FACTORS AFFECTING NITROGEN REMOVAL FROM DOMESTIC WASTE-WATER USING IMMOBILIZED BACTERIA

The parameters affecting the nitrogen removal process by the immobiliz ed bacteria in the anoxic-oxic process have been studied by investigat ing two bench scale Runs A and B. The hollow polypropylene pellets hav e been dosed into the anoxic reactor in Run A and into the oxic reacto rs of both Runs up to 24% of volume. Run B was operated with no pellet s in the anoxic reactor as a control. The maximum nitrification rate o f 0.4 kg NH4-N/m(3)d was achieved in sufficient DO (6.5 mg/l) at 15 de grees C in the reactor with both activated sludge and immobilized micr o-organisms. The volumetric nitrification rate was found to be greatly dependent on bulk oxygen concentration especially when the DO was mai ntained below 4 mg/l. A mathematical model developed successfully simu lated the experimental results showing the variation of nitrification rate with DO. In the case of denitrification, the contribution of immo bilized bacteria was prominent when lesser concentration of MLSS was p resent in the activated sludge in the combined immobilized and activat ed sludge system. The presence of immobilized bacteria in the anoxic r eactor will be effective when higher nitrate nitrogen loadings am expe cted and the maintenance of higher MLSS than 2 g/l in an activated slu dge facility is not feasible. (C) 1998 Published by Elsevier Science L td. All rights reserved.