Enhance The Response And Regulation Of Microorganisms In A~2/O System To The Changeable Characteristics Of Rural Sewage

At present,the problem of water pollution in rural areas caused by the substandard effluent quality of rural domestic sewage has attracted extensive attention.However,in rural areas,the population density is small,the villagers live scattered,the sewage collection is difficult,and the water quality is changeable,resulting in substandard effluent quality and high operation and maintenance costs.Based on this,this paper takes rural domestic sewage as the research object.On the basis of investigating the influence of the changeable characteristics of sewage on the treatment effect of A²/O biological contact oxidation process,this paper focuses on the response mechanism of microorganisms in the sewage treatment process,and puts forward the corresponding regulation strategies,which provides theoretical and technical support for the efficient and stable treatment of rural domestic sewage.In this paper,first,through fieldwork and literature survey,we summarize and summarize the water quality,discharge methods and laws of rural domestic wastewater,and conclude that there are four typical characteristics of the variable characteristics of rural domestic wastewater:time variation,day variation,high concentration of low flow rate,low concentration of high flow rate.In response to the changeable characteristics of rural wastewater,A²/O biological contact oxidation method was selected as the treatment process.Under steady-state conditions,the A²/O biological contact oxidation reactor showed excellent removal of pollutants from wastewater,with average removal rates of COD,NH₄⁺-N,and TN of 92%,98%,and 70%,respectively,and water quality of effluent meeting the criteria of level a of the pollutant discharge standards of the municipal WWTP（GB18918-2002）;Microbial mechanistic studies revealed that both enzymes critical for denitrification（NAR,NIR,nor,N₂OR）and nitrification（AMO,Hao）retained high activities;Both denitrifying microorganisms（Acidovorax,Bacteroidetes,thermomonas,etc.）and nitrifying microorganisms（erythrobacter,Sphingomonas,Nitrospira,etc.）maintained high relative abundances;The key functional genes for assimilatory nitrate reduction（nasA,narB）,dissimilatory nitrate reduction（nrfA）,denitrification（narG,norB and nosZ）,nitrification（amoA,Hao）were all detected in the reactor,which could benefit the smooth progress of nitrification and denitrification processes.Reactor performance studies on pollutant removal under variable characteristic condition impingement showed that time-varying,day-to-day variations,as well as high and low flow conditions at high concentrations did not significantly affect the pollutant removal efficacy.Under low concentration high flow conditions,the removal rate of TN from wastewater by the reactor decreases and the stability becomes poor due to insufficient influent carbon source;Microbial mechanistic studies showed that the activities of key enzymes of denitrification were decreased to various degrees compared with those of steady-state conditions at low and high flux concentrations,and the relative abundances of denitrifying microorganisms,including Acidovorax,Bacteroidetes,thermomonas,etc;Analysis of genes with functions in nitrogen metabolism revealed that the relative abundances of genes critical for assimilatory nitrate reduction（nasA,narB）,dissimilatory nitrate reduction（nrfA）,and denitrification（narG,norB）with functions in denitrification were also decreased to various degrees compared with those under steady-state conditions.In response to the problem that the low and high flow rate characteristics of rural domestic wastewater can cause a large impact on the water treatment system,the napkin waste fermentation was selected as the influent to supplement the carbon source,and it was found that after the supplementary administration of the carbon source,the TN removal rate was significantly improved,and the stability of the TN removal rate was even better than the steady-state condition;Mechanistic studies showed that the enzymatic activities of key enzymes of denitrification were enhanced to various degrees after the supplementary administration to the fermentation broth of naphus waste,compared with the low concentration and high flow conditions,and the richness of microbial population structure was enhanced compared with the low concentration and high flow conditions;The relative abundances of key genes involved in assimilatory nitrate reduction（NASA）,dissimilatory nitrate reduction（NrfA）and denitrification（narG,norB）were increased to varying degrees compared to the low and high flow conditions.