UV and UV/H₂O₂ treatment of methylisoborneol (MIB) and geosmin in water

The presence of taste and odour-causing compounds in water can lead consumers to perceive the water as unsafe and thus is a great concern for water utilities. This study examined the effectiveness of direct ultraviolet (UV) photolysis and the UV/hydrogen peroxide (H₂O₂) advanced oxidation process (AOP) for removing methylisoborneol (MIB) and geosmin from raw source water and treated water. Low Pressure (LP) and Medium Pressure (MP) direct UV photolysis removed 10% and 25–50% of the compounds by 1000 mJ cm⁻² UV fluence, respectively. The addition of H₂O₂ created advanced oxidation conditions, and oxidized greater than 70% of these compounds at a UV fluence of 1000 mJ cm⁻². MP UV + H₂O₂ was consistently faster than LP UV + H₂O₂ for MIB oxidation, but water quality affected both of the UV + H₂O₂ AOPs. The UV + H₂O₂ AOP oxidation of these taste and odour contaminants in natural waters was effectively modelled using the steady state OH radical concentration model. Finally, electrical energy per order (E_EO) values for oxidation of MIB and geosmin were determined for a model UV reactor, and indicated that the UV + H₂O₂ AOP requires less than 5 kWh of UV energy to oxidize 90% of MIB or geosmin in 1,000 gallons (3,785 liters) of clearwell or raw blend water, corresponding to a cost of less than US$0.35 per 1000 US gallons (3,785 liters).