Bioenergy2020+ GmbH, Konrad-Lorenz Str. 20, A-3430 Tulln/Donau, Austria.
University of Natural Resources and Life Science, Department IFA-Tulln, Institute of Environmental Biotechnology, Vienna, Austria.
Sci Total Environ. 2017 Oct 1;595:912-919. doi: 10.1016/j.scitotenv.2017.03.074. Epub 2017 Apr 19.
The results presented in this study were carried out as concomitant experiments during the start-up and operation of a biomethanation unit to evaluate the effect of process parameters on carbon conversion, product formation (methane and acetate) and community composition. For that, two different samples were withdrawn from a trickle-bed reactor with immobilized enrichment culture of hydrogenotrophic methanogens adapted from sewage sludge. One sample was taken from the recirculation liquid during start-up phase while the other was withdrawn directly from the carrier material in the reactor. Elevated acid levels especially during start-up were shown to affect the overall carbon conversion. This effect was also seen during the acid tolerance testing reported here. Final acid concentrations of 1.6±0.3g/L resulted in a reduced conversion ratio of only 46%. Without acid addition complete conversion of CO in the headspace was achieved. However, maximum methane production of 0.55±0.02mmol after 4days of incubation was monitored at moderate initial acetate concentration of 0.4g/L. In both analyzed inoculation materials Methanobacterium species were by far the most dominant Archaea with 21.8% in the recirculation liquid during start-up and 84.8% in the enrichment culture immobilized on the carrier material. The microbial composition of the two analyzed samples is in accordance with the results obtained for the carbon conversion and product formation. With approximately 50% of Bacteroidetes and Firmicutes present during reactor start-up the acetic acid production significantly contributed to the overall carbon conversion. In contrast, methane was produced almost exclusively in trials representing continuous operation where acetogenic bacteria accounted only up to 17.5%. In summary, the acid accumulation monitored during reactor start-up of a biomethanation unit is most likely to result from the microbial composition present. Nevertheless, complete adaptation to hydrogenotrophic conditions was proven to alter the consortium and yield methane as main product alongside high carbon conversion of up to 70.5±1.8%.
本研究的结果是在启动和运行生物甲烷化装置的同时进行的伴随实验，以评估工艺参数对碳转化、产物形成（甲烷和乙酸）和群落组成的影响。为此，从用污水污泥中驯化的氢营养型产甲烷菌固定化富集培养物的滴流床反应器中取出两个不同的样品。一个样品取自启动阶段的回流液，另一个样品直接取自反应器中的载体材料。较高的酸水平，特别是在启动阶段，会影响整体碳转化。在本文报道的耐酸试验中也观察到了这种影响。最终酸浓度为 1.6±0.3g/L 时，转化率仅为 46%。没有添加酸时，完全转化了空气中的 CO。然而，在初始乙酸浓度为 0.4g/L 时，在 4 天的孵育后监测到最大甲烷产量为 0.55±0.02mmol。在两种分析的接种材料中，产甲烷菌属是迄今为止最主要的古菌，启动阶段回流液中占 21.8%，载体材料上固定化的富集培养物中占 84.8%。这两种分析样品的微生物组成与碳转化和产物形成的结果一致。在反应器启动期间，约有 50%的拟杆菌门和厚壁菌门存在，乙酸的产生对整体碳转化有显著贡献。相比之下，在连续运行的试验中，几乎只产生甲烷，其中产乙酸菌仅占 17.5%。总的来说，在生物甲烷化装置启动过程中监测到的酸积累很可能是由存在的微生物组成引起的。然而，完全适应氢营养条件被证明会改变生物群落，并产生甲烷作为主要产物，同时实现高达 70.5±1.8%的高碳转化率。
