High rate physico-chemical process as a pre-treatment to membranes used in water reuse
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The presence of NOM in the source water adversely affects drinking water treatments and water quality. NOM is thus known to increase disinfectant and coagulant demand, fouls membrane and favours biological regrowth in the distribution network. Extensive work has focused on enhanced coagulation, activated carbon adsorption and membrane processes as strategies to remove dissolved organic carbon. The main objective of this study is to assess the impact of Purolite®A SOOPS ion exchange resin on dissolved organic carbon (DOC) removal and fouling reduction of membrane filtration used as post-treatment. Moreover, the effect of Purolite® A500PS on hydrophilic and hydrophobic substances removal from biologically treated sewage effluent (BTSE) was also studied. Purolite® A500PS can effectively remov~ effluent organic matter (EfOM) from biologically treated sewage effluent. At a dose of 0.5g/L, Purolite® A500PS was able to remove as high as 84% of DOC from synthetic wastewater and 79% from real biologically treated sewage . effluent. It was found that DOC removal efficiency strongly depended on the size of Purolite® A500PS. An investigation of the adsorption equilibrium behaviour of Purolite® A500PS ion exchange indicated that the Langmuir and Freundlich models fitted wel I with the experimental data. In addition, kinetic adsorption of Purolite® AS OOPS with organic compound can be described by the Ho model. A series of batch experiments were conducted to evaluate the effect of different influent concentration on the performance of Purolite®A 500PS. The results indicated that the DOC adsorption rate of Purolite® A500PS dropped 76% to 45% when initial concentration increased from 10 mg/L to 20 mg/L. Fluidised bed Purolite® A500PS column can effectively remove 74.5% of DOC from wastewater effluent. The smaller size o(l 50--300 μm of Purolite® A500PS is more effective in DOC removal because of its higher detention time and longer bed depth. Purolite® ASOOPS fluidized bed treatment was significantly affected by bed depth and fluidization velocity. Higher bed depths and lower fluidization velocity led to a superior DOC removal from synthetic wastewater. An increase of 20% in the removal of efficiency was attained when GAC was used in the first step prior to Purolite® A500PS fluidized treatment. Moreover, adsorption of large MW compounds was significant when both GAC and Purolite® A500PS were used as a filter medium. Combination of GAC and Purolite® A500PS treatment removed larger molecular size fraction (more than 600 Da) more effectively whereas smaller molecular size fraction (below 300 Da) could also be removed to some extent. In addition, LC-OCD analysis demonstrated that pre-treatment of GAC on Purolite® A500PS decreased more than 95% of hydrophobic and hydrophilic from synthetic wastewater. Post-treatment by flocculation was considered to improve further DOC. It was found that the optimum flocculant dose reduced significantly from 40 mg/L to 18 mg/L when SWW was pre-treated by Purolite® A500PS fluidized column. The combined treatment Jed to a higher DOC removal efficiency of 84%. When the Purolite® A500PS fluidized column effluent was pumped into the submerged membrane reactor, an increase of l 0% in organic removal \Vas achieved after filtration. The critical flux of submerged membrane hybrid reactor system was increased from 20 L/m2.h to 35 L/rn2.h when a dose of 0.1 g/L particle size of l 50-300 μm of Purolite®A 500PS was added . The TMP was decreased from 30KPa with conventional submerged membrane system to 13KPa with submerged membrane hybrid reactor system.
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