Implementing chemical precipitation as a pretreatment for phosphorus removal in membrane bioreactor-based municipal wastewater treatment plants

Abstract

Chemical pretreatment prior to biological treatment is required for achieving wastewater reuse economically by a Membrane Bioreactor (MBR) and has significant potential in establishing a compact primary settling tank and a secondary biological treatment system. The purpose of this study was to investigate the factors that affect chemical phosphorus removal as a pretreatment for MBR-based municipal wastewater. Total Phosphorus (TP) removal from raw wastewater by ferric chloride was more effective compared with Polyaluminum Chloride (PAC), but PAC was superior to ferric chloride for filtered wastewater. TP removal and Suspended Solids (SS) removal correlated significantly, unlike TP removal and Total Nitrogen (TN) removal. The optimal pH values for TP removal was 6.5 and the overall removal efficiencies of TOC and TP were slightly lower compared with turbidity and color removal. Mixing had little effect on the removal of SS, TOC, turbidity, and color. Conclusively, the chemical coagulation/precipitation as a pretreatment can remove phosphorus effectively and can apply MBR-based municipal wastewater treatment.