A sufficient detention time is needed to adequately stabilize the sludges. Both of these factors are easily monitored and maintained. Dewatering This process is the most likely contributor to the low solids content of the dewatered sludges. The sludge from the digester is pumped to three centrifuges that remove the water using rotational centrifugal forces. Two of the centrifuges were recently rebuild.
Polymer is added to the digested sludge prior to entering the centrifuges.
The polymer has the effect of binding the sludge particles together which aids in dewatering while in the centrifuges. The polymer feed rate is adjusted solely by visual checks of the centrifuge discharge water. This unscientific non-analytical method for controlling the polymer feed rate can produce sludges with different consistencies and solids contents depending on the operator doing the checking. The solution to increase the efficiency of this process is two-fold. First, the centrifuges need to be checked to verify that they are operating according to design and manufacturer s recommendations.