CHARACTERISTICS OF DENITRIFYING PHOSPHORUS REMOVAL AND N2O EMISSION OF AN AOA-SBR UNDER DIFFERENT CARBON TO NITROGEN RATIOS(C/N)
In the paper,the simultaneous nitrogen and phosphorus removal process(SNDPR)of domestic sewage was accomplished in the anaerobic/aerobic/anaerobic SBR(AAO-SBR)by gradually reducing the external carbon source addition,to reduce the carbon nitrogen ratio(C/N)of influent water,reducing the aerobic aeration rate,and increasing the residence time of aerobic and anoxic stages.The competition between PAOs and GAOs in AOA-SBR under different reaction conditions was investigated by the stoichiometric method,and the nitrogen and phosphorus removal performance,as well as the N2O emission ratio of the system were determined.The results showed that reducing the aerobic aeration rate and increasing the aerobic residence time were conducive to the proliferation of PAOs in AOA-SBR under the condition of low carbon to nitrogen ratio,which promoted denitrification and phosphorus removal.When the C/N ratio decreased from 7.0 to 3.3,the average TN removal rate reached more than 80%,and the average TP removal rate increased from 65.2%to 81.2%.Under different C/N conditions,the changes of microbial endogenous substances in AOA-SBR at anaerobic,anoxic and aerobic stages showed the coexistence characteristics of PAOs-GAO.AOA-SBR tended to enrich the characteristics of GAOs endogenous substances at a higher C/N.Higher C/N condition promoted the endogenous denitrification process of DGAOs and increased the release of N2O,and lower C/N promoted the proliferation of DPAOs.The coupled endogenous denitrification process of DGAOs-DGAOS promoted the reduction of N2O,which reduced the emission of N2O.As the C/N decreased from 7.0 to 3.3,the N2O release decreased from 2.23 to 1.05 mg/L,and the emission ratio decreased from 7.21%to 3.94%.The collaboration between DGAOs endogenous denitrification and DPAOs endogenous denitrification phosphorus removal processes can make full use of carbon sources in raw domestic sewage,which may break the bottleneck of nitrogen removal in urban domestic sewage.
carbon to nitrogen ratioAOA-SBRsimultaneous nitrification and denitrification phosphorous removal process(SNDPR)N2O emission