Sandfilter

The contaminated water is fed through the supply pipe (1) to the filter. The water enters the filter bed (4) through the supply pipe (2) and the distributors (3). This water is purified as it flows up through the filter. The filtrate is discharged through the top of the filter (5). The filter bed moves down as the water flows up. Dirty sand (6) is constantly extracted from the sand bed and washed, after which it is placed back on top of the sand bed (7).

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 (8). Intensive washing movements separate the impurities from the sand particles. At the top of the pipe, the air is released and the dirty water is drained away (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. In doing so, the last traces of contamination are removed from the sand. The flow is caused by a difference in level between the filtrate (11) and the rinsing water (9).

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

(See picture)