Emulsified oily wastewater treatment via fertilizer drawn forward osmosis using a corrugated thin film composite membrane

Membrane fouling and draw solution recycle are two important challenges faced by forward osmosis (FO) process in treating wastewater. In this study, we innovatively designed a corrugated TFC FO membrane(#FO-C) by conducting interfacial polymerization (IP) on a commercial corrugated polyvinylidene fluoride (PVDF) substrate and utilized fertilizer as the draw solution to treat emulsified oily wastewater for mitigating membrane fouling and recovering draw solution simultaneously. The corrugated-pattern membrane, #FO-C, had a similar separation performance compared with conventional flat TFC membrane (#FO-F), demonstrating that the corrugated pattern makes a little difference on IP process. Inspiringly, compared with #FO-F, #FO-C tested at parallel and vertical modes exhibited lower decrease of water flux in oily wastewater treatment when used 1 M (NH4)2SO4 (SOA) and three different types of oily wastewater (prepared by neutral and negatively/positively charged surfactants) as draw and feed solutions, respectively. In addition, the declined permeability of #FO-C could easily recover with performing surfactant cleaning and osmosis backwashing, which that of #FO-F only recovered partially. The result of computational fluid dynamics (CFD) simulation illustrated that the corrugated pattern of #FO-C would bring about vortex and higher shear stresses, which effectively alleviate the foulant deposition of on the membrane surface. Moreover, the diluted fertilizer draw solution was utilized to irrigate the plants directly and presented a promising result, readily achieving the recovering of draw solution. This work provides a promising strategy for meeting the challenges in FO process, having an important reference value. Graphical abstract