Kaelin David, Manser Reto, Rieger Leiv, Eugster Jack, Rottermann Karin, Siegrist Hansruedi
Eawag, Swiss Federal Institute of Aquatic Science and Technology, Uberlandstrasse 133, P.O. Box 611, 8600 Dübendorf, Switzerland.
Water Res. 2009 Apr;43(6):1680-92. doi: 10.1016/j.watres.2008.12.039. Epub 2009 Jan 3.
Although traditionally not taken into account by most of activated sludge models the production of nitrite as an intermediate of the nitrification-denitrification processes becomes of interest in some specific plant operational situations or in case of high sensitivity of the receiving ecosystems. The Activated Sludge Model No.3 (ASM3) was therefore extended for two-step nitrification and two-step denitrification in order to better describe nitrite dynamics especially during the treatment of communal wastewater. Nitrite was included as a new model compound and as an intermediate product of biological processes, both for heterotrophic and autotrophic bacteria. Two new model compounds replace X(A), the original autotrophic biomass: Ammonium Oxidizing Bacteria, X(AOB) and Nitrite Oxidizing Bacteria, X(NOB). Growth and decay processes of nitrifiers were split into AOB and NOB processes (3 additional processes) and heterotrophic anoxic processes were also doubled in order to account for two-step denitrification (4 additional processes). Default values from literature as well as laboratory measurements were considered for the choice of kinetic and stoichiometric parameters. The model was calibrated and validated with laboratory scale tests in batch reactors and with data from an Eawag activated sludge pilot plant configured conventionally with nitrification and pre-denitrification for the treatment of communal wastewater.
