| Research on the microbial degradation of refractory toxic organics is inseparable from DMSO as an organic cosolvent.The Partial Nitrification process is a new type of nitrogen removal process.The coupling of the Partial Nitrification process and Anammox has been used to remove high-ammonia-nitrogen wastewater in industries and other fields.As part of the traditional nitrogen removal process,the Denitrification process is more common in the treatment of industrial wastewater or domestic sewage.Although DMSO is considered to be non-toxic,there are few reports about its impact on the microbial performance and community structure in the water treatment process.Therefore,this study selected Partial Nitrification process and Denitrification process to explore the effect of DMSO on the nitrogen removal performance and microbial community structure of these two processes.Firstly,four kinds of DMSO concentrations commonly used in scientific research experiments are selected,and the effluent water quality and typical cycle water quality data are analyzed to evaluate the feasibility of starting the Partial Nitrification process in the presence of DMSO and analyze the influence of DMSO on the reaction endpoint of the PN process and the structure of the microbial community.At the same time,the effect of Denitrification process on total nitrogen removal rate and whether DMSO can be used as a carbon source for denitrifying bacteria is explored.Finally,high-throughput technology is used to analyze the microbial community diversity and community structure changes in the Partial Nitrification and Denitrification process in the presence of DMSO,and further predict and analyze the impact on functional genes,and explore the degradation pathways of DMSO and the two reactions Process influence mechanism.The main conclusions are as follows:(1)The start-up time of PN gradually increases with the increase of DMSO concentration.DMSO at a concentration of 0.1%accelerates the start of the PN process,and DMSO at a concentration of 3.5%makes the start-up time of PN more than 40 days.DMSO only changed the start time of the PN process,and did not change the end point of the PN reaction.(2)After the PN process is stable,although DMSO inhibits the activity of AOB,it increases the abundance of AOB.The typical cycle results show that,except for R4,the time for PN to reach the end of the reaction has not changed.(3)The analysis of the microbial community structure showed that under certain PN conditions,the abundance and diversity of the microbial community in the control group gradually decreased with the running time compared with the initial sludge,but DMSO promoted the increase in the abundance and diversity of the microbial community.DMSO has a certain influence on the microbial community structure.The microbial community structure in the low-concentration DMSO reactor is similar to the control group,and the high-concentration DMSO makes the microbial community structure a great change.(4)0.1%DMSO increased the denitrification rate,and 1%and 2%DMSO had a certain inhibitory effect on the denitrification rate.The 3.5%concentration of DMSO has a higher inhibitory effect on the denitrification rate.The time for complete reduction of nitrate to nitrogen is twice that of the control group,and the inhibition process mainly occurs in the process of nitrite reduction.(5)The analysis of the microbial community structure showed that the presence of DMSO increased the relative abundance of the Proteobacteria,and the relative abundance of the Proteobacteria reached 91.7%at a concentration of 0.1%.Although the relative abundance of Proteobacteria gradually decreased with the increase of DMSO concentration,the relative abundance of Proteobacteria in the 2%concentration DMSO reactor was still higher than that in the control group.The relative abundance of Proteobacteria in the 3.5%concentration DMSO reactor was lower than that in the control group,and the relative abundance of Bacteroides phylum gradually increased with the increase of DMSO concentration.The cluster analysis results show that the concentration of DMSO has a greater impact on the community structure of denitrifying microorganisms.(6)The R5 reactor containing only DMSO as the carbon source always maintains the total nitrogen removal rate below 10%during the denitrification process,indicating that DMSO can hardly be used as a carbon source for denitrification in the denitrification process.However,the analysis of the microbial community structure shows that denitrifying bacteria are still maintained at a high level,and the community structure is very similar to R3,so DMSO can provide the carbon source and energy required for the growth of denitrifying bacteria. |
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