Topic Area: 2d. Biobarrier Implementation and Management

Formatted Title:

Permeable Reactive Barriers: In Situ Treatment Strategies to Mitigate Nitrate Discharge to Surface Water

Background/Objectives:

Eutrophication due to excessive nutrient loadings to surface water bodies is a global environmental issue. High concentrations of nitrate in groundwater can occur from fertilizer usage, manufacturing, or septic systems. On Cape Cod in Massachusetts and eastern Long Island in New York, 60% to more than 80% of wastewater is conveyed to septic systems, which are the leading contributor of nitrate to the groundwater. Eutrophication results in health, environmental, and financial impacts where it occurs, including drinking water treatment, recreation, tourism, property valuation, and fisheries.

Approach/Activities:

Denitrification permeable reactive barriers (PRBs) can remove nitrate from groundwater prior to discharging to surface water through the addition of an organic carbon substrate to the subsurface to establish anaerobic conditions to enhance the activity of naturally occurring soil bacteria that denitrify nitrate to nitrogen gas. Organic carbon can be applied as a solid (e.g., wood chips) or as a liquid solution. Various methods of PRB construction can be used including injection wells, temporary injection points, trenching, large diameter boreholes, and as part of bulkhead replacement. Key factors for selecting the type of denitrification PRB and design parameters include depth of nitrate impacted groundwater, soil type, groundwater velocity, nitrogen concentrations, and distance to surface water.

Veronica Gonsalez

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Permeable Reactive Barriers: In Situ Treatment Strategies to Mitigate Nitrate Discharge to Surface Water