沼渣水热生物炭促进猪粪厌氧发酵中气态砷释放的作用过程及机理

Effective removal of arsenic in digested manure slurry (DMS) needs urgent solutions in its innocent treatment. Physical and chemical aftertreatments of DMS are inefficient and costly, which cause much secondary pollution. Addition of hydrochar can regulate AsH3 generation and arsenic methylation during anaerobic digestion, which enhance arsenic removal from DMS in situ by volatilization of arsine. This provides an inspiring and innovative idea and method to decrease arsenic content in DMS. This project aims to illustrate the promotion effect and mechanism of volatile arsenic generation in hyrochar-pig manure anaerobic digestion system. Based on the results of previous work, this project will be conducted using hydrochar produced from solid digestate in bench-scale mesophilic digestion of pig manure. Advanced techniques and methods, e.g., two-phase fermentation technology, purging capture-gas chromatography/inductively coupled plasma-mass spectrometry (PT-GC/ICP-MS) system, liquid chromatography-hydrate generation-atomic fluorescence spectrometry (LC-HG-AFS) system, scanning electron microscope-energy dispersive spectrometer (SEM-EDS), molecular biology and high-throughput sequencing technology, synchrotron radiation technique (extended x-ray absorption fine structure, EXAFS), are used to study the release characteristics and generation process of AsH3 and arsenic methylation after hydrochar addition in anaerobic digestion system. And on this basis, trophic link between functional microflora and microbial immobilization are further analyzed to reveal the regulation mechanism of hydrochar. These results will provide a feasible treatment approach to effectively remove arsenic from digested slurry and help to control arsenic pollution to soil and food after land use of digested slurry. This project has a fundamental theoretical significance and practical value for arsenic treatment in situ.

畜禽粪便沼液中砷的有效去除是其无害化处理过程中亟待解决的问题。将沼液进行物理或化学后处理，不仅效率低、成本高，而且产生大量的二次污染。在发酵过程中添加沼渣水热生物炭，能促进砷以气态形式释放出沼液，这为沼液中砷的“原位”削减提供了启发性的新思路和可行的新方法。本项目在前期工作的基础上，拟通过室内模拟猪粪中温厌氧发酵试验，利用厌氧两相发酵工艺、分子生物学和高通量测序、吹扫捕集-气相色谱/电感耦合等离子体质谱仪、液相色谱-氢化物发生-原子荧光联用技术、扫描式电子显微镜-X光微区分析、同步辐射等先进有效的手段和技术，探讨沼渣水热生物炭介导下猪粪中温厌氧发酵中AsH3和甲基砷化合物的释放特征和产生过程，重点解析功能菌群间互营关系和微生物固定作用对此过程的驱动机理，为沼液中砷的高效去除提供可行的技术手段，对沼液的资源化和无害化利用有十分重要的理论意义与实践价值。

畜禽粪便沼液中砷的有效去除是其无害化处理过程中亟待解决的问题。将沼液进行物理或化学后处理，不仅效率低、成本高，而且产生大量的二次污染。在发酵过程中添加沼渣水热生物炭，能促进砷以气态形式释放出沼液，这为沼液中砷的“原位”削减提供了启发性的新思路和可行的新方法。本项目通过室内模拟猪粪中温厌氧发酵试验，利用厌氧两相发酵工艺、分子生物学和高通量测序、吹高效液相色谱-电感耦合等离子体质谱仪（HPLC-ICP-MS）、扫描式电子显微镜-X光微区分析（SEM-EDS）等先进有效的手段和技术，探讨沼渣水热生物炭介导下猪粪中温厌氧发酵中甲基砷化合物的产生特征和作用过程，解析功能菌群间互营关系和微生物固定作用对此过程的驱动机理。研究结果：（1）探明了沼渣水热炭材料中As等金属的浸出特征，明确了猪粪和奶牛粪沼渣水热炭材料在厌氧消化体系中的吸附性和安全性；（2）厌氧条件下水热炭添加强化了ROX的甲基化，即ROX首先转化为无机态的As，进而转化为As(III)，并通过微生物的甲基化过程转化为一甲基砷（MMA）和二甲基砷（DMA）；约20—30%ROX随着生物甲基化过程运移到系统外，从而降低了残留砷的含量；（3）水热炭添加后厌氧消化体系中小颗粒含量降低，DOM含量增加，胶体含量和稳定性大幅提高，主要归因于水热炭促进了厌氧微生物的活性，具有较大的比表面积和丰富的表面功能基团，微生物的代谢产物与粪便中的大量铁、锰、铝、硫、氯等元素和生物炭结合，这对砷的吸附和进一步甲基化转运具有积极的作用；（4）添加猪粪水热炭后显著增加了影响厌氧产甲烷过程的微生物菌群多样性，显著（P<0.05）促进瘤胃球菌属（Ruminococcaceae sp.）、拟杆菌属（Bacteroides sp.）与Sphaerochaeta sp.属和Proteiniborus sp.的生长，甲烷粒菌属含量增加，特别是在水热炭添加量大的处理中增幅明显。这些菌群与MMA和DMA呈正相关关系，明确了水热炭添加介导的微生物群落结构变化对As甲基化转运的促进机制。