EVALUATION OF CHLORINE DIOXIDE FOR BIOFILM CONTROL IN A MODEL DISTRIBUTION SYSTEM
Abstract:The objective of this study was to examine the disinfection capabilities of chlorine dioxide in comparison to free chlorine and monochloramine in drinking water distribution systems. Annular reactors (ARs) were used to simulate drinking water distribution systems at the bench-scale level. Tap water was treated to remove free chlorine and background biodegradable organic carbon and was subsequently spiked with a known organic carbon cocktail. A biofilm was allowed to establish itself in each of the reactors in the absence of a disinfectant. Once a pseudo-steady state biofilm was established, disinfection was applied. In general, chlorine dioxide provided comparable or better results for inactivating suspended culturable cells, as quantified using heterotrophic plate counts (HPCs). On ARs containing cast-iron coupons, chlorine dioxide provided an inactivation of approximately 3-log reduction for suspended HPCs and 1.74-log reduction for biofilm HPCs at a residual concentration of 0.5 mg/L. At the same concentration, free chlorine provided an inactivation of approximately 1.5-log reduction for suspended HPCs and 1.0-log reduction for biofilm HPCs. However, log-reductions that are comparable to 0.5 mg/L of chlorine dioxide, were achieved by free chlorine at residual levels of 1.0 mg/L. In addition, live/dead counts with epiflouresence microscopy indicated that chlorine dioxide provided a much more significant kill of viable cells than what was observed with the HPC measurement. Thus, results from this study indicated that chlorine dioxide would be a viable alternative for secondary disinfection and biofilm control in the distribution system.
Document Type: Research Article
Publication date: 2002-01-01
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