CHLORINE SENSITIVITY OF ENVIRONMENTAL, DISTRIBUTION-SYSTEM AND BIOFILM COLIFORMS

Coliform bacteria, isolated from treated drinking water supplies, can be derived from a range of sources (e.g. infiltration, breakthrough at the treatment works or from the biofilm established within the pipewo rk). The sensitivity of these bacteria to chlorine may be related to t heir source and metabolic status. Strains of coliforms were isolated f rom sewage works effluents, river and reservoir waters as well as from the bulk water and biofilms from distribution systems. These were ass ayed for sensitivity to free and total chlorine using two assay proced ures. For E. coli, the isolates from the distribution system bull-wate r showed greater resistance to free chlorine than those from sewage ef fluents and equivalence to those from river waters. For non-E. coli co liforms (mainly strains of Klebsiella, Enterobacter and Citrobacter), those from distribution system biofilms showed the greatest sensitivit y to free and total chlorine whilst those from river water had the gre atest resistance. (C) 1997 IAWQ. Published by Elsevier Science Ltd.