Please cite this article as: Myat, D.T., Stewart, M.B., Mergen, M., Zhao, O., Orbell, J.D., Gray, S., Experimental and Computational investigations of the Interactions between model organic compounds and subsequent membrane fouling, Water Research (2013Research ( ), doi: 10.1016Research ( /j.watres.2013 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. The formation of aggregates of sodium alginate and bovine serum albumin (BSA) (as 13 representative biopolymers) with humic acid were detected by Liquid Chromatography (LC) 14 UV 254 response in the biopolymer region for mixture solutions. BSA interaction with humic 15 acid showed that aggregation occurred both in the presence and absence of calcium, 16 suggesting that multivalent ions did not play a part in the aggregation process. Similar 17 analyses of the alginate interaction with humic acid also showed a positive interaction, but 18 only in the presence of calcium ions. The fouling characteristics for the BSA-humic acid 19 mixture appeared to be significantly greater than the fouling characteristics of the individual 20 solutions, while for the sodium alginate-humic acid mixture, the fouling rate was similar to 21 that of the sodium alginate alone. The effectiveness of hydraulic backwashing, 10-15% 22 reversibility, was observed for the BSA-humic acid mixture, while the % reversibility was 23 20-40% for the sodium alginate-humic acid mixture. Increased humic acid and DOC 24 rejection were observed for both BSA-humic acid and sodium alginate-humic acid solutions 25 compared to the individual solutions, indicating that the biopolymer filter cakes were able to 26 M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT2 retain humic acids. When compared with BSA-humic acid mixture solution, greater removal 27 of humic acid was observed for alginate-humic mixture, suggesting that sodium alginate may 28 have a greater capacity for associations with humic acid when in the presence of calcium than 29 BSA. Complementary molecular dynamics simulations were designed to provide insights into 30 the specific mechanisms of interaction between BSA and humic acid, as well as between 31 alginate and humic acid. For the BSA-humic acid system; electrostatic, hydrophobic and 32 hydrogen bonding were the dominant types of interactions predicted, whilst divalent ion-33 mediated bonding was not identified in the simulations, which supported the LC-results. 34Similarly for the alginate-humic acid system, the interactions predicted were divalent ion-35 mediated interactions only and this was also supported the LC results. This work suggests 36 that LC-UV 254 might be used to ...

Previous work has shown that magnetic ion-exchange treatment before coagulation gives high natural organic matter (NOM) removal and reduced levels of disinfection byproduct when compared to conventional enhanced coagulation. The impact of the resin process on the downstream floc formation process after coagulation and the subsequent effect on clarification has not previously been shown. Water containing high concentrations of NOM were treated at pilot scale using (1) conventional enhanced coagulation and compared with (2) treatment using magnetic resin followed by coagulation at reduced doses of 50-70%. Bench scale testing was also carried out to determine floc properties for systems with and without resin pretreatment It was demonstrated that pretreatment using magnetic resin was able to significantly reduce the turbidity load onto filters as a result of the formation of a large and more robust floc. Resin pretreatment also improved NOM removal and reduced disinfection byproduct formation when compared with conventional coagulation. The turbidity load on to the filters following resin pretreatment was 1.5 +/- 0.7 NTU, whereas this value was 2.9 +/- 0.3 NTU for conventional coagulation. Flocs produced with resin pretreatment were larger than those produced by conventional coagulation, with a median floc size of 1000 microm compared to 600 microm. The improvement in floc properties following magnetic resin pretreatment was proposed to be due to the removal of NOM thatwas characteristic of carboxylic acids before the coagulation stage.

11 12Extensive organic characterisation of a wastewater using liquid chromatography with a 13 photodiode array and fluorescence spectroscopy (Method A), and UV 254 , organic carbon and 14 organic nitrogen detectors (Method B) was undertaken, as well as with fluorescence 15 excitation emission spectroscopy (EEM). Characterisation was performed on the wastewater 16 before and after ion exchange (IX) treatment and polyaluminium chlorohydrate (PAC) 17 coagulation, and following microfiltration of the wastewater and pre-treated wastewaters. 18Characterisation by EEM was unable to detect biopolymers within the humic rich 19 wastewaters and was not subsequently used to characterise the MF permeates. IX treatment 20 preferentially removed low molecular weight (MW) organic acids and neutrals, and moderate 21 amounts of biopolymers in contrast to a previous report of no biopolymer removal with IX. 22 PAC preferentially removed moderate MW humic and fulvic acids, and large amounts of 23 biopolymers. PAC preferentially removed proteins from the biopolymer component, with 24 tryptophan-like proteins removed to a lesser extent than tyrosine-like proteins and UV 210 25 adsorbing biopolymers. IX showed no preference for the removal of proteins compared to 26 general biopolymers. An increase in the fluorescence response of tryptophan-like compounds 27 in the biopolymer fraction following IX treatment suggests that low MW neutrals may 28 influence the structure and/or inhibit aggregation of organic compounds. Fouling rates for IX 29 and PAC treated wastewaters had high initial fouling rates that reduced to lower fouling rates 30 with time, while the ETP wastewater displayed a consistent, high rate of fouling. The results 31 for the IX and PAC treated wastewaters were consistent with the long term fouling rate being 32 determined by cake filtration while both pore constriction and cake filtration contributed to 33 the higher initial fouling rates. Higher rejection of biopolymers was observed for PAC and IX 34 waters compared to the untreated ETP water, suggesting increased adhesion of biopolymers 35 to the membrane or cake layer may lead to the higher rejection. 36 37

The aim of the research presented in this paper was to gain greater insight into the characteristics of NOM removed by MIEX® Resin. Previous studies have shown that MIEX® Resin increases the level of removable DOC when used in combination with coagulation, suggesting that these two processes target a different type of organics. Initially the characteristics of DOC in regenerant solutions from four different MIEX® Resin treatment plants were analysed and compared to DOC in the respective raw water. Following this the raw water and the regenerant solutions were coagulated and the characteristics of the residual DOC analysed and compared to the regenerant solutions prior to coagulation. From the regenerant solutions it was seen that MIEX® Resin targets DOC of increased UV254 absorbance, increased charge density and of mid to low molecular weight (5 to 2 kDa). In terms of hydrophobicity no preference of MIEX® Resin for a specific NOM type was seen. The presence of hydrophilic neutral acids in the regenerant solution was unexpected since the removal of only highly charged organic species was expected. Charge density measurements however revealed the presence of functional groups, allowing hydrophilic neutrals to be removed by anion exchange. Comparative coagulation of the raw water and regenerant solution showed that both a residual DOC of similar hydrophobicity in the sub 3 kDa area. Considering that this DOC fraction was present in the regenerant it was concluded that MIEX® Resin removes organics recalcitrant to coagulation from raw water and therefore increases DOC removal when both methods are combined.

11 12The performance of ion exchange (IX) resin for organics removal from wastewater was 13 assessed using advanced characterisation techniques for varying doses of IX. Organic 14 characterisation using liquid chromatography with a photodiode array (PDA) and 15 fluorescence spectroscopy (Method A), and UV 254 , organic carbon and organic nitrogen 16 detectors (Method B), was undertaken on wastewater before and after magnetic IX treatment. relative to the untreated water. However, at longer filtration times the rate of fouling of IX 30 treated waters was lower than untreated water and the relative fouling rates corresponded to 31 the amount of biopolymer material in the feed. It was proposed that the mode of fouling 32 changed from pore constriction during the initial filtration period to filter cake build up at 33 longer filtration times. The organic composition strongly influenced the rate of fouling during 34 the initial filtration period due to competitive adsorption processes, while at longer filtration 35 times the rate of fouling appeared to depend upon the amount of biopolymer material in the 36 feed water. 37 38