ASTRASAND^®

• ASTRASAND^® sand filtration is used in more than 500 facilities for continuous sand filtration of many types of wastewater, with unit capacity varying from only a few to several thousand m³/hour.
• IInterruptions are eliminated through the continuous self-cleaning process of ASTRASAND^®, in which the filter bed is cleaned during the filtration operation.
• It is a highly reliable system, which offers a short lead time and a better sand velocity distribution than conventional sand filters.
• Small footprint – easy to install in larger treatment systems.
• ASTRASAND^® continuous sand filtration allows for both biological and chemical nutrient removal (nitrification, denitrification, phosphate precipitation).

The continuous sand filter ASTRASAND^® is developed for different types of water, such as process, waste, surface, cooling and groundwater. The ASTRASAND® continuous sand filter has been used for removal of TSS, BOD, ammonium, nitrate and phosphate in various (waste) water applications.

• Polishing of municipal and industrial waste water
• Reuse of water, in combination with polishing, membrane filtration and disinfection
• Direct filtration of surface water with in-line flocculation
• Aerobic biological purification of water, e.g. for MAC and PAC degradation
• Wash water treatment in drinking and process water production processes
• (Biological) side stream filtration of cooling water

The contaminated water is fed to the filter via the supply line). The water enters the filter bed through the supply pipe and the distributors. This water is purified as it flows up through the filter. The filtrate is drained through the top of the filter. The filter bed moves downwards as the water flows upwards. Dirty sand is constantly extracted from the sand bed and washed, after which it is placed on top of the sand bed again.

The sand circulation is based on the airlift principle, in which a mixture of dirty sand and water is pushed up through a central pipe. Intensive washing movements separate the impurities from the sand particles. The air is released at the top of the pipe and the dirty water is drained. The sand then settles in the washer at the top of the filtration tank where the sand is washed with a small amount of filtrate. The last traces of contamination are removed from the sand. The flow is caused by a difference in level between the filtrate and the rinse water.

The installation can be equipped with a system that monitors the evenness of sand circulation and the process can be fully optimized for specific applications by using an advanced control system.