Research On The Performance Of Nitrogen And Sulfur Removal In Moving Bed Biofilm Reactor

In recent years,the pollution of SO₂ and NOx in the atmosphere caused by the combustion of fossil fuels has become a prominent problem,while the traditional flue gas desulfurization and denitrification process has the disadvantages of complex process flow and high operating cost.The technology of simultaneous biodegradation of sulfur dioxide and nitric oxide has attracted wide attention due to its advantages of high removal efficiency,low cost,simple process and less secondary pollution.Two kinds of simultaneous flue gas desulfurization and denitrification processes by chemical absorption combined with biological reduction were proposed by our guoup.The first process transfers SO₂ and NO from flue gas to liquid phase using alkaline absorption solution containing Fe???EDTA.Then the absorbed products were degraded simultaneously in a bioreactor.In the second process,SO₃^2-/SO₄^2-and Fe???EDTA-NO are produced by using alkaline and Fe???EDTA absorbents respectively to absorb SO₂ and NO from flue gas.The SO₃^2-/SO₄^2-produced was firstly reduced to S^2-,which was simultaneously removed by sulfur autotrophic denitrification in another autotrophic anaerobic reactor with Fe???EDTA-NO produced by denitrification.At present,the treatment load of sulfate and Fe???EDTA-NO from desulfurization and denitrification products is low,and there are a large number of untransformed sulfides in the reaction system.And there are few reports on the autotrophic denitrification of S^2-and Fe???EDTA-NO.In order to solve this problem,the removal process of sulfate and Fe???EDTA-NO and the control measures of sulfide degradation were studied in a moving bed biofilm reactor?MBBR?in this study.Regulation of sulfate reduction product to elemental sulfur while increasing treatment load The main results were as follows:?1?Bioreduction of sulfate and Fe?II?EDTA-NO was carried out in a moving bed biofilm reactor.The removal efficiencies of the sulfate and Fe???EDTA-NO were 96%and 92%with the influent loads of 2.88 kg SO₄^2-·m^-3·d^-1 and 0.48 kg NO·m^-3·d^-1.?2?Increasing the concentration of Fe???EDTA-NO and adding Fe?III?EDTA in influent can reduce the concentration of sulfide in effluent by autotrophic denitrification and chemical reaction.It was found that the dominant strain of sulfate reducing bacteria in the system was Desulfomicrobium.Pseudomonas,Sulfurovum and Arcobacter were involved in the reduction of Fe???EDTA-NO.?3?In MBBR reactor,the simultaneous removal of S^2-and Fe???EDTA-NO was completed.When the influent concentration was 7.5 mM and the loads were 0.72 kgS·m^-3·d^-1and 0.69 kgNO·m^-3·d^-1,the removal efficiencies were 93%and 89%respectively.The production of elemental sulfur was 0.51 kg·m^-3·d^-1,accounting for 71%of total sulfur.?4?When the S/N was 5:3,there were only the function of sulfur autotrophic denitrification in the reactor,and the main products of both were S⁰ and N₂.However,when the S/N was 1:1,there would be a small part of the chemical reaction process.,but the dominant was still sulfur autotrophic denitrification.The oxidation products of S^2-were still S⁰,while the reduction products of Fe???EDTA-NO were NH₄⁺and N₂,accounting for 6.7%and 80%respectively.The dominant bacteria in the reactor were Thiobacillus,Sulfurovum and Sulfurimonas,which could simultaneously remove S^2-and Fe???EDTA-NO by sulfur autotrophic denitrification.