Efficiency Study On Deep Denitrification And Decarbonization Of Comprehensive Tail Water In An Qing High-tech Chemical Industry Park

Urban sewage treatment plants generally have problems such as low treatment efficiency,large energy consumption and waste,and low energy resource recovery rate.There is an urgent need to improve the operation level,reduce energy and material consumption.In addition,the reuse of secondary treatment effluent generally faces the problems of deep reduction of nitrogen and phosphorus nutrients and removal of refractory organic matter.At the same time,the water quality of ordinary secondary treatment effluent reused for industrial and urban landscape ecological water cannot be guaranteed.The above-mentioned problems have restricted the pace of sewage resource utilization to varying degrees.Based on this,this study took the effluent from the secondary sedimentation tank of An Qing Cheng Xi Wastewater Treatment Plant and the effluent from the Shu Guang Chemical Contact Oxidation Tank as the treatment objects,and constructed a small-scale aerated biological filter and elemental sulfur biological packed bed respectively to investigate the reaction under different reaction conditions.The deep COD removal and deep nitrogen removal performance of the reactor.On this basis,by means of chemical analysis and microbial community structure analysis,the change rule of functional microorganisms in different operating stages of the reactor was discussed,and the key functional microorganisms in the reactor were analyzed to provide a theoretical basis for strengthening the operational efficiency of the reactor.In order to efficiently and economically remove the refractory or toxic organic pollutants remaining in the biological effluent,this study constructed a pilot plant for biological aerated filter.In the initial stage of the reaction,due to insufficient organic carbon sources that are easily available,some functional flora cannot complete normal growth and metabolism activities.After running for 25 days,the removal rate of COD basically fluctuates around 15%.However,after adding 100mg/L glucose to the reactor and 35 days of operation,the removal rate of COD increased by about 37%compared with the first stage,and some organic matter with larger molecular weight was gradually decomposed under the action of specific oxidase.When the effluent concentration is basically stable at 128mg/L,stop adding glucose.After running for 45 days,the activity of microorganisms in the reaction system has been improved.At this time,the removal rate of COD increased by 2.9%compared with the first stage,and the COD concentration of effluent basically stable at 100mg/L.At this time,the effluent after the ozone oxidation treatment was added to the reactor.After the action of microorganisms,the degree of mineralization of the organic matter was enhanced,and the removal rate of COD was stabilized at 18.9%.However,there are still some organic substances such as 2,4-di-tert-butylphenol and 3,5-di-tert-butyltoluene in the entire reaction stage.Compared with the treatment using ozone oxidation technology alone,combining the ozone oxidation process as a pre-treatment with a biological aerated filter can further improve the treatment efficiency of COD,thereby laying a certain foundation for the supporting and combining of subsequent processes.In order to solve the problem of deep denitrification in industrial parks,an elemental sulfur biological packed bed device with volume of 633ml was constructed.When HRT=9h,the reactor runs well.After 25 days of operation,the removal rates of TN and NO₃^--N are stable at about 78.5%and 95.2%,the functional microorganisms in the reaction system are gradually enriched.With the increase of NO₃^--N load in the influent,HRT was adjusted from 9h to 4h.After 30 days of operation,the content of nitrite decreased gradually,the removal rate of NO₃^--N increased by 2.8%and the removal rate of TN by 4.7%compared with the first stage,and the denitrification performance was gradually enhanced.When the concentration of NO₃^--N in the effluent water tends to be stable,the hydraulic retention time is further shortened to 2h,and the removal rates of TN and NO₃^--N continue to rise,basically stabilizing at 84.9%and 98%,and the nitrate is basically completely removed.For the degradation of organic matter,in the whole process of denitrification,with the reduction of hydraulic retention time,the COD removal rate gradually increased from the initial 18%to 30%,and finally stabilized at about 39%under the condition of HRT=2h.The reason for the above phenomenon may be due to the combined action of the specific oxidase secreted by the functional flora and the adsorption of the biofilm.The influent contains alkanes with carbon numbers between 7-12 and 3,5-di-tert.Butyl toluene and some more complex esters and halogenated hydrocarbons are transformed into organic compounds with simpler molecular structure.However,some substances,such as 2,4-di-tert-butylphenol,hexadecane,etc.,may not be used by microorganisms due to the limited types and number of functional flora.By analyzing the microbial community structure in the two reactors,it was found that,as the main participants of COD degradation,Acidovorax（2.9%）and Hyphomicrobium（17.2%）existed in BAF in the form of biofilms,occupying a certain advantage after the operation of the actual wastewater.By secreting some specific oxidases and acting with the substrate,the organic compounds with complex structures are mineralized to achieve the deep removal of COD in tailwater.On the other hand,the sludge samples were analyzed at the phylum,genus and species levels in the bio-filled bed with elemental sulfur.Among them,as important denitrification contributors,Sulfurimonas（19.2%）and Thiobacillus（9.5%）work together to use reduced sulfide or hydrogen as electron donors,and oxygen and nitrate as electron acceptors for deep denitrification.In addition,the elemental sulfur bio-packed bed also contains some relatively low abundance（2.5%）bacterial genera,such as Denitratisoma,Caldilineaceae and Thermomonas,which have a certain ability to remove nitrogen and other compounds.Therefore,the denitrification efficiency of the reactor is not only reflected by a single microbial population,but by the combined effect of multiple species and multiple levels.