DRINKING-WATER PRODUCTION BY COAGULATION-MICROFILTRATION AND ADSORPTION-ULTRAFILTRATION

Microfiltration (MF) and ultrafiltration (UF) pilot plants were operat ed to produce drinking water from surface water from 1992 to 1996. Mic rofiltration was combined with pre-coagulation by polyaluminium chlori de and was operated in a dead-end mode using hollow fiber polypropylen e and monolith type ceramic membranes. Ultrafiltration pilot was opera ted in both cross-flow and dead-end modes using hollow fiber cellulose acetate membrane and was combined occasionally with powdered activate d carbon (PAC) and granular activated carbon (GAC) adsorption. Turbidi ty in the raw water varied in the range between 1 and 100 mg/L (as sta ndard Kaolin) and was removed almost completely in all MF and UF pilot plants to less than 0.1 mg/L. MF and UF removed metals such as iron, manganese and aluminium well. The background organics in the river wat er measured as KMnO4 demand varied in the range between 3 and 16 mg/L. KMnO4 demand decreased to less than 2 mg/L and to less than 3 mg/L on the average by the coagulation-MF process and the sole UF process, re spectively. Combination of PAC or GAC adsorption with UF resulted in a n increased removal of the background organics and the trihalomethanes formation potential as well as the micropollutants such as pesticides . Filtration flux was controlled in the range between 1.5 and 2.5 m/da y with the trans-membrane pressure less than 100 kPa in most cases for MF and UF. The average water recovery varied from 99 to 85%. (C) 1998 Published by Elsevier Science Ltd