禽畜粪便厌氧消化制取沼气致毒及脱毒机理研究

Anaerobic digestion technology is becoming mature and has great commercial potential to deal with organic wastes. But sometimes organic acid accumulation caused by ammonia inhibition has led to operation failure when high nitrogen materials such as animal waste is used in the industrial biogas plant. Therefore, improving methane production and operation stability is a key problem needed to be solved urgently in the process of biogas industrial development. In order to solve ammonia inhibition problem when high nitrogen materials are used, some useful technologies including inoculum acclimation, trace elements addition, ammonia nitrogen removal both from fermenting broth and raw materials, ammonia nitrogen precipitation and C/N ratio modification of raw materials are proposed based on the toxicity analysis of high nitrogen materials anaerobic digestion in the study. The optimal combination of treatment process will be determined by adopting batch fermentation and Response Surface Methodology on Biochemiscal Methane Potential(BMP) device under mesophilic condition.In addition, the long term operation of anaerobic digestion for bigas production will be carried out on continuous stirred tank reactor(CSTR) and the fermentation parameters will be monitored in order to verify the validity of the optimal combination of different treatment approaches. Meanwhile, Fluorescence in situ hybridization (FISH) technology will be applied to track microbial population replacement,not only to reasonably deduce toxicity mechanism of ammonia inhibition caused by high nitrogen materials,but also to illustrate the detoxification mechanism by all the treatment methods involved. This study will provide a scientific reference for dealing with ammonia inhibition in process of industrial anaerobic digestion.

厌氧消化技术日趋成熟、推广潜力巨大，但在工业化运行的沼气工程中使用禽畜粪便等高氮原料时，依然时常存在氨氮抑制致使有机酸积累最终导致运行失败的情况。因此，提高沼气工程的甲烷产率和运行稳定性是实现沼气技术产业化亟待解决的关键问题。本研究在对高氮原料厌氧消化致毒水平分析基础上，提出接种物驯化、添加微量元素、发酵过程中氨氮脱除、原料氨氮脱除和氨氮沉淀、改变原料C/N比技术，以期解决高氮原料导致的厌氧消化氨氮抑制问题。采取中温条件下生物化学产甲烷潜力批次试验和响应面优化设计确定沼气发酵的最优处理工艺组合。通过中温条件下半连续喂料连续搅拌反应器连续厌氧发酵试验监测发酵工艺参数，验证发酵工艺的稳定性，同时，在连续发酵试验中使用荧光原位杂交技术跟踪微生物种群更替，以合理推断高氮原料厌氧消化过程中氨氮致毒机理、及使用相应工艺手段解毒的作用机理，为解决沼气发酵工艺中的氨氮抑制问题提供科学参考。

针对禽畜粪便厌氧消化制取沼气过程中常出现的氨氮抑制问题，本研究在厌氧消化致毒水平分析基础上，提出接种物驯化、添加微量元素、发酵液及原料氨氮脱除、氨氮沉淀、调节C/N比技术，以期解决高氮原料厌氧消化氨氮抑制问题。取得的主要成果如下：1）底物浓度为8 g VS L-1时，猪粪、牛粪、鸡粪、兔粪的比甲烷产量最高，分别为409.6、269.8、377.1和323.2 mL CH4 g-1VSadded。四种粪便均分别在16和32 g VS L-1时出现轻微的及明显的氨抑制；2）鸡粪、猪粪在有机负荷率为1.8 g VS L-1d-1条件下的比甲烷产量分别为0.199 L g-1 VSadded和0.211 L g-1 VSadded；有机负荷率为2.4 g VS L-1d-1时比甲烷产量分别为0.321 L g-1 VSadded和0.334L g-1 VSadded。荧光原位杂交菌群分析结果表明耐受性较强的八叠球菌数量增加，整体对高氮原料的适应性增强，达到了驯化目的；3）添加微量元素Se、Co后，餐厨垃圾厌氧发酵反应器运行稳定，荧光原位杂交分析结果表明乙酸裂解菌是适宜条件下厌氧发酵体系中的优势菌；4）在鸡粪连续厌氧发酵中，在70℃、pH值10条件下进行氨吹脱处理使鸡粪连续厌氧发酵在高有机负荷率（9 g VS L-1 d-1）条件下仍保持高产甲烷量（0.199 L g-1 VSadded）。该反应器中的优势菌由Methanosarcinales 向耐受抑制作用更强的Methanomicrobiales迁移，而其余反应器菌群中的优势菌因活性受到抑制而大量减少； 5）以鸡粪为底物，沸石为添加物的厌氧消化试验结果表明，沸石添加体积分数为5%的试验组在发酵第21天时甲烷含量达到最大值73.06%，比对照组提高了4.86%； 6）以鸡粪为单一原料的半连续厌氧发酵反应器在有机负荷率为2.4 g VS L-1d-1时产气量稳定，比甲烷产量为0.267 L g-1 VSadded。添加烂苹果使鸡粪中温厌氧消化体系的有机负荷率提高到4.8 g VS L-1d-1，反应器中Methanosarcinaceae 为古细菌菌群的优势菌，同时嗜氢产甲烷菌Methanobacteriaceae 呈现数量增加趋势。本研究为高氮原料厌氧消化的稳定高效运行奠定了理论及实践基础。