UV/Titanium dioxide AOP

Advanced Oxidation Processes can remove trace contaminants in water supplies

Many emerging contaminants cannot be removed efficiently by conventional water treatment methods. This has led to the application of alternative processes to remove or degrade these contaminants. One such group of processes is Advanced Oxidation Processes (AOP).

A number of advanced oxidation process technologies for trace contaminant removal have been identified, including ultraviolet- based applications, Fenton's reagent, ultrasound, pulsed plasma, wet air oxida- tion, photocatalysis, and ozone-based advanced oxidation processes. Many of these processes are either in their infant stages or have only been used in remediation applications. Although the remedia- tion applications show that the technologies are sound from a treatment perspective, they may not meet all drinking water regulations certification requirements or have not been proven to be practical to integrate into water treatment process trains. Only a few advanced oxidation processes are available for full-scale drinking water treatment, namely ultraviolet oxidation using ultraviolet and hydrogen peroxide, and Peroxone, which uses a combination of ozone and hydrogen peroxide.

Ozone/Hydrogen peroxide AOP

The type of advanced oxidation process required wil largely depend on the chemical properties of the contaminant and the quality of the water being treated. An important consideration that also needs to be addressed is by-product formation. By-product formation will depend on the water quality and which precursors are present in the raw water, as well as the type of advanced oxidation process used. For example, bromide-containing waters may not be suitable for ozone-based advanced oxidation processes, whereas waters with high levels of nitrate may not be suitable for treatment with ultraviolet-based advanced oxidation processes.

Once an advanced oxidation process technology has been identified, consideration must be given to incorporate it into the most suitable position within the overall treatment train. An advanced oxidation process could be slotted in upstream of the treatment plant if using a pump and treat method, or in various configurations within the treatment train (for example, pre-filtration advanced oxidation process or post-filtration advanced oxidation process). The potential impacts of upstream processes on the advanced oxidation process should be considered as well as the impact of an advanced oxidation process on downstream processes.

UV/Hydrogen peroxide AOP

The emerging technologies used for trace contaminant removal can also be applied to address taste and odour problems. For taste and odour applications, the advanced oxidation process is typically designed to be used seasonally, and is operated in regular ozone or ultraviolet mode for disinfection during the remainder of the year. In these cases, the advanced oxidation process offers a boost of treat- ment, which removes hardy taste and odour causing compounds like geosmin and MIB, an organic chemical.

Various criteria should be identified for consideration in selecting the appropriate technology, including full-scale technology experience, potable water treatment capability and experience, process integration, previously documented performance treating the contaminant of interest, regulatory approval of the advanced oxidation process technology, and ancillary considerations such as chemicals, power, and residuals management. Associated Engineering's recent experience with advanced oxidation processes includes ultraviolet oxidation (ultraviolet/ peroxide), Peroxone (ozone/peroxide), and photocatalysis with ultraviolet/titanium dioxide. For more information, contact Elia Edwards at edwardse@ae.ca or Linda Wojcicka at wojcickal@ae.ca.