Driving forces in the long range development of wastewater treatment plants

Wastewater treatment plants (WWTP) are planned and designed for a lifespan of 25 to 40years. The catchment area, discharge requirements, available technology, institutional conditions, operationalprocedures etc. of these plants may change drastically over this long time period. In the private sector suchdynamic development would possibly be considered in the planning and design phase based on a scenarioanalysis. However, conducting a scenario process requires knowledge about the driving forces of thisdynamic, which at the moment is very limited in the field of urban drainage. In this paper we take a first stepin closing this gap. In a case study we analyzed the development of a WWTP and its environment for a timeperiod of over a decade. From this investigation we identified the driving forces responsible for the observedstrong dynamic and their effect on the development of the WWTP. Based on the analysis of these forces, wededuce important aspects that will have to be considered in the future if scenario planning is to be appliedroutinely in the field of urban drainage.