ABSTRACT
Wastewater discharges containing nitrogen can be toxic to aquatic life, cause oxygen depletion and eutrophication in receiving water, and affect chlorine disinfection efciency (US EPA, 1993). Hence reducing nitrogen levels from wastewater discharges is necessary. Nitrogen compounds can be removed from wastewater by a variety of physicochemical and biological processes. As biological nitrogen removal is more effective and relatively inexpensive, it has been widely adopted over physicochemical processes. In most modern wastewater treatment plants (WWTPs) nitrogen, which is generally in the form of ammonium or organic nitrogen, is removed by biological nitrication/denitrication (Equation 5.3). In the rst step, ammonium is converted to nitrate (nitrication, Equation 5.1) which is then, in a second step, converted to nitrogen gas (denitrication, Equation 5.2). Benets of the process are high removal efciency, high process stability and reliability, relatively easy process control, low area requirement, and moderate cost.
