This report describes coagulation and sedimentation of bacterial cells suspended in water using sawdust coated with 1 wt% of an equimolar copolymer of N-benzyl-4-vinylpyridinium chloride with styrene (PBVP-co-ST). When the coated sawdust was mixed with suspension of Escherichia coli and allowed to stand, the coated sawdust precipitated and the bacterial cells formed flocks and accumulated over the precipitated sawdust. The supernatant layer became transparent, and bacterial population in the supernatant layer reduced to 1/1,000,000 or less during the procedure under appropriate conditions. (c) 2005 Elsevier B.V. All rights reserved.