Coliform MPN counts of municipal raw sewage and sewage treatment plant in relation to the water of Buckingham Canal at Kalpakkam (Tamil Nadu, India).

ABSTRACT

Most Probable Number (MPN) of Total Coliforms (TC) and Faecal Coliforms (FC), and the physicochemical variables - temperature, Dissolved Oxygen (D.O.), Biochemical Oxygen Demand (B.O.D.), Chemical Oxygen Demand (C.O.D.), nitrates, phosphates and chlorides of municipal raw sewage and that of aeration tank and secondary clarifier of the Sewage Treatment Plant (STP), in relation to water at the treated sewage out-fall point, down-stream and up-stream of the Buckingham Canal at Kalpakkam were analyzed. Total Coliform and Faecal Coliform MPN counts were higher, 170 and 70/100 mL respectively in the raw sewage. However, the counts of the former in the aeration tank though remained similar, that of FC decreased to 50/100 mL; both of the counts further decreased to 30 and 44/100 mL respectively, in the secondary clarifier and were 110 and 23/100 mL, respectively at the treated sewage out-fall point in the canal. Total coliforms MPN was more than 18 times less in the water at the up-stream than that of the treated sewage out-fall point in the canal. Interestingly MPN of the FC in the up-stream water was nil while it was 8/100 mL in the canal's down-stream point. It is concluded that the FC, B.O.D., C.O.D., nitrates, phosphates and chlorides decreased and the D.O. increased in the treated-sewage due to the treatment of raw sewage through the STP.