Efficacy Of Compound Biological Agents To Enhance The Stable Operation Of Urban Sewage

Urban sewage treatment is an important part of sewage treatment system,the urban sewage is mostly from people’s daily life,so the urban sewage is treated by biological method mostly.However,in the cold winter of Northeast China,the growth and proliferation and metabolic activity of microorganisms are significantly inhibited,so the urban sewage treatment plants are faced with the problems of low pollutant treatment efficiency and unstable running.Especially under the low temperature condition,how to improve the treatment efficiency of urban sewage treatment system and maintain stable operating state has become an important problem to be solved.The removal of organic nutrients such as nitrogen and phosphorus in urban sewage treatment system can be effectively improved by using the biofortification technology of adding compound biological agents adapted to low temperature.The research of composite biological agents suitable for urban sewage treatment at low temperature has a very realistic and far-reaching significance for the energy enhancement,sludge reduction,low temperature operation effect enhancement and nitrogen and phosphorus nutrient removal of sewage treatment plants.In this paper,efficient functional strains were screened out,and based on the principles of microbial co-metabolism,niche separation and adaptive principles of microorganisms,high efficiency composite biological agents were constructed by applying the theories of microbial physiological ecology,molecular ecology and environmental engineering.The optimum conditions for the application of the bacterial agent were determined and the comparative study of the application efficiency was carried out.Based on the start-up and operation of a simulated urban wastewater SBR system enhanced with composite biological agents,the composition and change of microbial community structure in the system at the early,middle and late stages of reactor operation were investigated.The relationship between the succession of community structure and effluent quality was explained from the microscopic point of view,which provided theoretical basis and technical support for the stabilization of urban sewage operation with composite biological agents.First,four types of functional bacteria were screened from the bottom sediment of the secondary sedimentation tank,which were COD degrading bacteria,aerobic denitrifying bacteria,nitrifying bacteria and phosphorus accumulation bacteria.According to the removal results of different pollution indexes,efficient functional strains were screened again.The 24h degradation rates of strain Z3 on COD and NH₄⁺-N are63.9%and 55.8%,respectively,while HF9 on NH₄⁺-N and TN are 68.1%and 66.1%,and the 24h degradation rates of strain X8 on NH₄⁺-N are 70.5%when the degradation rate of TP by PC5 reached 54.7%.Morphological observation,physiological and biochemical experiments,16S rRNA identification and growth curve determination were carried out to investigate the strain status comprehensively.The species and genus of the four strains were determined as follows:strain Z3 was Aeromonas hydrophila,strain HF9 was Acinetobacter johnsonii,strain X8 was Klebsiella grimontii,and strain PC5 was Pseudomonas chengduensis.The compound test of four strains of high efficiency bacteria was carried out to construct the compound biological agents.Through experiments,we can find that the optimal compound combination and mass ratio were Z3:HF9:X8:PC5=1:1:3:1.Under the optimal environmental conditions of pH 6.5,10℃,200rpm and 5%（V/V）dosage,the degradation rates of COD,NH₄⁺-N,TN and TP reached 83.8%,81.9%,79.6%and 81.2%,respectively.The purification effect of the bactericides can be improved by appropriately increasing the influent load（1200COD）and adding additional carbon sources（sucrose,fructose）when the bactericides are added at 10℃.The actual efficacy test results showed that the composite biological agent constructed in this study had similar treatment effect to the finished commercial bacterial agent,and had practical value.According to the operation of the SBR process strengthened by composite biological agents,it can be found that the effluent water quality of the reactor strengthened by bacteria agent is significantly better than that of the reactor without bacteria agent in the early period of system operation（0-10 days）,and the degradation rate of COD and NH₄⁺-N is 63%and 28.6%higher than that of the control group,respectively.After the reactor was strengthened,the degradation rate of TN reached 82.4%on the second day,the effluent TN was below 15mg/L,and the degradation rate of TP was also maintained at a high level（82.6%）.After the stable operation of the two systems,the effluent quality of the bioenhanced SBR reactor 2#was slightly better than that of the control reactor without adding bacteria agent.From the analysis of the microbial community structure samples in the two groups of reactors,it can be seen that with the extension of operation time,the microbial community composition in the two treatment systems changed greatly in the early and late stages.At the same time,there were differences in community structure composition between different reactor groups.The succession of microbial community is consistent with the fluctuation of effluent water quality.The experimental results in this paper provide some basis and guidance for the practical application and popularization of adding compound biological agents adapted to low temperature to strengthen the stable operation of urban sewage.