AWWA QTC97019

This study investigated the effects of the continuous and periodic presence of free chlorine in the influent of anthracite/sand (A/S) and granular activated carbon/sand (GAC/S) filters on the biological performance, i.e. removal of biodegradable organic matter (BOM), of such filters. Data were obtained at bench-scale using four parallel 50 mm ID glass filter columns. The influent of the columns was dosed with a cocktail of easily biodegradable substances. The results showed that the continuous presence of free chlorine (about 0.5 mg Cl2/L) in the influent of an A/S filter totally inhibited the bacterial degradation of several easily biodegradable components. However, an identically operated GAC/S filter led to an essentially total degradation of the organic substances within the filter, despite the presence of the free chlorine in its influent. The periodic presence of free chlorine, i.e. about 0.5 mg Cl2/L once per week for 6 hours, in the influent of an A/S filter, led to a substantially negative effect on the filter's biological performance