| The study aimed at the problem of low carbon source in domestic sewage.The activated sludge treatment system was taken as the research object.From the perspective of carbon source,compared the effect of each activated sludge system under the condition of sufficient carbon source and low carbon source.The effects of low carbon sources on the characteristics of sludge,extracellular polymers and microbial community structure were discussed in activated sludge system.The study was significant for further explore the denitrification mechanism of activated sludge treatment process under the condition of low carbon source.The study compared the denitrification efficiency with the SBR system and oxidation ditch system under the different COD concentrations of 300 mg/L(C/N=6)and 150 mg/L(C/N=3)in this study.The total nitrogen removal efficiency decreased by 14.62 % when compared with sufficient carbon source and low carbon source in the SBR system.TN removal efficiency decreased by 21.77 % in oxidation ditch system.The nitrogen removal efficiency of SBR system is better than that of oxidation ditch system under low carbon source condition.Based on the typical cycle,the study calculated the different carbon source utilization way of activated sludge system in two kinds of carbon source concentration.The study was discovered that different systems had different carbon source utilization way.The paper had shown that the percentage of denitrification COD when the carbon source is sufficient were higher than that of low carbon source in two systems.Under the condition of low carbon source,the percentage of denitrification COD in the SBR system was higher than in oxidation ditch.The percentage of denitrification COD was 57.01 % and 56.25 % in SBR system respectively,and the percentage of denitrification COD was 20.30 % and 11.96 % in the oxidation ditch system respectively.The study analyzed the sludge settleability to find that the settleability in the SBR system with low carbon source better than in the oxidation ditch system.The study also analyzed the EPS components by means of three-dimensional fluorescence,FTIR,high performance liquid chromatography and other analytical methods.In FTIR,the composition of EPS under the condition of low carbon source was simpler than that in sufficient carbon source.In the molecular weight distribution diagram,it was found that the low carbon source had an effect on the medium and low molecular weight matter of EPS.It was also found that the content of EPS in the low carbon source was lower than that in the sufficient carbon source.And the content of EPS in the SBR system was higher than that in the oxidation ditch system.The paper also researched the difference between microbial activity and community in SBR system and oxidation ditch system by high throughput sequencing analysis.The microbial diversity of low carbon source was lower than that of sufficient carbon source,and it was not conducive to the enrichment of denitrifying bacteria.Nitspira and Thauera were found to have a larger influence on the functional bacteria at low carbon source.Under the condition of low carbon source,the diversity of SBR system was slightly lower than that of oxidation ditch system,but the relative abundance of functional bacteria was higher.Acinetobacter,Clostridium sensu stricto and Thauera had significant differences between the two systems.In the microbial metabolic function,the relative abundance of energy metabolism function at low carbon source was obviously lower than that at sufficient carbon source.In addition,the membrane transport function was the most important factor to influent the denitrification of the SBR system and the oxidation ditch system.These differences in functional bacteria and metabolic function may be the root cause of the poor nitrogen removal effect of activated sludge systems at low carbon sources.And it was laso the reason of the difference in denitrification effect between the two activated sludge systems. |
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