正渗透膜-生物反应器支撑层污染机制研究

The fouling mechanism of supporting layer in novel forward osmosis membrane bioreactors (OMBR) during the application for wastewater treatment is firstly proposed in this project. The main contents are as follows: Firstly, the synergistic effect between draw solution and membrane foulants will be analysed to investigate the effects of reverse draw solute on the supporting layer fouling; Secondly, the methods such as gel filtration chromatography, fourier transform infrared spectrum and three-dimensional excitation-emission matrix fluorescence spectroscopy etc. will be adopted to intensively investigate the properties of activated sludge and dissolved organic matters of OMBR system. The connection between the characterizations of mixed liquor and supporting layer fouling is going to be found, and the priority foulants will be identified. The mechanism of supporting layer fouling is supposed to be figured out in this project; Thirdly, the pilot-scale OMBR will be established to study the effects of the operation condition, such as membrane orientation, aeration intensity, cross-flow velocity of draw solution etc. on the supporting layer fouling potential; Finally, the membrane fouling performance of OMBR is monitored under the long-term operation. The supporting layer fouling properties and microbial diversity under the elevated salt condition is systematically investigated, and the dominant microbial community in the pore and surface of supporting layer is identified. This research is aim to figure out the fouling mechanism of supporting layer during the application of OMBR for wastewater treatment and provide the theory basis for the practical application of OMBR.

本项目对正渗透膜-生物反应器（OMBR）技术在污水处理中应用时支撑层污染机制进行系统研究。分析不同种类驱动液与膜污染物的协同作用，探究驱动液的逆向渗透对支撑层污染机制带来的影响；利用傅立叶红外光谱、凝胶色谱、三维荧光光谱等方法，对OMBR系统中活性污泥及溶解性物质性质进行深入分析，建立混合液性质与支撑层污染之间的本质联系，揭示系统支撑层污染机制，识别优先污染因子；建立现场OMBR小试装置，考察膜朝向、曝气强度、驱动液循环速率等运行参数对支撑层污染趋势的影响；对长期运行的OMBR系统支撑层污染性能进行监测，考察高盐度环境下支撑层污染特性，并对高盐情况下系统微生物菌群多样性进行分析，鉴定优势污染菌群，阐明支撑层孔内及表面生物污染特性。本项目旨在深入研究OMBR中正渗透膜支撑层污染机制，为OMBR技术在污水处理领域的实际应用提供理论依据。

本研究借助一套正渗透膜评价装置和两套不同泥龄下运行的正渗透膜生物反应器，对正渗透膜的基本性能和处理生活污水时支撑层污染机制进行探讨。主要表征了正渗透膜基本性能参数，重点研究了膜朝向、汲取液种类、汲取液浓度和膜面错流速率流速四个因素对去离子水为原料液时的正渗透过程的影响规律。确立了错流速率、清洗时间和清洗剂种类对膜通量恢复情况的相对最佳选择。以此确定了正渗透膜反应器长期运行的操作条件和膜清洗的操作条件，监测并分析了正渗透膜反应器长期运行对有机物、营养盐的去除能力等指标，污泥性质的变化和支撑层污染物组成。.通过比较实验，确立了膜生物反应器运行膜朝向为AL-FS，这在长期运行中具有更高的出水通量和较低的膜污染水平。结果表明最佳正渗透膜操作条件为汲取液为0.5mol/L的NaCl溶液，错流速率为10cm/s。膜清洗条件则为1%Alconox在20cm/s的错流速率下清洗30min。.在FOMBR运行过程中，发现对CTA膜高锰酸钾指数和总磷的截留率较高，分别达到了86.2%和接近100%。对氨氮的截留效率最低，仅为52.1%。接近稳定运行时，反应器的水通量在2.5 L/(m2h)左右，而反应器内TDS为5.46~8.59g/L。FOMBR运行过程中，支撑层膜污染的清洗的效率并不高，恢复至初始水通量的56.7%和61.0%，可见不可逆污染在整个膜污染中占据了不少的比重。活性污泥在整个运行过程中逐渐被驯化，SS和VSS由启动时的迅速下降至趋于稳定和微小的回升。细胞活性受到盐分的干扰有所降低，EPS分泌减少，SMP整体保持稳定。FOMBR过程运行结束时，通过SEM观测和EDX分析显示，膜表面的污染物以有机物为主，无机污染物中Si、Al、Fe、Ca、Mg等元素占据主要部分。.CTA和TFC正渗透反应器长期浓缩生活污水时，对原料液COD和TP的截留率较高，均大于99%；但对NH4+-N和TN的截留率较低。卷式CTA正渗透膜反应器稳定运行时，水通量维持在 (6.3±0.6) L/(m2h)，盐通量为 (5.0±0.7) g/(m2h)。浓缩液水质COD、NH4+-N、TN、TP浓度分别为 (568±58) mg/L、(44.5±4.5) mg/L、(74.7±4.8) mg/L和 (18.3±1.4) mg/L。该项目研究结果表明正渗透膜分离技术用于实现生活污浓缩具有很好的应用前景。