Mechanism on the effects of floc aging and pH adjustment on reflux feed water and coagulation
YU Jun-jie1,2,3, XU Hui1,3, SUN Hong-yan4, JIN Zhi-yuan1,2, WANG Dong-sheng3,5
1. State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; 2. College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China; 3. Yangtze River Delta Branch, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Jinhua 322000, China; 4. School of Environmental and Chemical Engineering, Foshan University, Foshan 528000, China; 5. College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China
Abstract：Effects of floc aging and pH adjustment on the particle composition and coagulation of the reflux water were investigated using laser particle size analyzer, and the mechanisms of aging and pH adjustment on floc properties were explored by the aging experiments of Al(OH)3 gel (Al-gel). The results showed that the particle size of raw water displayed a unimodal distribution, and the particle size of the influent flocs presented a bimodal distribution. Meanwhile, there was a decrease of the particle d50 of reflux water with the increase of aging time. The growth rate of the flocs increased as the reflux flocs that were subjected to reflux coagulation after being aged at pH=5 for 12h had the highest floc d50 growth rate (1.16μm/s) and produced the flocs with a higher fractal dimension (2.35). The results of Al-gel aging experiment demonstrated that hydroxyl-bridging and crystallization reactions occurred during aging, leading to a reduction in the number of reactive groups on the floc surfaces, which was not conducive to the interaction with raw water particles. The pH adjustment had different effects on the flocs. For example, the aging at pH=5accelerated the hydroxyl-bridging and crystallization reactions, while the aging at pH=9 may involve dissolution-precipitation-crystallization interactions.
庾俊杰, 徐慧, 孙鸿燕, 金之源, 王东升. 絮体老化与调节对回流进水及混凝的影响机制[J]. 中国环境科学, 2022, 42(10): 4612-4620.
YU Jun-jie, XU Hui, SUN Hong-yan, JIN Zhi-yuan, WANG Dong-sheng. Mechanism on the effects of floc aging and pH adjustment on reflux feed water and coagulation. CHINA ENVIRONMENTAL SCIENCECE, 2022, 42(10): 4612-4620.
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