Experimental assessment of the efficacy of microfiltration and ultrafiltration for Cryptosporidium removal

In order to evaluate the efficacy of microfiltration and ultrafiltration for Cryptosporidium oocyst removal, a bench-scale experiment was carried out using two 0.2m(2) modules, MF (nominal pore size 0.25 mu m) and UF (nominal cut-off MW 13,000 daltons) in cross flow mode at an oocyst level of 10(6)/L. Both of the membranes eliminated the oocysts from the influents with removal efficiency estimated to be >7 log(10). As for the MF, an additional experiment was conducted at a much higher oocyst level up to 10(8) oocysts/L in both cross-flow and dead-end modes and which achieved >7 log(10) removal, although some oocysts appeared in the filtrate in both modes. Based on these results, microfiltration and ultrafiltration are conclusively considered to be excellent processes for drinking water treatment as a single process that produces safe tan annual risk 10(-4)) water from highly polluted source waters. (C) 1998 IAWQ. Published by Elsevier Science Ltd. All rights reserved.