According to CPCB20, the Total Coliforms level should not exceed 50 MPN/100ml to recommend the water as
potable without conventional treatment but after disinfection and the class of water is “A”. The concentrations
shall be 500 MPN/100ml or less the water would be recommended for outdoor bathing only and the class of
water is “B”. But the level of total coliforms organism shall be 5000 MPN/100ml or less must the water source
used for drinking after conventional treatment and disinfection and the class of water is “C”. In the present
investigation minimum Total Coliform levels in River Cauvery and Bhavani was 110 MPN/100ml in
Nerinjipettai station and 130 MPN/100ml Periyakodiveri and Bangalapudur respectively. The water quality
class of these rivers is “B” and it is recommended for outdoor bathing only. The maximum of 1800 MPN/100ml
in Vairapalayam station and 920 MPN/100ml in Bhavani Sagar station, the water was not fit for drinking
without treatment and disinfection. The class of water is “C”.