What happens to sludge that settles at the bottom of a sedimentation basin?

In a water supply system or wastewater treatment plant, the solids that settle at the bottom of a sedimentation basin are known as sludge.12

Once this sludge accumulates, it is moved along the bottom of the tank by mechanical scrapers and collected in a hopper. From there, it is pumped out for further processing. Because this raw sludge is a thin slurry, it typically undergoes thickening to reduce its volume, followed by processes such as digestion and dewatering.345

The ultimate goal of these treatments is to stabilize the organic materials and reduce the sludge's volume, making it easier and safer to handle. Final disposal methods include burial in a sanitary landfill, application to agricultural land as a fertilizer, or incineration to convert the solids into inert ash.67