Department of Molecular Biosciences and Bioengineering, University of Hawai'i at Mānoa, Honolulu, HI, 96822, USA.
Department of Civil and Environmental Engineering, Imperial College, London, United Kingdom.
Water Res. 2019 Dec 1;166:115080. doi: 10.1016/j.watres.2019.115080. Epub 2019 Sep 11.
This study developed an intermittent oxidation-reduction potential (ORP)-controlled micro-aeration system for high solids anaerobic digestion (AD) of lignocellulosic biomass without volatile fatty acids (VFA) accumulation at high organic loading rate (OLR). Traditional AD of Napier grass, a model lignocellulosic biomass, at an OLR of 5 g volatile solids (VS)/L/day resulted in an accumulation of total VFA concentration up to 9.2 g/L as acetic acid (HAc) equivalent, causing rapid drops in pH and methane yield, and driving the digester to the verge of failure. Once intermittent (every 24 h) ORP-controlled micro-aeration (at ORP of -470 mV) was initiated, the total VFA concentration rapidly decreased to 3.0 g HAc/L and the methane yield improved, resulting in stable digester performance without the need for alkalinity supplementation or OLR reduction. By combining reactor performance results, mass balance analyses, microbial community characterization data, and a bioenergetic evaluation, this study suggested that rapid VFA conversion and CH production were carried out by facultative anaerobes and hydrogenotrophic methanogens under micro-aerobic conditions. This novel operating approach can be applied as an effective control strategy for high OLR AD processes especially in the event of VFA accumulation.
本研究开发了一种间歇氧化还原电位（ORP）控制的微曝气系统，用于木质纤维素生物质的高固体厌氧消化（AD），在高有机负荷率（OLR）下不会积累挥发性脂肪酸（VFA）。传统的 Napier 草（一种木质纤维素生物质模型）AD 在 OLR 为 5 g 挥发性固体（VS）/L/天时，导致总 VFA 浓度积累高达 9.2 g/L，相当于乙酸（HAc），导致 pH 值和甲烷产量迅速下降，并使消化器濒临失效。一旦开始间歇（每 24 h）ORP 控制的微曝气（ORP 为-470 mV），总 VFA 浓度迅速降至 3.0 g HAc/L，甲烷产量提高，消化器性能稳定，无需补充碱度或降低 OLR。通过结合反应器性能结果、质量平衡分析、微生物群落特征数据和生物能量评估，本研究表明，在微需氧条件下，兼性厌氧菌和氢营养型产甲烷菌可快速进行 VFA 转化和 CH 生成。这种新颖的操作方法可作为高 OLR AD 工艺的有效控制策略，特别是在 VFA 积累的情况下。
