Modelling of wastewater treatment plants – how far shall we go with sophisticated modelling tools?

Abstract

Several levels of complexity are available for modelling of wastewater treatment plants. Modelling local effects rely on computational fluid dynamics (CFD) approaches whereas activated sludge models (ASM) represent the global methodology. By applying both modelling approaches to pilot plant and full scale systems, this paper evaluates the value of each method and especially their potential combination. Model structure identification for ASM is discussed based on a full-scale closed loop oxidation ditch modelling. It is illustrated how and for what circumstances information obtained via CFD (computational fluid dynamics) analysis, residence time distribution (RTD) and other experimental means can be used. Furthermore, CFD analysis of the multiphase flow mechanisms is employed to obtain a correct description of the oxygenation capacity of the system studied, including an easy implementation of this information in the classical ASM modelling (e.g. oxygen transfer). The combination of CFD and activated sludge modelling of wastewater treatment processes is applied to three reactor configurations, a perfectly mixed reactor, a pilot scale activated sludge basin (ASB) and a real scale ASB. The application of the biological models to the CFD model is validated against experimentation for the pilot scale ASB and against a classical global ASM model response. A first step in the evaluation of the potential of the combined CFD-ASM model is performed using a full scale oxidation ditch system as testing scenario.

In situ characterization of local hydrodynamic parameters in closed-loop aeration tanks

“…This value is higher than the one usually measured on pilot scale (from 2.5 to 4.0 mm for EDPM membrane diffusers [13][14][15] and than the one used to simulate hydrodynamics and oxygen transfer in aeration tanks [4,16]. This order of magnitude of the average bubble size is the same as the one observed in bubble columns.…”

Hydrodynamic Mathematical Modelling of Aerobic Plug Flow and Nonideal Flow Reactors: A Critical and Historical Review

“…The first authors who implemented the ASM1 into the CFD code through the use of classical convective scalar transport equations were Glover et al (2006). The obtained model, subsequently called CFD-ASM1, was then analyzed at different levels and was validated with an experimental study and two numerical studies of an SBR-oxidation ditch (Vermande, 2005).…”

Hydrodynamic study of a novel membrane aerated biofilm reactor (MABR): Tracer experiments and CFD simulation

“…The use of experimental techniques (tracer experiments) combined with modern tools as the computational fluid dynamic (CFD), which is a powerful approach that provides a detailed spatial distribution of flow fields providing two or threedimensional visualization of the system (Klusener et al, 2007), might provide reliable quantitative results on hydrodynamics performance facilitating the development of integrated models (hydrodynamic-reaction kinetics) to optimize variables such as reactor design, nutrient removal and energy consumption (Glover et al, 2006;Essemiani et al, 2004).…”