Model-based characterisation of hydraulic, kinetic and influent properties of an industrial WWTP

Abstract

This paper illustrates the modelling of a full-scale industrial wastewater treatment plant. First, the hydraulics of the plant were characterised by a model-based interpretation of the results of a tracer test. The plant consists of three parallel reactors. The hydraulics of each reactor could be modelled by two tanks in series with non-equal volume. These results were confirmed by calculation of the single pass residence time distribution. Also it was found that the influent flow and the recycle flow were not distributed equally to the three reactors, resulting in different loading rates. Secondly, off-line respirometric experiments were performed to characterise the influent and to determine the sludge kinetics. The same model structure could be applied to describe the influent characteristics and the biokinetics over a period of 1 year. It was found that all wastewaters could be fractionated into three fractions and that one of the fractions was acetate-like. Concentrations of the fractions changed significantly over the year. From on-line respirometric experiments the diurnal dynamics of the influent characteristics and the kinetics of the sludge were assessed. Analysis of the respirograms showed that the wastewater composition and kinetics of the sludge did not change significantly over a short-term period of 40 hours.