Operational control of storm sewage at an activated sludge process

Operational control of storm sewage at a wastewater treatment plant has attracted intensive concern over the last decade in the context of river basin management. The focus is on the exploitation of the full capacity of the wastewater treatment plant in attenuating storm sewage, and minimizing a direct storm sewage bypass to the river. Attention is particularly paid to the surge of storm water on the activated sludge process. Based on two typical rain events, this paper discusses the performance of several practical controllers in achieving an optimal effluent performance under storm loadings, without risking internal biomass stability and sludge overflow. The control algorithms tested include various controls of recycle rate, step-feed and step-sludge. Prediction errors of influent characteristics and process responses are also under consideration in the assessment. The results illustrate well the desirability, effectiveness and robustness of the tested controllers.