原位渗透脱水调控污泥含固率对FO-MBR厌氧消化效能的强化与作用机制

When treating sludge of high solid content, anaerobic digestion process has advantages of small reactor volume and high volumetrically methane production rate, but also shows a slow start-up, poor mass transfer and high energy consumption by mixing. To solve this dilemma, based on traditional anaerobic digestion process, a simultaneous removal of moisture from the system by forward osmosis (FO) in a FO-MBR process was proposed in this project. The simultaneous dewatering is to achieve the purpose of real-time regulating the solid content, and to solve the above-mentioned problems. In theory, the moisture removal process can make full use of the digestate heat, and less heat consumption would be needed to keep the system temperature constant. Literature digging shows that there is no similar research worldwide, making this project of practical significance and innovation. In this study, based on previous work, the relationship and interaction between the moisture production and each key parameter or performance indicator would be studied, such as energy consumption in mixing, mass transfer coefficient, volume sludge load, methane production rate, and the degradation rate of VS. And then optimization of key process parameters would be conducted. For the inhibitory and toxic substances to the process, such as trace organic pollutants, heavy metals, ammonia nitrogen, their distribution between liquid and sludge, as well as the accumulation mechanism is to be explored. The fouling potential of anaerobic digestion solution for forward osmosis membrane, as well as its main influencing factors, will also be studied. The completion of this research will lay a theoretical foundation for practical application of this novel anaerobic digestion process.

传统高含固率污泥厌氧消化虽容积负荷高，但以脱水污泥为进料导致启动慢、传质差、搅拌能耗高。本研究尝试构建正渗透膜生物反应器（FO-MBR）进行污泥厌氧消化，FO单元可原位脱除污泥水分以调控含固率实现高固污泥厌氧消化，具有膜污染轻、有机物降解率高、能耗低等显著优势，但FO-MBR中含固率与厌氧消化效能之间的关系等关键问题尚不明确。拟首先解析FO-MBR厌氧消化工艺在不同情形下含固率和固体停留时间对污泥流变性能和传质性能的影响，进而明确与微生物群落组成及有机物降解率、甲烷产率等主要效能指标之间的关系，建立FO-MBR污泥厌氧消化系统关键工艺参数间的协同优化策略；阐明系统内因FO膜的超高截留所致难降解有机物、重金属、自由氨等物质的累积分配与形态转化，及其对消化污泥颗粒形态、和系统效能的影响；明晰厌氧消化液对正向渗透膜的污染潜能及其主要污染物质。上述研究结果可为FO-MBR污泥厌氧消化强化工艺的应用研究奠定基础。

随着剩余污泥产量的日益增长，其处理处置对经济和环境均带来一定压力。对污泥进行厌氧消化处理能够在实现污泥稳定化的同时获得甲烷等资源而受到广泛的关注和研究。传统高含固率污泥厌氧消化虽容积负荷高，但以脱水污泥为进料导致启动慢、传质差、搅拌能耗高。本项目构建了具有一定创新性的正渗透膜生物反应器（FOMBR）进行污泥厌氧消化，正渗透（FO）单元可原位脱除消化污泥水分以调控含固率，从而实现污泥厌氧消化的动态调节。项目研究了含固率、有机负荷等工艺参数对系统效能的影响，研究结果显示，FOMBR可高效提升厌氧消化系统的含固率；与传统消化工艺相比，FOMBR可提升消化污泥流变性，提升VS降解率和甲烷产率，在较高含固率时搅拌能耗降低接近39%。针对FOMBR中盐反向渗透累积的问题，研究发现累积盐浓度较低时对污泥水解和酸化具有较为正面的影响，但盐度超过20~30 g/L时对于产甲烷阶段的不利影响严重。构建了流动电容去离子技术（FCDI）与FOMBR耦合工艺以降低反向渗透盐积累，优化了流动电极组成、FCDI膜材料、电压、流体流速等工艺参数，有效缓解了反应器内反向渗透所致的盐积累，并由此带来VS降解率和甲烷产率等多方面的优势。研究了FOMBR中多种重金属累积特征和赋存形态的变化，发现FOMBR使多种重金属赋存形态趋于稳定化，并阐明了FOMBR中高腐殖质含量使重金属稳定化这一重要机理。明晰了厌氧消化液对FO膜的污染潜能及其主要污染物质，研究了膜清洗策略及效果。另外，针对污泥水解效果较差的问题，项目还开展了利用生物膜载体强化污泥水解产酸的研究，优化了生物膜载体材料和投加量，揭示了生物膜载体强化污泥水解产酸的机理。上述研究结果可为FOMBR污泥厌氧消化强化工艺的应用研究奠定理论基础，为后续建设低碳、高效的污泥资源化工程提供支撑。