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The effects of physicochemical wastewater treatment operations on forward osmosis

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journal contribution
posted on 25.10.2016 by Tobias Hey, Niada Bajraktari, Jörg Vogel, Claus Hélix Nielsen, Jes la Cour Jansen, Karin Jönsson

Raw municipal wastewater from a full-scale wastewater treatment plant was physicochemically pretreated in a large pilot-scale system comprising coagulation, flocculation, microsieve and microfiltration operated in various configurations. The produced microsieve filtrates and microfiltration permeates were then concentrated using forward osmosis (FO). Aquaporin InsideTM FO membranes were used for both the microsieve filtrate and microfiltration permeates, and Hydration Technologies Inc.–thin-film composite membranes for the microfiltration permeate using only NaCl as the draw solution. The FO performance was evaluated in terms of the water flux, water flux decline and solute rejections of biochemical oxygen demand, and total and soluble phosphorus. The obtained results were compared with the results of FO after only mechanical pretreatment. The FO permeates satisfied the Swedish discharge demands for small and medium-sized wastewater treatment plants. The study demonstrates that physicochemical pretreatment can improve the FO water flux by up to 20%. In contrast, the solute rejection decreases significantly compared to the FO-treated wastewater with mechanical pretreatment.


The authors gratefully acknowledge VA SYD, Sweden Water Research AB, Svenskt Vatten, VA-teknik Södra and VINNOVA (Nr. 2014-00717, The warm and clean city) for their financial support. Claus Hélix-Nielsen and Niada Bajraktari also acknowledge support from the Danish Innovation Foundation via the IBISS (Nr. 097-2012-4) and MEMENTO (Nr. 4106-00021B) grants.