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

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

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.

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.