Most sludge de-watering applications will benefit from sludge conditioning ahead of the thickening or de-watering device. Coagulants and flocculants, polymers, are widely used in many industries to remove water from wet solids (sludge).
Note that flocculants alone are often all that is required to improve sludge de-watering.
This process is known as sludge conditioning. Water release from sludge is affected by electrostatic forces of attraction and repulsion that control floc formation and size. Floc size and uniformity controls the flow of water through the sludge under gravity (de-watering boxes), or under pressure (belt presses and plate and frame filter presses). A large robust uniform floc will de-water more easily. Untreated sludges often are comprised of a wide range of floc sizes making it more difficult for water to pass through and out of the sludge. Chemical conditioning produces a much more consistent floc size that allows water to pass through.
Bench scale or pilot scale testing is the best way to determine which flocculents are right for your de-watering application.