Transformation of phosphorus and relevant intracellular compounds by a phosphorus‐accumulating enrichment culture in the presence of both the electron acceptor and electron donor

Abstract

This study was conducted to obtain a better insight into the metabolic behavior of denitrifying phosphate-accumulating organisms relative to the transformations of relevant intracellular compounds as well as phosphorus and nitrate for enhanced biological phosphorus removal under different combinations of electron acceptor (oxygen or nitrate) and electron donor (acetate). Under anoxic conditions, the amount of polyhydroxybutyrate (PHB) produced per acetate taken up considerably increased with the increasing amount of nitrate reduced whereas the amounts of nitrate reduced and phosphorus released per acetate taken up remained almost constant. However, glycogen utilization occurred during PHB production and then was again observed in response to the initial supplementation of acetate after glycogen accumulation was transiently observed during anoxic phosphorus uptake using nitrate as an electron acceptor. On the other hand, under subsequent aerobic conditions, the additional supplementation of acetate again caused aerobic phosphorus release and PHB production, which showed that PHB production was associated with polyphosphate cleavage regardless of electron acceptor conditions. In contrast to anoxic conditions, glycogen accumulation was observed during PHB production. Based on these observations, the preliminary model for the metabolic behavior of denitrifying phosphate-accumulating organisms was proposed and could well account for the complex transformations of PHB and glycogen together with phosphorus release in the presence of acetate under different electron acceptors.

Effects of acetate and nitrite addition on fraction of denitrifying phosphate-accumulating organisms and nutrient removal efficiency in anaerobic/aerobic/anoxic process

“…1a). This is because an electron donor (carbon substrate) and an electron acceptor (nitrite or nitrate) were simultaneously present under anoxic condition, which allowed DNPAOs to take up an external carbon substrate and release phosphate instead of taking it as previously reported [20]. This result obviously shows that phosphorus removal deteriorates when the external carbon substrate is added under anoxic condition.…”

“…Generally, the addition of an external carbon substrate like sodium acetate inhibits phosphate uptake by PAOs under aerobic conditions [20], allowing DNPAOs to maintain their activities in an AOA process. Such an attempt was chosen as the test run (Type 2).…”

Enhancement of Nitrogen and Phosphorus Removal in an Anaerobic/Oxic/Anoxic Sequencing Batch Reactor as Affected by the Amount of External Carbon

“…These results clearly indicate that the oxic phosphate uptake by PAOs was suppressed by the addition of external carbon, and consequently, phosphorus removal was not completed at the end of the oxic phase. This is probably because the addition of external carbon produces reduction equivalents through the TCA cycle in the presence of external carbon, leading to PHA production with phosphate uptake under oxic condition as previously reported (Ahn et al, 2002b).…”

“…The strategy is the addition of external organic carbon at the beginning of oxic phase to retard phosphate uptake by PAOs . This is derived from the special property of DNPAOs that is, they release phosphate while synthesizing PHA even in the presence of both electron donor and acceptor (Ahn et al 2002b). The addition of external carbon eventually creates the anoxic environment where DNPAOs can take up phosphate with nitrite or nitrate produced in the previous oxic phase.…”

Advanced nitrogen and phosphorus removal in A2O-BAF system treating low carbon-to-nitrogen ratio domestic wastewater

“…Secondly, the A 2 O process of this system has a shorter period as an aerobic volume and longer as an anoxic volume, and then it can provide a favorable environment for the propagation of Denitrifying Phosphorus Accumulating Organisms (DPAOs). It is well known that DPAOs can use nitrate and/or nitrite rather than oxygen as an electron acceptor when exposed to an anoxic environment [10][11][12][13]. This means that phosphorus removal and denitrification can be reached simultaneously, which is beneficial especially for weak wastewater.…”