EFFECT OF SEWAGE CHLORINATION ON BIOCHEMICAL OXYGEN DEMAND

Abstract

The Biochemical Oxygen Demand, B.O.D., test is used to characterize the sewage qualitatively and quantitatively in many a Industries and institutions pay fees for waste disposal, based on the B.O.D. load. An understanding of the principles involved in sewage chlorination will enable those using the process to apply it in particular treatment plants with maximum efficiency and economy. Owing to limited work being available about the kinetics of B.O.D. of chlorinated sewage, a study has been made to investigate thr, qualitative and quantitative changes which take place in the decomposable organic matter in chlorinated sewage under various chlorine doses, contact times (10,g3 and 30.Mts.) and temperatures (30° and 3/QC). The values of unimolecular parameters used in the equation, representing the first stage of the B.O.D. reaction, were computed from the daily B.O.D. determinations made over a period of 9 days after taking into account the nitrification effect. The following important conclusions were drawn: 1. The B.O.D. reduction is maximum at the first appearance of ovetat i4 residual chlorineo5Pir...al-20 minutes period of contact for the two tempe.atures 30° and 370C. 2. The specifications such as 2 P.P.M. B.O.D. removed per P.P.M. of chlorine stabsorbed" or similar other criteria cannot be generalized. (Contd 3. There are both qualitative and quantitative changes in decomposable matter in sewage as a result of chlorination as indicated by the reduction of the values of unimolecular parameters "K" (reaction velocity constant) and "Loi(ultimate first stage B.O.D.) 4. Magnitude of the parameters "X" and "L" vary with the period of observation, contact time, chlorine dose and temperature .for the same sewage and, the variation is not regular. 5. Chlorination of sewage delays the onset of nitrification