Research On Sewage Denitrification Technology Based On Sulfur Autotrophic Denitrification Synthetic Materials

Nitrate pollution has become one of the most serious environmental pollution problems in the world due to excessive use of nitrogen fertilizer and uncontrolled discharge of sewage.With the improvement of nitrate treatment requirements,deep denitrification technology has attracted much attention.Sulfur autotrophic denitrification synthetic materials provide a new way for advanced denitrification due to their advantages of simultaneously satisfying sulfur source,carbon source and alkalinity required by sulfur autotrophic denitrification,but its application parameters and mechanism of action in practical applications are not yet clear,which limits the large-scale application of synthetic materials.In this study,an autotrophic/heterotrophic mixotrophic denitrification system was constructed using sulfur autotrophic denitrification synthetic materials,and the effect of different inoculated sludge and electron donors on denitrification performance was explored.Based on the discussion of its denitrification mechanism,a continuous up-flow synthetic material mixotrophic denitrification reactor was constructed,and the actual feasibility of synthetic material denitrification was determined through actual field experiments.Synthetic materials can achieve high-efficiency denitrification under inoculation of different sludges（autotrophic,heterotrophic and mixotrophic）.The mixotrophic denitrification system inoculated with mixed sludge（autotrophic:heterotrophic 1:1）achieved a higher reaction rate when the theoretical value of glucose was added(k=0.0286h^-1),and after the organic carbon source was exhausted,it still had a high nitrate removal rate(k=0.0156h^-1),and the microbial community structure analysis showed that sulfur autotrophic denitrifying bacteria（Thiobacillus and Sulfurimonas）and heterotrophic denitrifying bacteria（Enterobacter,Pseudomonas,Thaurea and unclassified＿f＿Enterobacteriaceae,etc.）were enriched in the system,the material balance calculation showed that the contribution rates of heterotrophic and sulfur autotrophs were 53.8% and 46.2%,respectively.Under the mixed sludge inoculation,the sulfur autotrophic/heterotrophic mixotrophic denitrification system constructed by synthetic materials has higher denitrification performance than that of sulfur.In the change of the glucose concentration which reduced from 1.5 times the theoretical value to 1 and 0.5 times the theoretical value,the contribution rate of autotrophic denitrification gradually increased from 21.7%to 45.5%and 94.8%.The MPN count and material balance calculation of the synthetic material system under the theoretical glucose concentration showed that as the reaction progressed,sulfur autotrophic denitrification gradually replaced heterotrophic denitrification as the main nitrate reduction process.The continuous flow column experiment of synthetic material showed that when HRT=0.5h and the influent carbon source concentration was 0.5 times the theoretical glucose,the system denitrification performance was the best（NO₃^--N removal efficiency and rate were 100%and48.64 mg-N/（L·h）,respectively）.When no carbon source is added,the reactor could still maintain a high nitrate removal rate（90.5%±2.3%）.The actual field experiment showed that the synthetic material had efficient and stable denitrification performance,the TN removal rate was over 84%,and the actual system operation denitrification material cost is 0.117 yuan/ton.Compared with the traditional processing equipment,the actual operation system denitrification cost is significantly reduced.In this study,an autotrophic/heterotrophic mixotrophic denitrification system based on sulfur autotrophic denitrification synthetic materials has achieved good denitrification performance in different inoculated sludges,electron donors and continuous operation systems.This provided technical parameters and theoretical support for the practical application of synthetic materials,and opens up a new way for deep denitrification technology.