【作者】 罗艳；

【导师】 罗兴章； 郑正；

【作者基本信息】 南京大学 ， 环境工程， 2011， 硕士

【摘要】 互花米草(Spartina alteriflora)是分布在沿海潮间带的耐盐耐淹的多年生多碳草本植物,每年干物质产率高达3154.8g/m2,是一个丰富的资源库。通过厌氧发酵产沼气,将其转化为清洁能源对我国生物质能源的发展具有重大的现实意义。前期的研究表明,互花米草通过一次发酵后仍然有大量的有机物残留在沼渣中,未被微生物所降解。针对以上问题,本文对互花米草一次发酵后沼渣二次发酵特性进行了探讨。本文将取回的互花米草鲜样直接进行厌氧发酵,发现单位VS产气量285.27 mL/g,仅为理论产气量的40%,CH4含量在65%左右波动,沼渣中仍含有较高的纤维素和半纤维素,两者之和为59.56%,表明厌氧发酵后的互花米草沼渣仍具有较大的产气潜力。对沼渣用不同浓度的NaOH溶液碱处理后进行二次发酵,结果表明,4%、6%、8%的NaOH溶液处理后,均能很好的产气,单位TS产气量分别为：262、276、282mL/gTS,甲烷总含量相差不大,分别为72%、72%、69%,随着NaOH浓度的增加,产气速率有不同程度的提高。pH值均在微生物适应生长范围内波动,VFAs也保持在较低水平,未出现酸抑制现象。综合经济方面因素考虑,选取6%的NaOH溶液为沼渣处理的合适浓度。在6%的NaOH溶液处理后,考察不同TS浓度的互花米草沼渣二次发酵特性。在TS浓度为8%、10%、12%的条件下,单位TS产气量分别为217、227、228 mL/g,甲烷含量均在65%以上,最高达79%。随着TS浓度的增大,产气率呈增大趋势。系统的pH值相对稳定,丙酸、丁酸浓度较低,未出现酸积累现象。由此可知,沼渣二次发酵不易出现酸化,可适当的提高TS负荷。比较了NaOH碱处理、添加土豆以及二者联合作用对沼渣二次发酵特性的影响。结果表明,不同处理下均能产生沼气,其中累积产气量为：联合处理>NaOH碱处理>添加土豆处理,最大值为287mL/g,最小值仅为91mL/g。其中联合处理造成一定程度的酸抑制。接着比较了沼渣经6%的NaOH处理后,土豆添加比例对其二次发酵特性的影响。当混合比例为3：1,4：1,6：1时,产气量分别为：278,287,175mL/g。随土豆添加比例的提高,酸化现象越明显,混合比例为4：1时单位TS产气量最大。一次发酵利用的是互花米草中易生物降解的有机物,而二次发酵原料为互花米草一次发酵沼渣,利用的是互花米草中难生物降解的有机物。两次发酵过程中,单位TS产气量相当,CH4含量二次发酵略高于一次发酵。经过一次发酵和二次发酵,互花米草生物转化率大大提高,沼渣产生量减少,降低了后续处理的难度,对工程化应用具有重大意义。更多还原

【Abstract】 As a perennial salt marsh grass, S. alterniflora is native to the Atlantic and Gulf Coasts of North America.The average net primary production (NPP) of S. alterniflora exceeds 3154.8g dry mass m-2year-1 which become an abundant biomass resource.Considering the growing shortage of firewood and rising cost of fossil fuels, anaerobic digestion is an attractive technique for biosolids treatment in order to get the byproducts biogas and biofertilizer. Early study showed that anaerobic digestion of S. alterniflora was feasible,but for the high content lignocellulose inhibitory factor, the biotransformation rate was only 40% under mesophilic conditions.Most of organic substances were still remained to biogas residue.To improve digestion efficiency and biogas yield, digestion of biogas residue was researched in this paper. The pH value, theVFA (volatile fatty acid), and the biogas yield have been analyzed under the complete mixture anaerobic digestion condition.In order to improve the gas yield of Spartina alterniflora anaerobic digestion and confirm the ideal dosage of NaOH, the NaOH solutions in different concentration of 4%,6%,8% were used to treat the fermented Spartina alterniflora. The results showed that the anaerobic digestion capability of the Spartina alterniflora was enhanced remarkably by NaOH treatment,the rate of the second anaerobic digestion were 262mL/gTS,276 mL/gTS,282 mL/gTS and the methane content were 72%,72%,69% respectively. Considered the economic factor, NaOH concentration of 6% was selected.After Spartina alterniflora’s biogas residue being treated by NaOH solution of 6% for 48h at room temperature, the effect of different loading rates for secondary anaerobic digestion was studied. Efficient biogas production was observed at TS loading rates of 8%,10%,12% at (35±1)℃.The peaks of daily gas production were 10,14,13 mL/g and the rates of cumulate gas production were 217,227,228 mL/g respectively. With the increasing of loading rate, the cumulate gas production improved. The methane content exceeded 65%. The lowest pH value was 7.04, acid accumulation was not observed for fermented material as non-degradation organic compound decomposing slowly. For anaerobic digestion of Spartina alterniflora’s biogas residue, TS loading rate can increase to over 12%.Secondary anaerobic digestion were performed for mono-digestion of fermented S. alterniflora and co-digestion at fermented S. alterniflora to potato ratio (SA:P) of 6:1,4:1 and 3:1 (based on TS) after NaOH solution treatment. Co-digestion at SA:P of 4:1 without NaOH solution treatment was also evaluated. Optimal conditions for gas production of secondary anaerobic digestion were combined NaOH solution treatment and potato addition at SA:P of 4:1 while the highest gas yield was 288mL/gTS.The results showed that combined NaOH treatment and addition of potato to fermented S. alterniflora followed by secondary anaerobic digestion break complex organic material into simpler and more biodegradable constituents to enhance biogas production.Readily biodegradable organic matter was decomposed by microorganisms in first anaerobic digestion while the secondary fermentation of raw materials was Spartina’s biogas residue which was inbiodegradable organic matter. After secondary fermentation, the amount of residue was decreased and reduced the difficulty of subsequent processing, biotransformation was greatly increased. Gas production of first and secondary anaerobic anaerobic digestion was about the same while CH4 concentration of the secondary anaerobic digestion was slightly higher. Secondary anaerobic digestion is of great significance to engineering applications.更多还原