Enhanced Biological Phosphorus Removal from Wastewater by Biomass with Different Phosphorus Contents, Part II: Anaerobic Adenosine Triphosphate Utilization and Acetate Uptake Rates

Abstract

Data from laboratory-scale sequencing batch reactors operated in an anaerobic-aerobic cycle showed that a low influent phosphorus/chemical oxygen demand (COD) ratio feed favored a glycogen-accumulating metabolism (GAM)-dominated culture and that a high influent phosphorus/COD ratio feed favored a polyphosphate-accumulating metabolism (PAM)-dominated culture. The PAM-dominated culture anaerobically took up acetate approximately 7 times faster than the GAMdominated culture. Adenosine triphosphate (ATP) balances were performed assuming eight different metabolic scenarios that included the Entner-Doudoroff or the Embden-Myerhof glycolytic pathway, acetyl-coenzyme A (CoA) synthase or the acetate kinase-phospho-transacetylase (AK-PTA) system for acetyl-CoA synthesis, and ATP synthesis or no ATP synthesis during fumarate reduction. The ATP available for transport of acetate into the cell (a) was calculated using these balances. The assumed quantity of ATP produced during fumarate reduction had a relatively small effect on a, particularly when PAM was dominant. When GAM was dominant, little or no ATP was available for acetate transport depending on the assumed scenario, and the Embden-Myerhof pathway was more feasible. The value of a increased with increasing PAM dominance for all eight metabolic pathways. The maximum calculated a value of 0.5 mol ATP/C-mol acetate uptake occurred at maximum PAM dominance and when the Embden-Myerhof pathway was active, when ATP was produced during fumarate reduction, and when the AK-PTA system was active. This value of a was higher than previously calculated values with the same metabolic assumptions. An acetate uptake mechanism was suggested that included acetyl-CoA synthetase and direct regeneration of the proton motive force by a proton-translocating pyrophosphatase. Polyphosphate-accumulating metabolism may have a competitive advantage over GAM through a higher anaerobic acetate uptake rate made possible by a greater use of energy for acetate uptake, by use of a different acetate uptake mechanism, or both. Water Environ. Res., 75, 499 (2003).

The impact of influent nutrient ratios and biochemical reactions on oxygen transfer in an EBPR process—A theoretical explanation

“…Previously, a total complete loss of EBPR activity was reported by Satoh et al (1994), and Hartman (1990, 1993). As per the general understanding, the PAOs and the GAOs seem to differ in their sources of energy as well as the efficiency of energy generation (Mino et al, 1998;Schuler and Jenkins, 2003a, 2003b, 2003c. It was found that PAO-dominated systems take up acetate seven times faster than the GAO-dominated system under similar process conditions, and PAOs have a competitive advantage over GAOs (Schuler and Jenkins, 2003c).…”

“…Most importantly, PAOs have the enhanced biological P removal feature, not present in GAOs. The unique characteristics of PAOs (a) to utilize the intracellular polyphosphate and consequently release orthophosphate under the anaerobic conditions while at the same time taking up carbon, and (b) to recover the intracellular polyphosphate under aerobic conditions, may provide a competitive advantage over the other groups of microorganisms (Mino et al, 1998;Schuler and Jenkins, 2003a, 2003b, 2003c. In general, the intracellular storage of carbon by the PAOs and GAOs limits availability of carbon for (a) denitrification by the ordinary heterotrophic organisms (non-PAOs and nonGAOs) in the upstream anoxic reactor, (b) aerobic carbon oxidation by the ordinary heterotrophic organisms, and (c) simultaneous-nitrification and denitrification within the aerobic reactor.…”

“…This is owing to the GAO uptake of the excess carbon. The anaerobic C uptake by GAOs would have taken place in an inverse-relationship to the population of PAOs and the phosphorus release, since PAOs appear to compete successfully with GAOs in utilizing the carbon Mino et al, 1998;Schuler and Jenkins, 2003c). At the same time, a complete deterioration of EBPR did not take place, given the observed anaerobic and anoxic phosphate release, and low effluent P concentration in the High N and Low N/P runs (Table III).…”

“…As per the general understanding, the PAOs and the GAOs seem to differ in their sources of energy as well as the efficiency of energy generation (Mino et al, 1998;Schuler and Jenkins, 2003a, 2003b, 2003c. It was found that PAO-dominated systems take up acetate seven times faster than the GAO-dominated system under similar process conditions, and PAOs have a competitive advantage over GAOs (Schuler and Jenkins, 2003c). In addition, the polyphosphate degradation by PAOs is a simpler mechanism that generates energy efficiently, whereas the glycogen fermentation to PHA and CO 2 by GAOs is a more complex mechanism that generates energy with a lower efficiency (Mino et al, 1998).…”

“…The presence of GAOs or at the minimum, the bacterial glycogen-accumulating phenomenon is integral to the EBPR process (Mino et al, 1998;Schuler and Jenkins, 2003a, 2003b, 2003c. As mentioned earlier, a relatively long SRTof 15 days was applied in this study.…”