餐厨垃圾厌氧消化起泡现象研究

Foaming phenomenon in anaerobic digestion system treating food waste

以餐厨垃圾中温厌氧消化反应器为研究对象,考察泡沫事件对反应器性能如比沼气产率(SBP)、比甲烷产率(SMP)和挥发性固体(VS)去除率等的影响;并通过分析泡沫前、后系统稳定性参数如挥发性脂肪酸(VFAs)浓度、VFA/总碱度(TA)值和氨氮(TAN)浓度等的变化情况,以及泡沫前、后(包括泡沫层与液体层)的细菌群落结构变化,解析泡沫事件产生的可能原因.结果表明,稳定期的SBP、SMP和VS去除率分别为(0.950±0.104)m^3/kg VS、(0.574±0.072)m^3CH_4/kg VS和(87.14±2.76)%,而泡沫事件显著影响了反应器效率(t检验,95%的置信区间),SBP、SMP和VS去除率分别降为(0.717±0.100)m^3/kg VS、(0.432±0.070)m^3CH_4/kg VS和(84.24±4.44)%.泡沫发生前,系统内出现了VFAs快速积累现象,且易被产甲烷菌消耗的乙酸比例下降,而对泡沫趋势具有增强作用的丙酸比例上升.并且泡沫出现后丝状菌Longilinea arvoryzae和Levilinea,以及黏细菌Cytophaga fermentans的条带强度明显增大,而丝状菌的丝状结构以及粘细菌产生的粘性物质对起泡有一定程度的贡献.综上,泡沫的产生可能是由系统内大量VFAs积累以及特定微生物大量繁殖的联合作用引起的.

A serious foaming incident occurred in a mesophilic food waste digester. The effects of foaming on reactor efficiency parameters were investigated, including specific biogas production（SBP）, specific methane production（SMP） and volatile solids（VS） removal rate. The possible causes of foaming were evaluated according to a series of stability parameters including volatile fatty acids（VFAs）, the ratio of VFA to total alkalinity（VFA/TA） combined with the ammonia nitrogen concentration（TAN）, as well as the bacterial community structure in pre-and post-foaming system. The SBP, SMP and VS removal rate during the stable stage were（0.950 ± 0.104） m3/kg VS,（0.574 ± 0.072） m3CH4/kg VS and（87.14 ± 2.76）%, respectively. However, those parameters decreased to（0.717 ± 0.100） m3/kg VS,（0.432 ± 0.070） m3CH4/kg VS and（84.24 ± 4.44）% with the appearance of the foaming incident, which indicated that the efficiency of the digester had been significantly influenced by the foaming incident. Prior to the foaming, there appeared to be a rapid accumulation of VFAs along with a reduction in the proportion of acetic acid in VFAs. The propionic acid, which is believed to play a major role in enhancing the foaming tendency, increased in its proportion in VFAs as well. The filamentous bacteria Longilinea arvoryzae, Levilinea and the myxobacterium Cytophaga fermentans had stronger band intensities after foaming. Their filamentous structure or mucilage can be a significant contributor to the initiation of foaming to some extent. In conclusion, foaming may be caused by the combination of VFAs accumulation and the proliferation of specific bacteria.