Understanding the Importance of the Application of the External Calibration Method to the UV/Cl AOP Through a Cost Analysis

Extensive bench and pilot scale research has demonstrated that UV advanced oxidation processes (AOPs) like UV/hydrogen peroxide (UV/H₂O₂) and UV/chlorine (UV/Cl) are dynamic systems where both UV dose and oxidant dose contribute to the generation of reactive oxygen species (ROS) and/or reactive chlorine species (RCS) that can degrade a wide range of contaminants, including many that cannot be removed through conventional water treatment processes. Non-target contaminants, including naturally occurring organic matter and inorganic ions, will also exert ROS and RCS demand, in some cases well beyond that exerted by the target contaminant. The demand associated with non-target contaminants is difficult to quantify and without understanding this demand, utilities may struggle to optimize their system. An external calibration method for quantifying this demand has been developed for UV/H₂O₂ and has led to the invention of a real time scavenging capacity monitor, but to date this method has not been demonstrated for other UV AOPs like UV/Cl. This paper presents cost curves which were developed by updating costing information published in USEPA’s Technologies and Costs Document for the Final Long Term 2 Enhanced Surface Water Treatment Rule and Final Stage 2 Disinfectants and Disinfection Byproducts Rule and USEPA’s Estimating Water Treatment Costs: Volume 2 Cost Curves Applicable to 1 to 200 MGD Treatment Plants. The cost curves illustrate the potential cost implications of different oxidant and UV doses for different AOPs, further highlighting the need for an efficient scavenging capacity monitor for UV/Cl. In addition, the preliminary steps taken to apply the external calibration method are presented in this paper, including the characterization of the UV lamp.