【作者】 赵晶；

【导师】 于晓华；

【作者基本信息】 北京交通大学 ， 环境科学与工程， 2022， 硕士

【摘要】 污泥作为污水处理过程中的伴生产物,近几年随着污水处理量提高,其产量急剧增加,截止2020年我国城镇干污泥总量达3578.3万吨,是2010年的1.63倍,因此如何高效的实现污泥的资源化和能源化是解决污泥问题的关键。基于有机物的厌氧转化过程,生物沼气可以作为一种天然的生物能源加以回收利用,抵消污水厂的能量消耗,降低污水厂碳排放。然而在污泥厌氧消化过程中,破壁效率始终是限制厌氧消化效能的关键因素。热水解被证明是一种高效的污泥预处理破壁技术,并且热水解+厌氧消化的高级厌氧消化工艺在国内外有十分广泛的应用。基于大量的应用案例,普遍认为最适的热水解温度范围是160～180℃,但是对于具体的热水解温度仍然需要进一步研究,以进一步优化热水解过程。除此之外,对热水解+厌氧消化内部微生物生态机制的研究往往局限于细菌和古菌的群落变化,忽略了真核生物在该体系中的作用,在群落调控和优化上仍然存在认知上的不足。以上两点不足之处,对如何进一优化厌氧消化条件带来了一定的限制,除此之外,也降低了进一步提出生态调控策略的可能。为此,本研究以北京市两个污水处理厂的污泥为研究对象,针对不同泥源,在普遍报道的最适热水解温度范围内(160～180℃)寻找最佳热水解温度条件,并解析在不同热水解条件下微生物群落动态(包括真核生物和原核生物)对泥质变化和反应器效能的影响。研究结果表明:(1)热水解后两种污泥的脱水性、溶解性和水解性都有提高,其中有机固体增溶20～30%,SCOD浓度提高3～6倍,说明热水解处理具有一定的普适性。热水解处理后污泥厌氧消化的产气率提高了30～50%(t-test,p<0.05),且两种来源的污泥都在170℃热水解后厌氧消化效能最高,HRT=25 d时产甲烷性能分别达到612.03和555.45 m~3/t＿VS,HRT=40 d时分别为488.28和464.95 m~3/t＿VS,表明170℃是最佳的热水解温度。(2)预处理后原核微生物群落的多样性大幅下降,群落组成也有明显变化:Chloroflexi、Caldatribacteriota等水解菌的占比下降,Firmicutes、Bacteroidota等发酵产酸菌丰度提高,产甲烷菌中嗜氢产甲烷菌Methanolinea占比提高,且170℃预处理后肠道微生物显著富集。Mantel检验、Spearman相关分析和RDA分析共同表明原核微生物群落组成与污泥性质(可溶蛋白、氨氮和碱度)存在显著强相关关系,说明污泥性质是引起群落组成变化的主要原因。FAPROTAX功能预测结果表明热水解后产甲烷活性显著提高,线性回归分析表明原核群落变化与系统产气率存在中度的因果关系(R~2=0.35,p<0.05)。(3)真核生物与原核生物在生物量、alpha多样性和群落结构上都有显著的强相关关系(如预处理后,物种拷贝数:r=0.6,p<0.001、系统发育多样性指数:r=0.65,p=0.049和主成分分析的主坐标:r=0.53,p<0.05),RDA结果显示加入真核生物因子后环境因子对群落结构差异的解释度提高到90%以上,证实微生物群落的组成和结构差异主要由污泥性质和真核生物因子共同决定,原核生物和真核生物群落共同的变化对产气率波动的解释度可达到70～80%,表明产气率的变化主要受到真核和原核生物的生态关系控制。网络分析发现真核生物中真菌Geotrichum与原核生物的Firmicutes关系最为密切(r=-0.79,p<0.05),且为负相关,说明原核生物的关键控制物种是Geotrichum。本研究证实了170℃是最佳的热水解处理温度,为进一步优化热水解条件提供了具体可参考的数据资料。此外,该研究发现了真核生物对原核生物群落结构的控制作用,找出了关键物种,进一步提出了产气率是由真核和原核生物共同决定的结论,这一结果为如何进一步的开发污泥厌氧消化的生态调控策略,能否进一步突破现有厌氧消化体系产能效率奠定了理论基础。更多还原

【Abstract】 Sludge,as an accompanying product of the sewage treatment process,has increased dramatically in recent years as the volume of sewage treatment has increased,with the total volume of urban dry sludge in China reaching 35,783,000 tons by 2020,1.63 times that of 2010,so how to efficiently realize the resource and energy of sludge is the key to solve the sludge problem.Based on the anaerobic conversion process of organic matter,biomethane can be recycled as a natural bio-energy source to offset the energy consumption and reduce the carbon emission of wastewater plants.However,in the anaerobic digestion of sludge,the breaking efficiency is always a key factor limiting the effectiveness of anaerobic digestion.Thermal hydrolysis has been proven to be an efficient sludge pretreatment wall-breaking technology,and the advanced anaerobic digestion process of thermal hydrolysis+anaerobic digestion has been very widely used in China and abroad.Based on a large number of application cases,the most suitable thermal hydrolysis temperature range is generally considered to be 160-180°C.However,further research is still needed for the specific thermal hydrolysis temperature to optimize the thermal hydrolysis process.In addition,the research on the microbial ecological mechanism inside the thermal hydrolysis+anaerobic digestion is often limited to the community changes of bacteria and archaea,ignoring the role of eukaryotes in this system,and there is still a cognitive deficiency in the community regulation and optimization.These two shortcomings bring some limitations on how to further optimize the anaerobic digestion conditions and,in addition,reduces the possibility of further proposing ecological regulation strategies.In this study,sludge from two wastewater treatment plants in Beijing was used to find the optimal thermal hydrolysis temperature conditions in the commonly reported optimal thermal hydrolysis temperature range(160-180°C)for different sludge sources,and to analyze the effects of microbial community dynamics(including eukaryotes and prokaryotes)on sludge quality changes and reactor efficiency under different thermal hydrolysis conditions.The results of the study are as follows:(1)The dewatering,solubility and hydrolysis of both sludge types were improved after thermal hydrolysis,with organic solids increasing by 20-30%and SCOD concentration increasing by 3-6 times,indicating that thermal hydrolysis has some general applicability.The gas production rate of anaerobic digestion of sludge after thermal hydrolysis treatment increased by 30-50%(t-test,p<0.05),and the highest efficiency of anaerobic digestion was achieved after thermal hydrolysis at 170℃for both sources,with methane production performance reaching 612.03 and 555.45m~3/t＿VS at HRT=25 d,and 488.28 and 464.95 m~3/t＿VS at HRT=40 d,respectively.This indicates that 170℃is the optimal thermal hydrolysis temperature.(2)The diversity of the prokaryotic microbial community decreased significantly after pretreatment,and the community composition also changed significantly:the percentage of hydrolytic bacteria such as Chloroflexi and Caldatribacteriota decreased,the abundance of fermentative bacteria such as Firmicutes and Bacteroidota increased,and the percentage of Methanolinea increased.In addition,gut microorganisms were significantly enriched in the digested sludge pretreated at170°C.Mantel test,Spearman correlation analysis and RDA analysis together showed that prokaryotic microbial community composition was significantly and strongly correlated with sludge properties(soluble protein,ammonia nitrogen and alkalinity),suggesting that sludge properties were the main cause of community changes.FAPROTAX functional prediction results indicated a significant increase in methanogenic activity after thermal hydrolysis.Linear regression analysis showed a moderate causal relationship between archaeal community and gas production rate(R~2=0.35).(3)Eukaryotes were significantly and strongly correlated with prokaryotes in terms of biomass,alpha diversity and community structure(e.g.,after pretreatment,species copy number:r=0.6,p<0.001,phylogenetic diversity index:r=0.65,p=0.049and principal coordinates of principal component analysis:r=0.53,p<0.05).the RDA results showed that the addition of eukaryotic factors increased the explanation of community variation by environmental factors to more than 90%,confirming that the differences in microbial communities were mainly determined by a combination of sludge properties and eukaryotic factors.Furthermore,the variation of the prokaryotic and eukaryotic communities together can explain 70-80%of the fluctuation of gas production rate,indicating that the gas production rate is mainly controlled by the ecological relationship between eukaryotes and prokaryotes.In particular,network analysis revealed that Geotrichum was most closely related to Firmicutes(r=-0.79,p<0.05)and negatively correlated,indicating that the key control species of prokaryotes was Geotrichum.(4)This study confirmed that 170°C is the optimal thermal hydrolysis temperature,which provides specific referenceable data for further optimization of thermal hydrolysis conditions.In addition,this study identified the controlling role of eukaryotes on the prokaryotic community,identified key species,and further proposed the conclusion that the gas production rate is jointly determined by eukaryotes and prokaryotes.This results provide a theoretical basis for how to further develop ecological control strategies for anaerobic digestion of sludge and whether to further break through the capacity efficiency of existing anaerobic digestion systems.更多还原