Mathematical modelling of simultaneous nitrification and denitrification in biological reactor systems - a review

Modelling bioprocesses is an essential aspect in process design of reactor systems in the context of wastewater treatment. Designing a biological reactor for simultaneous nitrification and denitrification requires consideration of both substrate and microbial kinetics along with the effect of other experimental parameters. Nitrogen removal from wastewaters can be economically and efficiently achieved using this single-staged process that has proved to be advantageous over nitrification and denitrification, occurring separately. For the last few decades several models have been developed to estimate and predict outcome of such processes based on both experimental results and modifications of classical mathematical models including activated sludge models. Models have been established for a number of different suspended and attached growth reactors considering several influencing and inhibitory parameters. This paper exhaustively reviews the existing models analysing different considerations and assumptions thereby identifying the research gaps that can be further addressed to develop a more versatile model of simultaneous nitrification and denitrification.