Performances And Microbial Community Structure Of Autotrophic Denitrification With Different Sulfur Sources

Sulfur based autotrophic denitrification is the stable and efficient biological nitrogen removal method.The reduced sulfur can be used for autotrophic denitrification have various valence states and forms.However,there is a lack of comparative study on autotrophic denitrification performance with different sulfur sources at present.Moreover,there is still no detailed information on bacterial community of autotrophic denitrification with different sulfur sources.In this study,sulfur autotrophic denitrification sludge were cultivated with S,Na2S2O3 and Na2 S as sulfur sources in three parallel SBRs,respectively.The nitrogen removal efficiency with different sulfur sources was compared,and then bacterial community structure was compared by 16 S rRNA based by high-throughput pyrosequencing technique.Furthermore,the mechanism of microbial metabolism utilizing the solid sulfur source was explored by metageome sequencing technology through the study of the metabolic pathway of sulfur granule surface and interstitial sludge.The performance of nitrogen removal efficiency with different sulfur sources indicated that the optimal dosage of sulfur source was 1.5,1.0 and 2.0 times of the theoretical value of S,Na2S2O3,Na2 S systems.The nitrogen removal rate of different sulfur source systems would rise with the increase of dosage when the dosage of alkalinity was in the range of 1.5~ 3.5 times of the theoretical dosage,while all the three sulfur source systems demonstrated inhibitory when the dosage of alkalinity was outside of this range.When the influent nitrate concentration was 50~125 mg/L,the system of S and Na2S2O3 achieved similar denitrification performance,while denitrification efficiency of Na2 S system was not every stable,and nitrite accumulation was serious under higher influent concentration.16S rRNA gene based high-throughput pyrosequencing indicated that sulfur sources posed obvious pressure on the bacterial community structure.Sludge of the S system had the richest microbial diversity,followed by Na2S2O3 and Na2 S respectively.S and Na2S2O3 systems demonstrated similar community structure.Under the similarity of 93%,the relative abundance of sulfur autotrophic denitrifying bacteria in S,Na2S2O3,Na2 S systems were 9.34~9.97%,24.3~25.0% and 28.8~29.6%,respectively.The most abundant autotrophic denitrifying bacteria in all the three systems was Thialkalivibrio thiocyanodenitrificans and the core functional microorganisms in the S and Na2S2O3 systems were Thiohalophilus thiocyanoxidans and Sulfurimonas denitrificans,respectively.The nitrogen and sulfur metabolic pathways of surface sludge and interstitial sludge were analyzed by metagenome sequencing.The abundance of functional genes related to assimilatory nitrate reduction was comparatively higher in surface sludge,while the abundance of functional genes related to N2 O reducted to N2,extracellular NO3-and NO2-transportation as well as denitrification in the interstitial sludge was higher than the surface sludge.The gene abundances in the surface sludge and interstitial sludge were similar.Sulfite was the inevitable intermediate of sulfur oxidation,and the gene abundance of sulfite oxidized into sulfate through pathway of APS oxidation was much higher than that of directly oxidation.It can be inferred that there is synergetic effect of the surface sludge and interstitial sludge during the autotrophic denitrification.