Yan Mingquan, Wang Dongsheng, Shi Baoyou, Wang Min, Yan You
Department of Environmental Engineering, College of Environmental Sciences, Peking University, Beijing, China.
Chemosphere. 2007 Nov;69(11):1695-702. doi: 10.1016/j.chemosphere.2007.06.014. Epub 2007 Jul 17.
Although ozone is widely used as a pre-oxidant before coagulation in water treatment, the effect of pre-ozonation on optimized coagulation for removal of particle and natural organic matter (NOM) is still not fully understood. In this paper, pilot-scale investigation was conducted to examine the impact of pre-ozonation on coagulation for particle and NOM removal. Changes in the particle and NOM distributions were characterized by various methods, including laser light granularity system, particle counter, ultrafiltration, and resin absorbent fractionation. A novel composite flocculant-HPAC was compared with the traditional ferric chloride coagulant in terms of coagulation efficiency under the influence of pre-ozonation. Typical micro-polluted North China surface water was used for pilot coagulation tests. The results show that the effect of pre-ozonation on coagulation is associated with the dosage of ozone, coagulant type, and water contamination characteristics. For FeCl(3), pre-ozonation acts as a coagulation aid at low dosage (1.0 mg L(-1) O(3)) for turbidity and UV(254) removal; while at higher dosage (2.0 mg L(-1) O(3)), pre-ozonation is detrimental to UV(254) removal although it is still beneficial for turbidity removal. In the case of composite flocculant-HPAC, pre-ozonation demonstrates negligible influence on both turbidity and UV(254) removal. Ozone can simultaneously aggregate fine particles and break down large ones, making them more mineralized and easier to remove. NOM with intermediate molecular weight and hydrophobic neutral property increases at lower ozone dosage, favoring removal by coagulation. At higher ozone dosages, NOM becomes more hydrophilic and its molecular weight becomes smaller, decreasing NOM removal.
尽管臭氧在水处理中作为混凝前的预氧化剂被广泛使用，但预臭氧化对去除颗粒和天然有机物（NOM）的优化混凝效果仍未得到充分理解。本文进行了中试规模的研究，以考察预臭氧化对去除颗粒和NOM的混凝效果的影响。通过多种方法对颗粒和NOM分布的变化进行了表征，包括激光粒度系统、颗粒计数器、超滤和树脂吸附剂分级。在预臭氧化的影响下，将一种新型复合絮凝剂-HPAC与传统的氯化铁混凝剂在混凝效率方面进行了比较。采用典型的华北地区微污染地表水进行中试混凝试验。结果表明，预臭氧化对混凝的影响与臭氧剂量、混凝剂类型和水污染特性有关。对于FeCl₃，低剂量（1.0 mg L⁻¹ O₃）的预臭氧化对去除浊度和UV₂₅₄起到助凝作用；而在高剂量（2.0 mg L⁻¹ O₃）时，预臭氧化虽然对去除浊度仍然有益，但对去除UV₂₅₄是有害的。对于复合絮凝剂-HPAC，预臭氧化对去除浊度和UV₂₅₄的影响均可忽略不计。臭氧可同时使细颗粒聚集并分解大颗粒，使其更易矿化且更易于去除。较低臭氧剂量下，中等分子量和疏水中性性质的NOM增加，有利于通过混凝去除。在较高臭氧剂量下，NOM变得更亲水且分子量变小，导致NOM去除率降低。
