Innovative Design of Sludge Drying Beds Using 3D GEOWEB Geocells
Wastewater treatment facilities have long had to contend with the challenge of dewatering sludge to minimize waste and achieve overall cost efficiency for disposal. Large-scale facilities commonly use mechanical filter presses or centrifuges to dewater sludge. This equipment is often too cumbersome and expensive for many smaller facilities, so they rely on sand filter drying beds for sludge dewatering. Because small tractors or loaders cannot be operated on the loose sands of a conventional drying bed, a system must be implemented to stabilize the sand and improve load distribution for routine cleanout operations.
Transforming Infill Material with the GEOWEB Geocells
Through an interconnected honeycomb-like network, 3D geocells confine and stabilize soils that would otherwise be unstable under loading conditions. Geocells are efficient and economical for fast-built unpaved roadways and retaining walls, erosion control of slopes, and stormwater channel protection. The GEOWEB 3D Stabilization System is the industry’s most complete geocell system, designed with fully engineered components to withstand the most challenging site problems. Made from robust high-density polyethylene (HDPE) since conception, GEOWEB geocells offer the highest, longest-lasting, and most proven performance of any geocell system in civil applications.
The GEOWEB System Improves Clean-Up System for Solid Waste Treatment Facility
A solid waste treatment facility in Florida was using vacuum-assisted drying beds to dewater chemically oxidized sewage sludge, but they were experiencing costly maintenance issues. The material deteriorated under constant use, and replacement costs were high.
The facility required a solution that would allow them to operate a small tractor over the sand filter bed to remove the sludge. They chose the GEOWEB 3D Confinement System because of its ability to support vehicular traffic over poor soils. The GEOWEB system provides complete structural support by limiting lateral movement of the confined material-in this case, very loose sand. The GEOWEB system was installed in the top layer of the loose material in one of the two sand filter drying beds.
The 10-inch-deep top layer was composed of uniformly graded filter sand, and below this was a graduated layer of river gravel. A geonet material was placed on top of the graded layer to ensure efficient sand placement. The complete cross-section consisted of a 2-inch sand layer placed over the 8-inch sand-filled cellular confinement system underlain by the geonet and gravel bed below.
After installing the multi-layer system, cleanout operations significantly improved. With the new system, cleaning the sand drying bed requires moving only one to two inches of sand that contain the sludge and allows the crews to load and clean one 1,700-square-foot drying bed in 48 hours, unlike the original system which could take several days. The GEOWEB Cellular Confinement System also acts as a natural depth gauge for the front end loader, the blade of which can easily be used to backdrag the final few inches of material during cleanout to protect the system against damage and preserve operational integrity. Overall, the GEOWEB system reduced maintenance costs for the facility by 50 percent.