After the sludge has been digested in the anaerobic digesters, the sludge is about 5% solids which is approximately the consistency of a thin milkshake. We use centrifuges to dewater the sludge to reduce the volume of the sludge for easier handling.

Each month we alternate between one of two centrifuges to dewater sludge. Each centrifuge has the ability to dewater sludge from about 5% solids down to 27% solids (the consistency of gooey clay topsoil). This reduces 1,000 gallons of sludge down to about 146 gallons. One centrifuge can process 6,000 gallons of sludge an hour.








The centrifuge has two main parts, an outer bowl and an inner scroll. The scroll spins at a slightly different rate than the bowl, and solids are carried longitudinally along the axis until it discharges into a screw conveyor. The speed of the bowl and scroll are controlled by variable speed drives.









Sludge is fed into the centrifuge through the red pipe. Below the centrifuges, is a horizontal conveyor that is slightly inclined to provide drainage of water. The horizontal conveyor serves both centrifuges, and moves the sludge from right to left in the photo. The sludge moves along the conveyor to two more conveyors (one vertical and one horizontal) that eventually discharge the sludge into a dump truck.








This dump truck receives the dewatered sludge for transport to a sludge storage building. The conveyor has three remotely controlled ports to dump at the front, center, and rear portion of the truck to provide uniform load distribution in the truck. Normally, we run only one centrifuge, for 12 hours a day to process 6,000 gallons of sludge an hour down to about 25 cubic yards of sludge a day.






To enhance dewatering of the sludge in the centrifuge, a polymer solution is added as the sludge enters the centrifuge. The polymer concentration optimizes the dewaterability of the sludge. Mixing and conditioning of the polymer solution is handled in one of the two polymer mixing systems. In this photo you can see the twin towers of polymer mixing systems. Each system has a mixing tank on the top and a feed tank on the bottom. The control panels for the polymer mixing system are on the front of each unit.

1. Preliminary Treatment
2. Primary Treatment
3. Roughing Filters
4. Activated Sludge
5. Effluent Filtration
6. Effluent Disinfection
7. Sludge Digestion
8. Sludge Dewatering
9. Sludge Storage
10. Other Unique Features