Evaluation of industrial biological treatment design on the basis of process modelling

This paper reviews the basic steps, often overlooked, in the design of acti vated sludge systems on the basis of recent concepts introduced for process modelling. Firstly, it evaluates the necessary data base for a rational de sign approach, emphasizing the required wastewater characterization. Second ly, it underlines the significance of functional relationships between reac tor biomass, volume and the sludge age recommended as the major design para meters. Then, it defines excess sludge production with specific reference t o VSS/SS ratio and to the importance of the influent fixed solids concentra tion. Finally, it deals in detail with the oxygen requirement of the system , outlining different modelling approaches to be used for such an evaluatio n and emphasizing the pitfalls to be encountered when using BOD5 parameter for this calculation. (C) 1998 Published by Elsevier Science Ltd. All right s reserved.