Treatment of Legacy Nitrogen as a Compliance Option to Meet Chesapeake Bay TMDL Requirements

In efforts to combat eutrophication, the U.S. Environmental Protection Agency has established aggressive nitrogen, phosphorus, and sediment reduction goals for states and regulated dischargers within the Chesapeake Bay watershed. Chesapeake Bay jurisdictions are struggling to meet the nutrient (N, P) reduction goals. This paper evaluates the efficacy of removing legacy N from groundwater as a compliance strategy for three potential classes of "buyers" of N reductions in the Chesapeake Bay watershed: permitted point sources, permitted municipal stormwater systems (called MS4s), and state nonpoint source (NPS) managers. We compare denitrifying spring bioreactors with conventional agricultural and urban NPS removal technologies using evaluative criteria important to each of these buyers. Results indicate that spring bioreactors compare favorably to other N removal technologies based on cost effectiveness, administrative costs, and certainty of N removal performance. Most conventional NPS technologies provide greater ancillary benefits. On balance, denitrifying spring bioreactors add a valuable compliance option to those tasked with achieving Bay N reduction goals.