Assessment of the denitrification potential for biological nutrient removal processes using OUR/NUR measurements.

The denitrification potential, a key parameter in nutrient removal activated sludge systems, is mathematically described in terms of mass balance expressions for different carbon sources, namely, easily biodegradable substrate, slowly biodegradable substrate and biomass. Mass balance was derived both for single-anoxic (pre-denitrification) and dual anoxic (Bardenpho) systems. Correction factors for anoxic growth were experimentally determined using respirometry for domestic sewage and meat processing wastewater. The denitrification potential expressions were evaluated for different process configurations such as pre-denitrification, Bardenpho process and University of Cape Town (UCT) process.

Experimental assessment and modelling of nitrate utilisation for primary sludge.

Electron acceptor utilisation potential of filtered primary sludge under anoxic conditions was experimentally investigated. Major kinetic and stoichiometric parameters were assessed by means of model evaluation of nitrate profile obtained in batch reactors. ASM1, modified for endogenous decay, and ASM3 were used for model simulation. Both models provided consistent interpretation of experimental data. ASM1 yielded mu(H) and Y(HD) values of 6.1 d(-1) and 0.64 g cell COD(g COD)(-1) respectively for heterotrophic anoxic growth. The corresponding storage mechanism associated with ASM3 could be characterised by a k(STO) of 13 g COD (g COD d)(-1) and a Y(STO) of 0.78 g COD(g COD)(-1). The high k(STO) value suggests re-evaluation of the concept of readily biodegradable substrate as defined in ASM3 and tested in the study.