Controlling membrane fouling of nanofiltration using poly-aluminum chloride and Moringa oleifera coagulants

Abstract

Membrane fouling control during nanofiltration (NF) of contaminated water sources is critical to establishing a cost-efficient advanced drinking water treatment system. This study aimed to evaluate the effect of pre-coagulation using Moringa oleifera (MO) or poly-aluminum chloride (PACl) coagulant on membrane fouling mitigation and final water quality during NF treatment of lake water. This study used four pre-coagulation methods: (i) full coagulation: coagulation-flocculation-sedimentation, (ii) coagulation and flocculation, (iii) rapid mixing alone, and (iv) without coagulant addition. The full coagulation with PACl or MO before NF treatment mitigated membrane fouling, and the optimum PACl or MO coagulant doses achieved the lowest membrane fouling. PACl or MO pre-coagulation with rapid mixing also mitigated membrane fouling, which suggested the potential use of inline coagulation. Turbidity in the coagulated water was the best indicator to predict the level of NF membrane fouling; thus, turbidity in the pre-coagulated water can be utilized to control NF membrane fouling. Regardless of the types of pre-coagulation methods, turbidity and dissolved organic matter concentrations in the NF permeate were equivalent. The results suggest that nanofiltration coupled with inline pre-coagulation can provide high-quality water.