Impact of salinity on the anaerobic metabolism of phosphate-accumulating organisms (PAO) and glycogen-accumulating organisms (GAO)

Abstract

The use of saline water as secondary quality water in urban environments for sanitation is a promising alternative towards mitigating fresh water scarcity. However, this alternative will increase the salinity in the wastewater generated that may affect the biological wastewater treatment processes, such as biological phosphorus removal. In addition to the production of saline wastewater by the direct use of saline water in urban environments, saline wastewater is also generated by some industries. Intrusion of saline water into the sewers is another source of salinity entering the wastewater treatment plant. In this study, the short-term effects of salinity on the anaerobic metabolism of phosphate-accumulating organisms (PAO) and glycogen-accumulating organisms (GAO) were investigated to assess the impact of salinity on enhanced biological phosphorus removal. Hereto, PAO and GAO cultures enriched at a relatively low salinity level (0.02 % W/V) were exposed to salinity concentrations of up to 6 % (as NaCl) in anaerobic batch tests. It was demonstrated that both PAO and GAO are affected by higher salinity levels, with PAO being the more sensitive organisms to the increasing salinity. The maximum acetate uptake rate of PAO decreased by 71 % when the salinity increased from 0 to 1 %, while that of GAO decreased by 41 % for the same salinity increase. Regarding the stoichiometry of PAO, a decrease in the P-release/HAc uptake ratio accompanied with an increase in the glycogen consumption/HAc uptake ratio was observed for PAO when the salinity increased from 0 to 2 % salinity, indicating a metabolic shift from a poly-P-dependent to a glycogen-dependent metabolism. The anaerobic maintenance requirements of PAO and GAO increased as the salinity concentrations risen up to 4 % salinity.

Calcium effect on the metabolic pathway of phosphorus accumulating organisms in enhanced biological phosphorus removal systems

“…Such a deviation might be originated from the relative large error of the percentage of Ca-polyP (Table 2), estimated by EDX analysis. Notably, the PAO metabolic shift from PAM to GAM was also observed as the salinity of the system was elevated to a certain level (Welles et al, 2014). In our study, as the influent calcium concentration was increased from 15 to 96 mg/L, the salinity changed slightly.…”

“…PAOs may tune their metabolic pathway to partially use GAO metabolism under certain conditions (Erdal et al, 2008;Barat et al, 2006Barat et al, , 2008Zhou et al, 2008;Acevedo et al, 2012;Welles et al, 2014). The metabolic pathway of PAOs could be shifted between the dominance of PAM and GAM along with the change of intracellular polyP level, which was confirmed by the evolution of PHA and glycogen in EBPR systems (Acevedo et al, 2012).…”

Accumulibacter clades Type I and II performing kinetically different glycogen-accumulating organisms metabolisms for anaerobic substrate uptake

“…The influent of SBR-S contained a 75%-to-25% mixture of acetate-to-propionate: 280 mg HAc/L (9.5 C-mmol/L, 300 mg COD/L, 645 mg NaAc$3H 2 O) and 67 mg/L HPr (2.72 C-mmol/L, 100 mg COD/L, 6.675 Â 10 À2 mL C 3 H 6 O 2 ), leading to an influent P/C ratio of 0.066 (P-mol/C-mol). Further details regarding other macronutrients and trace elements can be found elsewhere (Smolders et al, 1994;Welles et al, 2014).…”

“…The differences in operational factors between the SBR are listed in Table 1. Further details regarding the operational conditions of SBR-L, SBR-S and SBR-W can be found elsewhere (Welles et al, 2014).…”

Treatment of Rural Wastewater Using a Spiral Fiber Based Salinity-Persistent Sequencing Batch Biofilm Reactor

“…Bassin et al [41] reported that at high salinity levels (33.0 g/L NaCl), GAOs gained advantage over PAOs in their long-term experiment. Welles et al [42] conducted a short-term experiment and also suggested that salinity higher than 6.0 g/L of NaCl favored GAOs over PAOs. Thus, the activity of PAOs in this system was almost not observed.…”