The effect of Purolite® A502PS IEX on the removal of dissolved organics (DOC) and the organic micro-pollutants was studied using an MF–IEX hybrid system (Figure 1 ). A hollow fibre MF membrane was submerged in the reactor tank containing 3 L of ROC. The flow of influent (ROC) and effluent (treated water) was controlled using two master flux peristaltic pumps. The TMP of the membrane filtration was measured using a pressure gauge. Different doses of Purolite® A502PS (5 g/L, 10 g/L; 20 g/L) were added to the reactor tank. The flux of influent and effluent was 36 L/m2·h which maintained a constant water level in the reactor. The reactor tank was fed with continuous air flow at 1.5 m3/m2 membrane area h (pre-determined) to keep the Purolite® A502PS particles in suspension to enhance the removal of contaminants. The hybrid system was found to be effective for two reasons. First, because the prior removal of organics/other charged compounds before they reach the membrane surface reduced fouling/scaling effects on the membrane surface, and second, because the airflow produces shear stress across the membrane surface, and its scouring effect further reduces the deposition of organics and reduces fouling [25 (link),26 (link)].
The loss of volatile organic compounds (VOCs) due to aeration was neglected as the wastewater used in this study was previously biologically treated and stabilized. The primary purpose of hollow fibre MF was to remove tiny purolite particles, if any, from treated water. The TMP of the MF–IEX hybrid system was measured using a pressure gauge (Novus log box).
The MF membrane alone can remove less than 10% of the DOC from the wastewater due to the larger pore size, which is not small enough to retain organic molecules [26 (link)]. Purolite®A502PS was added to enhance the removal of organics from the ROC in the MF–IEX hybrid system. The authors’ previous study [19 (link)], reported that 1 g/L of Purolite® A502PS was optimum in removing organics from RO feed using pre-adsorption of organics. Since ROC is ~5 times more concentrated than RO feed, a 5-fold increase in Purolite® A502PS dosage (5 g/L) was used in MF–IEX hybrid system to achieve optimum organic removal. Further, higher doses (10–20 g/L), were also trialled to enhance the removal of micro-pollutants so as to overcome the competitive effect of the organics for Purolite® A502PS exchange sites.
In addition, the authors have performed a similar short-term experiment with GAC at varying dosages of 5 g/L, 10 g/L, and 20 g/L using the ROC as the feed for the same experimental conditions. The respective DOC removals were observed to be 20–50%, 60–80%, and 70–90% over 4 h of operation [26 (link)]. Though GAC was found to reduce the organic load in several studies, it also reduced the sites available for sorption and removal of other micro- or priority organic pollutants [27 (link)]. Further, the removal of humics with ion-exchange resin (Purolite) is excellent compared to GAC [3 (link)]. In this context, the performance of Purolite®A502PS in the MF–IEX hybrid system was studied for the removal of organic fractions and organic micro-pollutants at the dosage of 5 g/L, 10 g/L, and 20 g/L. The ion-exchange resin was added only at the start of the experiment and no further additions were made during the experimental run.
The loss of volatile organic compounds (VOCs) due to aeration was neglected as the wastewater used in this study was previously biologically treated and stabilized. The primary purpose of hollow fibre MF was to remove tiny purolite particles, if any, from treated water. The TMP of the MF–IEX hybrid system was measured using a pressure gauge (Novus log box).
The MF membrane alone can remove less than 10% of the DOC from the wastewater due to the larger pore size, which is not small enough to retain organic molecules [26 (link)]. Purolite®A502PS was added to enhance the removal of organics from the ROC in the MF–IEX hybrid system. The authors’ previous study [19 (link)], reported that 1 g/L of Purolite® A502PS was optimum in removing organics from RO feed using pre-adsorption of organics. Since ROC is ~5 times more concentrated than RO feed, a 5-fold increase in Purolite® A502PS dosage (5 g/L) was used in MF–IEX hybrid system to achieve optimum organic removal. Further, higher doses (10–20 g/L), were also trialled to enhance the removal of micro-pollutants so as to overcome the competitive effect of the organics for Purolite® A502PS exchange sites.
In addition, the authors have performed a similar short-term experiment with GAC at varying dosages of 5 g/L, 10 g/L, and 20 g/L using the ROC as the feed for the same experimental conditions. The respective DOC removals were observed to be 20–50%, 60–80%, and 70–90% over 4 h of operation [26 (link)]. Though GAC was found to reduce the organic load in several studies, it also reduced the sites available for sorption and removal of other micro- or priority organic pollutants [27 (link)]. Further, the removal of humics with ion-exchange resin (Purolite) is excellent compared to GAC [3 (link)]. In this context, the performance of Purolite®A502PS in the MF–IEX hybrid system was studied for the removal of organic fractions and organic micro-pollutants at the dosage of 5 g/L, 10 g/L, and 20 g/L. The ion-exchange resin was added only at the start of the experiment and no further additions were made during the experimental run.
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