Experimental Study On Two-stage AO Series Process For Treatment Of Wastewater With Low Carbon And Nitrogen Ratio

In view of the low C/N ratio of municipal sewage treatment plants and the increased requirements for effluent water quality,this paper has established and tested two two-stage AO tandem reactors to treat low-carbon-nitrogen ratio sewage biological denitrification processes,through two-stage reactions The different process flow of the reactor strengthens the utilization efficiency of the influent carbon source and promotes the efficient operation of the nitrification and denitrification process;by adding ammonia nitrogen adsorbent to the first-stage reactor to enhance the nitrification and denitrification effect,in the efficient use of carbon sources,On the basis of increasing the rate of nitrification and denitrification,the denitrification effect is further strengthened.(1)Through the screening of a variety of adsorbents,it was finally determined that the activated clay adsorbent was used as the ammonia nitrogen adsorbent,and it was added to the biological treatment process to reduce the subsequent biological treatment load.Through single factor tests such as activated clay and alkali modification,the influence of different factors on the removal of ammonia nitrogen was analyzed.When the dosage is 2g/L,the p H value of the water is 7～8,the adsorption time is 2 hours,and the water temperature is 25℃,it has a good removal rate of ammonia nitrogen,which can be used in the subsequent process of ammonia nitrogen adsorption.,Add the prepared adsorbent into the reactor,observe its influence on the reactor and analyze it.(2)In this paper,two-stage SBR reactors are operated in series.The two-stage SBR uses actual domestic sewage as the inlet water.The operation process of the first-stage oxidation ditch is anoxic-precipitation-effluent-aerobic,and the second-stage oxidation ditch adopts anoxic In the process of aerobic-precipitation-effluent,the effluent of SBR I directly enters SBR II.The advantage of this is that the primary SBR reactor only passes through the anoxic stage,the biochemical reaction of aerobic microorganisms is inhibited,and the COD consumed in the denitrification process is also lower,so the effluent of SBR I can be maintained at a higher value at the same time,SBR II reactor can also have enough carbon source to maintain the biological denitrification process in the reactor.In addition,the remaining ammonia nitrogen concentration in the firststage reactor is relatively high,and it enters the aerobic stage for nitrification under higher MLSS conditions,which improves the utilization efficiency of carbon sources and achieves the purpose of saving carbon sources.After a period of effluent testing,the results showed that the final effluent results of the two-stage SBR COD,total nitrogen,and ammonia nitrogen were 16.18 mg/L,5.50 mg/L and 2.59 mg/L,with an average removal rate of 87.69% and 84.91%.And 91.62%,respectively,the effluent indicators can meet the first level A standard of COD,total nitrogen,and ammonia nitrogen in the pollutant discharge standard GB18918-2002 for urban sewage treatment plants.(3)Study the denitrification effect of the two-stage oxidation ditch system,experiment with actual domestic sewage as influent,set the operation process of the first stage oxidation ditch as anoxic-precipitation-effluent-aerobic,and adopt the second-stage oxidation ditch In the process of anoxic-aerobic-precipitation effluent,the effluent of oxidation ditch I directly enters oxidation ditch II,and only passes through the denitrification reaction in the anoxic zone,and then directly enters the second oxidation ditch.Therefore,it contains high COD sewage,so it is satisfied It improves the nitrification and denitrification efficiency of the first oxidation ditch and the utilization rate of carbon source while improving the biochemical reaction of the second oxidation ditch,so as to achieve the purpose of meeting the emission standard of low carbon to nitrogen ratio sewage.The parameters for controlling the reactor are: DO is controlled at 2.5～5mg/L at the beginning of the aerobic zone,1.0～2mg/L at the end,and controlled at 0.5～1mg/L of dissolved oxygen in the hypoxic zone.The first-stage oxidation ditch is operated with a higher MLSS,and its concentration is controlled at6000～8000mg/L.The second-stage oxidation ditch adopts the MLSS of the normal sewage plant,and its concentration is controlled at 3000～4000mg/L.After the effluent quality is stable,Continuous data measurement for half a month.Combined with the measured data,the operation of each process section and the overall operation effect of the process are analyzed and discussed.The operation results show that the process has a significant treatment effect on domestic sewage.With the carbon-nitrogen ratio maintained at its 3.89,the COD,total nitrogen,and ammonia nitrogen concentrations are 28.11mg/L,3.18mg/L and 1.93mg/L,The removal rate reached 86.38%,90.23%,and 93.33%.By optimizing the operating conditions,the effluent index can reach the first level A standard of the pollutant discharge standard for urban sewage treatment plants without increasing the advanced treatment process.