The effects of varying influent phosphate and acetate concentrations on enhanced biological removal of phosphate from wastewater.

摘要

Operation of metabolisms involved in enhanced biological phosphorus removal (EBPR) were studied in laboratory-scale sequencing batch reactors with an anaerobic-aerobic sequence, synthetic feed, and acetate as the primary carbon source. High influent P/COD produced a biomass exhibiting characteristics of a polyphosphate-accumulating metabolism (PAM), including high non-soluble P (Pns) content (to 0.36--0.40 mg Pns/mg volatile suspended solids (VSS)) and high anaerobic soluble phosphate (Psol) release/acetate uptake (to 0.75--0.80 mol/C-mol). Low influent P/COD produced a biomass exhibiting characteristics of a glycogen accumulating metabolism (GAM), including low Pns/VSS content (to approximately 0.02 PnsNSS) and high anaerobic CH degradation/acetate uptake (approximately 0.8 C-mol/C-mol). VSS yields for PAM and GAM were approximately the same. Total suspended solids (TSS) changes suggested a PP molecular weight of 93.9 g/mol phosphorus (P). Balances over the anaerobic phase showed carbon and reducing equivalent deficits at high Pns/VSS values, and suggested the flux of carbon to the TCA cycle or the glyoxylate bypass in PAM. The ATP usage for anaerobic acetate uptake was higher by PAM (approximately 0.5 mol ATP/acetate C-mol) than by GAM (approximately 0 mol/C-mol). This may be linked to higher rates of anaerobic acetate uptake by PAM (at least 6 times greater than by GAM). Accumulation of the dense storage product PP in the biomass was shown to improve settling characteristics (SVI and effluent TSS) by increasing solids density. SVI and effluent TSS increased rapidly as solids density approached the liquid density and PP storage approached 0, which was shown to be consistent theoretical predictions. Changes in settling characteristics and biomass density before and after aerobic Psol uptake verified density changes were responsible for changes in density and settling characteristics, rather than increased filamentous organism population or slime bulking. Low density sludge can be problematic to solids settling, and induction of PP storage can improve settling characteristics.