Evaluation of the chlorine requirements for a water treatment plant

Water from Dhamni reservoir is subjected to alum dosing and chlorination before being used as raw water for Tarapur Atomic Power Station (TAPS)-3 and 4 units. In the present study the water samples from the lake were used to evaluate their alum dose and chlorine requirements. The monsoon fed lake water, with low turbidity (<2.N.T.U.), low conductivity, low alkalinity, and low B.O.D. (<1 mg/L), exhibited a low alum requirement (2 mg/L). The water samples were hypochlorinated, using NaOCl, with doses varying from 1 to 7 mg/L, and the reaction time ranging from 0.5 to 4.0 hours. The results revealed a low consumption of chlorine, which was in accordance with the lake water characteristics. The exponential of Tara's relationship in the lake water revealed the possible presence of nitrogen in the form of simple amino acids. Hence a chlorine dose of 3mg/L and a alum dose of 2mg/L was suggested for use at WTP. (author)