Review of Activated Sludge Modelling, 1999 Environmental Conference Proceedings

Bruce Gall

Hydromantis, Inc.

A model is a representation of a system that is used to predict the behavior of the system. The application of dynamic models of wastewater treatment processes depends on fundamental process knowledge, synthesis of this knowledge into a model, and implementation of the model in a simulator. These three have converged to provide tools that can be used for process design, analysis, and operation. By using models that encompass fundamental biological and chemical processes, a better understanding of the performance of a wastewater treatment facility is available.

Applications of the models presented in this paper show that better understanding and predictive capability can be used to improve plant performance or reduce the cost of plant operations or upgrades. At a municipal plant, a proposed upgrade based on modeling resulted in significant capital cost savings, in the order of $5 to 10 million, since plant expansion (e.g., building new aeration tanks) for nitrification could be avoided or significantly delayed. At an industrial facility, analysis with a dynamic model revealed that reducing the target F/M by 50% would decrease annual biological sludge disposal costs by 8% without adversely impacting effluent quality.