Collection
A sewage system may convey the wastewater by gravity to a sewage treatment plant. Where pipeline excavation is difficult because of rock or there is limited topographic relief (i.e., due to flat terrain), gravity collection systems may not be practical and the sewage must be pumped through a pipeline to the treatment plant. In low-lying communities, wastewater may be conveyed by vacuum. Pipelines range in size from pipes of six inches (150 mm) in diameter to concrete-lined tunnels of up to thirty feet (10 m) in diameter.
Community sewage can also be collected by an effluent sewer system, also known as a STEP system (Septic Tank Effluent Pumping). At each home, a buried collection tank is used to separate solids from the liquid effluent portion. Only the liquid portion is then pumped through small diameter pipe (typically 1.5" to 4") to downstream treatment. Because the wastestream is pressurized, the pipes can be laid just below the ground surface along the land's contour.
Sewage can also be collected by low pressure pumps and vacuum systems. A low pressure system uses a small grinder pump located at each point of connection, typically a house or business. Vacuum sewer systems use differential atmospheric pressure to move the liquid to a central vacuum station. Typically a vacuum sewer station can service approximately 1,200 homes before it becomes more cost-effective to build another station.
Read more about this topic: Sewage Collection And Disposal
Famous quotes containing the word collection:
“It’s rather grisly, isnt it, how soon a living man becomes nothing more than a collection of stocks and bonds and debts and real estate?”
—John Dos Passos (1896–1970)
“The society would permit no books of fiction in its collection because the town fathers believed that fiction ‘worketh abomination and maketh a lie.’”
—For the State of Rhode Island, U.S. public relief program (1935-1943)
“All urbanization, pushed beyond a certain point, automatically becomes suburbanization.... Every great city is just a collection of suburbs. Its inhabitants ... do not live in their city; they merely inhabit it.”
—Aldous Huxley (1894–1963)