The ASTRASAND&reg filter was developed for physical-chemical and/or biological treatment of different types of water, such as process, waste, surface, cooling and groundwater. Working as a continuous process, the filter bed is cleaned during the filtration operation. Thus, interruptions are eliminated. The filtration technology can be used for many types of industrial and municipal applications: biological nitrification/denitrification and polishing of municipal and industrial wastewater, filtration of flocculated contaminants in surface water, washwater treatment in fresh and process water production, biological sidestream filtration of cooling water, and biofiltration for BOD and heavy metal removal.