R-PFR与CSTR厌氧消化餐厨垃圾运行效率及微生物群落结构对比

以中温餐厨垃圾(FW)厌氧消化反应器为研究对象,结合稳定运行过程中的微生物群落结构特征,考察了两种常见的厌氧消化反应器—完全混合式反应器(CSTR)和有回流的推流式反应器(R-PFR)的运行效率和稳定性.结果表明,两种构型的反应器均能在3.0 kg·m-3·d-1(以VS计)负荷下稳定高效地运行.R-PFR具有更稳定的稳定性指数,如总碱度(TA)和挥发性脂肪酸比TA值(VFA/TA),以及更低的氨氮(TAN)和游离氨(FAN)浓度,但产气效率(如比甲烷产率(SMP))不及CSTR.R-PFR中以Chloroflexi门(37.35%)和Firmicutes门(31.22%)为优势细菌,而CSTR中以Bacteroidetes门(31.14%)与Firmicutes门(44.41%)为优势细菌.CSTR和R-PFR均以Methanosaeta属为优势产甲烷菌(98.72%和84.90%),乙酸型产甲烷途径为主要的产甲烷途径.但CSTR中除Methanosaeta属以外还有一定丰度的混合营养型的Methanosarcina,以及氢营养型Methanospirillum和Methanolinea.CSTR中具有对VFA和TAN更具耐受性的产甲烷菌群,更有利于餐厨垃圾产甲烷过程的稳定进行.由于R-PFR的敏感性较低,有利于处理剧烈变化的底物,但R-PFR容易出现严重的局部酸化现象,不利于长期处理过高负荷的易降解底物(如餐厨垃圾).这些结果可为优化餐厨垃圾厌氧消化工艺设计提供基础依据.

Comparison of R-PFR and CSTR performance and microbial community structure during anaerobic digestion of food waste

To identify the most efficient system for conversion of food waste (FW) into biogas, FW fermentation was investigated in two types of reactors:a completely-stirred tank reactor (CSTR) and a plug-flow reactor with a reflux ratio (R-PFR). The efficiency, stability, and microbial community structure in the reactors were compared. Stable fermentation was achieved under an organic loading rate (OLR) of 3.0 kgVS·m^-3·d^-1 in both reactors. Compared with the CSTR, total alkalinity (TA) and ratio of volatile fatty acids (VFA) to TA (VFA/TA) were more stable, and inhibitors such as total ammonia-nitrogen (TAN) and free ammonia-nitrogen (FAN) concentrations were lower in R-PFR. However, specific methane production (SMP) was higher in the CSTR. The phyla Chloroflexi (37.35%) and Firmicutes (31.22%) were predominant in the R-PFR, whereas Firmicutes (44.41%) and Bacteroidetes (31.14%) were more abundant in the CSTR. The genus Methanosaeta accounted for 98.72% and 84.90% of the total population in the CSTR and R-PFR, respectively, indicating that the main methanogenic pathway in both reactors was acetoclastic methanogenesis. In addition to Methanosaeta, mixotrophic methanogens such as Methanosarcina (9.72%) and hydrogenotrophic methanogens such as Methanospirillum and Methanolinea were detected in the CSTR. The methanogenic community obtained in the CSTR had a greater tolerance to high ammonia and VFA levels, which is conducive to stable and efficient methanogenesis. R-PFR may be more appropriate for highly variable substrate, as shock loads can vary spatially in the reactor. However, R-PFR systems are not suitable for long-term treatment of highly degradable substrate such as FW, as local acidification may occur. Our results provide a basis for the optimization of anaerobic FW digestion.