Advanced oxidation (AOX) remediation systems using hydrogen peroxide (peroxide) and ultraviolet light (UV) are designed to inject hydrogen peroxide in controlled ratios to the water, mixing the peroxide, and exposing the water and peroxide solution to UV radiation to form hydroxyl radicals (•OH). Peroxide and hydroxyl radicals are strong oxidizing agents capable of oxidizing 1,4-dioxane and several VOCs. The AOX process is a proven technology used for the oxidation of a wide range of COCs in water and some color removing applications.
Advantages of UV-AOX Treatment
The following are advantages of the UV AOX System:
- Proven and Mature Technology – AOX equipment suppliers draw from years of experience in the disinfection of municipal wastewater. AOX systems are available from highly reputable technology and equipment suppliers.
- Control of 1,4-dioxane – Advanced oxidation is the only cost-effective technology used to control chemicals like 1,4-dioxane which is not removed by activated carbon. UV systems offer a technically and economically feasible alternative to treating water and wastewater impacted with several hard-to-treat chemicals.
- Eliminates Ozone as a Reactant – AOX with UV eliminates the use of ozone. Ozone is an irritant, and small releases of ozone may affect neighbours, and tenants. For projects where the production bromate or oxidation of metals such as chromium III is a factor, UV peroxide may outperform ozone based oxidation systems.
UV AOX Systems
The UV AOX systems are pressurized ultraviolet (UV) light reactors that require low energy and have high UV-light outputs. The pressurized AOX systems generally include a stainless steel reactor, UV lamps, flanges, support structures, and outdoor rated 304 stainless steel panels for the Power Distribution Center (PDC) and System Control Center (SCC).
The UV-AOX systems are PLC-controlled systems that automatically optimize UV-lamp operation by adjusting light intensity, and flow-pace peroxide pumps to reduce operation costs. The PLC control logic and uses several online measurements to control ballast power and peroxide flows that provide the required treatment level.
UV peroxide systems have drawbacks that require management through process design and operations and maintenance. Advanced oxidation systems based on UV are sensitive to interference from dissolved metals in water including iron. The presence of low concentrations of TSS can also impact the performance of the UV light. Solids formation in groundwater treatment systems cannot always be fully predicted since these involve inorganics and algal growth. To minimize the potential impact of solids, the equipment layout in the field should be designed for flexibility to upgreade the process with anti-scaling systems and filtration systems.