Ageing of polyvinylchloride membranes in ultrafiltration of drinking water by chemical cleaning

Sodium hypochlorite (NaOCl) is a common cleaning agent in ultrafiltration (UF) treatment. Despite the efficiency of fouling removal, acceleration of degradation and loss in membrane integrity are caused. In this paper, hollow fiber membranes made from polyvinylchloride (PVC) were treated with different concentration of NaOCl solution for different periods of time, and both virgin and polluted membranes were taken into study. Effects on the membrane were evaluated using transmembrane pressure (TMP), bovine serum albumin (BSA) permeability, and FESEM analysis. Enlargement of pore size was observed after exposure to NaOCl less than 1%, and twist and wrinkles appeared when NaOCl was above 1%, which caused TMP and BSA rejection first declined and rose then. Polluted membranes had worse situation than virgin ones during NaOCl cleaning. 1% NaOCl should be avoided in cleaning.