Application of Micellar-enhanced ultrafiltration for nutrient removal

Abstract

The feasibility of micellar-enhanced ultrafiltration to remove nutrients, nitrate and phosphate, was investigated with a cationic surfactant, cetlypyridinium chloride (CPC). The effects of surfactant molar ratios on the rejection of nitrate and phosphate and flux decline were studied. In the nitrate/phosphate/CPC system, as the molar ratio of nitrate : phosphate : CPC increased from 1 : 0.06 : 1.06 to 1 : 0.06 : 3.18 and to 1 : 0.06 : 5.30, the rejection of nitrate increased from 77 % to 84 % and to 92 %, while phosphate rejection increased from 83 % to 87 % and to 95 %, respectively. The rejection of CPC increased as the molar ratio increased and the concentration of CPC in the permeate was negligible because the size of CPC micelle was lager than pore size of the membrane, which indicated that the secondary pollution by surfactant might be insignificant. The reduction of permeate flux induced by the addition of surfactant was due to the gel layer formed on the surface of the membrane.