| Denitrifying glycans are a kind of denitrifying bacteria with similar denitrifying bacteria's metabolic process.They can absorb organic matter and synthesize PHB in the anaerobic section,and can use PHB as energy source and nitrate in the anoxic section.Or nitrite is an electron acceptor for denitrification,which does not contribute to the removal of phosphorus in the system.DGAOs can convert the external carbon source into an internal carbon source to drive denitrification and denitrification.If this characteristic of denitrifying glycan bacteria is applied to the treatment of low carbon,nitrogen and phosphorus ratio wastewater,it will effectively solve the traditional process plus carbon source and phosphorus.The shortcoming of the source,therefore,the development and utilization of the internal carbon source to improve the effective use of the carbon source is of great significance for improving the nitrogen removal efficiency of the system and reducing the cost of water treatment.In this paper,four SBR reactors were used to culture nitrate-type and nitrite-type DP AOs,nitrate-type and nitrite-type DGAOs,and different influent C/N ratios,different electron acceptors and external carbon sources were investigated.The effects of nitrogen and phosphorus removal on microorganisms,analysis of internal carbon source conversion and N2O release,and detection and analysis of microbial communities in the system,the main conclusions are as follows:The inoculated activated sludge with denitrifying and dephosphorizing properties was cultured in five stages by anaerobic/aerobic,anaerobic/anoxic/aerobic and anaerobic/anoxic modes,and the nitrate type was successfully cultured.Nitrite-type DPAOs and nitrate-type,nitrite-type DGAOs.The existence of anaerobic/aerobic alternating environments is a prerequisite for DPAOs and DGAOs to have denitrifying phosphorus removal or denitrification of internal carbon sources.The cultured nitrite-type DPAOs had a TN removal rate of 95.6%at an initial nitrite concentration of 55 mg/L in the anoxic zone,and consumed 1.4 g of nitrite per liter of phosphate.The nitrite-type DGAOs were The total nitrogen removal rate was 93.3%under the initial nitrite concentration of 25 mg/L.The optimum influent C/N ratios for denitrifying and phosphorus removal of nitrate and nitrite-type DPAOs are 5 and 3.6,respectively,which can save carbon sources.Phosphate absorption is inhibited in acid-type DPAOs with nitrite as electron acceptor,while denitrifying phosphorus removal is not affected when nitrite-type DPAOs use nitrate as electron acceptor.In the DGAOs system,the optimal C/N ratio for nitrate-type and nitrite-type DGAOs systems is 6;nitrite inhibits nitrate-type DGAOs activity;nitrite-type DGAOs denitrifies when nitrate is used as electron acceptor The rate is improved;without the participation of phosphate in the absence of oxygen,DP AOs can not use the PHA stored in the body to efficiently denitrify with nitrate or nitrite as the electron acceptor,and the total nitrogen removal rate is low under the condition of no phosphorus.At 15%.The presence of carbon sources outside the anoxic zone can cause conventional denitrification reactions in DP AOs and DGAOs systems.The presence of carbon sources in the denitrifying phosphorus removal system will affect the removal of phosphorus;while the conventional denitrification reaction rate in the DGAOs system is higher than the denitrification efficiency of the internal carbon source,and the rate is faster.The presence of carbon sources outside the anoxic zone can cause conventional denitrification reactions in DP AOs and DGAOs systems.The presence of carbon sources in the denitrifying phosphorus removal system will affect the removal of phosphorus;while the conventional denitrification reaction rate in the DGAOs system is higher than the denitrification efficiency of the internal carbon source,and the rate is faster.For the conversion of internal carbon sources,the amount of PHD synthesized by each of the nitrate-type and nitrite-type DPAOs per consuming 1 mg/L of COD is 0.2 mg/(gˇMLSS),and the PHB per 1 mg/(gˇMLSS)is consumed.The amount of synthetic glycogen was 0.7 mg/(gˇMLSS)and 0.8 mg/(gˇMLSS)respectively.The amount of PHB synthesized in the anaerobic section increased with the increase of the influent C/N ratio,and the carbon in the anoxic section was added.After the source,the phosphorus removal efficiency decreases due to the reduction of the synthetic PHB amount due to the competition of the carbon source by the conventional denitrification reaction.The amount of COD synthesized by nitrate and nitrite-type DGAOs per consuming 1 mg/L is 0.1 mg/(gˇMLSS)and 0.2 mg/(gˇMLSS),respectively,and each consumption is 1 mg/(gˇMLSS).The amount of PHB synthetic glycogen was 0.7 mg/(gˇMLSS).With the increase of influent C/N ratio,the synthesis of PHB in anaerobic nitrite-type DGAOs increased first and then remained unchanged.When the external carbon source was added to the anoxic section,the conventional denitrification reaction mainly occurred,and the amount of PHB synthesis and degradation decreased.Nitrate-type DPAOs and nitrite-type DPAOs will undergo N2O accumulation and degradation after denitrifying phosphorus removal.Nitrate-type DGAOs have no N2O accumulation during denitrification by internal carbon source,and there is an external carbon source.N2O accumulation and subsequent degradation occurred in the conventional denitrification reaction;N2O emission continued to accumulate in the endogenous denitrification and conventional denitrification of nitrite-type DGAOs,with the highest concentration being 325.8 ng/ul.The microbial communities of nitrate-type and nitrite-type DP AOs have certain similarities,and the microbial communities in the latter are more abundant than the former.The dominant flora in the water level of the door is Proteobacteria.At the level,the dominant bacteria are ?-proteobacteria and y-proteobacteria;the nitrate-type and nitrite-type DGAOs have similar microbial communities,and the level of the gate is similar.The dominant flora is Proteobacteria,and the dominant flora at the level is ?-proteobacteria and y-proteobacteria.The anaerobic/micro-oxygen SBR mode was used to couple the simultaneous nitrification and denitrification with the internal carbon source denitrification.Preliminary studies showed that the total nitrogen removal rate in the micro-oxygen stage without external carbon source reached 28.4%,indicating that the internal carbon was used in the system.The source is simultaneously nitrifying and denitrifying. |
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