Efficiencies of a Hydrodynamic-Settling Device
Project Number: BQY28
Project Chief: Judy Horwatich
Project Topics: Stormwater control practice
Cooperators: National Sanitation Foundation International, Waukesha City Group and WDNR
Period of Project: July 2005 – December 2007
The purpose of this project is to measure the pollutant reduction effectiveness of a Downstream Defender stormwater treatment device.
Administrative rules to address the control of polluted runoff from urban land-use activities in Wisconsin went into effect on Oct 2, 2004. Performance standards in subchapter III of NR151 details total suspended solids (TSS) reductions for post construction in new development and redevelopment, and describe requirements to reduce TSS in developed urban areas for all municipalities subject to storm water permits. Eighty percent of the annual TSS load that would normally run off a new development site needs to be controlled. The reduction goal for redevelopment is 40 percent. Municipalities required to control solids loads from developed urban areas must achieve a 40-percent reduction in the annual TSS loads by 2013.
The purpose of this project was to measure the pollutant reduction effectiveness of a Downstream Defender stormwater treatment device. This is a proprietary treatment device manufactured by Hydro International. It represents a very common type of device being promoted for reducing the level of pollutants in urban runoff. The primary process for removing the pollutants is settling. More than six manufacturers are offering settling-type devices in Wisconsin.
Results from this project will be applied to an effort to select and verify a method for sizing single-chamber settling devices in Wisconsin. Additional pollutant-reduction data are available from the monitoring of two other settling devices installed in Wisconsin. These three projects will provide sufficient data to select and verify a sizing method to be recommended in a technical standard for single-chamber treatment devices.
Twenty-three runoff events monitored for flow volume and water quality at the device’s inlet and outlet were used to calculate the percentage of pollutant reduction for the device. Efficiency of the settling device was calculated using the efficiency ratio and summation of loads (SOL) methods.
Publications and Reports
Horwatich, J.A., and Bannerman, R.T., 2012, Parking lot runoff quality and treatment efficiencies of a hydrodynamic-settling device in Madison, Wisconsin, 2005–6: U.S. Geological Survey Scientific Investigations Report 2011–5145, 35 p. plus 11 app.