This invention relates to methods for disposing of high-water sludge materials, particularly to methods of electrically dewatering sewage sludge.
A variety of methods have been developed for disposing of sewage. In particular, a variety of biodegrading schemes have been perfected. Most of these schemes produce, as a final product, a sludge which is refractory to further biodegradation. The sludge consists of inorganic matter, proteins, cellulosic material, hydrocarbons and the like. Disposal of this sludge is a major problem for large sewage treatment facilities that may generate up to 100 tons a day of sludge.
One of the problems with sludge is that although it may appear to be very viscous or nearly solid, it is about 80 percent by weight water. Therefore, it is virtually non-combustible.
One method for dewatering sludge is what is herein referred to as electro-dewatering. In this process and electric field is applied to a mass of sludge. This tends to free the water, presumably because the constituent molecules of the sludge move in response to the electric field.
Fremont in U.S. Pat. No. 4,671,874 discloses an electro-dewatering system using a chopped and time varied current. The conveyors shown are not electrified, but have electrodes behind them.
Roslonoski in U.S. Pat. No. 4,655,932 adds an electrolyte to the sludge to increase efficiency.
Bastegen in U.S. Pat. No. 4,402,834 teaches a conveyor which dewaters by vacuum, centrifugal, static pressure and pressure means.
Sneek in U.S. Pat. No. 4,101,400 teaches a pair of electrode conveyors inside a pair of motive conveyors.