Comparison of Low Pressure and Medium Pressure UV Lamps for UV/H₂O₂ Treatment of Natural Waters Containing Micro Pollutants

Abstract

UV/H₂O₂ advanced oxidation is an effective barrier against organic micro pollutants. Several studies have focused on the degradation of a wide range of pollutants, but regarding the comparison of low-pressure mercury lamps (LP) with medium-pressure mercury lamps (MP) with respect to energy consumption by the UV/H₂O₂ process, little is known so far. Although the absorbance of H₂O₂ at 254 nm is low, the results of this research show that the yield of hydroxyl radical formation (OH_CT) with LP lamps is comparable or higher than with MP lamps. In a water matrix with a background absorbance due to organics and nitrate, H₂O₂ absorbs UV light very effectively at 254 nm. Generally, due to the contribution of direct photolysis, the degradation of pollutants is better with MP-UV/H₂O₂ than with LP-UV/H₂O₂ at the same UV fluence. Therefore, with LP-UV/H₂O₂ micro pollutants are predominantly degraded through reaction with OH radicals. However, due to the much higher efficiency of LP lamps in converting electrical energy to UV-C light, the energy required to achieve 90% degradation (E_EO) of pesticides and pharmaceuticals can be significantly lower with LP-UV/H₂O₂ than with MP-UV/H₂O₂. Results of bench-scale tests show E_EO data of the LP-UV/H₂O₂ process to be 30%–50% lower than for the MP-UV/H₂O₂ process. At these process conditions MS2 phage inactivation was found to be more than 8 logs for both MP-UV/H₂O₂ and LP-UV/H₂O₂.

Keywords:

• UV/H₂O₂
• AOP
• Disinfection
• Oxidation
• Low Pressure
• Medium Pressure
• Degradation
• Pesticides
• Pharmaceuticals
• MS2
• OH_CT
• E_EO

Notes

As of 2008, Dr. Guus F. IJpelaar works for Royal Haskoning, P.O. Box 151, 6500 AD Nijmegen, the Netherlands.