Abstract
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 natural organic matter (NOM) were characterized and the impact of Ca2+ on these characteristics and on the performance of the MF membrane was determined. The multi-cycle MF experiments with hydraulic wash between cycles were conducted for raw and coagulated humic-rich water, and the performance was evaluated by measuring the permeate water quality, resistance to filtration, and permeability recovery with cleaning. Coagulant (polydiallyldimethyl-ammonium chloride) additions from 50% to 100% 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-NOM and resulted in the highest permeability recovery. The median diameter and the two-dimensional 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.
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