Wastewater Treatment Models

Abstract

The state-of-the-art level reached in modeling wastewater treatment plants (WWTPs) is reported. For suspended growth systems, WWTP models have evolved from simple description of biological removal of organic carbon and nitrogen in aeration tanks (ASM1 in 1987) to more advanced levels including description of biological phosphorus removal, physical–chemical processes, hydraulics, and settling tanks. For attached growth systems, biofilm models have progressed from analytical steady-state models to more complex 2-D/3-D dynamic numerical models. Plant-wide modeling is set to advance further the practice of WWTP modeling by linking the wastewater treatment line with the sludge handling line in one modeling platform. In recent years, the focus of plant-wide models has been extended with the prediction of greenhouse gas formation, and increasingly also the fate of micropollutants in the WWTP. Application of WWTP models is currently rather time consuming and thus expensive due to the high model complexity, and requires a great deal of process knowledge and modeling expertise. Efficient and good modeling practice therefore requires the use of a proper set of guidelines, thus grounding the modeling studies on a general and systematic framework. Last but not least, general limitations of WWTP models – more specifically, activated sludge models – are introduced since these define a boundary of validity for WWTP model applications.