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与传统活性污泥法处理系统相比, MBR具有占地面积小、处理效率高、脱氮效果好的优势[1-2],在水处理领域受到越来越多的关注。然而,高TMP增长和因膜污染导致的运行成本增加、维护难度增大问题,已成为 MBR推广应用的主要障碍[3-4]。目前,研究人员已探索出多种控制膜污染的策略,如优化运行条件(包括调整曝气策略、间歇抽吸、定时反冲洗等),在反应器中投加生物载体以改善污泥性能等。活性炭具有吸附性好、比表面积大等优势,同时目前研究表明,在MBR中添加活性炭能有效减缓膜污染[5],延长MBR的运行周期。
根据现有研究,在生物反应器中添加活性炭可能会产生以下影响:1)冲刷膜表面,对滤饼层形成有抑制效果[6];2)吸附作用可降低上清液中溶解性有机物(如SMP(soluble microbial products)和EPS)的质量浓度[7];3)增强活性污泥的聚集,改变污泥絮体的粒径分布,使其尺寸更大[4]。但是,活性炭的投加会对有机高分子膜表面造成损伤,因此在传统有机膜MBR中较少使用。平板陶瓷膜具有使用寿命长,化学、机械和热稳定性好的优点,在MBR中展现出较好的应用前景[8-9]。然而,关于活性炭粒度对平板陶瓷膜MBR膜污染的影响还少有研究。
针对以上问题,本论文从TMP增长速率、污泥混合液EPS含量、污泥粒径、滤饼层形貌、微生物种群等方面展开了系统研究,阐释了PAC和GAC在MBR运行过程中对膜污染控制和除污染效能的影响,研究结果可为平板陶瓷膜MBR的有效应用提供理论和技术支持。
平板陶瓷膜MBR膜污染优化控制—活性炭粒径的影响
Effective control of membrane fouling in MBR with flat-sheet ceramic membrane—Effect of particle size of activated carbon
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摘要: 采用机械强度高、耐刮擦性能好的平板陶瓷膜,构建了膜生物反应器(MBR)城市污水处理系统,对比研究了颗粒活性炭(GAC)和粉末活性炭(PAC)在膜污染控制与污染物去除中的作用。结果表明,GAC组在运行初期由于颗粒炭较强的刮擦作用表现出较好的膜污染减缓效果,跨膜压(TMP)增长速率降低17%,但中后期效果不明显。PAC组在运行中后期展现出明显的抗污染优势,TMP增速降低了28%。机理分析结果表明,PAC组混合液中胞外聚合物(EPS)含量降低了49%,污泥絮体平均粒径增大了102 μm。此外,PAC的投加使得MBR总氮(TN)去除率提升了17%,COD去除率也有所提高。研究结果为平板陶瓷膜MBR膜污染的优化控制与高效运行提供了技术支持。Abstract: Membrane bioreactor (MBR) was constructed for municipal wastewater treatment using flat-sheet ceramic membrane with high mechanical strength and excellent scrabbing resistance, and the roles of granular activated carbon (GAC) and powdered activated carbon (PAC) in membrane fouling control and pollutant removal were comparatively studied. The results showed that GAC exhibited a better fouling mitigation effect in the early stage of MBR operation due to its stronger scrabbing on membrane surface, and the growth rate of transmembrane pressure (TMP) decreased by 17%, but the fouling mitigation effect of GAC was not obvious in the middle and later operation stages. In comparison, PAC displayed a significant advantage in membrane fouling control during the middle and later operation stages, the TMP growth rate decreased by 28%. Mechanism analyses showed that the extracellular polymeric substances (EPS) content in the mixed liquor of PAC-MBR was decreased by 49%, while the average size of activated sludge flocs increased by 102 μm. Moreover, the addition of PAC in MBR increased the total nitrogen (TN) removal by 17%, the removal rate of COD also increased. The results of this study provide a technical support for the effective membrane fouling control and efficient operation of MBR with flat-sheet ceramic membranes.
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表 1 膜污染速率比较
Table 1. Comparison of membrane contamination rates (kPa·d)−1
阶段 空白 PAC GAC 第1阶段 10.23 6.87 5.70 第2阶段 4.96 3.64 4.85 第3阶段 32.61 23.20 31.58 表 2 不同样品多样性指数统计表
Table 2. Statistics of diversity indices of different samples
样品 序列数 OTUs Shannon Chao Simpson Shannoneven 覆盖率 空白 381 69 740 4.78 764.1 0.045 63 0.724 2 0.998 7 PAC 308 27 721 5.31 738.2 0.017 39 0.806 6 0.998 6 GAC 336 50 695 4.85 769.6 0.020 46 0.741 3 0.997 0 -
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