陶瓷膜MBR耦合生物电化学过程的原位膜污染控制系统与机制研究

Membrane fouling is the main obstacle for membrane bioreactor (MBR) effectiveness and widespread application. Recent reports had revealed that applied electric field or bio-electrochemical MBR could mitigate membrane fouling in a certain level. However, owing to the lack of scientific consensus on major foulants identification, membrane fouling behavior and control mechanisms, it is difficult to eventually control fouling occurrence in an MBR. Based on ceramic membrane own merits, including intrinsic hydrophilic and high modifiable surface morphological properties, which could be modified into high conductivity and selectivity by using ionic liquid polymerization and solidification, and surface morphological optimization, an electrochemical ceramic membrane bioreactor (E-CMBR) with stably effective electricity and hydrogen peroxide generation could be developed. Micro-particle image velocimetry (micro-PIV) will be employed to help visualize and investigate the impact of applied electrical field to the deposition possibility of sludge flocs particles onto membrane surface. The major foulant in E-CMBR retained by ceramic membrane will be identified, which would not be formed without continuous sludge particles deposition on the membrane surface, or be destructed or eliminated by generated hydrogen peroxide in E-CMBR cathode. Therefore, its membrane fouling will be eventually minimized or controlled, and then a high membrane flux driven by a relative low-pressure will be stably obtained in the system. Afterwards, several typical persistent organic pollutants are expected to be accumulated on membrane surface and then enhanced decomposed by generated hydrogen peroxide in E-CMBR. Accordingly, the cost-energy-effectiveness and stability of the established E-CMBR system will also be evaluated. The obtained results in this project will be very useful to understand ceramic membrane-based system and its filtration mechanisms, and is also important to break the bottleneck during its application in wastewater treatment, energy recovery and utilization.

膜污染是限制膜生物反应器（MBR）效能与应用的主要原因，研究表明外加弱电场或生物电化学MBR可一定程度地缓解膜污染。然而，由于在主要膜污染物质、膜污染行为与控制机制等方面未得到共识，目前仍较难实现膜污染的根本性控制。本申请利用咪唑类离子液体聚合物对表面亲水与形貌可控的陶瓷膜进行导电改性与布局优化，将其作为阴极耦合生物电化学过程，构建稳定高效产电与产H2O2的E-CMBR系统。利用显微粒子测速技术解析外加弱电场对絮体颗粒在膜表面沉积的影响机制。识别E-CMBR中的主要膜污染物质，利用阴极产H2O2对其靶向破坏或去除，结合内生电场降低絮体颗粒沉积效应，实现动态条件下膜污染的根本性控制与系统在低外压驱动下的稳定高通量运行。探索共存难降解物质在膜表面富集与被H2O2强化去除行为，评价系统的稳定性与综合效能。课题的开展可望深入认知陶瓷膜分离行为，突破其在污水处理、能源回收与利用中的技术瓶颈。

膜污染是限制膜生物反应器（Membrane Bioreactor，MBR）效能与应用的主要原因。电化学过程可在一定程度上缓解膜污染，本研究对基膜进行导电改性，并利用改性膜构建外加电场作用下的好氧MBR、厌氧MBR和MFC-MBR装置，考察其运行效能和膜污染缓解机制。通过对比各改性方式及改性掺杂材料，发现离子液体BVIMBF4掺杂导电聚合物单体吡咯进行原位氧化聚合的导电改性方法最为稳定，因此在该条件下对有机PVDF膜及无机陶瓷膜进行了导电改性。改性后膜的表征结果表明，在中性及酸性条件下导电膜性能稳定，其通量下降率较基膜减少30%，膜孔径和孔隙率与基膜相当。改性膜的抗污染效果、亲水性、导电性和截留效果均大幅提高。随后将导电膜应用在好氧MBR中，实验表明外加电场MBR具有较高的污染物去除率，出水COD和NH4+-N的去除率均可达到93%。为减小外加电场导致的能源消耗，构建了MFC-MBR系统以利用污水中微生物原位产电，结果表明在不影响出水水质的基础上实现了对膜污染的控制，有效延长了膜的运行周期。此外，考察了弱电场对AnEMBR的作用规律，结果显示当通入间断式（2 min/10 min）时1 V/cm电压时，AnEMBR具有最佳的出水水质和产甲烷速率，而且外加电场可以显著促进厌氧产甲烷菌的代谢活性。弱电场作用下，牺牲阳极（铁）比惰性阳极（石墨）更适合MBR中污染物的去除,这是因为活泼金属为阳极时，增强的静电斥力和释铁絮凝作用可以共同发挥污染物排斥作用。外加电场显著地缓解膜污染的原因在于：改性陶瓷膜与污泥界面能显著升高，而且电泳作用最大提供了2.42 L/（m2•h）的等值反冲洗当量。MBR中污泥性质也发生了有利于污染控制的改变，如污泥粘度降低、污泥粒度均匀性提高、表面Zeta电位增大、污泥SMP、EPS含量显著降低、PN/PS比值下降等。综上，外加电场能够同步实现导电陶瓷膜生物反应器污染物高效降解与膜污染控制，对MBR技术的推广应用具有重要意义。