Loose nanofiltration - membrane distillation integrated process for resource recovery from leachate MBR effluent: Performance and membrane fouling

Abstract

The hybrid membrane bioreactor (MBR)-nanofiltration (NF)/reverse osmosis (RO) process is a prevalent strategy for leachate treatment. However, high-pressure NF/RO face significant challenges including limited resource recovery, severe membrane fouling, and refractory saline concentrate. Herein, a novel loose nanofiltration (LNF)-membrane distillation (MD) integrated process was proposed to replace the conventional NF/RO for sustainable management of leachate. The LNF can effectively fractionate organics/salts, and subsequent MD can recover salts and produce high-quality water. The effects of operating conditions on membrane fouling behaviors and recovery efficiency in individual LNF and MD were first systematically evaluated, and then a semi-continuous LNF-MD integrated process was performed. The results show that increasing operating temperature increased the potential of organic-inorganic composite fouling and decreased the fractionation efficiency of organics/salts in LNF process. Appropriately lowering feed pH (e.g., pH 5.0) alleviated membrane fouling/scaling and improved separation efficiencies. For the MD, no fouling or wetting was observed under any feed temperature conditions (40–60 °C). 95.5 % organics, 86.5 % salts, and 81.9 % high-quality water were recovered from leachate MBR effluent using this novel LNF-MD integrated process, which presented great potential for industrial and agricultural reuse. Our work provides a sustainable management solution for leachate towards resource recovery and zero liquid discharge.