Humic Acid fouling mitigation by antiscalant in reverse osmosis system.

The mitigation of humic acid (HA) fouling on reverse osmosis (RO) membrane was investigated by using an environmentally benign antiscalant, polyaspartic acid (PASP). In the presence of PASP, HA fouling decreased with increasing Ca(2+) concentration. This positive effect of Ca(2+) was not due to the electrostatic repulsion as measured by zeta potential, but probably due to the formation of a stable water-soluble complex HA-Ca-PASP through Ca(2+) bridging. Fouling inhibition efficiency phi increased with increasing PASP concentration, but overdosing could lead to an adverse effect. At higher feedwater pH, HA fouling was alleviated and the phi was slightly improved. HA fouling increased when increasing initial permeate flux and decreasing cross-flow velocity, but the fouling behaviors became less susceptible to the two hydrodynamic parameters in the presence of PASP. The phi was hardly affected by the initial permeate flux and the cross-flow velocity. HA fouling decreased with decreasing feed temperature in the presence of PASP, likely owing to the improved stability of HA-Ca-PASP at lower temperature. The implication of this paper is that it presented an attractive and feasible approach for organic fouling control in RO system by dosing antiscalant.