Sewage is a household waste and occasionally some liquid waste from industry and commerce that is disposed off via sewers. It contains organic and inorganic impurities and pathogenic and nonpathogenic microbes. Upon contamination of fresh water with sewage, the aerobic pathogenic bacteria add nitrites, sulfates, nitrates while anaerobic one add methane, H2S, phosphine causing the offiensive smell to water bodies. These pathogenic microbes cause many water borne diseases.