Moringa oleifera coagulation as pretreatment prior to microfiltration for membrane fouling mitigation

Abstract

Coagulation using Moringa oleifera (MO), a natural coagulant, is an attractive approach in drinking water treatment to break away from conventional chemical coagulation using aluminium or iron salts. This study aimed to evaluate the effect of coagulation pretreatment using pre-filtered MO on the fouling mitigation in the microfiltration (MF) process. MF treatment of river water without pretreatment promoted a considerable reduction in membrane permeability (i.e. membrane fouling), which was not sufficiently recovered by conventional backwashing. In contrast, MF treatment after MO coagulation substantially reduced membrane fouling. Over six filtration cycles (or a 6 h filtration period), the fouling mitigation level with MO coagulation was comparable to that with aluminium sulphate (alum) coagulation. In addition, the major water quality parameters (turbidity and colour) after MF treatment were equivalent between MO and alum coagulation. Pretreatment by MO coagulation has an advantage of maintaining water pH after MF treatment. The results obtained here suggest that MO coagulation can be employed as an effective and low-cost fouling mitigation technique for the MF process in drinking water treatment.