Thickening

A volume reduction of approximately 30 – 80 % can be reached with sludge thickening before a further treatment. At smaller wastewater treatment plants, where the sludge is driven off regularly, thickening usually takes place directly in the sludge storage tank. The sludge is compressed at the tank bottom only by the force of gravity, while above the sludge a cloudy water layer is formed, which is taken off and led back into the inlet.

On larger plants separate thickening basins exist. These basins are equipped with slow rotating vertical rods, which create micro canals in the sludge for a better dewatering. Also pure machine thickening is gaining more significance with e.g. non-stabilised sludges, that could rot during the storage.

More information about sludge treatment and reduction are on the following pages:

Stabilisation
Dewatering
Sludge drying
Copious growth of filamentous organisms - problems and solutions

Filter presses for sludge treatment

Centrifugation and centrifuges