Effects Of Sulfate On Nitrite/Nitrate-denitrifying Anaerobic Methane Oxidation

N-DAMO（nitrate-/nitrite-denitrifying methane anaerobic oxidation）technology can achieve nitrogen removal and methane reduction simultaneously.Sulfate is generally found in natural water and wastewater.N-DAMO microorganisms live in natural or artificial water bodies containing different sulfates.In order to find out the effect of different concentrations of sulfate on N-DAMO process,this paper is based on Nitrite-DAMO system with N-DAMO bacteria as the dominant species and Nitrate-DAMO system where N-DAMO archaea and N-DAMO bacteria coexist.Short-and long-term experiment were carried out to find out the effects of sulfate on N-DAMO process and the response mechanisms of two N-DAMO systems under the action of sulfate,and the dynamics and stoichiometry of the process were also analyzed.In this study,the short-term experimental results indicated that the performance of the Nitrite-DAMO system was promoted firstly then inhibited under the condition of 0-200 mg SO₄^2-/L and the performance of the Nitrate-DAMO system was promoted firstly then inhibited under the condition of 0-380 mg SO₄^2-/L.The denitrification kinetics conformed to Edward and Han-Levenspiel equation and the initial inhibitory concentration and completely concentration of sulfate on the Nitrite-DAMO system were 189.70 and 302.75 mg SO₄^2-/L,respectively.The denitrification kinetics conformed to non-substrate inhibition equation and Haldane equation and the initial inhibitory concentration and completely concentration of sulfate on the Nitrate-DAMO system were 78.00 and 389.66 mg SO₄^2-/L,respectively.In addition,sulfate can affect the growth cycles of N-DAMO microorganisms in two N-DAMO systems.The doubling time of Nitrite-DAMO bacteria with 0,80 and 200 mg SO₄^2-/L were16.41,13.48 and 22.80 days,and the doubling time of Nitrate-DAMO microorganisms with 0,40 and 80 mg SO₄^2-/L were 24.73,19.52 and 28.75 days.Therefore,the effect of sulfate on the N-DAMO system was promoted first and then inhibited within a certain range.Among them,the optimal sulfate concentration of the Nitrite-DAMO system was 80 mg SO₄^2-/L and that of Nitrate-DAMO system was 40 mg SO₄^2-/L.During short-and long-term tests,there were no sulfate consumed in the two N-DAMO systems,which showed that no sulphate reduction coupled anaerobic oxidation of methane occurred during the tests.On the one hand,the sulfate concentration of 80 mg SO₄^2-/L played a significant role in promoting the Nitrite-DAMO system.After 90 days of long-term experiment,the formic acid content increased,and the acetic acid content decreased significantly in Nitrite-DAMO system.SEM analysis revealed that more EPS was produced on the cell surface,and proteins dominated the EPS components,followed by humic acid and polysaccharides.Through the high-throughput sequencing technology,the unclassfied＿c＿ABY1 of the Patescibacteria Phylum and the norank＿f＿LD-RB-34 of the Bacteroidetes Phylum in the Nitrite-DAMO system were the main reasons for the increase of the nitrogen removal rate in Nitrite-DAMO system.Meanwhile,the Nitrite-DAMO system was slightly inhibited by the sulfate concentration of200 mg SO₄^2-/L.After 90 days of long-term experiment,the VFAs content in the Nitrite-DAMO system decreased.Through SEM analysis,it was found that a large amount of EPS and some thin strips appeared on the cell surface.The total amount of EPS increased,in which the protein content increased while the content of humic acid and polysaccharides decreased.Through the high-throughput sequencing technology,the decrease of the Patescibacteria Phylum was the main reason for the reduction of the nitrogen removal rate in Nitrate-DAMO system.Sulfate could affect the diversity of the microbial community structure and species richness of the Nitrite-DAMO system.And proteins could stabilize the Nitrite-DAMO system under the action of sulfate.On the other hand,the sulfate concentration of 40 mg SO₄^2-/L played a significant role in promoting the Nitrate-DAMO system.After 90 days of long-term experiment,the methanol content increased in the Nitrate-DAMO system.Through SEM analysis,it was found that more EPS was produced on the cell surface and the junctions between cells,and proteins dominated the EPS components,followed by polysaccharides and humic acid.Through the q PCR technology,the abundance of ANME-2d archaea increased significantly in the Nitrate-DAMO system.The Nitrite-DAMO system was slightly inhibited by the sulfate concentration of 80 mg SO₄^2-/L.After 90 days of long-term experiment,the methanol content decreased in the Nitrate-DAMO system.Through SEM analysis,it was found that a large amount of EPS was produced on the cell surface and the junctions between cells.The total amount of EPS decreased because of the reduction of humic acid and protein content.Through the q PCR technology,the abundance of ANME-2d archaea in the Nitrate-DAMO system decreased significantly.That is,the abundance of ANME-2d archaea was greatly affected by sulfate.This research focuses on the N-DAMO and the effects and mechanisms of sulfate on the two different N-DAMO systems were investigated and explored.From the results,the conclusion can be made that the performance of the Nitrite-DAMO system was promoted first and then inhibited with 0-200 mg SO₄^2-/L and the optimal sulfate concertratin was 80 mg SO₄^2-/L.The performance of the Nitrate-DAMO system was promoted first and then inhibited with0-380 mg SO₄^2-/L and the optimal sulfate concertratin was 40 mg SO₄^2-/L.And no sulfate was consumed in all the experiments.Unclassfied＿c＿ABY1 of Patescibacteria and norank＿f＿LD-RB-34 of Bacteroidates in nitrite-DAMO system were the most influenced genera.And the abundance of ANME-2d archaea was greatly affected by sulfate.