In most cases, modern compounds are designed for safe disposal, although a few may require some pH adjustments before disposal. The main focus is generally on the solids portion of the wastewater. The wastewater will contain the residue from the media which is comprised of the binder, a ceramic or plastic, and whatever abrasive it contains. There will also be fine particles of the metal being cut. Filtering systems, gravity systems and centrifugal separators are suitable processes for recirculating systems or flow-through systems.
Filtering
The filters employed must be capable of removing particles in the five-micron range as a minimum requirement. The least expensive is the bag or sock filter. Bag filters are easy to use, but do not have a large surface area, thus will have to be changed or cleaned more often. Wound filament filters
have tremendous surface area and therefore a large capacity for residue. The filter is put in-line and requires a pump to force the wastewater through it. Careful analysis must be made to be aware of the ongoing running costs of these systems, especially in processes that involve heavy cutting and produce
large amounts of sludge.
Gravity
Gravity has an inherent advantage over a filter in that no matter how much sludge is produced, the efficiency does not dwindle. The basic principle is to have a large reservoir of water to give gravity time to pull down the solids so the cleaner water can be tapped off the top. The tank will usually contain upright baffles to cause the water to flow up over the baffle and drop out the heavier particles. It can be as simple as a few fifty-gallon drums interconnected or a long stainless steel tank with removable baffles for cleaning. The water must be either pumped up to a raised tank and gravity fed to the deburring machine or gravity fed to the tank and returned to the deburring machine by a pump. Systems have been set up that can run the same few hundred gallons of water in a closed loop for one month.
Centrifugal Separation
Centrifugal separators spin at high speeds to accelerate the gravitational effect. Water enters a spinning bowl in the center and exits out the top. The sludge clings to the outer wall as the water is forced out from the center opening. The advantage of this system is that it is very compact and needs very little reserve water. Since it works ten times faster than gravity alone, much less water is required. The centrifuge can also be used first to remove most of the sludge, followed by the use of a filter for further refinement.
