewage systems has raised concerns on the potential adverse impact on wastewater treatment plants MBR systems, which have been widely used since 1990s for municipal wastewater treatment, are traditionally not designed to cope with the removal of nanoparticles At present, the effect of this new emerging pollutant, ZnONPs, on the performance of MBR system is still largely unknown In this study, the effect of zinc oxide nanoparticles (ZnO-NPs) on the system performance and its removal behaviour in an MBR system were investigated A lab-scale submerged MBR system was operated continuously for 242 days Three experimental phases were conducted, with 0, mg/L and 10 mg/L of ZnO NPs added into the system over the whole duration Significant changes in COD, TN and phosphorous removal efficiency of the system were observed with the addition of mg/L and 10 mg/L ZnO NPs Concentrations of proteins and polysaccharides in SMPs showed significant changes while that of EPSs were affected to a smaller extent The MBR system was efficient in removing ZnO-NPs from the wastewater, achieving higher than 95% removal efficiency on almost all days Sorption onto biomass works well as the main removal mechanism at low ZnO-NPs vii concentration while membrane rejection also plays a part in the removal of Zn when concentration was increased to 10 mg/L ZnO-NPs caused a major shift in the bacterial community structure but no significant change in community diversity as revealed from 16S rRNA genebased PCR-DGGE analysis In addition, the type of EPS also changed from those enveloping the sludge to those forming a dense matrix around the bacteria cells KEYWORDS Membrane bioreactor; municipal wastewater treatment; zinc oxide nanoparticles; membrane fouling; extracellular polymeric substances (EPS), bacterial community dynamics viii LIST OF TABLES Table 2.1 Potential fate of nanoparticles in aquatic systems 13 Table 2.2 Concentration of nanomaterials in consumer products (in g/kg or mg/kg product) and the consequent added concentration and releases in the Dutch reaches of the Rhine and Meuse 14 Table 2.3 Modeled concentrations of ZnO nanoparticles released into environmental compartments in different countries, shown as mode (most frequent value) and as range of the lower and upper quantiles (Q0.15 and 0.85) 15 Table 2.4 Some common nanoparticles, their respective applications, and some estimates of their potential environmental size concentrations 16 Table 2.5 Typical MBR effluent quality 31 Table 3.1 Composition of synthetic wastewater 50 Table 4.1 Summary of effects of ZnO NPs on nutrient removal in 70 wastewater Table 4.2 Shannon-Wiener diversity index of the bacterial community in MBR 98 ix 100 Markus, A.A., Parsons, J.R., Roex, E.W.M., Kenter, G.C.M., Laane, R.W.P.M., 2013 Predicting the contribution of nanoparticles (Zn, Ti, Ag) to the annual metal load in the Dutch reaches of the Rhine and Meuse Science of the Total Environment 456–457, 154–160 101 Martinew-Castanon, G.A., Nino-Martinez, N., Martinez-Gutierrez, F., Martinez-Mendoza, J.R., Ruiz, F., 2008 Synthesis and antibacterial activity of silver nanoparticles with different sizes J Nanopart Res 10, 1343-1348 102 Mei, X., Wang, Z., Zheng, X., Huang, F., Maa, J., Tang, J., Wu, Z., 2014 Soluble microbial products in membrane bioreactors in the presence of ZnO nanoparticles Journal of Membrane Science 451, 169–176 103 Meng, F., Chae, S R, Drews, A., Kraume, M., Shin, H S., Yang, F., 2009 Recent advances in membrane bioreactors (MBRs): Membrane fouling and membrane material Water Research 43, 1489-1512 104 Metzger, U., Le-Clech, P., Stuetz, R M., 2007 Characterisation of polymeric fouling in membrane bioreactors and the effect of different filtration modes Journal of Membrane Science 301, 180-189 105 Mikkelsen, L H., Mascarenhas, T Nielsen, P H., 2002 Key parameters in sludge dewatering: Testing for the shear sensitivity and EPS content Water Sci Technol., 46 (10), 105 106 Miller, R.J., Lenihan, H.S., Muller, E.B., Tseng, N., Hanna, S.K., Keller, A.A., 2010 Impacts of metal oxide nanoparticles on marine phytoplankton Environmental Science & Technology 44 (19), 73297334 107 Molina, R., Al-Salama, Y., Jurkschat, K., Dobson, P.J., Thompson, I.P., 2011 Potential environmental influence of amino acids on the behavior of ZnO nanoparticles Chemosphere 83, 545–551 108 Moore, M.N., 2006 Do Nanoparticles Present Ecotoxicological Risks For The Health Of The Aquatic Environment? Environ Int 32, 967-976 109 Mu, H., Chen, Y.G., 2011 Long-term effect of ZnO nanoparticles on waste activated sludge anaerobic digestion Water Res 45 (17), 56125620 110 Mu, H., Chen, Y.G., Xiao, N.D., 2011 Effects of metal oxide nanoparticles (TiO2, Al2O3,SiO2 and ZnO) on waste activated sludge anaerobic digestion Bioresour Technol 102 (22), 10305-10311 111 Mudunkotuwa, I.A., Rupansinghe, T., Wu, Chia-Ming, Grassian, V.H., 2012 Dissolution of ZnO nanoparticles at circumneutral pH: a study of size effects in the presence and absence of citric acid Langmuir 28, 396– 116 403 112 Mueller, N.C and Nowack, B., 2008 Exposure modeling of engineered nanoparticles in the environment Environ Sci Technol 42, 4447-4453 113 Musee, N., Zvimba, J N., Schaefer, L M., Notal, N., Sikhwivhilu, L.M., Thwala, M., 2014 Fate and behavior of ZnO- and Ag-engineered nanoparticles and a bacterial viability assessment in a simulated wastewater treatment plant Journal of Environmental Science and Health, Part A 49, 59-66 114 Navarro, E., Baun, A., Behra, R., Hartmann, N., Filser, J., Miao, A.J., Quigg, A., Santschi, P., Sigg, L., 2008 Environmental behavior and ecotoxicity of engineered nanoparticles to algae, plants, and fungi Ecotoxicology 17 (5), 372-386 115 Navorrow, E., Piccapietra, F., Wagner, B., Marconi, F., Kaegi, R., Odzak, N., 2008 Toxicity of silver nanoparticles to Chlamydomonas reinhardtii Environ Sci Technol 42 (23), 8959-8964 116 Niu, M., Zhang, W., Wang, D., Chen, Y., Chen, R., 2013 Correlation of physicochemical properties and sludge dewaterability under chemical conditioning using inorganic coagulants Bioresour Technol 144, 337– 343 117 Nowack, B., 2009 The behavior and effects of nanoparticles in the environment Environ Pollut 157, 1063–1064 118 Nowack, B., Ranville, J.F., Diamond, S., Gallego-Urrea, J.A., Metcalfe, C., Rose, J., Horne, N., Koelmans, A.A., Klaine, S.J., 2012 Potential scenarios for nanomaterial release and subsequent alteration in the environment Environmental Toxicology and Chemistry 31, 50-59 119 Oskam, G., 2006 Metal oxide nanoparticles: synthesis, characterization and application Journal of Sol-Gel Science and Technology 37 (3), 161164 120 Otero-González, L., Field, J.A., Sierra-Alvarez, R., 2014 Fate and longterm inhibitory impact of ZnO nanoparticles during high-rate anaerobic wastewater treatment Journal of Environmental Management 135, 110117 121 Pan, X., Redding, J E., Wiley, P.A., Wen, L., McConnell, J.S., Zhang, B., 2010 Mutagenicity evaluation of metal oxide nanoparticles by bacterial reverse mutation assay Chemosphere79, 113–116 122 Park, H., Kim, H Y., Cha, S., Ahn, C H., Roh, J., Park, S., Kim, S., Choi, K., Yi, J., Kim, Y., Yoon, J., 2013 Removal characteristics of engineered nanoparticles by activated sludge, Chemosphere 92, 524–528 117 123 Pollice A., Brookes A., Jefferson B., and Judd S., 2005 Sub-critical flux fouling in membrane bioreactors – A review of recent literature Desalination 174, 221 –230 124 Pomory, C.M., 2008 Color development time of the lowry protein assay Anal Biochem 378, 216-217 125 Premanathan, M., Karthikeyan, K., Jeyasubramanian, K., Manivannan, G., 2011 Selective toxicity of ZnO nanoparticles toward Gram-positive bacteria and cancer cells by apoptosis through lipid peroxidation Nanomedicine: Nanotechnology, Biology, and Medicine (2), 184-192 126 Puay N.Q., Qiu, G., Ting, Y.P., 2014 Effect of ZnO nanoparticles on biological wastewater treatment in a sequencing batch reactor (SBR) J Cleaner Prod http://dx.doi.org/10.1016/j.jclepro.2014.03.081 127 Qiu, G., Song, Y., Zeng, P., Duan, L and Xiao, S., 2013 Combination of upflow anaerobic sludge blanket (UASB) and membrane bioreactor (MBR) for berberine reduction from wastewater and the effects of berberine on bacterial community dynamics J Hazard Mater., 246-247, 34-43 128 Qiu, G., Ting, Y.P., 2013 Osmotic membrane bioreactor for wastewater treatment and the effect of salt accumulation on system performance and microbial community dynamics Bioresour Technol 150, 287-297 129 Qiu, G., Ting, Y.P., 2014 Short-term fouling propensity and flux behavior in an osmotic membrane bioreactor for wastewater treatment Desalination 332, 91-99 130 Rejeski, D., Kuiken, T., Polischuk, P., Pauweis, E., 2011 The Project on Emerging Nanotechnologies Available from: http://www.nanotechproject.org/inventories/consumer/analysis_draft/ 131 Remenarova, L., Pipiska, M., Hornik, M., Rozloznik, M., Augustin, J., Lesny, J., 2012 Biosorption of cadmium and zinc by activated sludge from single and binary solutions: Mechanism, equilibrium and experimental design study J of the Taiwan Institute of Chemical Engineers 43, 433–443 132 Roco, M C., 2005 Environmentally responsible development of nanotechnology Environ Sci Technol 39, 106A–112A 133 Sapkota, A., Anceno, A.J., Baruah, S., Shipin, O.V., Dutta, J., 2011 Zinc oxide nanorod mediated visible light photoinactivation of model microbes in water Nanotechnology 22 (21), 5703-5707 134 Seviour, T., Yuan, Z., Van Loosdrecht, M., Lin, Y., 2012 Aerobic sludge granulation: a tale of two polysaccharides? Water Res 46, 4803–4813 118 135 Schwarz, A O., Rittmann, B E., Crawford, G V., Klein, A M., Daigger, G T., 2006 Critical review on the effects of mixed liquor suspended solids on membrane bioreactor operation Sep Sci Technol., 41, 1489 136 Shafer, M.M., Overdier, J.T., Armstrong, D E., 1998 Removal, partitioning, and fate of silver and other metals in wastewater treatment plants and effluent-receiving streams Environmental Toxicology and Chemistry 17 (4), 630-641 137 Shen, Y.X., Xiao, K., Liang, P., Sun, J.Y., Sai, S.J., Huang, X., 2012 Characterization of soluble microbial products in 10 large-scale membrane bioreactors for municipal wastewater treatment in China J Membr Sci., 415-416, 336-345 138 Sheng, G.P., Xu, J., Luo, H.W., Li, W.W., Li, W.H., Yu, H.Q., Hu, F.C., 2013 Thermodynamic analysis on the binding of heavy metals onto extracellular polymeric substances (EPS) of activated sludge Water Res 47, 607–614 139 Sheng, G.P., Yu, H.Q., Li, X.Y., 2010 Extracellular polymeric substances (EPS) of microbial aggregates in biological wastewater treatment systems: a review Biotechnol Adv 28, 882–894 140 Sheng, Z., Liu, Y., 2011 Effects of silver nanoparticles on wastewater biofilms Water Research 45, 6039-6050 141.Springer, F., Laborie, S., Guigui, C., 2013 Removal of SiO2 nanoparticles From industry wastewaters And subsurface waters by ultrafiltration: Investigation of process efficiency, deposit properties and fouling mechanism Sep Purif Technol 108, 6-14 142 Stampoulis, D., Sinha, S.K., White, J.C., 2009 Assay-dependent phytotoxicity of nanoparticles to plants Environ Sci Technol 43, 94739479 143 Sun, X., Sheng, Z., Liu, Y., 2013 Effects of silver nanoparticles on microbial community structure in activated sludge Sci Total Environ Vol 443, 828–835 144 Sun, T., Gottschalk, F., Hungerbuhler, K., Nowack, B., 2014 Comprehensive probabilistic modelling of environmental emissions of engineered nanomaterials Environmental Pollution185, 69-76 145 Tiede, K., Boxall, A.B.A., Wang, X., Gore, D., Tiede, D., Baxter, M., 2010 Application of hydrodynamic chromatography–ICP-MS to investigate the fate of silver nanoparticles in activated sludge J Anal At Spectrom 25, 1149–1154 119 146 Till, S., and Mallia, H., 2001 Membrane bioreactors: Wastewater treatment applications to achieve high effluent quality 64th Annual Water Industry Engineers and Operators Conference, Bendigo, September 5-6, 57 147 (UNEP), U.N.E.P., 2007 Chapter 7: Emerging challengesnanotechnology and the environment GEO Year Book 2007 United Nations Environment Programme Division of Early Warning and Assessment, Nairobi, 61–70 148 U.S.EPA, 2009 Targeted national sewage sludge survey sampling and analysis technical report, Environmental Protection Agency: Washington, DC: United States http://www.epa.gov/waterscience/biosolids/tnssstech.pdf 149 Wang, Y., Westerhoff, P., Hristovski, K D., 2012 Fate and biological effects of silver, titanium dioxide, and C60 (fullerene) nanomaterials during simulated wastewater treatment processes Journal of Hazardous Materials 201-202, 16-22 150 Wang, Z., Huang, F., Mei, X., Wang, Q., Song, H., Zhu, C., Wu, Z., 2014 Long-term operation of an MBR in the presence of zinc oxide nanoparticles reveals No significant adverse effects on its performance Journal of Membrane Science, http://dx.doi.org/10.1016/j.memsci.2014.08.024 151 Wang, Z, Wu, Z., Yin, X., Tian, L., 2008b Membrane fouling in a submerged membrane bioreactor (MBR) under sub-critical flux operation: Membrane foulant and gel layer characterization Journal of Membrane Science 325, 238-244 152 Wang, Z.P., Lee, Y.H., Wu, B., Horst, A., Kang, Y.S., Tang, Y.J.J., Chen, D.R., 2010 Antimicrobial activities of aerosolized transition metal oxide nanoparticles Chemosphere 80, 525–529 153 Water Environmental Federation, American Society of Civil Engineers, Environmental and Water Resources Institute (2009) Design of municipal Wastewater treatment plants, 5th ed WEF Manual of Practice No.8, ASCE Manual and Report on Engineering Practice No 76, McGraw-Hill: New York 154 Water Environmental Federation, Membrane Bioreactors Task Force of the WEF (2012) Membrane Bioreactors, WEF Manual of Practice No.36, WEP Press, Virginia 155 Weinberg, H., Galyean, A., Leopold, M., 2011 Evaluating engineered nanoparticles in natural waters Trends Anal Chem 30, 72–83 120 156 Weir, A., Westerhoff, P., Fabricius, L., Hristovski, K., von Goetz, N., 2012 Titanium dioxide nanoparticles in food and personal care products Environ Sci Technol 46, 2242–50 157 Wilén, B.M., Jin, B., Lant, P., 2003 The influence of key chemical constituents in activated sludge on surface and flocculating properties Water Res 37, 2127–2139 158 Woodrow Wilson Database, 2011 The Project on Emerging Nanotechnologies: Consumer Products Inventory Woodrow Wilson International Center for Scholars Washington DC 〈http://www.nanoproduct.org/inventories/consumer/〉 (Accessed September 4, 2011) 159 Woodrow Wilson Database, 2011 The Project on Emerging Nanotechnologies: Consumer Products Inventory Woodrow Wilson International Center for Scholars Washington DC (http://nanotechproject.org/44) 160 Wu, B., Wang, Y., Lee, Y.H., Horst, A., Wang, Z., Chen, D., Sureshkumar, R., Tang, Y.J., 2010 Comparative eco-toxicities of nanoZnO particles under aquatic and aerosol exposure modes Environ.Sci.Technol.44, 1484–1489 161 Yang, W., Nazim, C., John, I., 2006 State-of-the-art of membrane bioreactors: Worldwide research and commercial applications in North America Journal of Membrane Science 270, 201-211 162 Yang, J., Guo, G.H., Chen, T.B., Zheng, G.D., Gao, D., Yang, S.C., Song, B., Du, W., 2009 Concentrations and variation of heavy metals in municipal lsludge of China China Water Wastewater 25,122–124 163 Yang, X., Cui, F., Guo, X., Li, D., 2013 Effects of nanosized titanium dioxide on the physicochemical stability of activated sludge flocs using the thermodynamic approach and Kelvin probe force microscopy, Water Research 47, 3947 - 3958 164 Ye, F., Ye, Y., Li, Y., 2011 Effect of C/N ratio on extracellular polymeric substances (EPS) and physicochemical properties of activated sludge flocs J Hazard Mater 188, 37–43 165 Yi, T., Harper, W F., Jr., Holbrook, D., Love, N G., 2006 Role of particle size and ammonium oxidation in removal of 17-Ethinyl Estradiol in bioreactors J Environ Eng (Reston, Virginia), Nov, 1527 166 Zhang, C., Liang, Z., Hu, Z., 2013 Bacterial response to a continuous long-term exposure of silver nanoparticles at subppm silver 121 concentrations in a membrane bioreactor activated sludge system Water Research doi: 10.1016/j.watres.2013.10.047 167 Zhang, Y Y., Chen, Y., Westerhoff, P., Crittenden, J., 2009 Impact of natural organic matter and divalent cations on the stability of aqueous nanoparticles.Water Res 43, 4249–4257 168 Zheng, X., Wu, R., Chen, Y., 2011 Effects of ZnO nanoparticles on wastewater bio-logical nitrogen and phosphorus removal Environ Sci Technol 45 (7), 2826–2832 169 Zhong, Z.X., Li, W.X., Xing, W.H., Xu, N.P., 2011 Crossflow filtration of nanosized catalysts suspension using ceramic membranes Sep Purif Technol 76, 223-230 170 Zhou, D., Keller, A.A., 2010 Role of morphology in the aggregation kinetics of ZnO nanoparticles Water Res 44, 2948–2956 171 Zhu, X.S., Zhu, L., Duan, Z.H., Qi, R.Q., Li, Y., Lang, Y.P., 2008 Comparative toxicity of several metal oxide nanoparticles in aqueous suspensions to zebrafish (Danio rerio) early developmental stage J Environ Sci Health A Toxic Hazard Subst Environ Eng 43 (3), 278284 172 Zhu, X., Wang, J., Zhang, X., Chang, Y., Chen, Y., 2009b The impact of ZnO nanoparticle aggregates on the embryonic development of zebrafish (Danio rerio) Nanotechnology 20, 1-9 122 APPENDIX Appendix A1: Standard curves Figure A1.1 Standard curve for COD (High concentration) Figure A1.2 Standard curve for COD (Low concentration) 123 Figure A1.3 Standard curve for NH4+-N Figure A1.4 Standard curve for NO2 N 124 Figure A1.5 Standard curve for NO3 N Figure A1.6 Standard curve for PO43 P 125 Figure A1.7 Standard curve for Polysaccharides Figure A1.8 Standard curve for Proteins 126 Appendix A2: EDX Analysis Figure A2.1: Elemental content of sludge on Day 69 127 Figure A2.2 Elemental content of sludge on Day 140 128 Figure A2.3 Elemental content of sludge on Day 214 129 Figure A2.4 Elemental content of sludge on Day 240 130 [...]... reported ZnO NP concentrations of 10 ng/l in natural surface water and 430 ng/l in treated wastewater in Europe, 1 ng/l in natural surface water and 300 ng/l in treated wastewater in US and 13 ng/l in natural surface water and 440 ng/l in treated wastewater in Switzerland, as shown in Table 2.3 14 Table 2.3 Modeled concentrations of ZnO nanoparticles released into environmental compartments in different... micron sized pollutants, but very 6 little information is currently available on the fate of nanoscale materials in treatment processes Several studies had confirmed that a considerable amount of the NPs, including zinc oxide, released into the activated sludge process can be absorbed by the activated sludge, resulting in a reduction of NPs in the effluent and an accumulation in the biomass (Kaegi et al.,... products are retained by wastewater treatment plants (Benn and Westerhoff, 2008; Kiser et al., 2009; Tiede et al., 2010) However, the fate of ZnO-NPs during and after wastewater treatment remains largely unknown Conventional wastewater treatment plants are not designed to remove nanoparticles from wastewater stream, and the effect of nanoparticles on the treatment efficiencies of wastewater process also... main advantages of choosing MBR over the conventional activated sludge system (CAS) in wastewater treatment are lower sludge production and smaller carbon footprint Conversely, the main challenges are in higher energy and equipment costs and membrane fouling In wastewater treatment using MBR, ultrafiltration (UF) membranes of pore size 0.1-0.4 µm are typically used, and thus able to remove bacteria... bacteria and other micron-sized pollutants from wastewater The question of how effective MBR is in removing nanoparticles, specifically ZnO-NP, now arises Typical wastewater treatment systems, MBRs included, are not designed to treat wastewater containing significant amounts of nanoparticles The mechanisms of particle transport and the impact of particle size during wastewater treatment have traditionally... shown in Table 2.1 12 Table 2.1 Potential fate of nanoparticles in aquatic systems (Klaine et al., 2008, Weinberg et al., 2011) Various properties of ZnO-NPs have made them attractive constituents in many consumer products In European Union countries alone, annual production of ZnO-NPs in 2012 was 1600 tonnes (Sun et al., 2014) Zinc oxide is used mainly in sunscreens and paints or coatings Usage data published... et al (2011) indicate that about 40% of the German population can be expected to use sunscreen, for about 20 days a year Combining the scarce available data which included indicative figures on the content of nanomaterials in various products and usage profiles, an estimate on the contribution of nanoparticles to the annual metal load of two Dutch rivers was reported by Markus et al., 2013 It was predicted... occur in wastewater and the potential toxicity, if any In view of these issues, it is important that the fate and transformation of ZnO-NPs during the wastewater treatment process be examined in detail Lastly, it is also important to study the changes in bacteria community structure due to longterm exposure of ZnO-NPs in order to gain more insight into the microbialNPs interaction in wastewater treatment. .. Wilson Database, 2011) Occasionally, accidental spillages or permitted release of industrial effluents in aquatic systems could also lead to direct exposure to nanoparticles for humans via inhalation of water aerosols, skin contact and direct ingestion of contaminated drinking water or particles adsorbed on vegetables or other foodstuffs (Moore, 2006) More indirect exposure could arise from ingestion of. .. hindered aggregation of both morphologies Chaúque et al., 2013 discussed the impacts of stability of ZnO-NPs in wastewater treatment It was found that the release of zinc from ZnO-NPs in wastewater was more significant under acidic conditions and low ionic strength, but the release of zinc from ZnO-NPs in wastewater is lower compared to de-ionized water, indicating the role of biomass present in wastewater ... of zinc oxide nanoparticles 19 2.2.1 Mechanisms of zinc oxide nanoparticles 21 2.2.2 Effects of zinc oxide nanoparticles on bacteria 23 2.2.3 Effects of zinc oxide nanoparticles on wastewater treatment. .. of this project I would also like to express appreciate to all my laboratory mates, namely Divya Shankari Srinivasa Ragha, Shruti Vyas, Subhabrata Das, Thulasya Ramanathan and Gayathri Natarajan,... industrial effluents in aquatic systems could also lead to direct exposure to nanoparticles for humans via inhalation of water aerosols, skin contact and direct ingestion of contaminated drinking water