Nitrification and denitrification kinetics in the activated sludge process

The bi-substrate active-site death regeneration model, developed by Dold, Ekama and Marais (1980), to describe the aerobic activated sludge process, was extended to provide a reliable description of the behaviour of the nitrification-denitrification single sludge activated sludge process under constant, cyclic or unsteady conditions of flow and load. The extended model applies to series reactor systems containing aerated and non-aerated reactors and to single reactor systems having alternating aerated and non-aerated periods. The extension describing the behaviour in the anoxic state required no change in the basic equations describing the aerobic state. The numerical values of the kinetic constants in the anoxic state equations were found to be the same as those in the aerobic state equations, except for one: The value of the utilization rate constant for slowly biodegradable material in an anoxic environment is a fraction of approximately 0,38 of the value of this constant in an aerobic environment. Nitrification is affected in so far that growth of nitrifiers takes place in an aerobic environment, whereas death of nitrifiers takes place in both aerobic and anoxic environments. The existing empirical denitrification models (valid for constant flow and load conditions) could be deduced from the solutions of the basic equations. The empirical denitrification rate constants could be interpreted in terms of the expressions for utilization of easily and slowly biodegradable organic substrates in an anoxic environment. These constants were shown to have no fundamental kinetic significance; they are only apparent constants, the result of kinetic reactions which, fortuitously, show little variation under normal operational conditions.

Grantor dc:publisher.institution

Department of Civil Engineering

Year dc:date.issued

1981

Author dc:creator

• Van Haandel, Adrianus Cornelius

Advisor dc:contributor.advisor

• Marais, Gerrit van Rooyen

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/11427/15664

OAI identifier oai:identifier

oai:open.uct.ac.za:11427/15664