Rainwater ponds for buffering and purification of moderately polluted water
Dimensioning: 10% -20% of the connected surface area
Application: For moderately to well drained soils with a not too low groundwater level
Advantage: Relatively little space required
Disadvantage: Maintenance is necessary
In areas that experience moderately polluted rainwater, one option is to realise rainwater ponds for temporary storage and purification using vegetation. The polluted water might also undergo an additional pre-purification treatment in a sand filter in the bank zone.
Water is purified in a pond with vegetation because the pollutants settle on the bottom and the plants break down and absorb the pollutants. Introducing a circulation system can guide the water specifically along the planted bank zones to increase the purification. An attractive artwork or playground element might be made part of such a circulation system.
The pond should ideally be at least 1.5 metres deep. That depth limits the degree to which the water heats up in the summer and diminishes the risk of problems with the water quality. In the winter, water that deep will not freeze solid and the pond will continue to offer a zone for fish to live in.
If the ground permits, the overflow from the pond can be designed to act as an infiltration system. [Geiger et al., 2009]