AWWA ACE92106

This paper reviews the current state-of-the-art of mechanical dewatering systems, and addresses some of the issues that must be considered in the design of these systems. There are several types of mechanical dewatering systems available for increasing the solids content and reducing the volume of residual streams from water treatment plants. Some of these systems use sedimentation principles to separate excess water from liquid sludge; some use a positive pressure differential as the driving force; while others combine freezing or drying concepts, or electric and ultrasonic fields with mechanical dewatering techniques to improve the dewatering process. Mechanical systems most commonly used for the dewatering of residual streams discussed in this paper are: diaphragm filter press; conventional filter press; belt filter press; solid bowl centrifuge. Innovative mechanical systems that are likely candidates for future use discussed include: mechanical freeze-thaw machine; continuous high- pressure filter press; expressor press; tubular filter press; crossflow microfiltration process; Som-A-System screw press; HIW screw press; Hi- Compact press; compactor; Carver-Greenfield process; electroacoustic dewatering system; and pyrodisintegrator.