Denitrification Kinetics in Biological Nitrogen and Phosphorus Removal Activated Sludge Systems Treating Municipal Waste Waters

Using plugflow anoxic reactors and batch tests, an experimental investigation was undertaken into the kinetics of denitrification in nitrification denitrification biological excess phosphorus removal (NDBEPR) systems. It was found that (1) in the primary and secondary anoxic reactors, the specific rate constant for denitrification associated with the utilization of slowly biodegradable COD (SBCOD) was respectively 2½ and 1½ times higher than in these reactors in nitrification denitrification (ND) systems and (2) in the primary anoxic reactor, the rapid rate of denitrification attributable to readily biodegradable COD was absent. The increased rate is hypothesized to be due to a stimulation in the active sludge mass of an increased rate of hydrolysis of SBCOD in these anoxic reactors of the NDBEPR system apparently induced by the presence of the anaerobic reactor in these systems.