Innovative Approaches to Complying with Very Low National Pollutant Discharge Elimination System (NPDES) Permit Limits for Metals

The NPDES permit issued to the Savannah River Site (SRS) in 2003 contained very low metals limits for several outfalls. Copper, lead and zinc limits were as low as seven micrograms per liter (7 ug/l), 1 ug/l, and 100 ug/l, respectively. The permit contained compliance schedules that provided SRS with only three to five years to select and implement projects that would enable outfall compliance. Discharges from a few outfalls were eliminated or routed into other locations relatively inexpensively. However, some outfall problems were much more difficult to correct. SRS personnel implemented several innovative projects in order to meet compliance schedule deadlines as inexpensively as possible. These innovations included (1) connecting several outfall discharges to the site's Central Sanitary Wastewater Treatment Facility (CSWTF), (2) constructing a treatment wetlands and completing a water-effects ratio (WER) on its effluent, (3) installing a stannous chloride feed system to remove mercury in an existing air stripper, and (4) constructing a humic acid feed system to increase effluent dissolved organic carbon (DOC) content and take advantage of biotic ligand modeling to raise effluent limits.