VanLare Wastewater Treatment Facility - Dewatering

An average of 500,000 gallons of sludge per day (feed sludge) is pumped by duplex piston pumps to ten beltpresses for dewatering. Cationic polymer is added to the feed sludge before it reaches the beltpress. This is done to provide a charge to the sludge particles for dewatering. Beltpresses by three different manufacturers are used. Each beltpress produces 1500 dry pounds of sludge per hour. The beltpress operators regulate the production output according to incinerator operators needs. The end product from the beltpresses, known as 'Cake', is conveyed to the incinerators for thermal destruction.

The original design from 1976 used vacuum filters to change the by-product of sludge into cake before it was sent to the incinerator. The problem with the vacuum filters was that they did not remove enough water out of the sludge. This resulted in the sludge remaining in the plant for too long which led to backclog. Backclog created a terrible odor problem in the communities surrounding the plant. In order to fix the odor problem, a newer dewatering technology needed to be developed.

The new technology that replaced the ineffective vacuum filter was the beltpress. Switching to the beltpress not only fixed the odor problem, but it greatly reduced the cost of incinerating the wet sludge. The result of dewatering using vacuum filters was only 13% solids, whereas the result of dewatering using beltpresses is 25% solids. As the percentage of solids rises (e.g. 25% solids = 1 ton of solids to 3 tons of water), the fuel demand and therefore fuel costs for incineration of wet sludge decreases.