Abstract:

Membrane filtration is an efficient water treatment technology, which has been widely used in industrial wastewater treatment, domestic wastewater reuse and seawater desalination in recent years. However, the long-term operation of ultrafiltration can cause membrane fouling. This study used different forms of aluminum coagulants [Al₂(SO₄)₃, AlCl₃ or poly aluminum chloride (PAC)] to treat simulated raw water containing different dissolved organic matter (DOM) components (humic acid, bovine serum albumin and kaolin solution). Online coagulation combined with ultrafiltration was used to investigate the effects of different aluminum forms and components and their interactions on the ultrafiltration membrane fouling process were also studied. This study established a flow attenuation model to simulate the membrane fouling process. An infrared attenuated total reflection (IR-ATR) combined with multivariate curve resolution-alternating least squares (MCR-ALS) was used to qualitatively and quantitatively analyze various pollutants on the membrane. The results showed that both aluminum sulfate and aluminum chloride coagulants can significantly improve the membrane-specific flux and mitigate membrane fouling. The coagulant dosage was lower than the conventional treatment and significantly reduced membrane fouling. The coagulation effect of aluminum chloride was better when the dosage of AlCl₃ was 0.4mg/L. The coagulation effect of aluminum sulfate was better when the dosage was 2.4mg/L. Low dosage of PAC (0.2mg/L and 0.4mg/L) was not obvious to alleviate the degree of membrane fouling, but rather aggravate the membrane fouling. The fouling of ultrafiltration membrane by bovine serum albumin was more serious than humic acid because the presence of BSA greatly reduced the effect of coagulation and hindered the formation of the loose filter cake layer. When aluminum sulfate was added to the raw water, membrane fouling mainly occurred in the pre-filtration stage due to narrowing and clogging of the membrane pores. At the end of filtration, a loose cake layer was formed on the membrane surface, which had little effect on the membrane flux and membrane fouling was slowed down.

Key words: ultrafiltration membrane, membrane fouling, aluminum coagulant, infrared attenuated total reflection (IR-ATR), multivariate curve resolution-alternating least squares (MCR-ALS)

摘要：

超滤是一种高效的水处理技术，近年来被广泛应用于工业废水处理、生活污水回用、海水淡化预处理等领域。然而，超滤长期运行会造成膜污染。本文采用了在线混凝结合超滤工艺，使用不同形态的铝系混凝剂（硫酸铝、氯化铝或聚合氯化铝），处理含有不同溶解性有机质组分（腐殖酸、牛血清白蛋白和高岭土）的模拟原水，研究不同铝形态、不同组分及其相互作用对超滤膜污染过程的影响。本研究建立了流量衰减模型模拟膜污染过程，结合衰减全反射红外光谱（IR-ATR）和多变量曲线分辨-交替最小二乘法（MCR-ALS）的数据处理方法对膜上的多种污染物进行定性和定量分析。结果表明硫酸铝和氯化铝混凝剂均可明显提高膜比通量，减缓膜污染。该工艺混凝剂投加量低于常规处理工艺即可明显减缓膜污染。混凝剂投加量为0.4mg/L时，氯化铝混凝效果较好，混凝剂投加量为2.4mg/L时，硫酸铝混凝效果较好。低投加量（0.2mg/L、0.4mg/L）下，PAC对缓解膜污染程度不明显，反而加重膜污染。牛血清白蛋白对超滤膜的污染比腐殖酸严重。因为牛血清白蛋白的存在大大降低了混凝的效果，阻碍疏松滤饼层的形成。向原水中投加硫酸铝混凝剂，膜污染主要发生在过滤前期，即膜孔窄化、堵塞。过滤后期，膜表面形成疏松滤饼层，对膜通量影响不大，膜污染减缓。

关键词: 超滤膜, 膜污染, 铝系混凝剂, 衰减全反射红外光谱, 多变量曲线分辨-交替最小二乘法