阳离子聚丙烯酰胺对水热预处理污泥高含固厌氧消化产甲烷的影响及其自身降解机制研究

Cationic polyacrylamide (cPAM) is the most widely used agent to improve sludge dewatering efficiency at present, however, it has been reported that cPAM can reduce sludge anaerobic digestion, and the degradation product acrylamide (AM) is toxic and has the potential of carcinogenicity. Base on the preliminary feasibility study, it was found that hydrothermal pretreatment could reduce the inhibitory effect of cPAM on the methane production of high solid sludge anaerobic digestion. Therefore, this project will explore the influence mechanism of cPAM on sludge hydrothermal pretreatment of dissolved organic matter, sludge morphology, anaerobic digestion effect and mixed microbial community. The degradation law of cPAM will be mastered and the influence mechanism of key metabolites on the process of sludge anaerobic digestion will be revealed after hydrothermal pretreatment through the identify the degradation products of cPAM in the process of hydrothermal pretreatment and anaerobic digestion. The effects of anaerobic digestion temperature, hydraulic retention time and other process conditions on cPAM degradation and methane production from sludge will also be studied by combining with continuous flow process, then the succession rules of microflora and related microorganisms of cPAM degradation in continuous flow process will be clarified. This project is expected to provide technical support and theoretical basis for improving the efficiency of anaerobic digestion sludge based on hydrothermal pretreatment and provide guidance for cPAM pollution control technology, which has important scientific significance and application value.

阳离子型聚丙烯酰胺（cPAM）是目前使用最广泛的改善污泥脱水性能的药剂，但是cPAM会降低污泥厌氧消化甲烷产率，此外cPAM降解产物丙烯酰胺具有潜在毒性和致癌性。申请人前期的研究发现水热预处理可以降低cPAM对脱水污泥高含固厌氧消化产甲烷的抑制效果，在此基础上本项目将探究cPAM对污泥水热预处理溶解性有机物、污泥形态、厌氧消化效果、混合微生物群落的影响机制；识别cPAM在水热预处理及厌氧消化过程中降解产物，掌握cPAM的降解规律，揭示关键代谢产物对水热预处理后污泥厌氧消化过程的影响机制；结合连续流工艺研究厌氧消化温度、水力停留时间等工艺条件对cPAM降解及污泥产甲烷的影响，阐明连续流工艺微生物菌群及cPAM降解相关微生物的演替规律。本项目将对提高含cPAM的污泥高含固厌氧消化效率提供理论依据和技术支持，为污泥的无害化、资源化利用及cPAM污染控制技术提供指导，具有重要的科学意义和应用价值。

阳离子型聚丙烯酰胺（cPAM）是目前使用最广泛的改善污泥脱水性能的药剂。cPAM无毒，但其降解后可能产生伤害人或动物神经系统的物质丙烯酰胺（AM），因此污泥或者废水中的cPAM/PAM是一种潜在的环境风险物质。本课题以污泥中具有潜在环境风险的cPAM为研究对象，研究基于水热预处理的污泥厌氧消化过程中，cPAM自身的降解情况及其对污泥厌氧消化的影响机制。.在0-20 mg cPAM/g TS 含量范围内，典型cPAM均未对污泥直接厌氧消化产甲烷速率和最终甲烷产量产生显著影响；170 oC-0.5 h水热预处理后，cPAM可作为碳源促进污泥产甲烷（12.2 mL CH4/g TS），但仍然有部分物质存留在液体或者固体中，不可被产甲烷菌充分降解。cPAM对厌氧消化产甲烷微生物群落结构影响发现：相比不含cPAM的样品，细菌Cloacimonetes和Chloroflexi在cPAM的样品中的丰度分别由4.9%和1.5%增加到7.1%和8.7%，Chloroflexi是被证明与PAM的降解密切相关的微生物，在本研究中得到富集。.对cPAM水热及厌氧消化降解机理研发发现，cPAM水热预处理后的产物非常复杂，产物中既有小分子的物质还有分子量跨度较大的主链碳分解产物（200-1000 kDa）。170 oC-0.5 h水热预处理，cPAM溶液产甲烷效率由7.4%提高到76.3%；阳离子基团中的酰氧基、酰胺基首先发生了水解，生成胆碱、氨氮等小分子有机物和不同聚合度的含羧基聚合物；水解生成的胆碱进一步反应生成了分子量更小的三甲胺、乙醇等高生物降解性（94%）的产物。对非离子型PAM对比实验表面，PAM的生物降解性能还与其侧链基团类型及离子度有关。本研究为提高含cPAM的污泥的无害化利用及含cPAM废弃物污染控制技术提供了重要参考。