Water Reclamation from Primary Municipal Wastewater Treatment Plant Effluent by Membrane Distillation

Abstract

In this work, Direct Contact Membrane Distillation (DCMD) was applied for the treatment of municipal wastewater collected from the primary clarifier of a municipal wastewater treatment plant (MWWTP). The water flux at 60℃ and 20℃ for the feed and permeate side, respectively was 51 kg/m2h in treating the primary effluent. Meanwhile, the electrical conductivity of distillate was in the good range at 1.5 – 1.8 S/cm. Most of the representative parameters for water reuse (SS, nitrate, nitrite, phosphate, total coliform, and turbidity) in the primary effluent were completely removed in MD module operation with PTFE (polytetrafluoroethylene)/ PP (polypropylene) bi-composite membrane. However, limited rejection rate was observed only in ammonia removal due to the volatility of ammonia. Pretreatment of the primary MWWTP effluent by NaOCl showed only 15% decline in water flux for 28 hours of continuous operation. Periodic membrane cleaning with 3% HCl applied for non-pretreated feed recovered initial permeate flux up to 80 - 95% and yielded highly purified distillate in long-term operation of MD system.