Fate of coliforms and pathogenic parasite in four full-scale sewage treatment systems in India

The occurrence and removal of fecal indicators (total coliforms (TC), fecal coliforms (FC), fecal streptococci (FS)) and pathogens (helminthes eggs) were studied in various municipal wastewater treatment processes (UASB + FPU, ASP, EA, WSP). The reductions in TC and FC concentrations were usually between 2.0 and 2.5 log units in up-flow anaerobic sludge blanket reactor incorporated with final polishing unit (UASB + FPU). Almost similar reduction was observed in activated sludge process system (ASP) and waste stabilization ponds system (WSP), while it was log 3.0 in extended aeration system (EA). UASB + FPU and WSP systems were observed more efficient to reduce helminthes eggs at almost 100%, whereas only 97% removal was observed in case of ASP and EA system. In addition to monitoring of indicator organisms, turbidity, suspended solids (SS), and biochemical oxygen demand (BOD) were used as indirect measure of the potential presence of microorganisms. Interrelationship of BOD, SS, and turbidity with fecal indicator bacteria concentration in influent and effluent manifest that improvement of the microbiological quality of wastewater is strongly linked to the removal of BOD and SS.