Water Science and Technology Vol 38 No 8-9 pp 283–289 © IWA Publishing 1998
Evaluation of the impact of disinfection processes on the formation of biofilms in potable surface water distribution systems
Maggy N. B. Momba*, T. E. Cloete**, S. N. Venter** and R. Kfir***
*Department of biochemistry and Microbiology, P/Bag x 1314, University of Fort Hare Alice 5700 South Africa
**Department of Microbiology and Plant Pathology, University of Pretoria 0001 Pretoria South Africa
***Technology Management, CSIR, P.O. Box 395 Pretoria 0001 Pretoria South Africa
ABSTRACT
In this study, surface water was used to evaluate the impact of disinfection processes (chlorination, chloramination, ozonation, UV irradiation and hydrogen peroxide) on biofilm formation in potable water distribution systems. Biofilm formation was obvious, even in the presence of residual disinfectant 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 steel coupons than on cement coupons within the first 8 days. Viable bacteria numbers on cement coupons were similar ( 2 log cfu.cm-2) in chlorinated, ozonated and in the control. Biofilm formation was related to the depletion of residual disinfectant concentration. Monochloramine and hydrogen peroxide had a longer residual effect controlling growth of biofilm cells in the system for a longer period before regrowth occurred. Once no residual concentrations could be detected there was no significant difference between the viable bacterial counts on any of the coupons in the various systems.
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