The impact of aeration on the competition between polyphosphate accumulating organisms and glycogen accumulating organisms

Abstract

In wastewater treatment plants (WWTPs), aeration is the major energetic cost, thus its minimisation will improve the cost-effectiveness of the process. This study shows that both the dissolved oxygen (DO) concentration and aerobic hydraulic retention time (HRT) affect the competition between polyphosphate accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs). At low DO levels, Accumulibacter PAOs were shown to have an advantage over Competibacter GAOs, as PAOs had a higher oxygen affinity and thus largely maintained their aerobic activity at low DO levels, while GAO activity decreased. Bioreactor operation at low DO levels was found to increase the PAO fraction of the sludge. Furthermore, an increase in aerobic HRT (at a DO level of 2 mg O2/L), promoted the proliferation of GAOs over PAOs, decreasing the EBPR efficiency. Overall, this study shows that low aeration can be beneficial for EBPR performance through selecting for PAOs over GAOs, which should be incorporated into WWTP models in order to minimise energetic costs and improve WWTP sustainability.

Advanced nutrient removal from surface water by a consortium of attached microalgae and bacteria: A review

“…Some bacterial groups such as Achromobacteria, Alcaligenes, Bacillus, Hydrogenophaga and Pseudomonas can carry out heterotrophic nitrification and aerobic denitrification, converting ammonium ions to nitrogen aerobically (Yao et al, 2013;Chen et al, 2015). Polyphosphate (polyP) accumulating bacteria such as Accumulibacter and Pseudomonas are capable of taking up large amounts of phosphorus aerobically and storing it as intracellular polyphosphate (Oehmen et al, 2007;Carvalheira et al, 2014). Therefore, the varying nutrient removal capacity and preferred habitats stress the key role of species composition and consortium structure in efficient nutrient removal.…”

“…For instance, the dominance of aerobic denitrifying bacteria typically results in a high nitrogen removal under aerobic conditions (Zhang et al, 2012;Guo et al, 2013), and similarly a high abundance of polyP accumulating bacteria such as Accumulibacter boosts phosphorus removal (Carvalheira et al, 2014). However, the control of consortium composition and systems performance under natural conditions in surface water is difficult due to the dynamic fluctuations of solar irradiance, temperature, pH, DO, pollutants loading and population of invertebrate grazers (Markou and Georgakakis, 2011;Shurin et al, 2013).…”

Experimental Methods in Wastewater Treatment

“…when acetate or propionate are present as the sole carbon source, when temperatures exceed 20 °C, at pHs below 7.0, and/or at dissolved oxygen (DO) concentrations higher than 2 mg L -1 ) (Oehmen et al, 2007;Lopez-Vazquez et al, 2009a,b;Carvalheira et al, 2014). GAOs have an apparently similar metabolism to that of PAOs, but they rely solely on their intracellularly-stored glycogen pools as the source of energy and reducing equivalents that drive the anaerobic storage of VFA as PHAs without any contribution from poly-P (Figure 2.2.2).…”

Conditions Favoring Proliferation of Glycogen Accumulating Organisms for Excess Biological Carbon Removal in Treating Nutrient Deficient Wastewater

“…acetate, propionate, etc.) [8,9], influent phosphorous to carbon ratio (P/C) [10,11], nitrite content [12], pH [13,14], temperature [15], DO (dissolved oxygen) concentration and aerobic HRT (hydraulic retention time) [16] have been pointed out as determining factors to influence the PAO-GAO competition. Tu and Schuler [17] found in a long-term lab-scale sequencing batch reactor (SBR) experiment that growth of GAOs may not be a direct cause of PAO failure, but the consequence under high anaerobic acetate availability at lower pH values.…”