Effect of chemical dose on phosphorus removal and membrane fouling control in a UCT-MBR

Abstract

To enhance phosphorus removal and make the effluent meet the strict discharge level of total phosphorus (TP, 0.5 mg/L), flocculant dosing is frequently applied. In this study, the performance of aluminum sulfate dosing in a University of Cape Town Membrane Bioreactor (UCT-MBR) was investigated, in terms of the nutrients removal performance, sludge characteristics and membrane fouling. The results indicated that the addition of aluminum sulfate into the aerobic reactor continuously had significantly enhanced phosphorus removal. Moreover, COD, NH4+-N and TN removal were not affected and effluent all met the first level A criteria of GB18918-2002. In addition, the addition of aluminum sulfate had improved the sludge activity slightly and reduced transmembrane pressure (TMP) increase rate from 1.13 KPa/d to 0.57 KPa/d effectively. The alleviation of membrane fouling was attributed to the increased average particle sizes and the decreased accumulation of the small sludge particles on membrane surface. Furthermore, the decline of extracellular polymeric substance (EPS) concentration in mixed sludge liquid decreased its accumulation on membrane surface, resulting in the mitigation of membrane fouling directly.