Is the whole the sumof its parts? Agent-basedmodelling of wastewater treatment systems

摘要

Agent-based models (ABMs) simulate individual units within a system, such as the bacteria in anbiological wastewater treatment system. This paper outlines past, current and potential futurenapplications of ABMs to wastewater treatment. ABMs track heterogeneities within microbialnpopulations, and this has been demonstrated to yield different predictions of bulk behaviors thannthe conventional, ‘‘lumped’’ approaches for enhanced biological phosphorus removal (EBPR)ncompletely mixed reactors systems. Current work included the application of the ABM approachnto bacterial adaptation/evolution, using the model system of individual EBPR bacteria that arenallowed to evolve a kinetic parameter (maximum glycogen storage) in a competitive environment.nThe ABM approach was successfully implemented to a simple anaerobic-aerobic system and itnwas found the differing initial states converged to the same optimal solution under uncertainnhydraulic residence times associated with completely mixed hydraulics. In another study, an ABMnwas developed and applied to simulate the heterogeneity in intracellular polymer storagencompounds, including polyphosphate (PP), in functional microbial populations in enhancednbiological phosphorus removal (EBPR) process. The simulation results were compared to thenexperimental measurements of single-cell abundance of PP in polyphosphate accumulatingnorganisms (PAOs), performed using Raman microscopy. The model-predicted heterogeneity wasngenerally consistent with observations, and it was used to investigate the relative contribution ofnexternal (different life histories) and internal (biological) mechanisms leading to heterogeneity.nIn the future, ABMs could be combined with computational fluid dynamics (CFD) models tonunderstand incomplete mixing, more intracellular states and mechanisms can be incorporated,nand additional experimental verification is needed.