5.3 Management of wastes from water treatment plants
From the water treatment process that you have just studied, make a list of the different wastes that arise.
You probably thought of the screenings from the coarse and fine screens, the sludge from the sedimentation tank, and backwash from the rapid gravity sand filter. There will be other wastes, such as packaging from chemicals used (typically plastic drums) and replacement equipment (which may come in wooden or cardboard boxes).
Coarse screenings are usually sent to a landfill or other waste disposal site. Fine screenings (in the form of a slurry) may be discharged to a sewer, if there is one, or sent to a landfill. The sludge from the sedimentation tank can be sent to landfill, or to a sewage treatment plant. In the latter it is added to the incoming sewage, where it can help settlement of solids.
The backwash from the sand filter is discharged into the sewer or returned to the river after settlement of solids. Packaging waste such as chemical drums can be returned to the supplier for reuse. Wood and cardboard waste can be recycled.
5.2.7 Supplementary treatment