Disinfection of secondary treated sewage by chlorine in a continuous flow reactor

Abstract

The purpose of this study was to determine the amount of residual chlorine that was necessary to adequately disinfect secondary treated sewage in a continuous flow reactor. Trickling-filter, clarified effluent collected prior to chlorination at the plant site was filtered sterilized and inoculated with two bacteria commonly found in sewage--Escherichia coli and Streptococcus faecalis. Eight different chlorine residuals were evaluated for contact times of 10, 20 and 30 minutes. The results indicated that the chlorine residuals needed to obtain 99.9% kill of E. coli and S. faecalis were 1.95 and 2.40 mg/1, respectively. The data showed that S. faecalis was more resistant to chlorine than was E. coli. Time of contact rather than chlorine residual concentration was determined to be more important in influencing chlorine effectiveness.