Bacterial removal from secondary sewage effluent by a combined downflow floating medium flocculator/prefilter and sand filter

摘要

A semi pilot-scale study conducted with the combined downflow floating medium flocculator/prefilter and sand filter indicated that, it is an effective filter system for removing bacteria from the secondary sewage effluent. Since the filter system can remove more than 99% faecal coliform and faecal streptococci from the secondary sewage effluent, the chlorine dose required to achieve the effluent discharge standard of 200 cfu/100mL will be significantly reduced. It was found out that a suitable alum dose of 35 mg/L obtained from jar test was found to be an optimum dose for the filter system. The results also indicated that there was no significant effect of filtration velocity on bacterial removal.