Where - South Cary Water Reclamation Facility, one of two wastewater treatment plants in Cary. (Sludge from the North Cary plant will also be dried there.)

More on Why

Cary hires companies to spray sludge on numerous pieces of farmland in the vicinity. However, this means hauling sludge by tractor-trailer as much as 60 miles. With development in the area, finding suitable land for disposal will become increasingly difficult.

North Carolina has strict rules getting rid of sludge and limiting exposure. Sometimes it goes into landfills, taking up valuable disposal space. Drying sludge into pellets decreases the volume to a small fraction of the original amount while producing a safe and useful landscaping product.

The Scoop on Sludge

Sludge is the residue of biological wastewater treatment and is referred to in the treatment industry as bio-solids. It contains the remains of organisms that digest solids left over after water in sewage has been removed, treated and either released into creeks or reused. Even so, sludge is almost entirely water.

At the South Cary plant, sludge is pumped from settling basins into a machine with porous belts that allow some of the liquid to drain off as it moves across the belts. Then thickening sludge drops into a hopper for pumping into storage tanks where biological decomposition continues.

Spin Cycle

With the new process, sludge in the holding tanks - still a soupy consistency - will move through a centrifuge. It throws off much more of the liquid, taking the sludge from 97 percent water to 80 percent water.

Into the Dryer

This is the final stage, where the sludge turns into tiny, round pellets that can be used as a fertilizer or soil amendment. This converts sludge into a product that the public can use. The pellets are stored in a silo until sold.

December 2001 award of engineering contract

Under construction photo1 (February 2005)
Under construction photo 2 (February 2005)
Under construction photo 3 (February 2005)
Under construction photo1 (May 2004)
Under construction photo2 (May 2004)
Under construction photo3 (May 2004)

201 Facilities Plan - Biosolids Management Facility