臭氧-混凝耦合工艺污水深度处理特性及其机制

针对传统混凝工艺对溶解性有机物去除效果有限的问题,本文利用臭氧-混凝耦合工艺对污水处理厂二级出水进行深度处理.与相同混凝剂投量下的预臭氧-混凝工艺和传统混凝工艺相比,该耦合工艺处理效果明显优于预臭氧-混凝工艺和传统混凝工艺的处理效果.在两种pH条件下耦合工艺对溶解性有机污染物的去除率最大,分别为37.96%和39.66%.为了进一步明确该耦合工艺去除溶解性有机物的机制,测定了两种pH和有无混凝剂Al Cl3·6H2O存在时对臭氧衰减的影响,结果表明较高的pH和有混凝剂存在时都能够加快臭氧的分解速度.同时,选择羟基自由基(·OH)的指示剂对氯苯甲酸(p-CBA)间接计算了·OH的暴露量,结果表明耦合工艺中存在涉及·OH产生的高级氧化机制,而混凝剂可以提高臭氧化工艺中·OH的产量.当混凝剂与臭氧接触后,铝系混凝剂及其水解产物将作为催化剂促进臭氧分解为氧化能力更强的·OH,强化臭氧化效果,提高溶解性有机物的去除效率.

Characteristics and Mechanism of Hybrid Ozonation-Coagulation Process in Wastewater Reclamation

Because of the limited dissolved organic matter removal efficiency in conventional pre-ozonation-coagulation process, the hybrid ozonation-coagulation (HOC) process was developed for wastewater reclamation in this study. In this process, coagulation and ozonation could synchronize within a single unit. Compared with the pre-ozonation-coagulation process and traditional coagulation process at the same coagulants dosage, the HOC process exhibited higher treatment efficiency, especially better organic matter removal performance at each pH value, which were 37.96% and 39.66%, respectively. In order to obtain the removal mechanism of dissolved organic matters by HOC process,ozone decomposition at two pH values either with or without AlCl₃·6H₂O was monitored in this study. The results showed that higher pH and the addition of coagulant could accelerate ozone decay. In addition, para-chlorobenzoic acid (p-CBA) was chosen as the hydroxyl radical (·OH) probe compound to indirectly calculate the ·OH exposure. The results revealed that the HOC process was involved in ·OH reaction and coagulant could promote ozone decomposition due to its enhancing effect on ·OH production during the ozonation process. Furthermore, the ozone depletion occurred more quickly at high pH due to its reaction with hydroxide ions (OH^-), leading to the formation of ·OH through a series of chain reactions. Moreover, the effects of tert-butanol, a well-known ·OH inhibitor on ozone decay and p-CBA decomposition were also investigated. The results indicated that ozone depletion and p-CBA decomposition were significantly inhibited by tert-butanol, which further proved that ozone was decomposed into ·OH radicals through chain reactions. In the HOC process, Al-based coagulants and hydrolyzed products could act as catalysts to enhance ozone decomposition into ·OH which is a powerful oxidant to improve the organics removal efficiency.