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Membrane Water Treatment   Volume 8, Number 5, September25 2017, pages 449-462
DOI: https://doi.org/10.12989/mwt.2017.8.5.449
 
Seawater-driven forward osmosis for direct treatment of municipal wastewater
Yan Sun, Yang Bai, Jiayu Tian, Shanshan Gao, Zhiwei Zhao and Fuyi Cui

 
Abstract     [Buy Article]
    Direct treatment of municipal wastewater by forward osmosis (FO) process was evaluated in terms of water flux decline, reverse salt diffusion, pollutants rejection and concentration efficiency by using synthetic seawater as the draw solution. It was found that when operating in PRO mode (active layer facing the draw solution), although the FO membrane exhibited higher osmotic water flux, more severe flux decline and reverse salt diffusion was also observed due to the more severe fouling of pollutants in the membrane support layer and accompanied fouling enhanced concentration polarization. In addition, although the water flux decline was shown to be lower for the FO mode (active layer facing the feed solution), irreversible membrane fouling was identified in both PRO and FO modes as the water flux cannot be restored to the initial value by physical flushing, highlighting the necessity of chemical cleaning in long-term operation. During the 7 cycles of filtration conducted in the experiments, the FO membrane exhibited considerably high rejection for TOC, COD, TP and NH4 +-N present in the wastewater. By optimizing the volume ratio of seawater draw solution/wastewater feed solution, a concentration factor of 3.1 and 3.7 was obtained for the FO and PRO modes, respectively. The results demonstrated the validity of the FO process for direct treatment of municipal wastewater by using seawater as the draw solution, while facilitating the subsequent utilization of concentrated wastewater for bioenergy production, which may have special implications for the coastline areas.
 
Key Words
    forward osmosis (FO); municipal wastewater; seawater; membrane foulin
 
Address
Yan Sun, Yang Bai, Jiayu Tian, Shanshan Gao and Fuyi Cui : State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology,
Harbin 150090, China
Zhiwei Zhao : Department of National Defense Construction Planning and Environmental Engineering,
Logistical Engineering University, Chongqing 401311, China
 

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