生物质垃圾ASBR消化的悬浮固体截留效应和微生物结构特征

Compared to high concentration wastewater, bio-waste has the characteristic of high suspended organic solid content. Suspended organic solid has been proved of a relatively slow hydrolysis speed in anaerobic digestion and its hydrolysis has been recognized as rate-limiting step of substrate biodegradation process. With the purpose of improving the conversion rate of substrate in anaerobic digestion process, it is necessary to prolong the retention time of the solid substrate and promote the activity of the microbial community. Anaerobic sequencing batch reactor (ASBR) is featured by suspended solid retaining and active microbial community incubation, which is suitable for treating high suspended solid feedstock. This proposal focused on the characterization of solid retaining process and syntrophic microbial community feature in ASBR to reveal the key factors accounting for the high system efficiency and stable operation. Base on this study, a quantitative model between solid retaining effect and suspended solid settleability will be built, which can be used as a design and control methodology for solid and microorganism retention time. For the microbial community analysis, the diversity and dynamic changes of methanoarchaea community and syntrophic bacteria community will be studied under various operation conditions. External disturbance such as shock load and over-stirring will be introduced into ASBR system to reveal the syntrophic relationship of microbial community, and finally incubation and control measures of active microbial community will be built. The achievements of this study will be theoretical basis for the technical optimizing and reactor operation control of high-suspended-solid anaerobic digestion by ASBR.

生物质垃圾与高浓度废水在厌氧消化中的最大区别在于前者悬浮有机固体含量高，与溶解性基质相比，悬浮有机固体水解速率慢，是有机物降解的限制因素。为了提高有机物转化率，需要延长固体基质停留时间和提高微生物活性。厌氧序批式反应器（ASBR）以悬浮固体基质/微生物截留和高活性微生物为典型特征，适用于高悬浮固体物料。本项目研究ASBR的固体截留效应，解析微生物互养群落特征，探索维持ASBR高效稳定运行的关键因素；构建ASBR固体截留效应与悬浮固体沉降性能的量化模型，为准确设计和控制固体基质及微生物停留时间提供方法学；明确ASBR中微生物的群落多样性及动态演变规律，获得在冲击负荷、过度搅拌等外在扰动下，产甲烷古菌及互养菌属的结构变化情况，分析微生物群落互养关系对ASBR高效性的影响，形成ASBR中高活性微生物的培养及控制方案。成果将为高悬浮固体ASBR厌氧消化的工艺优化和反应器运行控制提供理论基础。

生物质垃圾悬浮有机固体含量高，与溶解性基质相比，悬浮有机固体水解速率慢，是有机物降解的限制因素。在ASBR反应器中，出水前使反应器内部的污泥和未降解的固体基质沉降富集在反应器底部，一方面减弱出水的微生物流失，另一方面也延长了固体基质的停留时间，从而获得较高的产气量。ASBR中固体截留效率与物料沉降性能密切相关。水热后的城市生物质废物进行ASBR厌氧消化，由于水热物料沉降性能的改善，反应器内污泥有效沉降，实现了大部分固体有机物被截留在反应器中，有效延长SRT和MCRT，有利于固体有机物的充分降解和微生物在反应器中的富集。当HRT为20天和13.3天时，两个ASBR反应器的VSS截留率分别为83%~89.6%和47.6%~75.9%，SRT/HRT分别为11~16和3~3.3，MCRT/HRT分别为2.1~2.2和1.4~1.6。相对于CSTR，ASBR反应器的废物处理速率提高了75%，容积产气速率提高了100%。ASBR反应器能够有效截留固体有机物，但反应内污泥浓度存在最大值，当反应器内污泥浓度过高时，沉降困难，易导致易降解固体有机物和微生物的流失。因此，需要控制反应器内的污泥浓度，才能保证反应器的稳定运行，提高反应器的厌氧消化效率。通过解析不同粒径固体有机物的去除规律，初步明确了优化和调控厌氧消化速率和效率的有效途径，可以判断在现有的破碎条件下（平均粒径<3 mm），厌氧消化过程中大颗粒有机物到小颗粒有机物的瓦解过程不是厌氧消化的限速步骤，小颗粒有机物、大分子有机物（<0.74 µm）水解为单分子有机物的过程为厌氧消化系统的限速步骤。通过分析厌氧系统微生物的种群，获得了在不同运行阶段和条件下的微生物种群结构特征。DGGE分析发现，随着反应器运行时间和条件的变化，厌氧污泥中真细菌、古菌的优势菌种均发生了一定的改变。