ABSTRACT
Dewatering may be the only processing required before digested sludge can be beneficially reused. The sludge cake produced by common dewatering techniques has a consistency similar to turkey dressing. A nonfluid material, it is easily handled and surprisingly nonoffensive, and it can be readily land applied by conventional manure spreaders. Natural dewatering systems include sludge lagoons, sand drying beds, Wedgewater drying beds, Phragmites reed beds, and dewatering via freezing. These dewatering methods require far less purchased power than mechanical thickening and usually rely on the force of gravity, solar power, or biological processes as the source of energy for dewatering. Sand drying beds dewater the sludge by gravity drainage, by capillary action drawing the water through the sand, and by evaporation from the surface of the bed.
