| The secondary effluent from urban sewage treatment plants has the characteristics of stable water quality and quantity,which can be considered as the source of reuse water to solve the problem of urban water shortage in China.However,there is still a high residual nitrogen and phosphorus in the secondary effluent,which needs to be further reduced by advanced treatment.Compared with traditional activated sludge denitrification process,coupled autotrophic denitrification with ferrite has the characteristics of less sludge yield and higher simultaneous nitrogen and phosphorus removal,which has become a research hotspot.At present,the sulfur autotrophic denitrification coupled with iron and sulfur is mostly in the form of biofilter bed,which generally has problems such as long start-up time and easy hardening during long-term operation.To solve these problems,this article FeS2powder by hydrothermal synthesis method,the feasibility test chose an economic and efficient FeS2 as sulfur source denitrification,real time monitoring plus powder FeS2 as electron donor to the influence of sulfur autotrophic denitrification SBR process,and the system is analysed by high throughput sequencing microbes and related functional genes.In order to obtain powdered electron donor for SBR reactor,FeS2 solid powder was prepared by hydrothermal method and its feasibility was investigated.EDS energy spectrum shows that the solid powder has the highest proportion of iron sulfide,and it appears as a micro-sphere of ten microns under scanning electron microscope.IR absorption spectrum shows that the material has pyrite crystal type.XPS analysis of iron sulfide shows that the compound contains a small amount of FeSx in addition to FeS2.The feasibility test shows that when the influent NO3--N is 55 mg/L,the addition of FeS2 in 4g/L and 8g/L powder can remove all nitrate in the sludge within 9 days,and the FeS2 synthesized under 5h hydrothermal time can meet the requirements of nitrogen and phosphorus removal.Taking the standard of urban reuse water as the target,taking simulated secondary effluent as the treatment object,adding 0.8g/L FeS2 as the electron donor,the changes of NO3--N,NO2--N、PO43--P and p H in the water were investigated.It was found that nitrate was always reduced to nitrite in a short time,and nitrogen eventually accumulated in the system in the form of NO2--N.The treated effluent TON（NO3--N+NO2--N）≤10mg/L,the phosphate was completely removed,and the p H was moderately acidic.Pyrite and Na2S2O3 could not promote the autotrophic denitrification of sulfur in a short time.25℃is helpful for the utilization of FeS2 by sulfur autotrophic bacteria.The autotrophic denitrification efficiency could not be improved by additional alkali source.Under mixed nutrition,the denitrification efficiency of the system is higher than 90%,but the effluent will cause secondary pollution of organic matter,and the addition of external carbon sources will affect the dominant position of sulfur autotrophic bacteria.In order to explore the influence of FeS2 on the microbial community and related functional genes,high-throughput sequencing analysis showed that Thiobacillus was the dominant bacteria in the sludge adding powder FeS2,and the denitrification process was indeed dominated by sulfur autotrophic bacteria.Moreover,the microbial community structure was complex and there was an interspecific cooperation relationship.Combined with the experimental data and functional gene analysis,it can be seen that the addition of FeS2 can improve the capacity of oxidizing sulfide in the sludge and strengthen the reaction of nitrate reduction to nitrite.Actinomycetes accelerate the dissolution of solid powders by transferring FeS2 surface electrons,which plays an important role in nitrogen and phosphorus removal. |
