Aerobic microbial transformations of resuspended sediments in combined sewers - a conceptual model

Abstract

A methodology for characterisation and a concept for modelling of aerobic microbial transformations of resuspended sewer sediments based on long term measurements of oxygen utilisation rates (OUR's) are presented. The OUR measurements were evaluated applying a conceptual model for aerobic microbial transformations of sewer solids based on methodologies originating from description of activated sludge processes. Validation showed that yield coefficient and maximum growth rate could be considered constant when readily biodegradable substrate was added to the resuspended sewer solids during the OUR experiment. Maintenance energy requirement of the biomass was argued to be a better concept for modelling microbial transformations compared with either considering decay of biomass into hydrolysible substrate or including endogenous decay of biomass. OUR measurements are recommended as a valuable methodology for characterisation of suspended sewer sediments in terms of COD-fractions and related biotransformations.