Verified Performance

Hydro International has dedicated research and development facilities at both its UK and US offices, which allow for extensive full and model scale testing of units. These tests along with comprehensive Computational Fluid Dynamics (CFD) assessments build up an accurate picture of pollutant removal and retention at high and low flows. These findings have been independently verified through 3rd party testing and certification programmes - an example chemical and particle size distribution analysis of pollutants taken from an installed Downstream Defender® unit during an annual maintenance visit can be read here. A comprehensive review of assessments and approvals can be obtained from Hydro International on request.

Proven to Prevent Pollutant Re-Entrainment

Pollutant Re-Entrainment is defined as the tendency to re-suspend and discharge previously captured pollutants during high intensity storm events. Model Scale testing has shown that the Downstream Defender® retains in excess of 99% of captured pollutants, whereas simple gravity separation devices (e.g. simple catch pits) retain less than 5% of captured pollutants during extreme events.

Sizing

The table below shows the treatment flow rates at which the following mean removal efficiencies are achieved:

• Greater than 80% removal of grits and silts down to a particle size of 150 microns with a minimum specific gravity of 2.65
• Greater than 80% removal of light oil with a maximum viscosity of 5.5 (to EN858-1)

Flows in excess of the stated treatment flow can pass through the Downstream Defender® units, allowing the units to be sized according to the site conditions and specific treatment targets. An integral bypass facility is included within the units to pass high flows associated with extreme rainfall events. The Hydraulic Capacity shown is the maximum flow rate that can be passed by each Downstream Defender® unit without surcharging the upstream drainage system.