Regrowth of E. coli and S. faecalis in treated sewage after chlorination in a continuous-flow reactor

Abstract

The objective of this study was to examine the regrowth of E. coli and &. faecalis in chlorinated, secondary-treated sewage effluent using a continuous flow system. Regrowth was evaluated at varying chlorine contact times and chlorine residuals. In addition, chemical and physical characteristics of the sewage were evaluated in relation to regrowth. The results showed that while a 99% kill of E. coli could be achieved, regrowth always occurred regardless of the chlorine residual and contact time. S. faecalis never regrew in the chlorinated sewage. No single parameter could be identified as the most important in controlling the extent of regrowth.