Effect Of A/O Residence Time Ratio On EBPR Phosphorus Removal And Decay Of Phosphorus Accumulating Bacteria

At present,enhanced biological phosphorus removal（EBPR）process has been widely used in municipal wastewater treatment plants.However,many problems often occur in the enhanced biological phosphorus removal system and the effect of phosphorus removal is unstable.Therefore,further study on the characteristics of phosphorus accumulating bacteria in EBPR process and the factors affecting phosphorus accumulating bacteria is of great significance for efficient and stable phosphorus removal of municipal wastewater.Under normal temperature（22℃）,activated sludge from a sewage treatment plant was used as inoculated sludge,and phosphorus accumulating bacteria were cultured under A/O condition.The phosphorus removal effect of enhanced biological phosphorus removal system under different anaerobic aerobic hydraulic retention time（A/O）ratios was discussed.Maximum phosphorus uptake rate and phosphorus release per unit of acetic acid（ΔP/ΔHAc）.The microbial community structure in the sludge was determined and analyzed by fluorescence in situ hybridization（FISH）.Finally,the attenuation characteristics of PAOS were studied by enrichment culture sludge.The main conclusions are as follows:（1）The SBR reactor operated stably at room temperature（22℃）for 220 days,and the removal rate of phosphate was over 99%.The maximum anaerobic phosphorus release rate of sludge was 120 mg P·gvss^-1h^-1,the aerobic phosphorus uptake rate was 42 mg P·gvss^-1h^-1,and the acetic acid uptake rate was 230.76 mg HAc·gvss^-1h^-1（ΔP/ΔHAC）was 0.52.The content of polyphosphate in sludge is 130.06 mg P·gvss^-1h^-1.（2）A/O ratio is an important factor affecting the phosphorus removal performance of EBPR.When the A/O ratio was 1/2,1/3 and 1/5,the maximum phosphorus release rates were 63.7 mg P·gvss^-1h^-1,113.2 mg P.gvss^-1h^-1 and 125 mg P.gvss^-1h^-1,respectively,and the phosphorus uptake rates were 28.3 mg P·gvss^-1h^-1,35.3 mg P·gvss^-1h^-1 and 36.4mg P·gvss^-1h^-1,respectively.The shorter the HRT,the higher the maximum phosphorus release rate and the higher the phosphate removal rate.For the enhanced biological phosphorus removal system,the optimal A/O ratio is 1/5.（3）The proportion of PAOS in SBR sludge is different with different A/O ratio.When A/O ratio is 1/2,1/3 and 1/5,the proportion of phosphorus accumulating bacteria in sludge is 85%,90%and 90%respectively.（4）The decay rate and the order of utilizing endogenous substances of phosphorus accumulating bacteria were different under different environmental conditions.The average decay rate was 0.021 d^-1 under anaerobic condition and 0.076 d^-1 under aerobic condition;The order of utilization of endogenous substances in the degradation of phosphorus accumulating bacteria under anaerobic conditions was glycogen and Poly-P.In anaerobic condition,the order of energy supply by endogenous substances was PHB and glycogen.