Una alcantarilla sanitaria o alcantarillado sucio es una tubería subterránea o un sistema de túneles para transportar aguas residuales desde casas y edificios comerciales (pero no aguas pluviales ) a instalaciones de tratamiento o eliminación. Las alcantarillas sanitarias son parte de un sistema general llamado sistema de alcantarillado o alcantarillado .
Las aguas residuales pueden tratarse para controlar la contaminación del agua antes de descargarlas a las aguas superficiales . [1] [2] Las alcantarillas sanitarias que sirven a las áreas industriales también transportan aguas residuales industriales .
Los sistemas de alcantarillado sanitario separados están diseñados para transportar aguas residuales por sí solas. En los municipios que cuentan con alcantarillado sanitario, los desagües pluviales separados pueden transportar la escorrentía superficial directamente a las aguas superficiales. Las alcantarillas sanitarias se distinguen de las alcantarillas combinadas , que combinan las aguas residuales con la escorrentía de aguas pluviales en una tubería. Los sistemas de alcantarillado sanitario son beneficiosos porque evitan los desbordamientos de alcantarillado combinados .
Fondo
El tratamiento de aguas residuales es menos efectivo cuando los desechos sanitarios se diluyen con aguas pluviales, y los desbordamientos combinados de alcantarillado ocurren cuando la escorrentía de lluvias intensas o deshielo excede la capacidad hidráulica de las plantas de tratamiento de aguas residuales . [3] Para superar estas desventajas, algunas ciudades construyeron alcantarillas sanitarias separadas para recolectar solo las aguas residuales municipales y excluir la escorrentía de aguas pluviales, que se recolecta en drenajes pluviales separados. La decisión de construir un sistema de alcantarillado combinado o dos sistemas separados se basa principalmente en la necesidad de tratamiento de aguas residuales y el costo de proporcionar tratamiento durante eventos de lluvia intensa. Muchas ciudades con sistemas de alcantarillado combinados construyeron sus sistemas antes de instalar plantas de tratamiento de aguas residuales y no han reemplazado posteriormente esos sistemas de alcantarillado. [4]
Tipos
Alcantarillas convencionales por gravedad
En el mundo desarrollado, las alcantarillas son tuberías que van de los edificios a uno o más niveles de tuberías principales subterráneas más grandes, que transportan las aguas residuales a las instalaciones de tratamiento de aguas residuales . Las tuberías verticales, generalmente de hormigón prefabricado , llamadas bocas de acceso , conectan la red a la superficie. Dependiendo de la aplicación y el uso del sitio, estos tubos verticales pueden ser cilíndricos , excéntricos o concéntricos . Las alcantarillas se utilizan para acceder a las tuberías de alcantarillado para inspección y mantenimiento, y como medio para ventilar los gases de alcantarillado. También facilitan los ángulos verticales y horizontales en tuberías que de otro modo serían rectas. [6]
Las tuberías que transportan las aguas residuales de un edificio individual a una línea de alcantarillado por gravedad común se denominan laterales. Los ramales de alcantarillado suelen pasar por debajo de las calles que reciben los laterales de los edificios a lo largo de esa calle y descargan por gravedad en los conductos de alcantarillado en las alcantarillas. Las ciudades más grandes pueden tener alcantarillas llamadas interceptores , que reciben flujo de múltiples alcantarillas troncales. [7] [8]
Design and sizing of sanitary sewers considers the population to be served over the anticipated life of the sewer, per capita wastewater production, and flow peaking from timing of daily routines. Minimum sewer diameters are often specified to prevent blockage by solid materials flushed down toilets; and gradients may be selected to maintain flow velocities generating sufficient turbulence to minimize solids deposition within the sewer. Commercial and industrial wastewater flows are also considered, but diversion of surface runoff to storm drains eliminates wet weather flow peaks of inefficient combined sewers.[9]
Force mains
Pumps may be necessary where gravity sewers serve areas at lower elevations than the sewage treatment plant, or distant areas at similar elevations. A lift station is a sewer sump that lifts accumulated sewage to a higher elevation. The pump may discharge to another gravity sewer at that location or may discharge through a pressurized force main to some distant location.[8]
Effluent sewer
Effluent sewer systems, also called septic tank effluent drainage (STED) or solids-free sewer (SFS) systems, have septic tanks that collect sewage from residences and businesses, and the effluent that comes out of the tank is sent to either a centralized sewage treatment plant or a distributed treatment system for further treatment. Most of the solids are removed by the septic tanks, so the treatment plant can be much smaller than a typical plant. In addition, because of the vast reduction in solid waste, a pumping system, rather than a gravity system, can be used to move the wastewater. The pipes have small diameters, typically 1.5 to 4 inches (4 to 10 cm). Because the waste stream is pressurized, they can be laid just below the ground surface along the land's contour.[citation needed]
Simplified sewer
Simplified sanitary sewers consist of small-diameter pipes, typically around 100 millimetres (4 in), often laid at fairly flat gradients (1 in 200). Although the investment cost for simplified sanitary sewers can be about half the cost of conventional sewers, the requirements for operation and maintenance are usually higher. Simplified sewers are most common in Brazil and are also used in a number of other[which?] developing countries.[citation needed]
Vacuum sewer
In low-lying communities, wastewater is often conveyed by vacuum sewer. Pipelines range in size from pipes of 10 centimetres (3.9 in) in diameter to concrete-lined tunnels of up to 9 metres (30 ft) in diameter. 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.[10]
Mantenimiento
Sanitary sewer overflow can occur due to blocked or broken sewer lines, infiltration of excessive stormwater or malfunction of pumps. In these cases untreated sewage is discharged from a sanitary sewer into the environment prior to reaching sewage treatment facilities. To avoid this, maintenance is required.
The maintenance requirements vary with the type of sanitary sewer. In general, all sewers deteriorate with age, but infiltration and inflow are problems unique to sanitary sewers, since both combined sewers and storm drains are sized to carry these contributions. Holding infiltration to acceptable levels requires a higher standard of maintenance than necessary for structural integrity considerations of combined sewers.[11] A comprehensive construction inspection program is required to prevent inappropriate connection of cellar, yard, and roof drains to sanitary sewers.[12] The probability of inappropriate connections is higher where combined sewers and sanitary sewers are found in close proximity, because construction personnel may not recognize the difference. Many older cities still use combined sewers while adjacent suburbs were built with separate sanitary sewers.
For decades, when sanitary sewer pipes cracked or experienced other damage, the only option was an expensive excavation, removal and replacement of the damaged pipe, typically requiring street repavement afterwards. In the mid-1950s a unit was invented where two units at each end with a special cement mixture in between was pulled from one manhole cover to the next, coating the pipe with the cement under high pressure, which then cured rapidly, sealing all cracks and breaks in the pipe.[13] Today, a similar method using epoxy resin is used by some municipalities to re-line aging or damaged pipes, effectively creating a "pipe in a pipe". These methods may be unsuitable for locations where the full diameter of the original pipe is required to carry expected flows, and may be an unwise investment if greater wastewater flows may be anticipated from population growth, increased water use, or new service connections within the expected service life of the repair.
Another popular method for replacing aged or damaged lines is called pipe bursting, where a new pipe, typically PVC or ABS plastic, is drawn through the old pipe behind an "expander head" that breaks apart the old pipe as the new one is drawn through behind it.
These methods are most suitable for trunk sewers, since repair of lines with lateral connections is complicated by making provisions to receive lateral flows without accepting undesirable infiltration from inadequately sealed junctions.
Ventilación
Sometimes a sewer has a tall vent pipe to release foul gases well up away from people. Common names are, stink pipe, stink pole, stench pipe and sewer ventilation pipe.[14]
Historia
Sanitary sewers evolved from combined sewers built where water was plentiful. Animal feces accumulated on city streets while animal-powered transport moved people and goods. Accumulations of animal feces encouraged dumping chamber pots into streets where night soil collection was impractical.[15] Combined sewers were built to use surface runoff to flush waste off streets and move it underground to places distant from populated areas. Sewage treatment became necessary as population expanded, but increased volumes and pumping capacity required for treatment of diluted waste from combined sewers is more expensive than treating undiluted sewage.[16]
Ver también
- Blackwater (waste)
- Fatberg (sewer obstruction)
- Greywater
- Sewerage
- Sewer mining
- Stormwater
- Water pollution
Referencias
- ^ Metcalf, Leonard; Eddy, Harrison P. (1922). Sewerage and Sewage Disposal: A Textbook. New York: McGraw-Hill.
- ^ Staley, Cady; Pierson, George S. (1899). The Separate System of Sewerage, Its Theory and Construction. New York: Van Nostrand.
- ^ Report to Congress: Impacts and Control of CSOs and SSOs (Report). Washington, D.C.: U.S. Environmental Protection Agency (EPA). August 2004. p. ES-2. EPA-833-R-04-001.
- ^ Metcalf & Eddy, Inc. (1972). Wastewater Engineering: collection, treatment, disposal. New York: McGraw–Hill. p. 119.
- ^ Tilley, E., Ulrich, L., Lüthi, C., Reymond, Ph., Zurbrügg, C. (2014) Compendium of Sanitation Systems and Technologies (2nd Revised Edition). Swiss Federal Institute of Aquatic Science and Technology (Eawag), Duebendorf, Switzerland. ISBN 978-3-906484-57-0.
- ^ "Acu-Sewer Pressure Pipe for Sewer Mains". Acu-Tech Piping Systems. Retrieved 2018-10-03.
- ^ Lee, C.C., ed. (2005). Environmental Engineering Dictionary (4th ed.). Lanham, MD: Government Institutes. p. 423. ISBN 9780865878488.
- ^ a b Design and Construction of Sanitary and Storm Sewers. New York: American Society of Civil Engineers and Water Pollution Control Federation. 1969. pp. 2, 288.
- ^ Tyler, Richard G. (1959). "Section 9". Civil Engineering Handbook (4th ed.). New York: McGraw-Hill. pp. 1–24.
- ^ Wastewater Treatment/Disposal for Small Communities: Manual (Report). EPA. 1992. pp. 84–88. EPA 625/R-95/005.
- ^ Hammer, Mark J. Water and Waste-Water Technology (1975) John Wiley & Sons ISBN 0-471-34726-4 p.442
- ^ Steel, E.W.; McGhee, Terence J. (1979). Water Supply and Sewerage (5th ed.). New York: McGraw-Hill. p. 22. ISBN 0-07-060929-2.
- ^ "Sewer Sealing Machine Patches Cracks Underground." Popular Mechanics, April 1956, p. 86.
- ^ https://www.thenorthernecho.co.uk/history/3211527.just-tip-stink-pole/
- ^ Bellis, Mary (2018-03-31). "The History of Plumbing". Archived from the original on 2017-10-14. Retrieved 2018-05-14. Alt URL
- ^ Steel, E.W.; McGhee, Terence J. (1979). Water Supply and Sewerage (5th ed.). New York: McGraw-Hill. p. 318. ISBN 0-07-060929-2.