Kim H, Kwon S, Han S, Yu M, Kim J, Gong S, Colosimo M F
The University of Seoul Dept. of Environmental Engineering, Seoul, South Korea.
Water Sci Technol. 2006;53(6):145-51. doi: 10.2166/wst.2006.188.
Due to its efficiency and low capital demands, chlorination has been widely used for disinfection in many wastewater treatment plants. Since the oxidation power of free chlorine is bigger than combined chlorines which are formed from the reaction between chlorine and reducing agents in water (especially, NH4+ and organic nitrogen), for effective disinfection, excess amount of chlorine is added until all the reducing agents are oxidized and free chlorine is available. After chlorination, chlorine residues in wastewater are usually reduced with SO2 or sulfites before the treated wastewater is discharged, since they are toxic to aquatic life. Addition of excess amount of SO2 or sulfite should be avoided. Otherwise, they consume dissolved oxygen in a river or stream and may have adverse impact on the aquatic life. Determination of wastewater chlorine demand and of sulfite dosages for dechlorination has been a challenge to WWTP operators, due to the dynamic characteristics of wastewater. Recently, a new ORP/pH based approach to determine chlorine demand and sulfite dosage was proposed. The method utilizes significant points occurring on the pH and ORP profiles during chlorination and dechlorination titrations. In this study, the proposed automatic titration system has been implemented into a control system to optimize chlorine and sulfite doses for a pilot scale chlorination/dechlorination system. In short, the disinfection system with the pH/ORP based controller showed very successful results; complete inactivation of total coliforms, and almost zero residual chlorines and high DO in its effluent.
由于其效率高且资金需求低，氯化法已在许多污水处理厂中广泛用于消毒。由于游离氯的氧化能力大于由水中的氯与还原剂（特别是NH4+和有机氮）反应形成的化合氯，为了有效消毒，需添加过量的氯，直到所有还原剂被氧化且有游离氯存在。氯化处理后，在处理后的废水排放之前，通常用SO2或亚硫酸盐来降低废水中的氯残留，因为它们对水生生物有毒。应避免添加过量的SO2或亚硫酸盐。否则，它们会消耗河流或溪流中的溶解氧，并可能对水生生物产生不利影响。由于废水的动态特性，确定废水的氯需求量和用于脱氯的亚硫酸盐剂量一直是污水处理厂操作人员面临的一项挑战。最近，提出了一种基于氧化还原电位（ORP）/pH的新方法来确定氯需求量和亚硫酸盐剂量。该方法利用了氯化和脱氯滴定过程中pH和ORP曲线上出现的关键点。在本研究中，所提出的自动滴定系统已应用于一个控制系统，以优化中试规模氯化/脱氯系统的氯和亚硫酸盐剂量。简而言之，基于pH/ORP的控制器的消毒系统显示出非常成功的结果：总大肠菌群完全失活，其流出物中的残留氯几乎为零且溶解氧含量高。
