Microbiological and physicochemical analysis of radiation disinfected municipal sewage

The efficacy of gamma radiation for the disinfection of municipal sewage was assessed at the Sludge Hygienization Research Irradiator (SHRI) at Baroda city, Gujarat, India. It was observed that a gamma radiation dose of 2 kGy could effectively reduce the coliform load in raw sewage to acceptable safe levels of less than 100 cfu/ml. The treated effluents from the primary and final settling tanks required lower doses of radiation as the initial microbial load in the treated effluents was low compared to that in the raw sewage. The physicochemical parameters of the effluents such as electrical conductivity, total hardness, chemical oxygen demand (COD), biochemical oxygen demand (BOD) and dissolved oxygen, remained largely unaltered after exposure to gamma irradiation. These effluents could hence be gainfully employed in agricultural practice after radiation disinfection.