Degradation Kinetics of Common Odorants Emitted from WWTPs: A Methodological Approach for Estimating Half-Life Through Reactions with Hydroxyl Radicals

Abstract

In contemporary times, wastewater treatment plants (WWTPs) were recognized as substantial sources of odorous emissions, potentially impacting nearby communities’ sensory experience. This study investigates the half-lives (T½) of odorous compounds emitted from WWTPs and their degradation due to atmospheric hydroxyl radicals (•OH) in different environmental settings. The calculated half-lives of specific odorants in rural areas ranged from 31.36 min to 517.33 days, in urban areas from 42.50 min to 1550 days, and in the marine boundary layer from 42.50 min to 129,861 days. These results show that compounds with high reactivity and short T½, such as methanethiol and ethanethiol, degrade rapidly and are less likely to contribute to long-term odor nuisances. In contrast, compounds with longer half-lives, such as carbonyl sulfide and ammonia, persist longer in the atmosphere, with higher potential for sustained odor issues. The findings suggest that •OH plays a significant role in degrading odorous compounds. These insights into odorant–oxidant kinetics may aid in predicting atmospheric half-lives and their contribution to secondary aerosol formation, thus informing regulatory and mitigation strategies to improve air quality.