| With the advancement of agricultural and rural modernization,farmers’economic level and living standard have been greatly improved,and the amount of Rural organic waste（ROW）has increased.If it is not treated in time,it will cause serious environmental problems and endanger human health.At present,the mainstream garbage disposal methods at home and abroad are still sanitary landfill and incineration,but these methods will produce secondary pollution,and at the same time,the organic parts in ROW are not fully utilized,resulting in a lot of waste of resources.It is a good choice to use Anaerobic digestion（AD）technology to effectively biotransform rural organic wastes into methane-rich biofuels.This method will have a beneficial impact on the whole human environment and energy supply,and can be widely used in rural areas of developing countries.AD technology with high feed concentration has the advantages of low energy consumption,low operating cost,large capacity,high biogas residue concentration and simple subsequent treatment of biogas slurry biogas residue,which is an effective way to realize the resource utilization of solid waste.However,the nitrogen content in the AD system is high and the mass transfer efficiency is low when the feed concentration is high.However,previous studies show that the probability of ammonia nitrogen inhibition in high concentration feed AD system is relatively high.Metal-organic frameworks（MOFs）are porous materials with three-dimensional topological structure.Previous researchers have found that some unsaturated metal sites in the structure of MOFs materials can adsorb a large number of ammonia molecules,which can reduce the concentration of ammonia nitrogen in a fixed volume.Therefore,aiming at the problem of ammonia nitrogen accumulation in the process of high concentration AD,this study solves the problems of ammonia nitrogen inhibition,acidification and low gas production rate in AD system by preparing MOFs materials with high ammonia nitrogen adsorption performance.The main research contents and achievements are as follows:（1）Fe Mn-MOF/G was prepared and characterized.Then the influence of different ammonia nitrogen concentrations on the ammonia nitrogen adsorption capacity of Fe Mn-MOF/G material was studied in simulated ammonia nitrogen wastewater.The test results show that the average ammonia nitrogen adsorption capacity of Fe Mn-MOF/G in simulated ammonia nitrogen wastewater is 95.02 mg/g.The Fe Mn-MOF/G in the solution was recovered and desorbed and regenerated with Na Cl solution.The ammonia nitrogen adsorption capacity of Fe Mn-MOF/G was tested again,and the regenerated ammonia nitrogen adsorption capacity was 84.21 mg/g,which was 88.62%of the initial adsorption capacity.（2）The effects of Fe Mn-MOF/G on methane production in sequencing batch AD were studied at five TS concentrations of 8%,10%,12%,15%and 20%.The results show that the average ammonia nitrogen adsorption capacity of Fe Mn-MOF/G in AD is 102.68 mg/g under different TS concentrations,and the ammonia nitrogen adsorption effect decreases with the increase of TS.When Fe Mn-MOF/G was added to AD,the concentration of ammonia nitrogen and volatile fatty acids（VFAs）in the experimental group decreased to 2086.00 mg/L and 1510.34 mg/L,respectively.The methane production of each experimental group increased significantly,and the highest cumulative methane production of experimental group MOF-8 was 321.35 m L/g VS,which indicated that Fe Mn-MOF/G effectively reduced the inhibition of ammonia nitrogen and promoted the successful operation of AD.The results of vibrating sample magnetometer test show that Fe Mn-MOF/G has excellent superparamagnetism.Magnetic recovery is a promising method for recovering Fe Mn-MOF/G materials,which provides a broad prospect for the application of Fe Mn-MOF/G in AD.（3）The synthetic formula of Fe Mn-MOF/G was improved,and the adsorption capacity of three MOFs materials at different ammonia nitrogen concentrations was preliminarily studied.The results show that the three MOFs have the best ammonia nitrogen adsorption effect when the ammonia nitrogen concentration is 1000.00 mg/L,and the worst when the ammonia nitrogen concentration is 2000.00 mg/L.The maximum ammonia nitrogen adsorption effects of Fe Mn-MOF,Fe Mn/MOF-CFs and Fe Mn/MOF-CFC are 281.44 mg/g,269.46 mg/g and 239.52 mg/g,respectively.The MOFs materials in the solution were recycled,and the adsorption capacities of the three MOFs materials after regeneration were 218.37,224.54 and 192.29 mg/g,which were77.59%,83.33%and 80.28%of the initial adsorption capacity,respectively.（4）The application effects of Fe Mn MOF,Fe Mn/MOF-CFs,and Fe Mn/MOF-CFC materials in practical production were simulated by semi-continuous feeding at medium temperature.The experimental results indicate that all three MOFs materials can effectively improve the methane production process.After adding Fe Mn MOF,Fe Mn/MOF-CFs,and Fe Mn/MOF-CFC,the pool capacity gas production of each experimental group was 42.08 L/L-reactor,56.59 L/L-reactor,and66.96 L/L-reactor,respectively,which were 4.27 times,6.09 times,and 7.39 times higher than the control group（7.98 L/L-reactor）.At the end of CSTR experiment,the ammonia nitrogen concentrations in the experimental group were 2366.00 mg/L,2328.00 mg/L and 2052.00 mg/L,respectively,which were 31.06%,32.17%and 40.21%lower than those in the control group.The changes of enzyme activity and microbial community structure during methane production by CSTR（Continuous stirred tank reactor）were analyzed.The relative enzyme activities of the experimental group added with Fe Mn/MOF-CFC were also the highest,and the relative enzyme activities of ACP,ALP,α-glucosidase and coenzyme F420 reached 142.62%,151.97%,136.04%and 193.68%respectively.The results of microbial community analysis showed that Bacteroidota and Firmicutes were the dominant bacteria in all reactors during the whole CSTR experiment.At the genus level of archaea,Methanosarcina is dominant in AD system,followed by Methanoculleus and Methanomassiliicoccus. |
PDF Full Text Request