LEQUIA (University of Girona) and IEA-LTH (Lund University)

December 2005 (updated April 2007)

Many phenomena that cause operational problems in WWTPs are of qualitative nature. Some of them are caused by imbalances of microorganisms (filamentous bulking sludge, filamentous foaming or deflocculation) while some are caused by undesirable operating conditions (rising sludge). Currently these problems can not be considered in the Benchmark Simulation Models (BSMs), which are based on control algorithms and numerical models.

The inclusion of an add-on risk model to the BSMs based on qualitative aspects provides a 'third dimension' for the evaluation of control strategies, i.e. operational costs, effluent quality and operational risks, and thus overall more realistic results can be provided. The description of the Risk Model is presented using standard modelling description and equations to be platform independent.