| In recent years,China’s environmental governance level has been greatly improved,but water eutrophication and water resources recycling is still the focus of attention.The effluent of sewage treatment plant is one of the important point source pollution,the effluent nitrogen is mainly nitrate nitrogen.In order to meet the requirements for nitrogen discharge in receptive water bodies such as lakes and slow-flow waters,SBR denitrification processes with different external carbon sources were studied in this paper.Tailwater of sewage treatment plant with influent concentration of about 15mg/L was treated,and effluent concentration of less than 1mg/L was taken as the target.The feasibility and stability of the system operation and the economic analysis of carbon sources were investigated.At the same time,high-throughput sequencing technology was used to analyze the population structure of microorganisms in the sludge of each system to further study the principle of denitrification performance of the system.The aim is to improve the denitrification efficiency,reduce the operation cost,and provide an optimal strategy for carbon source addition in municipal sewage treatment plants.In this paper,four common liquid carbon sources,methanol,ethanol,glucose and sodium acetate,were used as external carbon sources to construct the denitrifying SBR deep nitrogen removal system with four single carbon sources.Successfully started and ran steadily for 70 cycles.Under the influent concentration of 15～20mg/L,the effluent water can reach the proposed removal target of nitrate nitrogen stably,and the removal rate of the four systems can reach more than 96.5%.The dosage of methanol 4.346 g,ethanol 1.959 g,glucose 8.15 g,sodium acetate 7.315 g were used to remove 1g of NO_x~--N carbon source in the four systems.The average nitrogen removal rates were 0.25,0.54,0.15 and 0.44 kg N/(m3·d),respectively.In order to study the influence of composite carbon source on denitrification and denitrification of tail water,ethanol and sodium acetate,the most effective single carbon source,were mixed with the least effective but cheapest glucose in the ratio of 1:1 and 1:3 respectively to form a mixed carbon source.The denitrification SBR deep denitrification study was carried out,and the influent deoxygenation was compared with no deoxygenation.The results showed that the accumulation degree of nitrite in denitrification process of composite carbon source was higher than that of single carbon source,but the nitrogen removal rate was slower,and the addition amount of composite carbon source was larger under the premise of meeting the removal target.The stability of sodium acetate/glucose complex carbon source system is good,while the stability of ethanol/glucose complex carbon source system is poor,and the system effluent is unstable for many times.The microbial community diversity in the denitrifying SBR system was lower than that in the secondary biological treatment system.Carbon source type has obvious influence on microbial structure,and the dominant population of each system is different to some extent: The microbial population structures of methanol,ethanol and sodium acetate were similar to some extent.Proteobacteria,Bacteroidetes,Chloroflexi and some unclassified Bacteria were the dominant Bacteria groups.At the family level,the bacteria abundance of Methylophilaceae in the methanol system was the highest.When glucose and complex carbon sources containing glucose were external carbon sources,Candidatus Saccharibacteri accounted for the highest proportion,up to about 40%,and mainly played a role in the decomposition of glucose,while the Proteobacteria phylum was the dominant microorganism to perform denitrification. |
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