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 ...

a b s t r a c tZeolites are potentially a more robust desalination alternative as they are chemically stable and possess the essential properties needed to reject ions. This work proposes to use zeolite membranes for desalination of saline recycled wastewater for the possibility of avoiding the costly pre-treatment needed for polymeric reverse osmosis membranes. The MFI-type zeolite membrane was developed on a tubular α-alumina substrate by a combined rubbing and secondary hydrothermal growth method. The prepared membrane was characterised by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and single gas (He or N 2 ) permeation, and underwent desalination tests with saline wastewater under different conditions. When saline wastewater was fed at 7 MPa to the zeolite membrane it showed a salt rejection of 80% based on electrical conductivity (EC) and a flux of 4 L m À 2 h À 1 . A 254 (organics absorption at the wavelength of 254 nm measured by a HACH DR5000 spectrophotometer) removal exceeded 90%. Slightly lower salt removal and A 254 results were observed when operating at a lower pressure of 3 MPa. During batch concentration runs on the saline wastewater, the EC of the feed water increased from the initial value of 1770 mS cm À 1 to 3100 mS cm À 1 over the 48 h test time which indicates that a 43% water recovery was achieved. EC reduction remained 470% and flux was maintained at around 2 L m À 2 h À 1 throughout the test period, indicating that the membrane resisted organic fouling. Chlorine stability studies showed that a long-term (7 days) strong hypochlorite clean did not significantly alter the flux or rejection confirming the chemical stability of zeolite membranes. Overall, the zeolite membrane showed excellent chemical resilience and produced a desalinated product suitable for reuse applications (e.g. irrigation, residential or industrial). Fluxes, however, need to be improved to be competitive with current polymeric membranes as do rejections for higher purity water applications.

An innovative concept is proposed to recover ammonia from industrial wastewater using a molecular sieve silica membrane in pervaporation (PV), benchmarked against vacuum membrane distillation (VMD). Cobalt and iron doped molecular sieve silica-based ceramic membranes were evaluated based on the ammonia concentration factor downstream and long-term performance. A modified low-temperature membrane evaluation system was utilized, featuring the ability to capture and measure ammonia in the permeate. It was found that the silica membrane with confirmed molecular sieving features had higher water selectivity over ammonia. This was due to a size selectivity mechanism that favoured water, but blocked ammonia. However, a cobalt doped silica membrane previously treated with high temperature water solutions demonstrated extraordinary preference towards ammonia by achieving up to a 50,000 mg/L ammonia concentration (a reusable concentration level) measured in the permeate when fed with 800 mg/L of ammonia solution. This exceeded the concentration factor expected by the benchmark VMD process by four-fold, suspected to be due to the competitive adsorption of ammonia over water into the silica structure with pores now large enough to accommodate ammonia. However, this membrane showed a gradual decline in selectivity, suspected to be due to the degradation of the silica material/pore structure after several hours of operation.

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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

Ostensibly hydrophilic alginates are known to foul hydrophobic membranes, under various conditions. Here, controlled experiments have been conducted at high and low pH on the fouling of a polypropylene membrane by alginate and the results suggest that the observed fouling is due to an intrinsic property of the alginate. Thus quantum chemical calculations on the M and G monomers of alginate reveal that M adopts an equilibrium geometry that is hydrophilic on one face and hydrophobic on the other, i.e. is potentially amphiphilic. Molecular dynamics simulations on short alginate chains of different sequences interacting with a modelled polypropylene surface, show that this characteristic is carried over to the polymer and results in hydrophobic patches along the chain that facilitate attractive interactions with the polypropylene surface. This concept is buttressed by an analysis of the binding characteristics of a previously reported X-ray structure of the mannuronan C-5 epimerase AlgE4 enzyme.

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Photocatalytic oxidation processes have interest for water treatment since these processes can remove recalcitrant organic compounds and operate at mild conditions of temperature and pressure. However, performance under saline conditions present in many water resources is not well known. This study aims to explore the basic effects of photocatalysis on the removal of organic matter in the presence of salt. A laboratory-scale photocatalytic reactor system, employing ultraviolet (UV)/titanium dioxide (TiO₂) photocatalysis was evaluated for its ability to remove the humic acid (HA) from saline water. The particle size and zeta potential of TiO₂ under different conditions including solution pH and sodium chloride (NaCl) concentrations were characterized. The overall degradation of organics over the NaCl concentration range of 500-2,000 mg/L was found to be 80% of the non-saline equivalent after 180 min of the treatment. The results demonstrated that the adsorption of HA onto the TiO₂ particles was dependent on both the pH and salinity due to electrostatic interaction and highly unstable agglomerated dispersion. This result supports UV/TiO₂ as a viable means to remove organic compounds, but the presence of salt in waters to be treated will influence the performance of the photocatalytic oxidation process.