The Relevance of Direct and Indirect Photolysis Degradation of Trace Organic Compounds With 254 nm UV Light

Abstract

Trace organic compounds, such as pharmaceuticals, hormones and disinfection by products, that persist after conventional wastewater treatment pose potential risks to the ecosystems and human health. Singlet oxygen, 1O2, is a reactive oxygen species that degrades organic compounds that are resistant to traditional wastewater treatment methods. It is not known if relevant amounts of 1O2 can be created with 254 nm UV light. Experiments using furfuryl alcohol (FFA) as a probe compound in deionized (DI) water and wastewater effluent were conducted to verify how relevant 1O2 would be for treating wastewater with 254 nm UV light. The experiments were repeated with an added photosensitizer, Perinapthenone (PN) and a singlet oxygen scavenger, sodium azide (NaN3) to compare how rapidly FFA was consumed with a guaranteed source of 1O2 and in the presence of a scavenger. These results were compared to direct photolysis experiments carried out in DI water and wastewater effluent. Unfortunately in wastewater, very low amounts of 1O2 appeared to be created. This was further verified by repeating the wastewater experiments with a variety of other TOrCs to further verify this. While most TOrCs were broken down to varying extents, Trimethoprim, notable for its extremely slow direct photolysis reaction rate, did not degrade. This suggests that very low amounts of 1O2 are created in wastewater effluent treated with 254 nm UV light.