Belt Filter Press
A belt filter dewaters by applying pressure to the feed solids to squeeze out the water. The solids are sandwiched between two tensioned porous belts are passed over and under rollers of various diameters. Increased pressure is created as the belt passes over rollers that successively decrease in diameter. Many designs of belt filtration processes are available, but all incorporate the following basic features: a polymer conditioning zone, gravity drainage zones, low pressure squeezing zones, and high pressure squeezing zones. Advanced designs provide a large filtration area, additional rollers, and variable belt speeds that can increase cake solids by five percent. Belt filter presses are continuous operations that do not require stoppage except for planned maintenance. Belt filter presses can produce a final product in the range of 30 to 50% dry solids depending on the nature of the feed material.

Plate and Frame Filter Press
The standard plate and frame filter press is also referred to as a recessed plate filter press. This is another variation of a solid/liquid separation process where the dewatering is achieved with the use of a contained volume, influent pumping pressure, and special filtering cloths through which the permeate can be discharged leaving the solids retained on the cloth. There is a wide range of these machines available commercially, ranging from nearly completely manual operations to nearly fully automatic. This unit is a batch operational process, as opposed to the continuous action of the belt filter press. This unit requires operator involvement, and the feed stream to the unit must be stopped when the plates have been fully loaded with feed solids. At this stoppage point, the plates are separated and the retained solids are dropped. After the solids removal, the plates are closed and feed can be resumed for the next cycle. These units can achieve a product dry solids concentration of 40 to 60%.

Membrane Plate and Frame Filter Press
This unit is a modification of the standard plate and frame filter press using specialty cloth, and an air-pressurized membrane that can put addition pressure on the water and solids to produce more permeate and thus a higher final dry solids concentration in the range of 50 to 65%. These units have the operational sequence of normal plate and frame presses and are operated in a batch mode, but are significantly more expensive than the standard units.