We intend to install specialist rainwater filter for installation within standard manhole shafts, 1000mm diameter. Suitable for heavily contaminated waters from trafficked areas, i.e. over 5000 vehicles per day. One unit of the filters is suitable for drained areas up to 650 m². The cleaned water has such an excellent water quality that it can be discharged directly into flat tanks and the wider environment.
The filter function is an up-flow process and this allows for a design with a minimal height difference between the inlet and outlet. In the filter shaft the rainwater is cleaned by basic operation of the following processes:
- Filtration; and,
- Chemical Precipitation.
Incoming rainwater is led down to the basal section of the filter shaft. A hydrodynamic separator built in the base section promotes particulate sedimentation. The water is led into this separator tangentially and generates a radial flow pattern. Particles settle into the silt trap located below the separation chamber.
Above the separation chamber are 4 filter elements, occupying the full shaft width such that all water must flow up through the filter. The Siltation of this filter is slow due to the upwards flow, and the fact that the filter is below the water level. The filter is easily exchanged.