Study On Membrane Separation-Biological Desulfurization Of Low Concentration Hydrogen Sulfur Biogas And Mechanism Analysis Of In-Situ Sulfur Prevention

With the rapid development of social economic and increasing water consumption,production of wastewater and waste activated sludge also increase rapidly.Anaerobic digestion(AD)is one of the commonly used technology for sludge stabilization in wastewater treatment plants(WWTPs).Organic compounds in sludge can be stabilized properly and clean energy can be produced during AD and thus,reduce the energy consumption of WWTPs to a certain extent.However,a certain concentration of HZS would produce in biogas during AD which is caused by the decomposition of sulfur-containing organic matters such as protein,would take influence on the further utilization of biogas for its toxicity and corrosive.Therefore,biogas desulfurization is necessary to reduce the H2S concentration before its utilizationThis study focus on the control and generation mechanism of low concentration H2S during high solid anaerobic digestion(HSAD).The membrane separation adsorption and biological desulfurization were combined to carry out the continuous biogas desulfurization experiments to remove the low concentration of H2S produced in HSAD and explored the influence of different operating conditions on the desulfurization efficiency.Based on the continuous experiments,the community structures characteristics of sulfur-oxidizing microorganisms in different systems were analyzed to study the growth characteristics of the microorganisms.For the phenomenon that H2S generated in HSAD was much lower than that in conventional AD,the mechanism of hydrogen sulfide in-situ prevention was investigated with NH4CI dosage to analyze the substances transformation regulation during decomposition of sulfur amino acids.The conclusions are as followingThe membrane separation-biological trickling filter(MS-BTF)and membrane separation-biofilms(MS-BF)reverse flow biological desulfurization continuous operation experiments were carried out to analyze the variation of outlet H2S concentrations under different operating conditions.The results showed that when the pH of the circulating liquid was 7.0-9.0,the empty bed residence time was 40s-100s,and the gas-liquid ratio was 2-5,the desulfurization efficiency was increased while the pH and empty bed residence time increased,but it decreased when the gas-liquid ratio increased Correlation analysis results indicated that influence level on desulfurization efficiency of three influencing factors in both desulfurization systems was pH>empty bed residence time>gas-liquid ratio.The H2S removal eff-iciency revealed that MS-BF desulfurization system that attached sulfur-oxidizing microorganisms to form biofilms on the membrane wire was the best desulfurization system.The optimal operation condition for MS-BF desulfurization system was empty bed residence time was 60s,gas-liquid ratio was 3 and the pH was 8.0Biofilm detection and metagenomic microbial classification and sequencing technology were applied to analyze the community structure characteristics of sulfur oxidizing microorganisms in different desulfurization systems.Apparent characteristics observation of sulfur-oxidizing microorganisms indicated that a thickness range from 50-300 μm of biofilms were formed after inoculum,which revealed that biofilm grew well in MS-BTF and MS-BF.The results of population structure analysis of sulfur-oxidizing microorganisms showed that the genus of bacteria involved in sulfur metabolism of MS-BF mainly belonged to Ignavibacterium and Rhodobacter,while that in the MS-BTF system mainly consisted of Rhodobacter,Thiovirga,Thiobacillus and Alishewanella Compared with the inoculum,the species of the genus of sulfur metabolism in the MS-BF did not change significantly,but the relative abundance of some genus was improved After inoculating to the MS-BTF,relative abundance of some genus related to sulfur metabolism declined to a certain extent,but the species of the genus became more abundant.Batch tests of sulfur-containing amino acids(cysteine and methionine)anaerobic digestion were carried out to investigate the mechanism of H2S in situ prevention based on NH4CI dosage.The analysis of anaerobic decomposition characteristics of cysteine and methionine showed that NH4CI had no significant inhibition effect on the anaerobic decomposition of cysteine to produce sulfides,while the concentration of sulfide produced during the anaerobic decomposition of methionine by digested sludge decreased by 90.4%after NH4CI dosage.NH4CI showed an inhibition effect on the anaerobic decomposition of methionine to produce sulfide.By using hydrolyzed bacteria and methanogens to analyze the anaerobic decomposition characteristics of methionine,it could be speculated that the main reason for the decrease of H2S concentration during HSAD was that the increased concentration of NH4CI increased with total solid took an inhibition effect on the collaboration anaerobic decomposition of methionine by methanogens to produce sulfides.