Study On Nitrogen Removal Efficiency Of Combined Process Of A~2/O And Side Pressure Biological Aerated Filter For Nitrification Enhancing

With the rapid development of economy and the continuous growth of population,the problem of water resource shortage and water environment pollution are increasingly prominent.In order to meet the increasingly strict pollutant discharge standards,most of the existing sewage treatment plants in China are facing the problem of upgrading,the demand for relevant technologies is urgent,and the market potential is huge.A²/O process,as the main technology of wastewater denitrification and dephosphorization,has played an important role in the field of urban sewage treatment in China in recent years.However,with the improvement of pollutant discharge standard,the sewage treatment plant with A²/O as the main process is faced with the problem that the indexes of ammonia nitrogen and TN cannot meet the first-level A standard in the pollutant discharge standard of urban sewage treatment plant,so it is urgent to upgrade and transform.Aiming at the problems of insufficient nitrification caused by aeration control in aerobic tank of sewage treatment plant and the floating of sludge in secondary sedimentation tank,this paper studies and develops the by-flow pressure biological filtration device based on biological aeration filter.Carry out a study on the removal efficiency of pollutants from bypassing pressure biological filter and summarize the key technical parameters of bypassing pressure biological filter.The influence of control parameters such as internal reflux ratio and aeration rate of A²/O nitrification fluid on system enhanced nitrification efficiency was studied under the condition that the by-flow pressure biological filter was combined with A²/O mainstream process.To explore the optimized operation conditions of increasing the partial oxygen pressure in the bypassing pressure biological filter to reduce the aeration rate,and promoting the release of dissolved water from the bypassing pressure biological filter to improve the escape rate of N₂ in the anoxic tank.When the bypassing pressure biofilter is operated under the same gas-water ratio,the dissolved oxygen in the reactor under pressure is significantly higher than that in the reactor under normal pressure.Pressure can greatly increase the concentration of dissolved oxygen in the reactor.However,with the increase of working pressure,the growth rate of DO in the reactor gradually slows down.The backwashing mode of the bypassing pressure biological filter is gas-gas-water combined rinse-water rinsing.The backwashing time is set as:gas rinsing for 5min,gas-water combined rinsing for 5min,water rinsing for 10min,gas rinsing intensity is 15L/?m².s?,water rinsing intensity is 8L/?m².s?,and the backwashing cycle is 7 days.The gas-water ratio of the bypass pressure biological filter?atmospheric pressure?is 3:1,the hydraulic residence time is2h,and the inlet water flow rate is 30L/h,the removal effect of COD,NH₃-N and TN is the best.At the pressure of 0.12MPa,DO=3.02mg/L,gas-water ratio of 2:1,inlet flow rate of 30L/h and HRT=2h,the removal effect of COD,NH₃-N and TN was the best,and the aeration rate was reduced under pressure,but the removal efficiency of pollutants was better.The reflux ratio of nitrifier in A²/O+bypass pressure biofilter combined process under pressure and atmospheric pressure was optimized.The optimum reflux ratio and pollutant removal efficiency of the two combined processes were determined.When the internal reflux ratio is 100%and the biological filter reflux ratio is 100%?a total of 200%?,the nitrogen removal efficiency of the two combined processes is the best.By comparing the pollutant removal efficiency of the two,compared with the combined process under atmospheric pressure,the combined process under pressure has lower aeration and better denitrification effect.Coordinate and optimize the combined process A²/O aerobic tank aeration?DO?and bypass pressure biofilter operation pressure?DO?.When the aeration rate of the aerobic tank is150L/h?DO=2.0-2.5mg/L?and the aeration rate of the filter tank is 90L/h?pressure is 0.14mpa,DO=3.41-3.6mg/L?,the removal rate of TN is not the highest,but the combined process operating under this working condition is significantly better than the traditional A²/O process.The removal efficiency of TN,TP,COD and NH₃-N in the combined process of A²/O+bypassing pressure biological filter after the actual domestic sewage was fed into the filter was compared with the deconfouling efficiency of the traditional A²/O process in the current sewage plant:the average removal rate of COD was 88.7%,and the average effluent concentration was46.28mg/L.The average removal rate of ammonia nitrogen was 95.41%,and the average effluent concentration was 2.15mg/L.The average removal rate of TN was 83.08%and the average effluent concentration was 10.64mg/L.The above three water quality indicators have reached the national level A emission standard.The average removal rate of TP was 72.1%,the average effluent concentration was 1.63mg/L,and the effluent did not meet the national level A emission standard.All pollutant removal indexes of the combined process are better than those of the traditional A²/O process,and while effectively improving the denitrification efficiency of the mainstream A²/O process,the optimization of aeration control is realized and the problem of sludge floating up in the secondary sedimentation tank is solved.