In this study, dewatered construction water (DCW) was used for the first time as the feed solution (FS) in a combined pretreatment-FO process to dilute seawater (i.e. draw solution (DS)) for further desalination. It was found that at a FS and a DS flow rate of 2.2 L.min-1 gave the optimum membrane flux with minimal fouling effects. The addition of a spacer in the membrane feed side was effective at low flow rates (0.8 and 1.5 L.min-1). The FS was then pretreated using two methods: settling and multimedia filtration and run in the FO unit at a low flow rate of 0.8 L.min-1 using a spacer at the feed side. Results revealed a significant increase in the FO membrane flux by 64.3% when multimedia filtration was carried out with a low flux reduction of 7.7%. While the settling method achieved only 13.5% increase in permeate flux and 12.5% flux reduction over time. The multimedia filtration process removed most of the fouling particles and resulted in an elevated and more consistent membrane flux. Results also showed that the water flux was 1.3 times higher when the membrane's active layer was facing the draw solution than when it was facing the feed solution. Cost analysis showed that FO treatment of DCW was USD 7.88 day-1 and it was slightly cheaper when the FO operates on the PRO mode.

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Abstract-Effective application of dielectrophoretic forces in membrane bioreactor (MBR) systems has the potential to suppress membrane fouling. Nevertheless, minimizing the impact of the electric field on biomass suspension is essential to maintain the efficiency of the wastewater treatment process. In this study, interdigitated cylindrical electrodes (IDE), placed inside the membrane module, were used to generate dielectrophoresis (DEP) in an MBR system. The viability of the biomass was determined at different voltages (5-150 V) after 1-hour exposure to a pulsed alternating current (AC) electric field. The results of the behavioral response of the microorganisms revealed that at low voltage applications, the bacteria exhibited good performance and no major impact was found on their viability/metabolism. Whereas at high voltage applications (beyond 100 V), the current intensity and medium temperature increased due to the joule heating effect and caused a significant decline in the bacterial activity and pollutant removal efficiency as a result of bacterial lysis.

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