Risk of overestimating odor control performance with the removal efficiency of a single odorant: Odorant interactions during the chemical absorption.

Abstract

Odor is a serious issue for municipal solid waste treatment process, and chemical absorption is a common technology for odor control. Interactions among odorants will influence the performance of chemical absorption, and they are still not fully understood. This work took the common and important odorants, including hydrogen sulfide (H₂S), methanethiol, propanethiol and acetaldehyde, as examples, to investigate the removal performance of mixed odorants by sodium hypochlorite (NaClO) solution at different concentrations, and interactions among the odorants. The absorption experiments were conducted in gas-washing bottles with single or mixture of H₂S, methanethiol, propanethiol and acetaldehyde as the inlet gases, and NaClO solutions at different concentrations as the absorption solutions. The thermodynamic equilibrium was simulated. Acetaldehyde was eliminated mainly by physical absorption, and the removal efficiency was not affected by the other three odorants. The removal efficiencies of H₂S, methanethiol, and propanethiol increased with the chlorine concentration ([Cl₂]), and reached nearly 100% by the NaClO solution of pH = 12.19, [Cl₂] = 158.00 mg/L. H₂S, methanethiol, and propanethiol competed for reacting with NaClO. H₂S was more effectively removed than methanethiol and propanethiol due to its lower pKa value. The removal efficiency of methanethiol decreased linearly with the increase in methanethiol and H₂S concentrations mainly due to the consumption of NaClO. Propanethiol removal was decreased by both methanethiol and H₂S, and methanethiol had more influence than H₂S due to the higher consumption of NaClO. The odor control performance could be overestimated when there are several important odorants, and only the removal efficiency of a single odorant was considered. Correspondingly, suggestions for chemical scrubber operation were provided, including the consideration of odorant interactions, the selection of monitoring odorants, and the optimization of operating parameters (pH and [Cl₂]) using machine learning methods.Implications: Chemical absorption is widely applied for odor control, and the interaction between odorants is an important influencing factor of the performance. Hydrogen sulfide, methanethiol, propanethiol and acetaldehyde are common and important odorants emitted during municipal solid waste treatment. This work investigated the removal performance of chemical absorption for the single and mixture of these odorants, and revealed the interaction between them, as well as the risk of overestimating odor performance with the removal efficiency of a single odorant, which can provide insights into optimizing odor control technologies.