The clarification allows
solid muds separation from purified water by the elimination of
suspended particles. Under the effect of their weight, the particles
revolve towards the bottom where they settle.
The decantation proceeds in continuous flow. There exist several types
of flow, namely:
- Horizontal flow
- Vertical flow
- Inclined flow out of lamellate decanter with counter-current
or Co-current
-
Filters planted with reeds
The principle of operation rests
on the existence of two stages of filters in series, furnished with
gravels and sands, on which purifying bacteria fix themselves. A
planted filter of reeds is a tight basin with a filtration aggregate
block in which reeds can be planted. The reeds which are planted on the
surface of the solid mass make it possible to limit the phenomena of
filling by the abundance of their rhizomes. Under good conditions of
design and operating, this technique allows to obtain very high
purifying outputs (95%) on the organic matters. The elimination of
nitrogen and phosphorous pollution can reach 70%.