Safaee Helia, Bracewell Alan, Safarik Jana, Plumlee Megan H, Rajagopalan Ganesh
Kennedy Jenks Consultants, 3200 El Camino Real, #200, Irvine, CA 92602, United States.
Orange County Water District, 18700 Ward St., Fountain Valley, CA 92708, United States.
Water Res. 2022 Jun 15;217:118300. doi: 10.1016/j.watres.2022.118300. Epub 2022 Mar 16.
Fouling of microfiltration (MF)) membranes during water/wastewater treatment is predominantly caused by colloidal particles (size <1 µm) in the feed water. Until recently no online technology was available to directly measure the occurrence of colloidal particles in these waters. This study evaluated the viability of a novel online light scattering technology (Nanoparticle Tracking Analysis) to continuously monitor colloidal particles in the membrane feed water (a secondary-treated wastewater) for targeted removal by injecting coagulant at a dosage proportional to the measured concentration of colloidal particles. A diurnal variation was observed in the colloidal particle concentration in the feed water with the lowest concentration occurring at approximately 6 am and the highest concentration occurring after mid-day. The peak colloidal particle concentrations were 4 to 6 times higher than the lowest concentrations measured on the same day. Bench-scale studies were performed to develop a relationship between colloidal particle concentration and the optimum coagulant dosage required for their removal. Subsequently, a pilot-scale study was performed using two MF pilot units operated in parallel, one receiving targeted coagulant dosing and the other with no coagulant dosing, to demonstrate the effectiveness of targeted coagulant dosing in preventing membrane fouling. The pilot unit that received targeted coagulant dose experienced only 4 to 20% of the transmembrane pressure increase of the increase experienced by the pilot unit that received no coagulant. Evaluation of fouling resistance indicated that targeted coagulation improved flux by predominantly lowering the irreversible fouling. The filtrate water quality measured by colloidal particle concentration, chemical oxygen demand (COD), and turbidity were very similar for the two pilot units. This suggests that although the efficiency of particle and organic materials removal does not change with coagulant addition, the particles filtered by the membrane in the control unit contributed to membrane irreversible fouling, while in the coagulant-treated unit, the coagulated colloidal particles were removed away from the membrane into the backwash stream during the frequent backwash/air scour procedures.
在水/废水处理过程中，微滤（MF）膜的污染主要是由进水口的胶体颗粒（尺寸<1微米）造成的。直到最近，还没有在线技术可用于直接测量这些水体中胶体颗粒的存在情况。本研究评估了一种新型在线光散射技术（纳米颗粒跟踪分析）的可行性，该技术通过以与测量的胶体颗粒浓度成比例的剂量注入混凝剂，来持续监测膜进水口（二级处理后的废水）中的胶体颗粒，以实现有针对性的去除。观察到进水口胶体颗粒浓度存在日变化，最低浓度出现在大约上午6点，最高浓度出现在中午之后。胶体颗粒的峰值浓度比同一天测量的最低浓度高4至6倍。进行了实验室规模的研究，以建立胶体颗粒浓度与去除它们所需的最佳混凝剂剂量之间的关系。随后，进行了中试规模的研究，使用两个并联运行 的MF中试装置，一个接受有针对性的混凝剂投加，另一个不投加混凝剂，以证明有针对性的混凝剂投加在防止膜污染方面的有效性。接受有针对性混凝剂投加的中试装置的跨膜压力增加量仅为未接受混凝剂投加的中试装置所经历增加量的4%至20%。对抗污染性的评估表明，有针对性的混凝主要通过降低不可逆污染来提高通量。两个中试装置通过胶体颗粒浓度、化学需氧量（COD）和浊度测量的滤液水质非常相似。这表明，虽然添加混凝剂不会改变颗粒和有机物质的去除效率，但在对照装置中被膜过滤的颗粒会导致膜的不可逆污染，而在经过混凝剂处理的装置中，在频繁的反冲洗/气洗过程中，凝结的胶体颗粒会从膜上被去除并进入反冲洗水流中。
