ABSTRACT
Sl u d g e is the watery mixture of solids that comes from primary and secondary treatment. The first step in treating these solids is to remove a large amount of the water. This leaves less sludge to treat. There ate a number of ways to thicken the sludge. Four of the most common methods used are centrifugation, gravity thickening, dissolved air flotation, and gravity belt thickening. Each of these present a different wry of concen trating sludge solids to make them easier and less expensive to treat.
