不同含固率下零价铁提升厨余垃圾高温厌氧消化产沼体系运行稳定性研究

Research on improving the operational stability of thermophilic anaerobic digestion system of kitchen waste by adding zero-valent iron under different solid content rates

相比中温(35℃)厌氧消化,高温(55℃)厌氧消化中微生物代谢活性强,处理效率高,且无害化水平高,适合厨余垃圾的资源化处理及利用.但由于厨余垃圾易降解,有机质含量高,水解速率快,极易在厌氧消化前期出现酸积累现象,这种现象在高温厌氧消化中更为显著,从而严重制约着高温厌氧消化的应用.本研究探究了零价铁(ZVI)对高温厌氧消化过程酸化现象的消除和控制,并对投加ZVI后不同含固率下厌氧反应器严重酸化现象缓和效果进行评价.结果表明,高温条件下含固率为4%、6%的反应器在ZVI的促进作用下很快恢复产沼,甲烷产率相较低负荷反应器分别提高了52.05%、10.51%.含固率为8%的投加ZVI反应器在经历一个月的延滞期后也消除了“过酸化”,甲烷含量稳定在60%以上,甲烷产率达到270.40 mL·g^(-1).以加ZVI反应器沼液作为接种物的H-ICS反应器能够降低氢分压,但未能消除“过酸化”.含固率为10%的反应器在反应结束后仍处于酸化状态.高通量测序结果表明,所有外加ZVI的反应器中嗜氢产甲烷菌是绝对的优势菌.在恢复产沼的H-ZVI反应器以细菌Defluviitoga产生的乙酸盐、CO_(2)、H_(2)和丁酸转化来的乙酸为底物,嗜氢产甲烷菌Methanothermobacter作为唯一优势产甲烷古菌,与互营乙酸氧化菌Syntrophaceticus相互作用,实现互营乙酸氧化产甲烷(SAO-HM)途径,恢复产甲烷代谢.

Compared with the mesophilic anaerobic digestion(35℃),thermophilic anaerobic digestion(55℃)has a stronger metabolic activity of microorganisms,higher treatment efficiency,and more harmless,which is suitable for resourceful treatment and utilization of kitchen waste.However,due to the kitchen waste’s good bio-degradability,high organic matter content and fast hydrolysis rate,votatile fatty acid(VFA)is easily accumulated at the early stage of anaerobic digestion.This phenomenon is more serious in thermophilic anaerobic digestion,which severely restricts its application.Excessive acidification during the thermophilic anaerobic digestion was eliminated and relieved though dosing zero-valent iron(ZVI)in this study,and the effects of ZVI on excessive acidification elimination at different solid contents were evaluated.The results showed that at TS conditions of 4%and 6%,thermophilic anaerobic reactors with ZVI dosing quickly recovered biogas production,and the methane yield increased by 52.05%and 10.51%,respectively,compared with the control reactor with low organic loading.The excessive acidification in reactor dosed ZVI at TS of 8%also could be eliminated after a one-month lag period,and the methane content stabilized above 60%,with methane yield of 270.40 mL·g^(-1).After inoculating digestate from reator with ZVI addition,H-ICS reactor could reduced its hydrogen partial pressure in the early stage,but failed to eliminate excessive acidification.At TS of 10%,the reactor with either ZVI dosing or not was still in acidification after a reaction period.The results of high-throughput sequencing showed that hydrogenotrophic methanogen was absolutely dominant in all reactors with ZVI dosing.Furthermore,in the ZVI reactors with recovering biogas production,the acetate,CO_(2),H_(2) produced by the Defluviitoga,as well as the acetic acid converted from butyric acid could be used as the substrate.Hydrogenotrophic methanogen Methanothermobacter interacted with the syntrophic acetate-oxidising bacteria Syntrophaceticus to achieve the syntrophic acetate oxidation and hydrogenotrophic methanogenesis(SAO-HM)pathway and recover the methanogenesis metabolism.