| Biogas production is an important part of Chinese energy strategy. Development of efficient desulfurization technology is essential to biogas effective utilization. Compared with the conventional chemical desulfurization, biological desulfurization technology has the advantages of low processing cost and no secondary pollution. An increasing number of researchers have recently turned their attention to biological desulfurization technology. The biological desulfurization of biogas is mainly composed of two parts. First, H2 S must be absorbed in the solution by the wet scrubber. Secondly, sulfide is subsequently converted to sulfur or sulfate by the bio-oxidation. Investigation on biological desulfurization technology in China is in the early stage. At first, analysis method of elemental sulfur was established. The operating parameters, including pH, dissolved oxygen(DO), hydraulic retention time(HRT), temperature and salinity were optimized in the bioreactor with simulated wastewater of sodium sulfide. PCR-DGGE methodology was used to identify the superiority strains in the biological desulfurization system with high salinity. 16 S rDNA cloning and sequencing method was used to investigate the bacterial diversity in the biological desulfurization reactor for treating high salinity wastewater. A pilot-scale experiment and a demonstration project of biological desulfurization with treating capacity of 100m3/d and 1000 m3/d biogas respectively were established in liuminying biogas station. A pilot-scale experiment of biological desulfurization was conducted to remove the high concentration hydrogen sulfide from biogas from the anaerobic digestion of activated sludge in Gaobeidian Sewage Treatment Plant.There is not suitable method for sulfur determination. A sensitive method was developed for the determination of elemental sulfur in complex environmental matrixes via the liquid-liquid extraction method followed by gas chromatography-mass spectrometry. CS2 as a solvent for the elemental sulfur extraction was better than that of CCl4. The calibration linear range for elemental sulfur was 5-200 mg/L and its detection limit was 0.11mg/L. The relative standard deviation for five replicates of 5mg/L elemental sulfur in water was 3.18%. Development of determination method of elemental sulfur is an innovation of the paper.The feasibility of biological desulfurization depends on the efficiency of converting sulfide into sulfur based on the desulfurization costs. Sodium sulfide dissolved in the tap water was pumped into bioreactor as the sulfide for biological desulfurization. The operating parameters were optimized in the bioreactor with simulated wastewater. The results indicate that the bacteria activity was the highest at pH 7.8-8.2. Increasing the DO decreased the yield of sulfur. The reactor had a higher sulfide removal load and yield of sulfur at 2.55 mg/L DO. The HRT had little effect on the desulfurization efficiency when the sulfide removal load was kept almost constant. The most effective desulfurization temperature was 33oC.The sulfide removal load decreased from 2.85 kg/(m3?d) to 0.51 kg/(m3?d) with increasing salinity from 0.5% to 2.5%(m/m). It was necessary to keep an appropriate salinity in the reactor based on the desulfurization load. The desulfurization load had little difference between combined packing and semi-soft packing. However, the sludge from combined packing posseses is easier to settle than that of semi-soft packing. Compared to polyaluminum chlorid, polymerization ferric chloride showes the higher removal efficiency for elementar sulfur.In order to develop the biological desulfurization technology, PCR-DGGE was used to identify the superiority strains in the biodesulfurization system. Experimental results showed that the superiority strains in high salinity desulfurization system were Thiobacillus sp. ISA11, Halothiobacillus sp. ST15, Marine bacterium HB-5, and Uncultured bacterium clone J69-151C-2A. The Thiobacillus sp. ISA11 and Halothiobacillus sp. ST15 were the desulfurization strains. It is important innovation of the paper to acclimate Halothiobacillus sp. ST15 to become the superiority strains in the desulfurization system.The results from PCR-DGGE is not sufficient to indicate the bacterial diversity. The bacterial diversity in the biological desulfurization reactor was studied by the 16 S rDNA cloning and sequencing method. Results from 16 S rDNA cloning and sequencing method indicated that the biological desulfurization reactor of high salinity existed dominant bacteria, where 33 clones belonged to 3 different published phyla, while 1 clone belonged to unknown phylum. The dominant bacterial community in the system was Proteobacteria, which accounted for 85.3%. The bacterial community succession was as follows: ?-Proteobacteria( 55.9%), ?-Proteobacteria(17.6%), Actinobacteridae(8.8%), ?-Proteobacteria(5.9%), ?-Proteobacteria(5.9%), and Sphingobacteria(2.9%). Halothiobacillus sp. ST15 and Thiobacillus sp. UAM-I were the major desulfurization strains.Based on the optimized operating parameters and analysis of bacterial diversity, the pilot-scale experiment with a biogas treatment capacity of 100 m3/d was carried in Liuminying Biogas Station. When the H2 S concentration in the inlet biogas was 2800-4200mg/m3, more than 90% H2 S removal efficiency was achieved under the conditions of pH 7.8-8.2, a gas and water ratio of 10:1 and 25?. Less than 5% of the removed sulfide was converted to sulfate.The bio-desulfurization demonstration project with a biogas treatment capacity of 1000 m3/d was built in the Liuminying Biogas Station. when the H2 S concentration in the inlet biogas was 2800-4200mg/m3,more than 90% H2 S removal efficiency was achieved under the conditions of pH 8, a gas and water ratio of 10 to 1 and contact time of 47 s. 85% sulfide was converted to elemental sulfur. Biodesulfurization technology was successfully selected to low carbon and saving energy technologies in Beijing city in 2012.The pilot-scale experiment of biological desulfurization in Gaobeidian Sewage Treatment Plant was run under the conditions of inlet biogas concentration of 7000-8400 mg/m3, a gas and water ratio of 10 to 1, pH 8.3 and contact time of 103 s. The H2 S outlet concentration was 115 mg/m3. The superiority strains of desulfurization in the reactor were Sulfurimonas sp. RS_Sur15-1, Halothiobacillus neapolitanus strain CIP 104769, Sulfurimonas autotrophica DSM 16294 and Thiobacillus sp. ISA11. The biological desulfurization technology of biogas was successfully applied to high concentration H2 S removal from sludge anaerobic digestion. |
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