Degradation of geosmin and 2-methylisoborneol in water with UV/chlorine: Influencing factors, reactive species, and possible pathways

Geosmin (GSM) and 2-methylisoborneol (2-MIB) are two common odor compounds in drinking water . In this paper, the performance of UV/chlorine was compared with that of chlorine and UV to degrade GSM (100 ng L −1 ) and 2-MIB (100 ng L −1 ) in water. UV/chlorine was further exploited, and a steady-state kinetic model was used to conduct a detailed study on efficiency, rate, reactive species and pathway. The results showed that UV/chlorine greatly could improve the removal ratio to 90% within 5 min, from approximately 20% with only UV or dark chlorine in 60 min. The removal ratio and rate depended on UV light intensity , free chlorine dosage, reaction time and water quality parameters (e.g. pH, concentrations of HCO 3 − and Cl − ). Among these factors, the first two obviously could accelerate the rate and increase the ratio. The degradation was also significantly improved in an acidic condition, while alkaline conditions and HCO 3 − had inhibitory effects, and Cl − created no difference. Contributions of OH and Cl to the degradation of 2-MIB and GSM were further revealed, and OH was found to be the most important reactive species. In the UV/chlorine process, 6 degradation byproducts of 2-MIB, including 1 alcohol, 2 ketones, and 3 olefins , were identified, and 14 degradation byproducts of GSM, including 6 ketones, 1 aldehyde, 2 alcohols, 3 naphthenes , and 2 olefins, were found by using solid-phase microextraction coupled to gas chromatography-mass spectrometry. The possible degradation pathways of GSM and 2-MIB in UV/chlorine thus were proposed.