Erik J. Rosenfeldt
With the increasing focus on removing emerging, unregulated drinking water contaminants, the use of advanced oxidation processes (AOPs) has become more prevalent. A commonly used AOP is the ultraviolet light/hydrogen peroxide (UV/H2O2) AOP. This process utilizes the formation of hydroxyl radicals to oxidize contaminants to less harmful forms. In this analysis, two alternative solid forms of H2O2, sodium perborate (SPB) and sodium percarbonate (SPC) were used as sources of H2O2 in the UV/H2O2 AOP. The potential advantage of SPB and SPC is that they are solids in nature, and as a result, the shipping costs and shipping energy requirements can be reduced significantly compared to that of liquid H2O2.
The yields of active H2O2 via SPB and SPC were investigated in deionized (DI) water and three natural water sources from the Northampton, MA Water Filtration Plant. In DI water, the active yields of H2O2 via SPB and SPC were much higher than in the vii natural water sources. The findings of this analysis indicate that both SPB and SPC are viable sources of H2O2, especially in waters that are treated to reduce the background carbonate concentration.
In highly finished waters similar to DI water, it is expected that the use of SPB and SPC will result in reduced oxidation rates of drinking water contaminants. Therefore, the use of SPB and SPC as H2O2 sources in the UV/H2O2 AOP in highly finished waters is not encouraged. In natural water sources, SPB and SPC appear to be viable alternatives to liquid H2O2 for use in the UV/H2O2 AOP up to active H2O2 concentrations of 5mg/L.
Using SPB and SPC has the potential for significant cost savings depending on the source of the water used in the drinking water treatment process. For facilities with surface waters as the source water, significant cost savings are possible. However water reclamation and reuse facilities have high purity source waters and SPB and SPC as sources of H2O2 are more costly alternatives. The reduction in treatment facilities carbon footprints‟ associated with shipping H2O2 is largely dependent on the location of the chemical production facilities of each reagent.