In-line coagulation with quaternary amine polymer prior to microfiltration of humic-rich water

Abstract

This work was designed to investigate the feasibility of using a low molecular-weight epichlorohydrin/dimethylamine (epi/DMA) polymer as a primary coagulant for the pretreatment of terrestrial humic-rich water prior to the microfiltration (MF) process, without removal of the flocs produced via the coagulation pretreatment. The main issue explored was the effects of different coagulation conditions on the particle characteristics that would also significantly affect the performance of membranes when filtering coagulated humic-rich water. The size distribution and morphological properties of flocs formed through the coagulation of humic-rich water were characterized and the impact of Ca2+ on these characteristics that were associated with the performance of the MF membrane was also determined. Epi/DMA additions from 50% to 150% of the charge neutralization dose substantially decreased fouling compared to when filtering raw humic-rich water. Short-term fouling was increased when 1mM Ca2+ was added, but the charge neutralization coagulation removed almost all of the fouling tendency that had occurred when filtering Ca–humic solution. The median diameter and the fractal dimension of flocs produced were increased as the zeta potential reached close to zero, which resulted in the formation of a cake layer that was easily removed from the surface of the membrane.