Date of Award:

5-2024

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Civil and Environmental Engineering

Committee Chair(s)

R. Ryan Dupont

Committee

R. Ryan Dupont

Committee

Joan E. Mclean

Committee

Randal Martin

Abstract

Per and poly-fluorinated alkyl substances (PFAS) are a class of chemicals that are persistent in the environment. PFAS was found in wastewater, which can be used after wastewater treatment for irrigation water, and in the biosolids that can be mixed with soils to provide nutrients and generally improve soil quality. This study found when wastewater was used it increases the level of PFAS in vegetables and forage grass. PFAS concentrations were tracked from the influent of the wastewater treatment plant to the effluent, to the irrigation water, to the soil, and finally into the vegetable and forage grass grown on this treated wastewater and biosolids. Similar to other studies, some PFAS compounds were found to increase in concentration after wastewater treatment but dropped in concentration as it mixed with surface water. Similar levels of PFAS were found in rainwater and treated wastewater irrigation spigots. The level of PFAS measured in vegetables even grown in background soils without exposure to treated wastewater or biosolids were high enough that their consumption would exceed the safe exposure levels for Perfluorooctanoic acid and Perfluorooctanesulfonic acid. This is suspected to be because of the PFAS concentrations that these background soils are exposed to rainwater. The use of biosolids in soil was also found to increase the level of PFAS in forage grass when compared to forage grass grown without the use of biosolids so the use of biosolids on home gardens using treated wastewater for irrigation is not recommended. Physical properties of PFAS are strongly correlated with the accumulation in various media, but to tease that out of data a linear mixed effect model had to be used.

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