Cranfield University School of Applied Sciences Centre for Water Science Thesis for the degree of M.Sc. By Research June 2009 Stuart Carroll Optimising powdered activated carbon dosing procedures for removal of natural organic matter Supervisors: Dr. Peter Jarvis Dr Bruce Jefferson Submitted in partial fulfilment for the degree of Master of Science by research. ©Copyright Cranfield University 2009. All rights reserved. No part of this publication may be reproduced without written permission of the copyright holder. Abstract. The performance of three different types of PAC was analysed for the efficiency at which they remove natural organic matter (NOM) from untreated (raw) water, with the objective of ultimately reducing disinfection bi-product (DBP) formation. The treatment of raw water by PAC was also examined in conjunction with the addition of iron salts in the form of ferric sulphate, for coagulation and flocculation of NOM. The optimum dosing of PAC was achieved at pH 3 and at a dose of around 20mgl-1 which gave 32.7% removal. Coagulation could be seen to give 88% removal and when used together PAC and coagulant gave between 93.6% and 97% removal of NOM. The dosing sequence of PAC and coagulant was investigated whereby it was found that optimum removal was achieved by dosing PAC prior to dosing coagulant, although if the delay between dosing PAC and coagulant was more than 30 seconds it was found to impair NOM removal and increase turbidity. Scale up trials of the dosing strategy were implemented at both Ewden water treatment works, in Yorkshire, and at the Pilot Hall in Cranfield University. The greatest reduction in DBP formation could be seen using Norit SA Super and coagulation. Dosing this activated carbon at 20mgl-1 resulted in a decrease of DBP formation by 86% in raw water and by 78.7% using coagulation alone. Dosing PAC before coagulant produced the lowest levels of DBPs, which were 27.2μgl-1. This is much lower than the 80μgl-1 limit to which water treatment works must adhere. i Acknowledgements. The author would like to thank the following people in no particular order for their assistance, general advice, and moral support. Dr Peter Jarvis for his time and effort in advising me and supervising the project, and for his invaluable comments and corrections on the drafts of the thesis. Dr Bruce Jefferson for his support and advice and assistance in keeping the project on schedule. Professors Simon Parsons and Sue White for giving up their time to attend the project review meetings. Dr Rhuksana Ormersher for her advice on all issues relating to health and safety. Mrs Jane Hubble for her expertise and training on all instrumentation techniques. Mr Paul Barton for his help with general equipment and support and Dr Keith Richards for advice regarding GC-ECD. Dr Jenny Banks and Yorkshire Water for their financial assistance with the project, and for the expertise and advice offered with the application of the on-site trials. All the technical staff at Ewden Water Treatment works for their patience and support while conducting experiments on-site. Miss Johanne Bromage for her moral support that kept me going throughout the entire project. ii Table of Contents Abstract i Acknowledgements ii Table of contents iii Keytoabbreviations v List of figures vii List of tables xi 1.Introduction 1 1.1.Aimsandobjectives 4 2. Literature review 6 2.1.Aimsandobjectives 6 2.2.Naturalorganicmatter 6 2.2.1. Characterisation 8 2.2.2.NOMremoval 13 2.3. Adsorbents 19 2.4. Adsorption 22 2.4.1.Measuringadsorption 30 2.4.2.AdsorptionofNOM 33 2.5. Powdered activated carbon 36 2.5.1. PAC pore size 37 2.5.2.PACporequantity 39 2.5.3. PAC dosing 41 2.6.Summary 42 3.Methods 44 3.1.Analyticaltechniques 44 3.1.1. TOC analysis 44 3.1.2. UV254 analysis 45 3.1.3.THManalysisoftreatedwater 46 3.1.4. HPSEC analysis 47 3.2. Water collection and location of on-site trials 48 3.3. Adsorption of natural organic matter onto powdered activated carbon. 48 3.3.1. Adsorbents 48 3.3.2. Measurements of particle size of PAC 49 3.3.3. Determination of Equilibrium point for NOM adsorption onto PAC 49 3.3.4. Assessment of the performance of PAC 50 3.3.5. Determination of coagulation and PAC InteractionfortheremovalofNOM 53 3.3.6. Floc analysis 55 3.3.7. Fractionation 56 3.4. Full-scale PAC trials 58 3.4.1.EwdenWTWs 58 3.4.2. Pilot Hall trials 60 3.5.Datahandlingandanalysis 63 iii 4. Results 64 4.1. Water characteristics 64 4.2. Powdered activated carbon characterisation 65 4.3.PACadsorptionofNOM 66 4.3.1. Equilibrium results and pH effect 66 4.3.2. Adsorption isotherms 72 4.4.PACandcoagulantinteractions 77 4.5. Characterisation of NOM removal 86 4.6. HPSEC analysis 87 4.7.ChargeofNOMandPAC 89 4.8.PACandcoagulantflocinteraction 91 4.9. On-site trials 94 4.10. Pilot Hall trials 96 5. Discussion 100 6. Conclusion 107 6.1.Activatedcarbonperformance 107 6.2.NOMremoval 108 6.3. Disinfection by-products 108 6.4. On site implications 108 7. References 110 8. Appendices 128 iv Key to Abreviations AC Activated carbon BET Brunauer, Emmett, and Teller CO2 Carbon Dioxide DAF Dissolved air flotation DBP Disinfection by-product DEFRA Department for environmental, food, and rural affairs DOC Dissolved organic carbon DWI Drinking water inspectorate DWQS Drinking Water Quality Standards EPA Environmentalprotectionagency FA Fulvic acid FAF Fulvic acid fraction GAC Granular activated carbon GCECD Gas chromatography electron capture device HA Humic acid HAA Halo-acetic acid HAF Humic acid fraction HAPAC High activity powdered activated carbon HP-A Hydrophilic acid fraction HP-NA Hydrophilic non-acid fraction HPSEC High performance size exclusion chromatography IC Inorganic carbon IUPAC International Union of Pure and Applied Chemistry Kf Freundlich constant NOM Naturalorganicmatter O2 Oxygen PAC Powdered activated carbon PSD Particle size distribution RW Raw water TAA Tri-halo acetic acid TC Total carbon v THM Tri-halo methane TOC Totalorganiccarbon YW Yorkshire water WHO World health organisation WTW Water treatment works vi List of figures 1 Introduction 2 Literature review Figure 1. The change in NOM levels, measured by TOC, over a year, 6 adapted from (□)Zanardi-Lamardo et al. 2004; (▲)Sasaki et al. 2005; (○)Chen et al. 2008. Figure 2. A suggested model of Humic acid, taken from Stevenson (1982). 11 Figure 3. The structure of Fulvic acid, form Buffle (1977). 12 Figure 4. The increase in NOM removal using PAC dosed at a lower pH. 35 (Adapted from Reed and Matsumoto et al., 1991; Duan et al., 2002; Tomaszewska et al., 2003) Figure 5. The percentage pore distribution of a number of commercially 40 available carbons in relation to total (BET) surface area (adapted from Pelakani & Snoeyink, 1998; Li et al., 2003a; Daifullah et al. 2004; Treguer et al., 2006). 3 Methods Figure 6. Comparison of isotherms for Norit SA Super in raw water. The 52 three isotherms are Freundlich (a), modified Freundlich (b) and Langmuir (c). Figure 7. An overview of the fractionation procedure as used by Goslan et 57 al., (2002). Figure 8. An overview of the dosing procedure used at Ewden water 59 treatment works. Figure 9. The Pilot-scale WTWs at Cranfield University. 60 Figure 10. An overview of the dosing procedure used at the Pilot Hall in 62 Cranfield University. 4 Results Figure 11. Comparison of particle distribution size for Norit SA Super, 64 Chemviron Pulsorb C and Pulsorb 207 CP-90. Figure 12. Mean ± S.D UV254 absorbance showing the equilibrium of PAC in 66 pH 1 (a) ph 7 (b) and pH 14 (c) raw water at a dose of 40mgl-1. Figure 13. Mean ± S.D UV254 absorbance showing the equilibrium of PAC in 67 pH 1 (a) ph 7 (b) and pH 14 (c) DAF water at a dose of 40mgl-1. Figure 14. Summary of the amount of removal of NOM in raw water, based 69 on the reduction in absorbance at UV254 for pH 3, 4, and 5.5 for Norit SA super, Pulsorb C, and Pulsorb 207 CP90 dosed at 20mgl-1. Figure 15. Summary of the amount of removal of NOM in raw water, based 70 on the reduction in absorbance at UV254 for pH 3, 4, and 5.5 for Norit SA super, Pulsorb C, and Pulsorb 207 CP90 dosed at 80mgl-1. vii Figure 16. Summary of the amount of removal of NOM in DAF water, based 70 on the reduction in absorbance at UV254 for pH 3, 4, and 5.5 for Norit SA super, Pulsorb C, and Pulsorb 207 CP90 dosed at 20mgl-1. Figure 17. Summary of the amount of removal of NOM in DAF water, based 71 on the reduction in absorbance at UV254 for pH 3, 4, and 5.5 for Norit SA super, Pulsorb C, and Pulsorb 207 CP90 dosed at 80mgl-1. Figure 18. The modified Freundlich isotherm showing the amount of TOC in 73 raw water at equilibrium per mg of Norit SA Super, (Qe±SD) against the amount of TOC removed per milligram of Norit SA Super, (Ce/Do±SD). Figure 19. The modified Freundlich isotherm showing the amount of TOC in 74 raw water at equilibrium per mg of Pulsorb C, (Qe±SD) against the amount of TOC removed per milligram of Pulsorb C, (Ce/Do±SD). Figure 20. The modified Freundlich isotherm showing the amount of TOC in 74 raw water at equilibrium per mg of Pulsorb 207 CP-90, (Qe±SD) against the amount of TOC removed per milligram of Pulsorb 207 CP-90, (Ce/Do±SD).