Evaluation of the impact of disinfection processes on the formation of biofilms in potable surface water distribution systems

In this study, surface water was used to evaluate the impact of disinfectio n processes (chlorination, chloramination, ozonation, UV irradiation and hy drogen peroxide) on biofilm formation in potable water distribution systems . Biofilm formation was obvious, even in the presence of residual disinfect ant concentrations (16.5 mgl(-1) hydrogen peroxide, 1 mg(-1) monochloramine , 0.2 mgl(-1) free chlorine) within the first day after disinfection in the laboratory scale unit. The yield in viable count was higher on stainless s teel coupons than on cement coupons within the first 8 days. Viable bacteri a numbers on cement coupons were similar (+/-2 log cfu.cm(-2)) in chlorinat ed, ozonated and in the control. Biofilm formation was related to the deple tion of residual disinfectant concentration. Monochloramine and hydrogen pe roxide had a longer residual effect controlling growth of biofilm cells in the system for a longer period before regrowth occurred. Once no residual c oncentrations could be detected there was no significant difference between the viable bacterial counts on any of the coupons in the various systems. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.