INTEGRATED MODELING - COMPARISON OF STATE VARIABLES, PROCESSES AND PARAMETERS IN SEWER AND WASTE-WATER TREATMENT-PLANT MODELS

All the parts of an urban drainage system, i.e., the sewer system, the wastewater treatment plant (WWTP) and the river, should be integrated into one single model to assess the performance of the overall system and for the development of design and control strategies assisting in its sustainable and cost effective management. Existing models for th e individual components of the system have to be merged in order to de velop the integrated tool. One of the problems arising from this metho dology is the incompatibility of state variables, processes and parame ters used in the different modelling approaches. Optimisation of an ur ban drainage system, and of the wastewater treatment process in partic ular, requires a good knowledge of the wastewater composition. As impo rtant transformations take place between the emission from the househo ld and the arrival at the treatment facility, sewer models should incl ude these transformations in the sewer system. At present, however, re search is still needed in order to increase our knowledge of these in- sewer processes. A comparison of the state variables, processes and pa rameters has been carried out in both sewer models (SMs) and activated sludge models (ASMs). An ASM approach is used for the description of reactions in sewer models. However, a difference is found in the expre ssion for organic material (expressed in terms of BOD) and heterotroph ic biomass is absent as a state variable, resulting in differences in processes and parameters. Reconciliation of both the models seems wort hwhile and a preliminary solution is suggested in this paper. (C) 1997 IAWQ. Published by Elsevier Science Ltd.