ABSTRACTSide-stream enhanced biological phosphorus removal process (S2EBPR) refers to modified EBPR configurations that have been demonstrated to improve the performance stability and offer a suite of advantages compared to conventional EBPR design. Design and optimization of S2EBPR requires modification of the current EBPR models that were not able to fully reflect the metabolic functions of and competition between the PAOs and GAOs under extended anaerobic conditions as in the S2EBPR conditions. In this study, we proposed and validated an improved iEBPR model for simulating PAO and GAO competition that incorporated heterogeneity and versatility in PAO sequential polymer usage, staged maintenance-decay and glycolysis-TCA pathway shifts. The iEBPR model was first calibrated against a bulk batch test experimental data. The improved iEBPR model performed better than the previous EBPR model for predicting the soluble orthoP, ammonia, biomass glycogen and PHA temporal profiles in a batch starvation testing under prolong anaerobic conditions. We further validated the model with another independent set of batch anaerobic batch testing data that included high-resolution cellular and population-level intracellular polymers measurements enabled by single-cell Raman microspectroscopy technique. The model accurately predicted the temporal changes in the intracellular polymers at cellular and population levels within PAOs and GAOs, further confirmed the proposed mechanism of sequential polymer utilization, and polymer availability-dependent and staged maintenance and decay in PAOs. These results indicate that under extended anaerobic phases as in S2EBPR, the PAOs may gain competitive advantage over GAOs due to the possession of multiple intracellular polymers and the adaptive switching of the anaerobic metabolic pathways that consequently lead to the later and slower decay in PAOs than GAOs. The iEBPR model can be applied to facilitate and optimize the design and operations of S2EBPR for more reliable nutrient removal and recovery from wastewater.
Modeling Side-Stream Enhanced Biological Phosphorus Removal (S2EBPR) System Using Agent-based Model with Adaptive Maintenance, Decay and TCA Metabolism
