Secondary Effluent Purification towards Reclaimed Water Production through the Hybrid Post-Coagulation and Membrane Distillation Technology: A Preliminary Test

Abstract

Shortage of water resource makes the production of high-grade reclaimed water become an important topic. This study proposed the post-coagulation and membrane distillation hybrid technology for further treatment of the secondary effluent to produce the reclaimed water with high quality. The emerging high-efficient polytitanium coagulant was utilized in post-coagulation unit, with the results suggesting its superior coagulation performance than the conventional polyaluminum chloride in terms of both particulates and organic matter removal. The titanium coagulated effluent then flowed to the subsequent direct contact membrane distillation unit for further purification. Permeated flux of the direct contact membrane distillation reached stable value of around 5.1 L/m2·h, which was accompanied by the production of the filtrate with high quality (turbidity < 0.4 NTU and dissolved organic carbon < 1.0 mg/L). Post-coagulation could not only withdraw the foulants from raw secondary effluent, but also improve the subsequent permeate flux and mitigate membrane fouling during membrane distillation process. The foulants attached on membrane surface was the main cause of membrane fouling during membrane distillation procedure. Both economical and practical prospect are included in this study, with the results demonstrated that post-coagulation of the secondary effluent followed by the subsequent membrane distillation procedure was a feasible and high-efficient strategy towards reclaimed water production.