Rain water filter insert held within mantle amorphous iron oxide and keeping discharge impurities to within legal limits

摘要

Rainwater draining from surfaces migrates to e.g. a sub-surface soakaway drain, the mantle (4) of which includes iron fixtures forming part of the water filter insert within the drain. The filter mantle consists of weather-resistant water-permeable materials including powdery to granular amorphous iron oxide.