Abstract: Steaming filter aid cakes in-place in a pressure leaf filter is a simple, inexpensive, and reliable technique for insuring that all collected pathogens are destroyed and never released back into the environment. Filter aids including diatomaceous earth reduce giardia and cryptosporidium by at least 6 logs. D.E. filtration allows the flexibility to adjust the dosage for bodyfeed and the grade to suit changing water conditions, and the process of bodyfeeding filter aids is the only technology that seals its own leaks. After sterilization, the filter aids can be recycled. With hydrocyclones the contaminants can be separated from the filter aids and up to 90% of the filter aid can be recovered. This makes filter aid treatment a very cost effective treatment for large plants as well as the smaller plants where this technology has been used in the past.

Abstract: A twin belt filter press system has an amendment such as sawdust, fed to a sludge or slurry being dewatered after the sludge/slurry has been initially dewatered in a gravity drain section to form a cake on a first porous belt. The amendment cascades into the partially dewatered cake off the first belt, allowing mixing of the cake and amendment in an essentially belt-wide drop zone so that the amendment partially and quickly desorbs the cake before the cake and amendment mixture progresses into a nip formed by the first belt and a porous second belt. The mixture subsequently is carried in a position between the belts for pressing to remove moisture from both the cake and amendment. In one embodiment a shear-minimizing mixer is arranged in the amendment drop zone to additionally mix the amendment with the cake.

Abstract: In a dewatering machine for dewatering wet solids in which an elastomeric covered roll applies pressure upon one or more dewatering valves, the improvement whereby the elastomeric roll covering is a multi-layer covering having a graded hardness across the covering layer. A typical covered roll of such a machine is one in which a soft rubber-like material adheres to the surface of the roll and is covered by a harder outer covering.

Abstract: A dual-belt method and apparatus for dewatering a water laden cake of material through the use of multiple primary dewatering rolls is disclosed. A pair of porous belts containing filter cake disposed between the belts are wrapped around a first and second primary roll so that the belts circumscribe more than a 180.degree. arc of each roll. The pressure applied to the belts, that is, to the filter cake, is greater on the second roll than on the first roll.