餐厨垃圾干发酵滚动式质热交换反应器设计与性能试验
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摘要
为解决干式厌氧发酵传质传热效果差,易造成微生物生长代谢不均匀等问题,该研究设计一款反应器,利用罐体滚动代替搅拌,使底物自由混合,大幅度解决了干式发酵的阻碍。通过中温批次发酵验证反应器性能,并与搅拌式反应器进行对比,结果表明:滚动式反应器发酵过程中甲烷体积分数最高达74.89%;发酵前期挥发性脂肪酸有一定程度的积累,但在中期被迅速消耗,且未对产气和pH值造成明显影响;底物挥发性固体去除率高达68.74%,发酵体系稳定。微生物群落结构随着发酵进行,不同时期呈现动态变化,厚壁菌门(Firmicutes)是发酵体系中绝对的优势细菌门,最主要的古菌门是广古菌门(Euryarchaeota)。混合营养型的甲烷八叠球菌属(Methanosarcina)伴随着发酵的推进成长为绝对优势甲烷菌属。
A large amount of kitchen wastes were produced every day, and they will pose a great threat to the environment and human health if it could not be disposed properly. Nowadays, most of the kitchen wastes are disposed in landfills or incinerated, which associates with different issues, such as rising costs, lack of space, leaching, public environmental concern and emission of toxic and greenhouse effect gases. Kitchen wastes contain a large amount of organic matters like lipid and protein. Anaerobic fermentation is considered as the most attractive method for the treatment and recycle of kitchen wastes since they reduce waste volume, generate an energy-rich gas in the form of methane, and yield nutrient-containing final products. Compared to wet anaerobic fermentation, dry anaerobic fermentation is favorable in terms of a low energy requirement for heating, and the residues can be composted directly because it contains less digester effluent. However, the efficiency of dry anaerobic fermentation system is usually very low due to the retarded mass and heat transfer rates caused by high solid content. In order to improve mass and heat transfer efficiency in dry anaerobic fermentation system, in this study we designed a rolling type mass and heat transfer reactor which made substrates be freely mixed. The whole equipment consists of two parts, a pre-fermenter and a fermenter. The effective volume of pre-fermenter and fermenter was 10 L. Substrates were added to the pre-fermenter firstly and the air was removed by adding nitrogen gas. Then the air-removed substrates were discharged into the fermenter through sealed pipe. By this way less oxygen was brought into the fermenter. The performance of the reactor was investigated under mesophilic conditions(37 °C) and the microbial community structure was investigated by analyzing 16 S rRNA genes. The methane content in the rolling type mass and heat transfer reactor was over 50% after 5 days, the maximum methane content was 74.89%. The main accumulated volatile fatty acids were propionate, followed by acetate. Propionate is hard to be utilized in common anaerobic fermentation systems and leads to acidification finally. However, the propionate showed less effect on gas production and pH value in the system of our designed reactor. The removal rate of volatile solid was 68.74% after 30 days' fermentation, and the anaerobic fermentation system was stable. The microbial community structure had dynamic changes at different periods of anaerobic fermentation. At phylum level, Firmicutes was the absolute dominant bacteria and Euryarchaeota was the dominant archaea in the system. For methanogens, Methanosarcina which can utilize all three known pathways for methane production was the absolute dominant one except in the ferment substance sampled on the first day, indicating that it is important for efficient methanogenesis in the fermentation system. Methanoculleus and Methanobacterium were the dominant genera only in the ferment material sampled on the first day, implying that they originated from inoculated sludge. The reactor we designed and the experimental data obtained in this study will be useful for the development of efficient dry anaerobic digestion system.
A large amount of kitchen wastes were produced every day, and they will pose a great threat to the environment and human health if it could not be disposed properly. Nowadays, most of the kitchen wastes are disposed in landfills or incinerated, which associates with different issues, such as rising costs, lack of space, leaching, public environmental concern and emission of toxic and greenhouse effect gases. Kitchen wastes contain a large amount of organic matters like lipid and protein. Anaerobic fermentation is considered as the most attractive method for the treatment and recycle of kitchen wastes since they reduce waste volume, generate an energy-rich gas in the form of methane, and yield nutrient-containing final products. Compared to wet anaerobic fermentation, dry anaerobic fermentation is favorable in terms of a low energy requirement for heating, and the residues can be composted directly because it contains less digester effluent. However, the efficiency of dry anaerobic fermentation system is usually very low due to the retarded mass and heat transfer rates caused by high solid content. In order to improve mass and heat transfer efficiency in dry anaerobic fermentation system, in this study we designed a rolling type mass and heat transfer reactor which made substrates be freely mixed. The whole equipment consists of two parts, a pre-fermenter and a fermenter. The effective volume of pre-fermenter and fermenter was 10 L. Substrates were added to the pre-fermenter firstly and the air was removed by adding nitrogen gas. Then the air-removed substrates were discharged into the fermenter through sealed pipe. By this way less oxygen was brought into the fermenter. The performance of the reactor was investigated under mesophilic conditions(37 °C) and the microbial community structure was investigated by analyzing 16 S rRNA genes. The methane content in the rolling type mass and heat transfer reactor was over 50% after 5 days, the maximum methane content was 74.89%. The main accumulated volatile fatty acids were propionate, followed by acetate. Propionate is hard to be utilized in common anaerobic fermentation systems and leads to acidification finally. However, the propionate showed less effect on gas production and pH value in the system of our designed reactor. The removal rate of volatile solid was 68.74% after 30 days' fermentation, and the anaerobic fermentation system was stable. The microbial community structure had dynamic changes at different periods of anaerobic fermentation. At phylum level, Firmicutes was the absolute dominant bacteria and Euryarchaeota was the dominant archaea in the system. For methanogens, Methanosarcina which can utilize all three known pathways for methane production was the absolute dominant one except in the ferment substance sampled on the first day, indicating that it is important for efficient methanogenesis in the fermentation system. Methanoculleus and Methanobacterium were the dominant genera only in the ferment material sampled on the first day, implying that they originated from inoculated sludge. The reactor we designed and the experimental data obtained in this study will be useful for the development of efficient dry anaerobic digestion system.
引文
[1]Zhang C,Su H,Baeyens J,et al.Reviewing the anaerobic digestion of food waste for biogas production[J].Renewable&Sustainable Energy Reviews,2014,38(5):383-392.
[2]Li P,Zeng Y,Xie Y,et al.Effect of pretreatment on the enzymatic hydrolysis of kitchen waste for xanthan production[J].Bioresource Technology,2017,223:84-90.
[3]Kim M S,Na J G,Lee M K,et al.More value from food waste:Lactic acid and biogas recovery[J].Water Research,2016,96:208-216.
[4]Li Y,Jin Y,Li J,et al.Effects of thermal pretreatment on the biomethane yield and hydrolysis rate of kitchen waste[J].Applied Energy,2016,172:47-58.
[5]董滨,王凯丽,段妮娜,等.餐厨垃圾中温干法厌氧消化快速启动实验研究[J].环境科学学报,2012(10):2584-2590.Dong Bin,Wang Kaili,Duan Nina,et al.Dry anaerobic digestion of food waste under mesophilic conditions:Rapid start-up with high-solid inoculums[J].Acta Scientiae Circumstantiae,2012(10):2584-2590.(in Chinese with English abstract)
[6]Chiumenti A,Da Borso F,Limina S.Dry anaerobic digestion of cow manure and agricultural products in a full-scale plant:Efficiency and comparison with wet fermentation[J].Waste Management,2017,71:704-710.
[7]王权,宫常修,蒋建国,等.NaCl对餐厨垃圾厌氧发酵产VFA浓度及组分的影响[J].中国环境科学,2014(12):3127-3132.Wang Quan,Gong Changxiu,Jiang Jianguo,et al.Effect of NaCl content on VFA concentration and composition during anaerobic fermentation of kitchen waste[J].China Environmental Science,2014(12):3127-3132.(in Chinese with English abstract)
[8]王金辉.餐厨垃圾固相物料干式厌氧消化处理研究[D].杭州:宁波大学,2017.Wang Jinhui.Study on Dry Anaerobic Digestion of Solid Phase Stuff of Food Waste[D].Hangzhou:Ningbo University,2017.
[9]Li Y,Park S Y,Zhu J.Solid-state anaerobic digestion for methane production from organic waste[J].Renewable&Sustainable Energy Reviews,2011,15(1):821-826.
[10]于美玲,张大雷,李玉婷,等.有机生活垃圾半干发酵菌群的分布变化特征[J].农业工程学报,2015,31(2):253-258.Yu Meiling,Zhang Dalei,Li Yuting,et al.Microbial community characteristics of semi-dry anaerobic digestion with organic waste[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2015,31(2):253-258.(in Chinese with English abstract)
[11]莫忠磊.秸秆-牛粪作为沼气原料的产气规律研究[D].重庆:重庆大学,2014.Mo Zhonglei.Research on the Discipline of Generating Gas of Straw-Cow Dung as Biogas Feedstock[D].Chongqing:Chongqing University,2014.(in Chinese with English abstract)
[12]Miner G.Standard methods for the examination of water and wastewater,21st Edition[J].Journal-American Water Works Association,2006(1):130.
[13]食品安全国家标准-食品中蛋白质的测定:GB5009.5-2016[S].2016.
[14]Christensen T H,Kjeldsen P.2.1-Basic biochemical processes in landfills[C]//Sanitary Landfilling Process Technology&Environmental Impact,1968:29-49.
[15]王巧玲.餐厨垃圾厌氧发酵过程的影响因素研究[D].南京:南京大学,2012.Wang Qiaoling.Study on Influencing Factors of Anaerobic Digestion Process of Kitchen Waste[D].Nanjing:Nanjing University,2012
[16]赵云飞,刘晓玲,李十中,等.餐厨垃圾与污泥高固体联合厌氧产沼气的特性[J].农业工程学报,2011,27(10):255-260.Zhao Yunfei,Liu Xiaoling,Li Shizhong,et al.Characteristics of high-solids anaerobic co-fermentation for converting food waste and excess sludge to biogas[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2011,27(10):255-260.(in Chinese with English abstract)
[17]Zonta Z,Alves M M,Flotats X,et al.Modelling inhibitory effects of long chain fatty acids in the anaerobic digestion process[J].Water Research,2013,47(3):1369-1380.
[18]Siegert I,Banks C.The effect of volatile fatty acid additions on the anaerobic digestion of cellulose and glucose in batch reactors[J].Process Biochemistry,2005,40(11):3412-3418.
[19]Chen Y,Cheng J J,Creamer K S.Inhibition of anaerobic digestion process:A review[J].Bioresource Technology,2008,99(10):4044-4064.
[20]Li Y,Yan X L,Fan J P,et al.Feasibility of biogas production from anaerobic co-digestion of herbal-extraction residues with swine manure[J].Bioresource Technology,2011,102(11):6458-6463.
[21]Xie S,Lawlor P G,Frost J P,et al.Effect of pig manure to grass silage ratio on methane production in batch anaerobic co-digestion of concentrated pig manure and grass silage[J].Bioresource Technology,2011,102(10):5728-5733
[22]杨雪梅.农村有机固体废弃物高效产沼气技术研究[D].南京:东南大学,2016.Yang Xuemei.Research on Efficient Technology of Biogas Production by Organic Solid Wastes in Rural Area[D].Nanjing:Southeast University,2016.(in Chinese with English abstract)
[23]Ye J,Li D,Sun Y,et al.Improved biogas production from rice straw by co-digestion with kitchen waste and pig manure[J].Waste Management,2013,33(12):2653-2658.
[24]Nozoe T.Mechanisms and suppression of the accumulation of volatile fatty acids and the production of methane in submerged paddy soil[J].Bulletin of the Tohoku National Agricultural Experiment Station,2000,97:75-129.
[25]Fernández A,Huang S,Seston S,et al.How stable is stable?Function versus community composition[J].Applied&Environmental Microbiology,1999,65(8):3697-3704.
[26]Goberna M,Gadermaier M,Frankewhittle I H,et al.Start-up strategies in manure-fed biogas reactors:process parameters and methanogenic communities[J].Biomass&Bioenergy,2015,75:46-56.
[27]Jetten M S M,Stams A J M,Zehnder A J B.Methanogenesis from acetate:A comparison of the acetate metabolism in Methanothrixsoehngenii,and Methanosarcina,spp[M]//FEMS Microbiology Letters:181-198.
[28]Ahring B K.Methanogenesisin thermophilic biogas reactors[J].Antonie Van Leeuwenhoek,1995,67(1):91-102.
[29]Cho S K,Im W T,Kim D H,et al.Dry anaerobic digestion of food waste under mesophilic conditions:Performance and methanogenic community analysis[J].Bioresource Technology,2013,131:210-217.
[30]De V J,Hennebel T,Boon N,et al.Methanosarcina:The rediscovered methanogen for heavy duty biomethanation[J].Bioresource Technology,2012,112(5):1-9.
[2]Li P,Zeng Y,Xie Y,et al.Effect of pretreatment on the enzymatic hydrolysis of kitchen waste for xanthan production[J].Bioresource Technology,2017,223:84-90.
[3]Kim M S,Na J G,Lee M K,et al.More value from food waste:Lactic acid and biogas recovery[J].Water Research,2016,96:208-216.
[4]Li Y,Jin Y,Li J,et al.Effects of thermal pretreatment on the biomethane yield and hydrolysis rate of kitchen waste[J].Applied Energy,2016,172:47-58.
[5]董滨,王凯丽,段妮娜,等.餐厨垃圾中温干法厌氧消化快速启动实验研究[J].环境科学学报,2012(10):2584-2590.Dong Bin,Wang Kaili,Duan Nina,et al.Dry anaerobic digestion of food waste under mesophilic conditions:Rapid start-up with high-solid inoculums[J].Acta Scientiae Circumstantiae,2012(10):2584-2590.(in Chinese with English abstract)
[6]Chiumenti A,Da Borso F,Limina S.Dry anaerobic digestion of cow manure and agricultural products in a full-scale plant:Efficiency and comparison with wet fermentation[J].Waste Management,2017,71:704-710.
[7]王权,宫常修,蒋建国,等.NaCl对餐厨垃圾厌氧发酵产VFA浓度及组分的影响[J].中国环境科学,2014(12):3127-3132.Wang Quan,Gong Changxiu,Jiang Jianguo,et al.Effect of NaCl content on VFA concentration and composition during anaerobic fermentation of kitchen waste[J].China Environmental Science,2014(12):3127-3132.(in Chinese with English abstract)
[8]王金辉.餐厨垃圾固相物料干式厌氧消化处理研究[D].杭州:宁波大学,2017.Wang Jinhui.Study on Dry Anaerobic Digestion of Solid Phase Stuff of Food Waste[D].Hangzhou:Ningbo University,2017.
[9]Li Y,Park S Y,Zhu J.Solid-state anaerobic digestion for methane production from organic waste[J].Renewable&Sustainable Energy Reviews,2011,15(1):821-826.
[10]于美玲,张大雷,李玉婷,等.有机生活垃圾半干发酵菌群的分布变化特征[J].农业工程学报,2015,31(2):253-258.Yu Meiling,Zhang Dalei,Li Yuting,et al.Microbial community characteristics of semi-dry anaerobic digestion with organic waste[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2015,31(2):253-258.(in Chinese with English abstract)
[11]莫忠磊.秸秆-牛粪作为沼气原料的产气规律研究[D].重庆:重庆大学,2014.Mo Zhonglei.Research on the Discipline of Generating Gas of Straw-Cow Dung as Biogas Feedstock[D].Chongqing:Chongqing University,2014.(in Chinese with English abstract)
[12]Miner G.Standard methods for the examination of water and wastewater,21st Edition[J].Journal-American Water Works Association,2006(1):130.
[13]食品安全国家标准-食品中蛋白质的测定:GB5009.5-2016[S].2016.
[14]Christensen T H,Kjeldsen P.2.1-Basic biochemical processes in landfills[C]//Sanitary Landfilling Process Technology&Environmental Impact,1968:29-49.
[15]王巧玲.餐厨垃圾厌氧发酵过程的影响因素研究[D].南京:南京大学,2012.Wang Qiaoling.Study on Influencing Factors of Anaerobic Digestion Process of Kitchen Waste[D].Nanjing:Nanjing University,2012
[16]赵云飞,刘晓玲,李十中,等.餐厨垃圾与污泥高固体联合厌氧产沼气的特性[J].农业工程学报,2011,27(10):255-260.Zhao Yunfei,Liu Xiaoling,Li Shizhong,et al.Characteristics of high-solids anaerobic co-fermentation for converting food waste and excess sludge to biogas[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2011,27(10):255-260.(in Chinese with English abstract)
[17]Zonta Z,Alves M M,Flotats X,et al.Modelling inhibitory effects of long chain fatty acids in the anaerobic digestion process[J].Water Research,2013,47(3):1369-1380.
[18]Siegert I,Banks C.The effect of volatile fatty acid additions on the anaerobic digestion of cellulose and glucose in batch reactors[J].Process Biochemistry,2005,40(11):3412-3418.
[19]Chen Y,Cheng J J,Creamer K S.Inhibition of anaerobic digestion process:A review[J].Bioresource Technology,2008,99(10):4044-4064.
[20]Li Y,Yan X L,Fan J P,et al.Feasibility of biogas production from anaerobic co-digestion of herbal-extraction residues with swine manure[J].Bioresource Technology,2011,102(11):6458-6463.
[21]Xie S,Lawlor P G,Frost J P,et al.Effect of pig manure to grass silage ratio on methane production in batch anaerobic co-digestion of concentrated pig manure and grass silage[J].Bioresource Technology,2011,102(10):5728-5733
[22]杨雪梅.农村有机固体废弃物高效产沼气技术研究[D].南京:东南大学,2016.Yang Xuemei.Research on Efficient Technology of Biogas Production by Organic Solid Wastes in Rural Area[D].Nanjing:Southeast University,2016.(in Chinese with English abstract)
[23]Ye J,Li D,Sun Y,et al.Improved biogas production from rice straw by co-digestion with kitchen waste and pig manure[J].Waste Management,2013,33(12):2653-2658.
[24]Nozoe T.Mechanisms and suppression of the accumulation of volatile fatty acids and the production of methane in submerged paddy soil[J].Bulletin of the Tohoku National Agricultural Experiment Station,2000,97:75-129.
[25]Fernández A,Huang S,Seston S,et al.How stable is stable?Function versus community composition[J].Applied&Environmental Microbiology,1999,65(8):3697-3704.
[26]Goberna M,Gadermaier M,Frankewhittle I H,et al.Start-up strategies in manure-fed biogas reactors:process parameters and methanogenic communities[J].Biomass&Bioenergy,2015,75:46-56.
[27]Jetten M S M,Stams A J M,Zehnder A J B.Methanogenesis from acetate:A comparison of the acetate metabolism in Methanothrixsoehngenii,and Methanosarcina,spp[M]//FEMS Microbiology Letters:181-198.
[28]Ahring B K.Methanogenesisin thermophilic biogas reactors[J].Antonie Van Leeuwenhoek,1995,67(1):91-102.
[29]Cho S K,Im W T,Kim D H,et al.Dry anaerobic digestion of food waste under mesophilic conditions:Performance and methanogenic community analysis[J].Bioresource Technology,2013,131:210-217.
[30]De V J,Hennebel T,Boon N,et al.Methanosarcina:The rediscovered methanogen for heavy duty biomethanation[J].Bioresource Technology,2012,112(5):1-9.