生物炭和石墨的电化学性质对剩余污泥厌氧消化产甲烷的影响

Effect of electrochemical properties of biochar and graphite on methane production in anaerobic digestion of excess activated sludge

以玉米秸秆为原料,分别在300、500和700℃的条件下热解制备生物炭(CS300、CS500、CS700),对其理化性质(pH、比表面积、灰分含量、元素组成)和电化学性质(电子供给能力(EDC)、电子接受能力(EAC)、导电率(EC))进行了表征,并将3种生物炭和导电型石墨分别加入消化反应器进行污泥中温厌氧消化批次实验。结果表明:CS300具有最高的EDC(0.598 mmol·g^-1),CS700具有最高的EAC(0.740 mmol·g^-1),石墨的导电性最强(2.0×10^4 S·m^-1);4种碳材料对污泥厌氧消化产甲烷均有促进作用,CS300、石墨、CS500和CS700实验组的甲烷累积总产量比对照组分别提高了42.4%、38.9%、28.9%和11.2%。微生物群落结构分析结果表明:甲烷生成的主要代谢途径是CO2还原代谢途径;3种生物炭材料均提高了Methanosarcina等氢营养型产甲烷古菌的相对丰度,CS300的富集能力最强,石墨的影响作用则不显著。冗余分析结果表明:4种碳材料的电化学性质对厌氧细菌群落组成变化的贡献度为52.7%,对厌氧古菌群落组成变化的贡献度为64.4%;具有氧化还原活性的生物炭通过反复供给、接受电子大幅增加体系中微生物可用电子数量来提高互养微生物种间电子传递效率;而导电性能优秀的石墨则主要通过促进微生物的直接电子传递来提高甲烷产率。研究为解析具有电化学活性的碳材料对厌氧微生物菌群代谢特征和电子传递的影响规律提供了一定的理论支撑,对提高污泥厌氧消化效率、实现能源高效回收具有重要理论价值和现实意义。

Biochar was prepared by pyrolyzing corn stover biomass at 300,500 and 700℃,respectively,and yielded CS300,CS500 and CS700.Their physicochemical properties including pH,surface area,ash content and elemental composition and electrochemical properties including EDC,EAC,EC were characterized.Then three types of biochar and the conductive graphite were dosed in digestion reactor to conduct the batch tests of mesophilic AD of sludge.The results showed that CS300 had the highest EDC of 0.598 mmol·g^-1,CS700 had the highest EAC of 0.740 mmol·g^-1,whereas Graphite had the highest EC of 2.0×10^4 S·m^-1.All the materials could promote AD of sludge.In comparison to the control group,the addition of CS300,Graphite,CS500 or CS700 elevated the cumulative methane production by 42.4%,38.9%,28.9% and 11.2%,respectively.Analysis of microbial community indicated that methane was primarily produced via CO2 reduction pathway,which is attributed to the syntrophic association between syntrophic anaerobes and hydrogenotrophic methanogens.The addition of biochar raised the relative abundance of Methanosarcina and other hydrogenotrophic methanogens.CS300 had the best performance on enrich these methanogens,while graphite did not make significant contribution.RDA analysis showed that the parameters reflecting the electrochemical properties of carbon-based materials explained 52.7% and 64.4% of the bacterial and archaeal community in the sludge digesters,respectively.Redox-active biochar could sustainably donate and accept electrons over many redox cycles,improve the available electron quantity of microorganism in the system and facilitate electron transfer to CO2 reduction,and thereby enhance methanogenesis.Alternatively,graphite could directly transport electrons so that promotes direct interspecies electron transfer(DIET)in syntrophic communities for enhanced methane productivity.It provides theoretical support for the analysis of the influence of conductive carbon materials on the metabolic characteristics and electron transport of anaerobic microbial community.And it has important theoretical and practical value for improving the anaerobic digestion efficiency of sludge and achieving energy efficient recovery significantly.