混合气体纳米气泡对玉米秸秆半连续厌氧发酵影响研究

Influence of Mixed Gas Nanobubbles on Semi-continuous Anaerobic Digestion of Corn Stover

摘要:

为优化玉米秸秆半连续厌氧发酵产甲烷效率,制备得到3种混合气体纳米气泡水(Nanobubble water,NBW):(H2 + CO2) - NBW (体积比为4∶1)、(CO2 + CH4) - NBW (体积比为2∶3)和(CO2 + H2 + CH4) - NBW (体积比为4∶1∶5),探究了不同混合气体NBW对产甲烷、底物降解、发酵液热物性以及微生物群落的影响规律。结果表明,(H2 + CO2) - NBW、(CO2 + CH4 ) - NBW和(CO2 + H2 + CH4 ) - NBW的平均日产甲烷量相比对照组分别提高15.76%、4.51%和6.87% ,甲烷体积分数最大提高8.01%、5.20%和8.37%。底物降解方面,混合气体NBW有利于提高半连续运行前期挥发性脂肪酸、还原糖和可溶性化学需氧量浓度。相比对照组,(H2 + CO2) - NBW、(CO2 +CH4) - NBW和(CO2 + H2 + CH4) - NBW组的总固体去除率分别提高40.10%、10.82%和16.36%。同时,混合气体NBW有效改善了发酵液传热和流动特性。(H2 + CO2 ) - NBW、(CO2 + CH4 ) - NBW和(CO2 + H2 + CH4 ) - NBW组发酵液平均导热系数相比对照组分别提高2.93%、2.87%和0.98% ;平均表观黏度相比对照组分别下降了10.51%、14.89%和14.79%。微生物群落分析表明,混合气体NBW的引入提高了氢营养型产甲烷菌(Methanolinea、Methanospirillum、Methanomassiliicoccus等)和水解酸化菌(ADurb. Bin120、Aminicenans、Clostridium等)的相对丰度。研究结果可为纳米气泡技术在厌氧发酵的工业化应用提供理论依据和数据支撑。

Abstract:

Aiming to optimize the methane production efficiency of semi-continuous anaerobic digestion of corn stover, three types of mixed gas nanobubble water ( NBW) were prepared: ( H2 + CO2 ) - NBW (volume ratio = 4∶1), (CO2 + CH4) - NBW (volume ratio = 2∶3), and (CO2 + H2 + CH4) - NBW (volume ratio = 4 ∶1 ∶5). The effects of different mixed gas NBW on methane production, substrate degradation, thermophysical properties of digestate, and microbial community structure were investigated. The results showed that compared with the control group, the average daily methane yield was increased by 15.76% , 4.51% , and 6.87% in the (H2 + CO2) - NBW, (CO2 + CH4 ) - NBW, and ( CO2 + H2 + CH4 ) - NBW groups, and the maximum methane volume fraction was increased by 8.01% , 5.20% , and 8.37% , respectively. In terms of substrate degradation, mixed gas NBW promoted higher concentrations of volatile fatty acids ( VFAs), reducing sugars, and soluble chemical oxygen demand (SCOD) in the early stage of semi-continuous operation. Compared with the control group, the total solid (TS) removal rates were enhanced by 40.10% , 10.82% , and 16.36% in the 3 NBW groups, respectively. Meanwhile, mixed gas NBW effectively improved the heat transfer and flow characteristics of the digestate. The average thermal conductivity of the digestate was increased by 2.93% , 2.87% , and 0.98% in the (H2 + CO2) - NBW, (CO2 + CH4) - NBW, and (CO2 + H2 + CH4) - NBW groups, respectively, while the average apparent viscosity was decreased by 10.51% , 14.89% , and 14.79% , respectively. Microbial community analysis revealed that the introduction of mixed gas NBW increased the relative abundance of hydrogenotrophic methanogens ( e. g. , Methanolinea, Methanospirillum, Methanomassiliicoccus) and hydrolytic and acidogenic bacteria ( e. g. , ADurb. Bin120, Aminicenans, Clostridium). These findings can be expected to provide theoretical basis and data support for the industrial application of nanobubble technology in anaerobic digestion.