The Eden Project is an environmental visitor attraction and educational project based in a former china clay pit in St Austell, Cornwall. Rainwater harvesting is just one of the ways in which the Eden Project sustainably manages the water needed by the 1.8 million visitors each year and 100,000 plants that live in the two biomes. The smaller biome replicates conditions in a Warm Temperate climate whilst the larger biome simulates the climate of the Humid Tropics. It is these biome roof structures that rainwater is collected off for use in humidification of the biomes, irrigating plants and toilet flushing.

The water which runs off the biomes is channelled into stylised concrete hoppers at the springing points of the biomes and eventually into two 120m³ underground sumps ready for filtration and treatment. A grit trap removes silt and grit and the water is disinfected by silver ionisation (whereby a low current is passed through a silver alloy electrode causing silver ions to be released and attach to and destroy bacteria present in the water). The treated rainwater is used for toilet flushing in staff and visitor facilities and as a humidification system.

The water is pumped to a pressure of 120 bar and dispersed via automated fogging nozzles in various parts of the Humid Tropics Biome which is kept at 90% humidity at night and 60% during opening hours ⁽¹⁾. The picture on the right shows fogging nozzles hanging down from the inside of a biome roof.

See a diagram of the Eden Project rainwater harvesting system.

References

(1) Mark Hyatt, Technical Services manager, Eden Project. (2005)Pers comm.

(2) Eden Project http://www.edenproject.org.uk