有机废弃物高固厌氧消化产甲烷途径及调控

Anaerobic digestion (AD) is one of the most important environmental technologies and clean energy technologies, and is used worldwide. In China, biogas industry is one of the most important industry and has attracted more and more investment. High-solid anaerobic digestion (HSAD) is an emerging technology and would be one of the mainstream techniques of AD of organic wastes in near future due to the small footprint, low energy demand and small digestate. However, high viscosity, high organic loading rate and high ammonia level in HSAD result in low methane production rate and complex control. And few related studies could be found in literature. This study aims at investigating into HSAD of organic wastes, especially the reaction kinetics and pathway of methane production in order to develop control methods and engineering measurements to support the realization of high methane production rate and high organic removal rate. The experiments will be conducted at lab scale and pilot scale. Furthermore, the impacts of solid content, organic loading rate, ammonia, substrates and reactor scale on the reaction kinetics and pathway of methane production of HSAD are to be studied systematically. Then we will recognize the controlling factors of methane production of HSAD through correlating and quantitatively analyzing kinetic parameters and microbiological properties. Finally, the methods and engineering strategy to control HSAD based on the understanding the microbial mechanism to improve the reaction rate and methane production rate will be proposed and tested. During the study, one of the highlights is the study about exclusively dominant methanogenesis pathway assisted by syntrophic acetate oxidation in HSAD discovered in our previous study. This study is of great scientific and practical engineering.

厌氧消化是重要的环保和能源技术，沼气工业也是国家重视发展的行业之一。高含固率厌氧消化（简称高固消化）反应器小、运行费低、沼渣少，可能成为有机废弃物厌氧处理的主流技术。高粘度、高有机负荷、高氨氮造成甲烷产率低、调控难度大。但研究较少。本申请以产甲烷和有机物去除双优为目标，结合小试和生产性装置，研究有机废弃物高固消化的反应动力学和产甲烷途径，研究含固率、有机负荷、氨氮、基质、反应温度、规模等影响，并通过动力学参数和微生物学特性的关联和定量分析，从中识别出高固消化产甲烷途径和过程的控制因子，找到从机理上引导和调控厌氧过程、提高反应速率和甲烷产率的方法，并构建工程策略。研究重点之一是前期发现的高固消化独特的完全由互营乙酸盐氧化菌辅助的氢营养型产甲烷途径承担产甲烷的过程，目前在文献中还没有发现该途径的相关报道。本研究具有较大的科学意义和工程价值。

厌氧消化是重要的环保和能源技术。高含固率厌氧消化(简称高固消化)反应器小、运行费低、沼渣少，已成为有机废弃物厌氧处理的主流技术。但高粘度、高有机负荷、高氨氮造成甲烷产率低、调控难度大。本项目以产甲烷和有机物去除双优为目标，开展系统研究，取得以下主要成果： .（1）70℃热处理可强化污泥、猪粪等有机质的溶解、水解和酸化，能提高其厌氧产气。热处理能提高难降解有机物的水解速率，但对容易降解有机物的促进不明显。.（2）基质对高固厌氧消化有明显影响。相同工艺下，有机物含量相当的污泥比猪粪难降解，而且相同含固率下，在相近SRT下，污泥系统比猪粪系统的氨氮高50%左右。氨氮5000mg/L的抑制并不明显，但游离氨1000mg/L左右已显示出对厌氧产生抑制。.（3）含固率增加，降解变缓，但SRT足够长，可以减轻甚至抵消含固率对厌氧消化系统的负面影响。高含固率下，微生物的最大比增长速率和蛋白质水解速率变小。.（4）发现了三种主要的产甲烷途径，分别是氢营养型为主的产甲烷途径，甲基营养型为主的产甲烷途径，以及乙酸盐营养型和氢营养型为主、甲基营养型产甲烷同时存在的产甲烷途径。前两种产甲烷途径中优势菌的丰度都远远高于文献报道过的情况。高固厌氧消化系统的优势菌往往是耐高负荷、高盐度、高氨氮的微生物。经过高固厌氧消化后，微生物的抗性基因增多。.（5）有机废弃物的推荐工艺参数是“70 °C热处理+高固中温厌氧消化”，热水解反应时间采用3ｄ。对于污泥，进泥含固率17%，厌氧消化SRT50ｄ；对于猪粪，进料含固率可以采用21%，厌氧消化SRT29d。.（6）.推荐的调控策略：采用热处理来提升甲烷产率和有机物去除率；提高pH，降低氨氮抑制；采用较长的厌氧SRT。.