Treatment Of Dewatering Construction Water Using An Integrated Forward Osmosis System

Abstract

Forward osmosis (FO) has gained substantial research attention in recent years as a new emerging water treatment technology with low energy consumption. In this study, forward osmosis has been used to treat dewatering construction water (DCW). The impact of flow rates of feed solution (FS) and draw solution (DS), the placement of a spacer on the support layer of the FO membrane and the pretreatment of the feed solution on the performance of the forward osmosis process were investigated. It was found that a feed solution and draw solution flow rate of 2.9 LPM gave the highest membrane flux with an initial value of 0.055 L/m2.min compared to 0.048 L/m2.min, 0.048 L/m2.min and 0.044 L/m2.min at the flow rates of 2.2 LPM, 1.5 LPM and 0.8 LPM, respectively. The highest recovery rate of 24% was obtained at a flow rate of 2.2 LPM compared to a recovery rate of 16%, 21% and 15% for flow rates of 2.9 LPM, 1.5 LPM and 0.8 LPM, respectively. The influence of pretreating DCW on the performance of the FO process was also investigated. Pretreatment by primary settling and multimedia filtration were carried out. Results showed that the recovery rate of the FO process increased the most after pretreatment by multimedia filtration with a recovery rate of 30% compared to 22% and 15% for pretreatment by settling and without treatment, respectively. Furthermore, it was found that when the membrane’s active layer was facing the draw solution in (DS-AL) operation mode, a better membrane flux was achieved when compared to the membrane’s active layer facing the feed solution (FS-AL).