基于能量解偶联的重力流膜生物反应器滤饼层调控与通量提高研究

Membrane bioreactor (MBR) is a promising technology for decentralized small-town wastewater treatment due to its small foot print and high removal efficiency. MBR system usually includes backwash, physical cleaning and chemical cleaning as well as auxiliary automatic control equipment, and these complicated operations and facilities would limit its application to the decentralized wastewater treatment. We developed a gravity-driven membrane bioreactor (GDMBR) system, which was allowed operation under low pressure without any backwash, physical cleaning and chemical cleaning. The flux can be stable at 2 L/m2h for a long period. However, the low flux would become an obstacle for GDMBR wide application. In order to address this, we will introduce energy uncoupling technology in this project for the control of physiological properties of suspended sludge as well as the structures of bio-fouling layer adhered on the membrane surface, and then increase the permeate flux. The main line of the project is: after adding the energy uncoupler, analyze the fate of the uncoupler in GDMBR system — evaluate the physiological properties of suspended sludge — assess the structures and properties of bio-fouling layer attached on the membrane surface. Determine the sludge yields, autoinducer-2 (AI-2) concentrations, ATP contents and EPS contents. Characterize the morphology and structure of the bio-fouling layer by advanced optical coherence tomography (OCT) and confocal laser scanning microscope (CLSM). Based on the analyses and characterizations, obtain the mechanisms of energy uncoupling technology improving the permeate flux of GDMBR system. The results of this study can provide theoretical and technical supports for the application of MBR process to small-town wastewater treatment.

膜生物反应器（MBR）占地面积小和除污染效率高，是解决小城镇分散式污水处理与回用的重要技术。MBR系统包括反冲洗和膜清洗等附属自控设备，过于复杂的系统影响其在分散式污水处理的应用。为此，申请人前期研究无反冲洗和无物理化学清洗特点的低压式重力流膜生物反应器（GDMBR），膜通量能长期稳定在2L/m2h，然而过低的通量限制该技术的应用。课题拟引入能量解偶联技术调控污泥的理化性质和膜表面生物滤饼层的结构，达到膜通量提高的目的。通过解偶联剂的投加，以GDMBR中解偶联剂的迁移转化—悬浮污泥的活性调控—膜表面生物滤饼层的功能解析为研究主线，测定污泥产率、信号分子浓度、ATP含量和胞外聚合物含量等理化指标，利用光学相干断层扫描仪和激光共聚焦扫描显微镜表征生物滤饼层的结构和形态，进一步揭示能量解耦联技术对膜通量提升的具体作用机理。课题研究成果将为MBR工艺在小城镇污水处理的应用提供理论依据和技术支持。

重力流膜生物反应器（GDMBR）工艺由于具有除污染效率高、能耗低（重力低水头）、易维护（无反冲洗、无物理和无化学清洗）和膜通量长期可稳定等特点，适合小城镇分散式污水处理与回用领域。然而，稳定时的膜通量较低（1-2 L/m2h），限制了其广泛应用。本项目分别引入生化（能量解偶联）和物化（化学混凝）手段，调控污泥的理化性质和膜表面生物滤饼层的结构，达到缓解膜污染和提高膜通量的目的。项目主要：（1）探索了解偶联剂DNP对超滤过滤污泥初期的影响，发现了DNP可将污泥产率降低37.5%；投量过低会释放更多SMP从而加重膜孔堵塞污染，而提高投量会抑制污泥EPS含量，无法形成生物滤饼层，进而缓解超滤膜污染。（2）明确了解偶联剂TCS对GDMBR污泥原位减量的机制，在于污泥EPS含量降低、絮体解体、且胞内物质并没有释放。（3）揭示了适量TCS可提高稳定时膜通量的机理，主要由于膜表面形成了较薄的、非均相的、且EPS含量较少的生物滤饼层，膜污染水力可逆阻力和滤饼层阻力可减少50%。（4）同时还发现，TCS投量较低时不会影响GDMBR对有机物的去除效率，而过量投加会加速溶解性芳香类蛋白质、色氨酸类蛋白质和小分子的腐殖质类物质的释放，进一步恶化水质。（5）探讨混凝预处理和原位混凝对GDMBR膜通量提高的可行性；发现了原位混凝可显著提高膜通量（>两倍），但通量不能达到稳定的现象；而预混凝作用下，膜通量提高程度不如原位混凝，但通量可长期达到稳定；揭示了混凝强化过程提高膜通量的机理：即混凝强化作用与膜表面生物滤饼层性质（厚度、表面粗糙度、孔隙率和EPS含量）的内在联系。综上，利用GDMBR处理分散式污水的设计中，采用混凝强化调控，需要明确投加方式；采用解偶联生物调控，需要优化解偶联剂的投量，实现同步污泥减量和膜污染缓解目的。本项目的研究成果可以为膜技术在小城镇污水处理与回用领域提供理论依据和技术支持。