Application Of A Novel Sulfur Autotrophic Denitrification Reactor For Advanced Denitrification

At present,a large number of industrial wastewater with high concentration of NO₃^--N and secondary effluent from municipal wastewater treatment plants are characterized by low C/N（NO₃^--N）.Biological denitrification has always been considered as the most economical and feasible technology for the removal of NO₃^--N from low C/N wastewater,which can be divided into autotrophic denitrification and heterotrophic denitrification.Traditional heterotrophic denitrification requires additional carbon source as electron donor,which is easy to cause secondary pollution,and has large sludge yield and high operation cost.Although sulfur autotrophic denitrification has high treatment efficiency,low sludge yield and low energy consumption,the H⁺generated in the reaction process will lead to a decrease in p H,thus affecting the denitrification rate,and the alkalinity substances commonly used in the study,such as limestone,will lead to an increase in effluent hardness.Therefore,in order to solve the problems existing in the denitrification system with a single electron donor,this study used Na₂S₂O₃and glucose as substrates to construct a sulfur autotrophic/heterotrophic cooperative denitrification system,to study its deep denitrification effect on the secondary effluent of high-concentration industrial wastewater and low-concentration municipal wastewater plant,and to study the microbial community and denitrification mechanism.The deep denitrification of high-concentration NO₃^--N wastewater（secondary treatment effluent of sucralose production wastewater）was carried out in a high-efficiency sludge bed denitrification reactor.The results showed that,under the conditions of 35℃,1.3/1/1.9 C/N/S,and NO addition of p H buffer,when the influent NO₃^--N concentration was 940mg/L,the influent NO₃^--N concentration was 940mg/L.When HRT was 6h,the effluent NO₃^--N concentration was 60mg/L,the NO₃^--N removal rate remained above 93%,the NO₃^--N removal load reached 3.52 kg/（m³·d）,and the effluent p H stabilized at about7.0.S⁰was generated in the reaction system,and the amount of SO₄^2-produced in the effluent was only 1/2 of that in the theory of single sulfur autotrophic denitrification.The sludge increment was only 68%of complete heterotrophic,and the optimum temperature for denitrifying bacteria was 25～35℃.The deep denitrification of low-concentration NO₃^--N wastewater（secondary treated effluent from municipal sewage treatment plant）was studied in a high-efficiency packed bed denitrification reactor.The results showed that the C/N/S of 1.3/1/1.9 was also suitable under the condition of 25℃and No p H buffer,and the influent NO₃^--N concentration was10.95mg/L.When HRT was 2h,the effluent NO₃^--N concentration was 0.7mg/L,the removal rate of NO₃^--N reached 93%,the removal load of NO₃^--N was 0.11 kg/（m³·d）,and the effluent p H stabilized at about 7.5.S⁰is also generated in the system,and the effluent SO₄^2-is 163.4mg/L.The braid packing layer in the lower zone can better enrich microorganisms,and the removal rate of NO₃^--N can reach 70%.With the rinsing flow of5L/（m²·s）and rinsing time of 2min,the reactor can be completely restored to the normal denitrification state in 1h.Proteobacteria was the dominant phylum,Gammaproteobacteria was the dominant class,and Thiobacillus was the dominant genus.The microbial composition of the collaborative denitrifying sludge at different concentrations was composed of heterotrophic denitrifying bacteria,facultative denitrifying denitrifying bacteria and autotrophic denitrifying bacteria,forming a denitrification mechanism with the autotrophic denitrifying bacteria as the main denitrification mechanism and the facultative and heterotrophic denitrifying bacteria as the auxiliary denitrification mechanism.