| With the increasingly stringent standards for urban sewage discharge in China,most of the sewage treatment plants can not meet the requirements of treatment standards on the existing process base.It is urgent for many sewage treatment plants to upgrade their standards.In this experiment,Denitrifying Phosphorus Accumulating Organisms?DPAOS?can use NOX--N as electron acceptor to absorb PO43--P in anoxic phase,and denitrify and dephosphorize simultaneously,which can realize the characteristics of"one carbon and two uses",and carry out pilot test.At the same time,batch experiments were conducted to explore the characteristics of denitrifying phosphorus-accumulating bacteria for nitrogen and phosphorus removal in pilot-scale sludge,and high-throughput sequencing was conducted to analyze the characteristics of microbial population in pilot-scale sludge.In order to provide reference and test data support for the upgrading of wastewater treatment plants.In order to understand the denitrifying and phosphorus removal characteristics of denitrifying phosphate accumulating organisms?DPAOs?,a pilot scale?20 m3?denitrifying and phosphorus removal experiment was carried out at low temperature?6-16??.The test results show that when temperature is?6-12??,HRT is 20h and SRT is 35d,the process can start up successfully and run steadily.When running steadily,the system can maintain 60%±5%nitrogen removal rate and 80%±5%phosphorus removal rate.The effluent concentrations of COD,NH4+-N,TN,and TP are 20 mg·L-1,5 mg·L-1,11mg·L-1,and 0.5mg·L-1,respectively.It can meet the first A emission standard of"Pollutant Discharge Standard for Urban Sewage Treatment Plant"?GB 18918-2002?.In order to further investigate the characteristics of nitrogen and phosphorus removal in the system,the reflux ratio from aerobic tank to anoxic tank was increased to 150%.After the system is stabilized,the system can obtain a higher nitrogen and phosphorus removal rate,of which 80%±10%and 90%±5%respectively.Among them,denitrifying phosphorus removal in anoxic tank accounts for 80%±4%of total biological phosphorus removal.The average effluent concentrations of COD,NH4+-N,TN and TP are 19.55 mg·L-1,0.1mg·L-1,7.8 mg·L-1 and 0.15 mg·L-1,respectively,which can meet the Beijing Standard A discharge standard.When the water quality of influent is affected by rainfall in summer,the fluctuation of NH4+-N TN and TP effluent is large.The main reason for this phenomenon is that the existence of some open channels leads to the influent quality being greatly affected by rainfall pecific manifestations are as follows:in the 60-day rainfall concentration period,the concentration of NO3--N in the influent water is greater than 1 mg·L-1 for 15 days,and the concentration of NO3--N in the influent water is greater than 2 mg·L-1 for 4 days.The influent concentration of NO2--N was higher than 0.5 mg·L-1 for 5 days,and the influent concentration of NO2--N was greater than 0.9 mg·L-1 for 3 days.The situation of influent COD concentration below 170 mg·L-1 appeared for 15 days,of which the situation of influent COD concentration below 150 mg·L-1 appeared for 7 days,and even one day the situation of influent COD concentration of 50 mg·L-1 appeared.As a result,the effluent water quality index fluctuates,and the effluent water quality tends to be stable when the influent water quality is stable.In order to explore the relationship and change of microbial population in pilot test at different stages,High-throughput sequencing of sludge from anoxic pond was carried out in pilot-scale tests with stable effluent quality reaching grade I A and Beijing Standard A?corresponding days running to 72 days and 115 days respectively?.At the class level,A large number of denitrifying phosphorus accumulating bacteria were Gammaproteobacteria,Alphaproteobacteria,Actinobacteria,Betaproteobacteria and Clostridia.Acinetobacter,Pseudomonas,Ilumatobacter and Blastocatella were the most abundant denitrifying phosphorus accumulating bacteria at generic level.In the batch experiments to explore the characteristics of nitrogen and phosphorus removal of DPAOs,it was found that when COD was not used as an inhibitor of anaerobic phosphorus release,COD concentration did not affect the phosphorus release rate of DPAOs;excessive COD in the anoxic phosphorus uptake stage inhibited the phosphorus uptake rate of DPAOs,and the time for DPAOs to absorb PO43--P completely was positively correlated with the amount of phosphate released by DPAOs in the anaerobic stage. |
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