Evaluation of stormwater control measures for the removal and fate of legacy and emerging contaminants

Sediment contamination poses a significant risk to ecosystem and human health due to the strong affinity many contaminants have for sediments. While efforts to control point sources have reduced pollutant inputs, nonpoint sources such as stormwater runoff continue to transport contaminants and contaminated sediments into receiving waters. Stormwater control measures (SCMs) are designed to reduce and treat this runoff before discharge, but their effectiveness depends on both the type of contaminant and the phase in which it is present (i.e. dissolved or particle bound). Evaluating SCM performance for legacy contaminants such as polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), as well as for emerging contaminants such as per and polyfluoroalkyl substances (PFAS), is essential to prevent sediment recontamination and to support practical and cost-conscious stormwater management. This dissertation assesses the solid and contaminant removal capabilities of multiple SCMs—including biofilters, a hybrid biofilter with a media filter, hydrodynamic separators, cartridge filters, and a retention pond—across military sites in the southwestern and northwestern United States. PAHs and PCBs were analyzed in both the dissolved phase and across different particle size fractions including clay, fine silt, coarse silt, and sand. PFAS were evaluated in both dissolved form and associated with total particulates. Stormwater samples were collected at both the inlets and outlets of each SCM during multiple storm events. Results for legacy contaminants showed that coarse particles carried the highest concentrations of organic carbon, which correlated with higher levels of PAHs and PCBs. Because these coarse particles tend to settle near outfalls, they present a high risk for sediment recontamination. Additionally, organic carbon normalized partition coefficients measured in the study were higher than typical literature values, suggesting lower contaminant bioavailability but a greater likelihood of long-term sediment accumulation. Most SCMs effectively removed particle bound contaminants, especially in the larger size ranges, although some exceptions were observed when systems were poorly maintained or there was inlet overflow. In contrast, removal of dissolved PAHs and PCBs was limited, allowing these contaminants to pass through to receiving waters. PFAS analysis showed a strong correlation between carbon chain length and solids affinity. Long chain compounds were more likely to bind to particles, while short chain PFAS, which made up the majority of the detected compounds, remained primarily in the dissolved phase. Within PFAS groups, sulfonates were more associated with sediments, while carboxylates were more frequently found in the aqueous phase. Similar to the legacy contaminants, dissolved PFAS were not effectively removed by SCMs. Additionally, there was evidence that PFAS precursors in stormwater transformed into more stable terminal PFAS, which persist in the water and sediment. The final chapter explores ways to improve SCM performance for dissolved PFAS through the use of sorbent polishing beds. Using real concentration and flow data from an airport affected by aqueous film forming foam (AFFF), the study estimated the required adsorber bed volumes, sorbent masses, and capital costs for different sorbent materials. Results showed that sorbent selection must be tailored to site-specific conditions in order to achieve compliance while managing cost. In summary, this work demonstrates the importance of evaluating both influent stormwater quality and SCM performance with attention to contaminant type and physical phase. The findings emphasize the need for improved treatment strategies for dissolved contaminants, provide a particle size–based framework for assessing risk of sediment recontamination, and offer practical guidance for enhancing PFAS removal using cost-effective sorbent systems.

Name thesis:degree_name

Doctor of Philosophy

Discipline thesis:degree_discipline

Chemical Engineering

Grantor

Texas Tech University

Year dc:date.issued

2025

Author dc:creator

• Gómez-Ávila, César Iván

Advisor dc:contributor.advisor

• Reible, Danny D.

Committee members dc:contributor.committeemember

• Rao, Balaji
• Li, Wei
• Gauthier, Joseph

Language dc:language.iso

English

Handle dc:identifier.uri

https://hdl.handle.net/2346/103276

OAI identifier oai:identifier

oai:ttu-ir.tdl.org:2346/103276