Using MBBR-MSL System To Treat Domestic Sewage And Research Of Microbial Community

As the country strengthens rural construction,rural sewage will be brought into the treatment.Limited by rural economic capacity and technical talents,traditional sewage treatment technology and facilities are not very suitable for China's rural reality.In this research,a new technology for the joint treatment of rural domestic sewage by MBBR and MSL was studied according to the characteristics of water quality and water quantity variation of rural domestic sewage,and combined with the unique advantages of MBBR and MSL technologies and their adaptability to rural domestic sewage treatment.The main results were as follows:?1?The COD removal rate of the combined process is maintained at more than 90%and can reach up to 96%.And the COD concentration of the effluent should be kept below 30mg/L and the minimum is only 15mg/L,reaching the standard of surface IV water or even surface II water.The removal rate of TP was kept above 92%or even close to 100%,and the effluent TP concentration was kept below 0.5mg/L,reaching the surface V water standard.The removal rate of NH4⁺-N was kept above 95%,the highest reaching 99%.And the effluent concentration was kept below 1.5mg/L,reaching the lowest level of surface IV water and surface II water.TN achieved a good removal rate after a long time of rise,from less than 20%to about 75%.And the effluent TN concentration was about 10mg/L.?2?The results of NGS and q PCR showed the correlation between the dynamic change of microbial community structure and the effect of water treatment.?3?The diversity of the MBBR bacterial community first rose and then fell,and then reached a stable state.Proteobacteria has always occupied a dominant position,and Bacteroidetes are in a state of rising with fluctuation,while Nitrospirae,as the third dominant bacteria,gradually reaches a stable position after rising and then falling.At the genus level,the relative abundance of Sphaerotilus decreased from 63.73%to0.15%,and that of Zoogloea increased from 0.83%to 22.97%,and then decreased to6.75%.These two bacteria genera contribute to the formation of biofilm,and their abundance changes can reflect the changes of biofilm.The abundance of Nitrosomonadaceae,which is a typical AOB family,was 0%in the early stage,increased to 2.165%at 40d,and remained at about 1.40%at the end of the combined process.As the main NOB in the community,Nitrospira increased from 3.36%to 13.18%and then decreased to 6.89%,and was the dominant colony in MBBR.According to the quantitative PCR results,the total bacterial population in MBBR reached the maximum of 8.397×10⁹copies/g.With the continuous operation of the combined process,the number of AOB and NOB is basically on the rise.?4?At the initial stage,the SMB in MSL took actinomycetes as the largest dominant phylum and distributed widely at the genus level.Denitrification related bacteria had not yet occupied the dominant position.After running for about 2 months,denitrifying bacteria such as Enterobacter,Bacillus,Dechloromanas,Dechlorobacter and Clostridium gradually occupied the dominant position.According to the results of q PCR,with the continuous running of the combined process,the total quantity of bacteria in MSL increased gradually up to 1.360×10¹² copies/g.The abundance of AOB,NOB and denitrifying bacteria increased gradually.And the effect of denitrification was also strengthened.AOB mostly grows in PL with high oxygen permeability,while the abundance in SMB is very low.NOB abundance is low in both SMB and PL.Denitrifying bacteria are more likely to grow in the middle anaerobic environment and the internal anaerobic zone of SMB.The quantity was about 1.260×10⁸-1.695×10⁹copies/g.The results of this study show that the combined process of MBBR and MSL can effectively treat the artificial sewage.And its treatment effect is closely related to the dynamic changes of the bacterial community in the biofilm of each system.The optimized microbial community structure is the basis for efficient treatment.