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 μ`_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 YSTO 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.