Impact of Influent Carbon to Phosphorus Ratio on Performance and Phenotypic Dynamics in Enhanced Biological Phosphorus Removal (EBPR) System - Insights into Carbon Distribution, Intracellular Polymer Stoichiometry and Pathways Shifts

Abstract

13This study investigated the impact of influent carbon to phosphorus (P) ratio on the variation in 14 P-removal performance and associated intracellular polymers dynamics in key functionally 15 relevant microbial populations, namely, PAOs and GAOs, at both individual and populations 16 levels, in laboratory scale sequencing batch reactor-EBPR systems. Significant variations and 17 dynamics were evidenced for the formation, utilization and stoichiometry of intracellular 18 polymers, namely polyphosphate, glycogen and Polyhydroxyalkanoates in PAOs and GAOs in 19 the EBPR systems that were operated with influent C/P ranged from 20 to 50, presumably as 20 results of phylogenetic diversity changes and, or metabolic functions shifts in these two 21 populations at different influent C/P ratios. Single cell Raman micro-spectroscopy enabled 22 quantification of differentiated polymer inclusion levels in PAOs and GAOs and, showed that as 23 the influent rbCOD/P ratio increases, the excessive carbon beyond stoichiometric requirement 24 for PAOs would be diverted into GAOs. Our results also evidenced that when condition becomes 25 more P limiting at higher rbCOD/P ratios, both energy and reducing power generation required 26 2 for acetate uptake and PHB formation might shift from relying on both polyP hydrolysis and 1 glycolysis pathway, to more enhancement and dependence on glycolysis in addition to 2 partial/reverse TCA cycle. These findings provided new insights into the metabolic elasticity of 3 PAOs and GAOs and their population-level parameters for mechanistic EBPR modeling. This 4 study also demonstrated the potential of application of single cell Raman micro-spectroscopy 5 method as a powerful tool for studying phenotypic dynamics in ecological systems such as 6 EBPR. 7KEYWORDS Enhanced biological phosphorus removal, EBPR, Raman microscopy, 8 polyphosphate, PHB, glycogen 9 10 phosphorus removal, the benefits are often offset, in practice, by the needs to have standby 1 chemicals for achieving reliable and consistent performance. There is still knowledge gap in 2 understanding the mechanism and factors that control the stability of the process, particularly for 3 achieving extremely low effluent limits and, as a result, process stability and system performance 4 have been seen to vary among facilities (Gu et al., 2005; Neethling et al., 2005; Stephens et al., 5 2004). 6EBPR performance and stability have been shown to be affected by many factors among 7 which, the competition of the two main functionally relevant populations, namely polyphosphate 8 accumulating organisms or PAOs and glycogen accumulating organisms or GAOs, were found 9 to be crucial for achieving successful operation of EBPR. Although deterioration of EBPR 10 performance has been attributed to the proliferation of GAOs in lab-scale EBPRs and also at full 11 scale EBPR facilities (Gu et al., 2005; Cech and Hartman, 1993; Saunders et al., 2003), others 12 (Gu et al., 2008; Tu and Schuler, 2013) have also shown that efficient EBPR could a...

Evaluating Long-Term Treatment Performance and Cost of Nutrient Removal at Water Resource Recovery Facilities under Stochastic Influent Characteristics Using Artificial Neural Networks as Surrogates for Plantwide Modeling

“…Simulated biological phosphorus removal processes also showed significant removal efficiencies. EBPR-A had higher TP removal efficiency compared with basic EBPR, showing the positive impact of maintaining a C/P ratio between 26 and 30 to avoid PAO carbon limitations . EBPR-S had the highest removal efficiency and narrowest effluent TP range as it dramatically reduced the amount of P returning from solids digestion and thickening operations to mainline treatment, alleviating carbon limitations and reducing sludge production (Figure c) …”