The water slowly percolates back to the groundwater supply which can then be pumped to the surface as it is needed. In more densely developed areas, sewers are used. These are underground pipes connected to a wastewater treatment facility. Once in the treatment plant, wastewater goes through a series of actions which will help to clean up the water. A wastewater treatment plant's basic function is to quicken the natural processes by which water purifies itself.
Wastewater treatment is vital to the purification of our water and the health of the population.
In the primary stage of treatment, solids are allowed to settle and are removed from the water. The screen removes large floating objects such as rags and sticks that may clog pumps and small pipes. After the sewage has been screened it passes into what is called a grit chamber where sand, grit, cinders and small stones are allowed to settle to the bottom. The unwanted grit or gravel from this process is usually disposed of by filling land near a treatment plant. With screening completed and the grit removed, the sewage still contains dissolved organic matter along with suspended solids.