Micro-siting and Nitrogen Removal Efficiency of Liquid Injection Permeable Reactive Barriers in Residential Watersheds of Southeastern Massachusetts

Tuesday, January 20, 2026 at 2:00pm to 5:00pm

Department of Estuarine and Ocean Sciences

PhD Dissertation Defense

"Micro-siting and Nitrogen Removal Efficiency of Liquid Injection Permeable Reactive Barriers in Residential Watersheds of Southeastern Massachusetts"

By: Jessica C. Thomas

Advisors

Dr. Miles Sundermeyer (UMass Dartmouth)

Dr. Micheline Labrie (UMass Dartmouth)

Committee Members

Dr. Mark Altabet (UMass Dartmouth), Dr. Pia Moisander (UMass Dartmouth), Dr. David Schlezinger (UMass Dartmouth),  and Dr. Roland Samimy (UMass Dartmouth)

Tuesday January 20, 2026

2:00 PM

SMAST East 101-103

836 S. Rodney French Blvd, New Bedford

and via Zoom

Abstract:

As the development of coastal areas continues to increase, nitrogen loads have also increased. In addition to human health impacts of nitrogen (as nitrate), severe water and habitat quality degradation of coastal and estuarine systems is occurring worldwide. Estuaries are impacted by nitrogen inputs at concentrations up to two orders of magnitude lower than those associated with direct human exposure, leading to nitrogen enrichment, eutrophication, and declines in ecosystem health. As a result of the ecological, economic, and social impacts of nitrogen enrichment, towns are currently investigating mitigation techniques, both traditional and non-traditional, as well as the development of new treatments. Due to the high costs of traditional Wastewater Treatment Facilities (WWTF), many coastal communities are turning to non-traditional techniques. One approach that has seen interest due to its cost, ease of installation, and low impact on the environment is the liquid injection Permeable Reactive Barrier (PRB).

This dissertation evaluates the performance, biogeochemical behavior, and long-term viability of liquid-injection PRBs as a nitrogen mitigation strategy in residential coastal watersheds. Chapter 1 examines how micro-siting techniques influence PRB installation, hydraulic interception, and cost-effectiveness, and quantifies nitrogen removal achieved following pilot-scale installation. Chapter 2 evaluates the secondary geochemical responses associated with PRB-induced reducing conditions, including the mobilization of iron, manganese, arsenic, and phosphate, and assesses their spatial extent and downgradient attenuation. Chapter 3 constrains the conservative longevity of the liquid carbon substrate, emulsified vegetable oil (EVO), through accelerated laboratory microcosm incubations designed to simulate field-relevant and extreme nitrate-loading conditions.

Field investigations were conducted at a pilot PRB installed within the Lagoon Pond watershed on Martha’s Vineyard, Massachusetts, USA. Hydrogeologic characterization, groundwater nitrogen transport, water-quality monitoring, and in-situ EVO transport experiments were used to evaluate PRB performance under real-world conditions. Laboratory incubations integrated biogas production and electron-acceptor stoichiometry to estimate EVO biodegradation rates and conservative substrate lifespans.

Results demonstrate that properly sited liquid-injection PRBs can achieve sustained nitrate removal at residential groundwater concentrations while maintaining localized control over secondary geochemical effects. Conservative longevity estimates indicate that modified EVO formulations can support multi-year to multi-decadal nitrogen removal, with substrate persistence constrained primarily by oxidant delivery rather than donor mass alone. Together, these findings support liquid-injection PRBs as a viable, low-maintenance, and transferable nitrogen mitigation strategy for coastal communities facing chronic groundwater nitrogen enrichment.

Join Meeting

https://umassd.zoom.us/j/99437771279

Note: Meeting ID and password required. Please email contact to obtain.

For additional information, please contact Callie Rumbut at c.rumbut@umassd.edu

SMAST East 101-103 : 836 S. Rodney French Boulevard, New Bedford MA 02744
Callie Rumbut
c.rumbut@umassd.edu
https://umassd.zoom.us/j/99437771279