Enhancement of anoxic phosphorus uptake of denitrifying phosphorus removal process by biomass adaption

Abstract

Economical and efficient phosphorus (PO4-P) removal technologies with low oxygen and organic carbon demand are needed to avoid eutrophication and reduce wastewater treatment costs. A sequencing batch reactor (SBR) treating synthetic wastewater with similar characteristics to real domestic wastewater using peptone and meat extract as carbon sources and nitrate as terminal electron acceptor was set up to enhance anoxic PO4-P uptake of denitrifying phosphorus removal process. In the anaerobic/anoxic/oxic SBR, activated sludge inoculum was gradually adapted to prolonged anoxic and shortened aerobic phase durations of 3.5 h and 1 h, respectively. During biomass adaption, anoxic PO4-P uptake fraction from total PO4-P (anoxic + aerobic) uptake was enhanced from 70.5 to 90.4%. SBR long-term operation results showed that dosed nitrate loading and aeration phase duration affected PO4-P and total nitrogen (TN) removal. The highest PO4-P removal of 22.4 mg PO4-P g−1 mixed liquor suspended solids (MLSS) and average TN removal efficiency of 74.2% were achieved with 1-h aeration duration. The best dosed nitrate loading ranges for effective PO4-P and TN removal were 11.3–13.7 and 11.1–19.4 mg N g−1 MLSS d−1, respectively. Chemical oxygen demand and dissolved organic carbon removal efficiencies remained unaffected by changes in operating conditions with average values up to 96.3% and 98.0%, respectively. Pyrosequencing results demonstrated that during biomass adaption microbial community changed and adapted sludge probably contained some novel denitrifying phosphorus accumulating organisms. Therefore, this research shows that biomass adaption enabled to achieve efficient denitrifying phosphorus removal without acetate/propionate addition in the conditions similar to real domestic wastewater.