ASTRASAND® is a new and improved continuous sandfilter, developed for physical-chemical and/or biological treatment of different types of water, such as process, waste, surface, cooling and ground water. ASTRASAND® works as a continuous process, in which the filter bed is cleaned during the filtration operation, and as a result process interruptions are eliminated. ASTRASAND® is self-cleansing.



Advantages of the ASTRASAND®
• Suitable for physical-chemical as well as biological treatment (or a combination);
• Continuous cleaning allows for continuous operation;
• High filtrate efficiency under varying process conditions;
• Compact installation with small footprint;
• Easily built into larger treatment systems;
• High efficiency through uniformity of the sand circulation rate;
• High availability and low maintenance due to a lack of moving parts;
• Low operational costs.

Working principle
The polluted water is transported into the filter by means of the feed pipeline (1). Water enters the filter bed (4) through the supply pipe (2) and the distributors (3). This water is purified as it flows upward through the filter. The filtrate is discharged from the upper part of the filter (5).

The filter bed moves downward as the water flows up. Dirty sand (6) is continuously extracted from the sand bed and washed, after which it is released back on top of the sand bed (7).

The sand circulation is based on the airlift principle, forcing a mixture of dirty sand and water upward through a central pipeline (8). Intensive scouring movements separate the impurities from the sand particles. At the top of the pipeline the air is released, and the dirty water is discharged (9). The sand then settles in the washer (10) at the top of the filtration tank where the sand is washed with a small amount of filtrate. This removes the final traces of pollutant from the sand. Flow is achieved through a difference in level between the filtrate (11) and the rinse water (9).

To view an animation of the working principle, click here.

The plant can be equipped with a universal monitoring system to monitor the uniformity of sand circulation, and the process can be fully optimised for specific applications by applying an advanced control system.

Applications
ASTRASAND® filtration can be utilised for many applications, with unit capacity varying from only a few, to several thousands m3/hour. A few examples:
• Biological (de)nitrification and polishing of municipal and industrial waste water.
• Re-use of water, in combination with polishing, membrane filtration and disinfection.
• Aerobic biological purification of water, e.g. for MAC and PAC degradation.
• Direct filtration of surface water with in-line flocculation.
• Wash water treatment in drinking and process water production processes.
• (Biological) side stream filtration of cooling water.
• Biofiltration for BOD and heavy metal removal.

Trial plants
Paques offers a wide choice of water treatment plants that can be deployed on a temporary basis. These can quickly show the suitability of the technology and allow the specific process conditions to be established. Contact us for more information!