How it works

The Downstream Defender® internal components are designed to enhance the separation process by minimising headloss, increasing efficiency and preventing re-entrainment of captured pollutants. Advanced hydrodynamic vortex separation is achieved by extending and stabilising the flow path, whilst isolating the captured pollutants in dedicated storage zones.

Contaminated stormwater entering the chamber is directed downwards and around the periphery of the chamber (green arrows).

Oils, litter and other floatable material is initially captured at the inlet and transferred to the oil storage zone as flows increase (brown area). The oil storage zone is protected from the treatment flow path and so prevents captured floatable material being re-entrained during peak flows.

As the flow continues to spiral around the periphery of the chamber, low energy vortex motion directs settleable solids into the base of the unit (yellow arrows). The internal components isolate the base of the chamber from the treatment flow path preventing washout of captured solids.

The treated stormwater exits the chamber via the orientated outlet pipe after ensuring the longest possible retention time within the unit (light blue arrow).

Excess flows by-pass both the vortex treatment chamber and also both the sediment and oil storage zones. These excess flows pass forward untreated via the orientated outlet pipe.

Access to the base of the chamber for sediment removal can be achieved via the centre shaft (dark blue arrow) using standard vacuum tanker equipment. The Downstream Defender® cover slab should be fitted with access hole(s) to enable removal of captured sediment and floatable materials.