Assessment of the quality of sewage effluents from dry weather flow channel, Calcutta.

The quality of sewage effluent of Dry weather Flow channel, Calcutta in respect of salinity, sodicity, chloride, sulphate and bicarbonate toxicity and heavy metal hazards was assessed in order to utilize it for irrigation. Although raw sewage in the winter season was toxic in respect of chlorides, sulphates, bicarbonate, BOD, COD; its dilution in the monsoon decreased the toxicity hazards considerably, making it worth using for irrigation. The sewage effluents were rich in N and K, but poor in P status with marginal concentrations of micronutrients (Fe, Cu, Zn & Mn). Heavy metal contents of the soil treated with effluents were also studied.