COLLABORATIVE PROPOSAL: Enhancing Nitrogen Removal in Stormwater Treatment Facilities For Transportation

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CAIT project no.: CAIT-UTC-045

Fiscal Year: 2013/2014

Status: Final

Rutgers-CAIT Author(s): Paul Imhoff, Professor, UDel, Patrick Szary, Ph.D.

External Author(s): Marianne Walch

Sponsor(s): FHWA - RITA, DelDOT Stormwater Quality Program


Stormwater discharge from roadways is a point source of pollution and thus subject to regulation under the NPDES permitting program. As a co-permittee along with municipalities, State DOTs must comply with Total Maximum Daily Load (TMDL) regulations for bacteria and nutrients and work towards achieving prescribed waste load allocations. TMDL is the maximum amount of a pollutant that a waterbody can receive without violating the water quality standards. In Delaware, nutrient loading to surface waters is one of the leading causes of water quality impairment, and in order to meet water quality standards in the state’s nutrient impaired waterways TMDL regulations require the systematic reduction of all point source discharges of nitrogen and phosphorus into these waterways – including those from roadways. Stormwater treatment technologies, such as detention ponds, can remove nutrients effectively. However, the increased nutrient removal required by TMDL regulations will be costly, since more real estate is required for increased treatment with existing technologies. New treatment technologies are needed that significantly reduce the footprint required for stormwater systems treating roadway runoff – which would result in significant cost reductions for State DOTs.