School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, Shaanxi Province 710055, China.
School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, Shaanxi Province 710055, China; School of Human Settlements and Civil Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi Province 712000, China.
Sci Total Environ. 2022 Mar 10;811:152413. doi: 10.1016/j.scitotenv.2021.152413. Epub 2021 Dec 16.
The removal of low molecular weight (MW) organics by coagulation is always a challenge in water treatment. In this study, we proposed a novel coagulation strategy: continuous dosing coagulation (CDC). The metallic coagulant and alkali were continuously dosed into water that was pre-acidized, rather than adding all the coagulant and alkali at once as in conventional coagulation (CC). The CDC process promoted the removal of different low MW organics, performing 15% better than the CC process. The best performance occurred at initial pH 6 and the coagulant dosing rate was 2 mg/(L·min). Under optimal conditions, the continuously dosed coagulant formed medium polymer Al in the early stages, which bound low MW organics to form complexes. Then, the subsequently dosed coagulant could adhere to the primary complexes and form coral reef-like surfaces with higher zeta potential and specific surface area. Each freshly formed surface bound contaminants and covered the previous surface. As a result, more dissolved low MW organic contaminants were included in the interior of flocs. However, in the CC process, all the coagulant was dosed at once, resulting in the rapid formation of aluminum hydroxide clusters, which had cotton-like surfaces with fewer binding sites. To achieve similar organic removal in treating secondary effluent, the CDC dosage was half of the CC dosage, indicating the potential economic benefits. The CDC process is a promising technology and the application in various water treatments should be further investigated.
在水处理中，去除低分子量（MW）有机物一直是一个挑战。在本研究中，我们提出了一种新型的混凝策略：连续投加混凝（CDC）。金属混凝剂和碱被连续投加到预先酸化的水中，而不是像传统混凝（CC）那样一次投加所有的混凝剂和碱。CDC 工艺促进了不同低 MW 有机物的去除，比 CC 工艺的去除率提高了 15%。在初始 pH 值为 6 和混凝剂投加速率为 2 mg/（L·min）时，效果最佳。在最佳条件下，连续投加的混凝剂在早期形成中等聚合度的 Al，与低 MW 有机物结合形成复合物。随后投加的混凝剂可以附着在初级复合物上，并形成具有更高动电电位和比表面积的珊瑚礁状表面。每个新形成的表面都会结合污染物，并覆盖之前的表面。因此，更多的溶解低 MW 有机污染物被包含在絮体的内部。然而，在 CC 工艺中，所有的混凝剂都是一次性投加的，导致迅速形成具有棉状表面和较少结合位点的氢氧化铝簇。为了在处理二级出水时达到类似的有机物去除效果，CDC 的投加量仅为 CC 的一半，表明其具有潜在的经济效益。CDC 工艺是一种很有前途的技术，应该进一步研究其在各种水处理中的应用。
