SAND FILTER BASINS
at a waterworks atop a
rise on Lake Constance.
A flocculation agent is
added to pre-filtered and
ozonized lake water to
facilitate sand filtering.
In the final stage the water
then seeps through 1.40 m
of quartzite sand in these
15 filter basins, each of
which is 20 m long, and
becomes drinking water.