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AstraSand Sand Filter
Operation
WATER
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 through the filter in an upward direction. The filtrate is
discharged from the upper part of the filter (5).
SAND
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).
AIR
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.
SAND WASHER
The sand washer (10) at the top of the filtration tank washes the sand 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).
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Sand Filter)
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