Control of an ideal activated sludge process in wastewater treatment via an ODE–PDE model

Abstract

Abstract. The activated sludge process (ASP), found in most wastewater treatment plants, consists basically of a biological reactor followed by a sedimentation tank, which has one inlet and two outlets. The purpose of the ASP is to reduce organic material and dissolved nutrients (substrate) in the incoming wastewater by means of activated sludge (microorganisms). The major part of the discharged flow through the bottom outlet of the sedimentation tank is recirculated to the reactor, so that the biomass is reused. Only two material components are considered; the soluble substrate and the particulate sludge. The biological reactions are modelled by two nonlinear ordinary differential equations and the continuous sedimentation process by two hyperbolic partial differential equations (PDEs), which have coefficients that are discontinuous functions in space due to the inlet and outlets. In contrast to previously published modelling-control aspects of the ASP, the theory for such PDEs is utilized. It is proved that the most desired steady-state solutions can be parameterized by a natural control variable; the ratio of the recirculating volumetric flow to the input flow. This knowledge is a key ingredient in a two-variable regulator, with which the effluent dissolved nutrients concentration and the concentration profile in the sedimentation tank are controlled. Theoretical results are supported by simulations.

Modeling and optimization of activated sludge bulking for a real wastewater treatment plant using hybrid artificial neural networks-genetic algorithm approach

“…Whereas, ASM3 (Chen et al, 2012;Gujer et al, 1999) introduced an alternative concept to the previous ASM biokinetics and aimed at simplifying the model application. Despite the availability of ASM models, the diagnosis of the process interactions and modeling of ASP in a real WWTP is still difficult (Diehl and Farås, 2013;Moral et al, 2008). This is due to the complex biological reactions, as well as the highly time-varying and multivariable aspects of operation of a real WWTP (Busch et al, 2013;Hong et al, 2003;Moral et al, 2008).…”

Sustainability and process control: A survey and perspective

“…Similarly, in the context of effluent/waste management, efforts have been directed towards modeling and estimation [129,130], monitoring [131,132], fault diagnosis [133,134], hybrid PI control [135], cascade control [136], data-driven control [137,138], fuzzy control [139], adaptive and robust control [140], nonlinear model-based feedback control [141], optimal control [142], linear MPC [143,144] and nonlinear MPC [145,146]. A hierarchical control strategy, motivated by the presence of multi-time-scale dynamics has also been implemented for a climate control [147] system and an integrated wastewater system [148].…”

Optimal Feedback Synthesis and Minimal Time Function for the Bioremediation of Water Resources with Two Patches

“…We assume that the output of the bioreactor is filtered by a settler, that we assume to be perfect, so that the water that returns to the resource is biomass free (see [9,10] for considerations of settler modeling and conditions that ensure the stability of the desired steady-state of the settler).…”