Characterization of aerosol emissions from wastewater aeration basins

Abstract

The emission of particulate matter (PM₁₀ and PM_2.5) and ammonia (NH₃) by aeration processes at wastewater treatment plants (WWTPs) with and without odor control units was examined. Local concentrations of PM_2.5, PM₁₀, and NH₃ at the aeration basins were within urban ranges. Emission fluxes of NH₃ and PM_2.5 for a medium-sized WWTP were determined to be 136 g day⁻¹ and 43 g day⁻¹, respectively, which are not substantial emission fluxes for urban environments. Odor control treatment using a granulated activated carbon bed reduced aerosol and NH₃ emissions substantially. Detection of sterols, in particular the fecal sterol campesterol, in the PM clearly demonstrates aerosolization of wastewater components in the aeration process. The presence of campesterol in PM_2.5 at a remote fenceline location in a WWTP facility illustrates that wastewater components are aerosolized in the fine PM fraction and transported beyond the facilities.

Implications:

Wastewater treatment plants are potential emission sources of particulate matter and gases. This study characterized particulate matter emissions from aeration basins and quantified emissions fluxes of particulate matter and NH₃. While fine and coarse particles as well as NH₃ are being emitted, the overall emissions are small compared to other urban sources. However, fecal steroid presence in particles at the fence of a treatment plant demonstrates that wastewater material is getting aerosolized and transported beyond the facilities.

Acknowledgments

This project was funded by Science Foundation Arizona grant CAA 0284-08. The authors thank the staff of the two anonymous utilities in the Phoenix area for their cooperation. They are grateful to Prof. Matt Fraser and Andrea Clements for assistance with sample analysis and access to their facilities.