Simulating the Cost and Legacy N Reduction Potential of Denitrifying Spring Bioreactors Installation in the Chesapeake Bay Watershed

The nitrogen reduction goals for the Chesapeake Bay are proving particularly difficult achieve. One of the contributing sources of N loading to the Bay is legacy N from groundwater springs. Denitrifying spring bioreactors are a best management practice that offers an opportunity to abate N from groundwater springs. The objective of this research is to estimate the regional abatement costs to remove legacy N using bioreactors. We identified 196 candidate springs for bioreactor installation that had a median spring flow of greater or equal to 100 m3 d-1 and greater or equal to 3 mg L-1. Under assumptions that 25% of the spring flow can be diverted to the bioreactor and a bioreactor N removal efficiency of 20%, we estimate that it would cost $3,325,400 yr-1 to abate 106,911 kg N yr-1. The driving factor of driving the unit costs of N removal is the amount of spring flow treated by the bioreactor. Further research is needed to understand how to optimize bioreactor performance and the benefits of increasing the percentage of spring flow treated given the impact these two factors on the cost-effectiveness of spring bioreactors in removing N.