Minimization of excess sludge production by increase of oxygen concentration in activated sludge flocs; experimental and theoretical approach

The disposal of excess sludge from waste water treatment plants represents a rising challenge in activated sludge processes. Hence, the minimization of excess sludge production was investigated by optimizing the process parameters. Laboratory scale experiments showed, that the excess sludge production was effected by the sludge loading and oxygen concentration. Therefore, a mathematical model that describes substrate removal, oxygen utilization, and excess sludge production within a microbial floc particle, surrounded by biodegradable substrate, will be presented. After calibration of the model parameters, the model validation has been carried out with experimental results. The model takes into account the mass transfer of substrate oxygen, the biological reaction within the floc particle, and the endogenous respiration process. So it allows a detailed calculation of the excess sludge production. The results indicate that the oxygen concentration in the bulk liquid has a significant effect on the amount of excess sludge produced.