RESPONSE OF EQUILISATION BASINS TO TIME VARIABLE B.O.D. INPUTS

Abstract

The inherent variability of waste water discharges have been reported to cause seriQusproblemsto the operation of biological treatment units, resulting in appreciable upsets in total plant efficiency. However in the conventional practice of the design, direct accounting of likely effects of the input variability of waste waters are neglected even though with the gradual depletion of dilution ratios in receiving waters, more stringent regulations might be desirable. For removing the variability of BOD5 inputs to the required degree, the response of Equalisation basins have been studied in this work. To evaluate the response of the equali-sation basins to time variable BOD5 inputs 2 cases have been studied viz. the data for Kanpur city sewage (as reported) and Industrial waste water from Indian Drugs and Pharmaceuticals Limited, Rishikesh. For the quantification of equalising capacities, a comparative study of the two methods viz. E.P.A. method and Novotony's approach have been made with the Kanpur BOD5 input data. While EPA method is based upon mass balance, technique, the Novotony's approach directly includes the statistical properties of the input raw waste water and takes into account the exact statistical nature in arriving at the rational value of detention time of the basins. The Kanpur city sewage data have been utilised and a model has been derived for ascertaining the size of equalisation basin vis-a-vis the variability removals achieved at the effluent end. vi Further it is concluded that Novotony's approach gives more rational results as compared to E.P.A. method, for ascertaining the degree of variability removal vis-a-vis the size of the unit. A similar study has been conducted on a high organic load and variable inputs for Indian Drngs and. Pharmaceuticals Limited factory at Rishikesh. The I.D.F.L. Waste's BOD5 inputs characteristics have been analysed for its trend, harmonic and random characters and direct use of the data have been incor-porated in studying the response of equalisation basins subjec-ted to variability inputs. Such basins are known to improve the chances of avoiding any likely toxic effects of high BOD value fluctuations in the biological treatment system that are expected from pharmecerticals waste, water and thus ascertaining the equalisation required. These two cases studied will go a long way.inframing more stringent regulations for better management and design of the treatment