Nitrogen-limitation-induced carbon and phosphorus fluxes in anaerobic/aerobic sequencing batch reactors

Abstract

Enhanced biological phosphorus removal (EBPR) has been applied widely in wastewater treatment plants. However, deterioration or failure of EBPR often happens because: (i) of the dominance of glycogen-accumulating organisms (Type I), or (ii) there is no anaerobic carbon uptake or phosphorus release (Type II). In this study, carbon and phosphorus fluxes under nitrogen-limitation conditions in anaerobic/aerobic sequencing batch reactors (SBR10 at 10 oC and SBR20 at 20 oC) without EBPR (Type II) were examined. Zoogloea sp. was detected in all samples from both reactors using the fingerprinting technique. In spite of the absence of EBPR, the biomass total phosphorus content of 3.8% in SBR10 and 4.8% in SBR20 was still high. Phosphorus removal could have occurred through biomass assimilation, chemical precipitation (including a precursor nucleation phase and then a crystallization phase), and contribution from extracellular polymeric substances. Under nitrogen-limitation conditions, the polyhydroxybutyrate content increased from 13.9% to 32.7% in SBR10 and from 8.3% to 28.8% in SBR20; while the intracellular carbohydrate content was 9.9% in SBR10 and 9.6% in SBR20, and the extracellular carbohydrate content was 7.8% in SBR10 and 6.0% in SBR20. KEY WORDS