Not infrequently we receive calls from firms seeking assistance with pond remediation. They will have a contract to remove sludge from a pond, and they want to dewater the sludge. Almost always the pond sludge is made up of biologically decomposed material that cannot be dewatered with the metal screens of a screw press. We explain that it is a belt press that they are looking for.
Recently a paper mill requested a proposal for pond remediation presses. Before we could explain why it would not work, it was explained to us how it did work: The mill had found that they could blend a press aid to make the sludge pressable. Furthermore, they had several sources of reject fiber in their operation that were quite suitable as press aid. They referred to this reject fiber as "sweetener".
In order to remediate the pond within six months, a large 30" press was called for. However previously the mill had rented a 10" press and tried it out at several locations in the plant. Because of the success of these other applications, our recommendation has been that they acquire four 16" presses. These will be available for use elsewhere in the mill following the pond remediation program.
This use of fiber as a press aid will not always work. In some cases, especially with sludge from a food plant, the biological particles do not adhere well to the fibers of the press aid. The result is that an excessive amount of the sludge passed through the screen of the press. The total capture rate of solids can be inadequate.