Evaluation of Microbial Population Dynamics in Anaerobic Digesters during Stable Operation, Reactor Failure and Performance Recovery

利用农业和工业废液作为厌氧生物反应器系统的原料，已成为一种很有前途的增值产品合成技术。将来自食品加工和生物燃料生产行业的动物粪便和废物转化为具有商业价值的生物产品(如沼气)可服务于环境回收、可再生燃料生产、温室气体减排和经济发展的多个目标。农业和工业废物的厌氧共消化在加拿大是一个正在发展的行业，具有显著扩张的潜力。厌氧消化器的长期挑战之一是面对不同的原料质量时的系统稳定性，以确保可靠的能源供应和不间断的运行。有毒、有机或水力过载可能导致工艺不稳定。导致毒性超载的因素包括有毒化合物(抗菌消毒剂、抗生素)意外溢出到进水中，而可变的进料浓度、过多的固体含量或停留时间不足可能导致有机超负荷。因此，为了避免天然气生产崩溃，消化器通常不会以其最大设计能力运行。需要更好地了解厌氧消化中涉及的复杂过程，以提高过程的稳定性、监控和整体效率。 拟议研究计划的主要目标是确定厌氧消化器微生物群落中的群体，这些群体可以作为各种过载条件下即将发生故障的早期预警指标。最终，可以在消化器的常规分析过程中针对这些群体，并制定管理策略以避免故障并保持稳定运行。为了确定是否存在这样的可识别指标组，将在连续进料厌氧消化器中进行一系列故障预测试验，在监测微生物群落演变的同时诱发工艺故障。向牛粪消化器中添加三种不同类型的共消化底物将导致有机超载：废甘油、废脂肪酸(均为工业生物柴油设施的副产品)和废青贮料。通过引入奶牛场操作中常用的化合物：硫酸铜(用于足浴的抗菌溶液)和土霉素(一种常见的兽用抗生素)，将引发毒性休克。将确定不断变化的微生物群体，并用尖端的元基因组学方法评估不断变化的种群的重要性。使用高通量光照测序将能够全面复盖微生物群落并确定其特征，同时提供接触相对丰度较低的生物体的途径。

The co-utilization of agricultural and industrial waste streams as feedstock for anaerobic bioreactor systems has emerged as a promising technology for value-added product synthesis. Conversion of animal manures and waste streams originating from food processing and biofuel production industries to commercially important bio-products (such as biogas) serves multiple goals of environmental reclamation, renewable fuel production, greenhouse gas mitigation, and economic development. Anaerobic co-digestion of agricultural and industrial wastes is a growing industry in Canada with potential for significant expansion. One of the enduring challenges of anaerobic digesters is system stability in the face of varying feedstock quality to ensure reliable energy supplies and uninterrupted operations. Process instability can be caused by toxic, organic, or hydraulic overload. Factors leading to toxic overload include accidental spillage of toxic compounds (antimicrobial disinfectants, antibiotics) into the influent, while variable feed consistency, excessive solids content or insufficient retention time can lead to organic overload. Consequently, digesters are usually not operated at their maximum design capacity in order to avoid collapse of gas production. A better understanding of the complex processes involved in anaerobic digestion is needed to improve process stability, monitoring and overall efficiency. The main goal of the proposed research program is to identify groups within the microbial community of an anaerobic digester that can serve as an early warning indicator of impending failure under a variety of overload conditions. Ultimately, these groups can then be targeted during routine analysis of digesters, and a management strategy can be developed to circumvent failure and maintain steady operation. In order to determine if there are such identifiable indicator groups, a series of failure prediction tests will be conducted in continuous-feed anaerobic digesters, where process failure will be induced while the evolution of the microbial community is monitored. Organic overload will be brought on by adding three different types of co-digestion substrates to dairy manure digesters: waste glycerol, waste fatty acids (both by-products of an industrial biodiesel facility), and waste silage. Toxic shocks will be induced by introducing chemical compounds commonly used on dairy-farm operations: copper sulfate (antibacterial solution used for foot-baths) and oxytetracycline (a common veterinary antibiotic). Changing microbial groups will be identified and the significance of the changing population evaluated with a cutting-edge metagenomic approach. The use of high-throughput Illumina sequencing will allow for comprehensive coverage and characterization of the microbial community while providing access to organisms with a low relative abundance.