Marine outfall
A marine outfall is a pipeline or tunnel that discharges municipal or industrial wastewater
Wastewater is any water that has been adversely affected in quality by anthropogenic influence. It comprises liquid waste discharged by domestic residences, commercial properties, industry, and/or agriculture and can encompass a wide range of potential contaminants and concentrations...

, stormwater
Stormwater is water that originates during precipitation events. It may also be used to apply to water that originates with snowmelt that enters the stormwater system...

, combined sewer overflows
Combined sewer overflow
A combined sewer is a type of sewer system that collects sanitary sewage and stormwater runoff in a single pipe system. Combined sewers can cause serious water pollution problems due to combined sewer overflows, which are caused by large variations in flow between dry and wet weather...

, cooling water, or brine
Brine is water, saturated or nearly saturated with salt .Brine is used to preserve vegetables, fruit, fish, and meat, in a process known as brining . Brine is also commonly used to age Halloumi and Feta cheeses, or for pickling foodstuffs, as a means of preserving them...

 effluents from water desalination plants to the sea. Usually they discharge under the sea's surface (submarine outfall). In the case of municipal wastewater, effluent is often being discharged after having undergone no or only primary treatment
Wastewater Treatment
Wastewater treatment may refer to:* Sewage treatment* Industrial wastewater treatment...

, with the intention of using the assimilative capacity of the sea for further treatment. Submarine outfalls are common throughout the world and probably number in the thousands. More than 200 outfalls alone have been listed in a single international database maintained by the Institute for Hydromechanics at Karlsruhe University for the International Association of Hydraulic Engineering and Research
International Association of Hydraulic Engineering and Research
The International Association for Hydro-Environment Engineering and Research , founded in 1935, is a worldwide, non-profit, independent organisation of engineers and water specialists working in fields related to the hydro-environment and in particular with reference to hydraulics and its practical...

 (IAHR) / International Water Association
International Water Association
The International Water Association is a self-governing non-profit organization which aims to cover all facets of the water cycle. The body is headquartered in London, with a global secreteriat based in The Hague and offices in Beijing, Bucharest, Nairobi, Singapore and Washington DC.The group's...

 (IWA) Committee on Marine Outfall Systems.

In Latin America and the Caribbean there were 134 outfalls with more than 500 m length in 2006 for wastewater disposal alone, according to a survey by the Panamerican Center for Environmental Engineering (CEPIS) of PAHO. According to the survey, the largest number of municipal wastewater outfalls in the region exist in Venezuela (39), Chile (39) and Brazil (22).


According to the Australian engineer Sharon Beder
Sharon Beder
Sharon Beder is a professor in the Faculty of Arts at the University of Wollongong in New South Wales, Australia. Her research has focussed on how power relationships are maintained and challenged, particularly by corporations and professions...

 the main advantages of marine outfalls for the discharge of wastewater are:
  • the natural dilution
    Dilution may refer to:* Reducing the concentration of a chemical* Serial dilution, a common way of going about this reduction of concentration* Homeopathic dilution* Dilution , an equation to calculate the rate a gas dilutes...

     and dispersion
    Dispersion (chemistry)
    A dispersion is a system in which particles are dispersed in a continuous phase of a different composition . See also emulsion. A dispersion is classified in a number of different ways, including how large the particles are in relation to the particles of the continuous phase, whether or not...

     of organic matter
    Organic matter
    Organic matter is matter that has come from a once-living organism; is capable of decay, or the product of decay; or is composed of organic compounds...

    , pathogens and other pollutants
  • the ability to keep the sewage field submerged because of the depth at which the sewage
    Sewage is water-carried waste, in solution or suspension, that is intended to be removed from a community. Also known as wastewater, it is more than 99% water and is characterized by volume or rate of flow, physical condition, chemical constituents and the bacteriological organisms that it contains...

     is being released
  • the greater die-off rate of pathogens due to the greater distance they will have to travel to shore.

They also tend to be less expensive than advanced wastewater treatment plants, using the natural assimilative capacity of the sea instead of energy-intensive treatment processes in a plant. For example, preliminary treatment of wastewater is sufficient with an effective outfall and diffuser. The costs of preliminary treatment are about one tenth that of secondary treatment. Preliminary treatment also requires much less land than advanced wastewater treatment.


Marine outfalls for partially treated or untreated wastewater remain controversial. Still according to Sharon Beder
Sharon Beder
Sharon Beder is a professor in the Faculty of Arts at the University of Wollongong in New South Wales, Australia. Her research has focussed on how power relationships are maintained and challenged, particularly by corporations and professions...

, the design calculation and computer models for pollution modeling have been criticized, arguing that dilution has been overemphasized and that other mechanisms work in the opposite direction, such as bioaccumulation
Bioaccumulation refers to the accumulation of substances, such as pesticides, or other organic chemicals in an organism. Bioaccumulation occurs when an organism absorbs a toxic substance at a rate greater than that at which the substance is lost...

 of toxins, sedimentation
Sedimentation is the tendency for particles in suspension to settle out of the fluid in which they are entrained, and come to rest against a barrier. This is due to their motion through the fluid in response to the forces acting on them: these forces can be due to gravity, centrifugal acceleration...

 of sludge
Sludge refers to the residual, semi-solid material left from industrial wastewater, or sewage treatment processes. It can also refer to the settled suspension obtained from conventional drinking water treatment, and numerous other industrial processes...

 particles and agglomeration
In the study of human settlements, an urban agglomeration is an extended city or town area comprising the built-up area of a central place and any suburbs linked by continuous urban area. In France, INSEE the French Statistical Institute, translate it as "Unité urbaine" which means continuous...

 of sewage particles with grease
Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...

. Accumulative mechanisms include slick formation, windrow formation, flocculate formation and agglomerated formation. Grease or wax can interfere with dispersion, so that bacteria and viruses could be carried to remote locations where the concentration of bacterial predators would be low and the die-off rate much lower.


Outfalls vary in diameter from as narrow as 15 cm to as wide as 8 meters; the widest registered outfall in the world with 8 m diameter is located in Navia (Spain) for the discharge of industrial wastewater. Outfalls vary in length from 50 meters to 55 km, the longest registered outfalls being the Boston
Boston is the capital of and largest city in Massachusetts, and is one of the oldest cities in the United States. The largest city in New England, Boston is regarded as the unofficial "Capital of New England" for its economic and cultural impact on the entire New England region. The city proper had...

 outfall with a length of 16 km and an industrial outfall in Ankleshwar (India) with a length of 55 km. The depth of the deepest point of an outfall varies from 3 m to up to 60 m, the deepest registered outfall being located in Macuto, Vargas
Macuto, Vargas
Macuto is a city in Vargas state, Venezuela.Macuto was founded in August 1740 on the site of an indigenous village called Guaicamacuto . It is known for its beaches, and for the town of Galipán, famous for its flowers....

 (Venezuela) for the discharge of untreated municipal wastewater.

Outfall materials include polyethylene
Polyethylene or polythene is the most widely used plastic, with an annual production of approximately 80 million metric tons...

, stainless steel
Stainless steel
In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....

, carbon steel, glass-reinforced plastic
Glass-reinforced plastic
Fiberglass , is a fiber reinforced polymer made of a plastic matrix reinforced by fine fibers of glass. It is also known as GFK ....

, reinforced concrete
Reinforced concrete
Reinforced concrete is concrete in which reinforcement bars , reinforcement grids, plates or fibers have been incorporated to strengthen the concrete in tension. It was invented by French gardener Joseph Monier in 1849 and patented in 1867. The term Ferro Concrete refers only to concrete that is...

, cast iron
Cast iron
Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...

 or tunnels through rock. Common installation methods for pipelines are float and sink, bottom pull and top pull.


Submarine outfalls exist, existed or have been considered - among many others - in the following locations:

  • Casablanca
    Casablanca is a city in western Morocco, located on the Atlantic Ocean. It is the capital of the Grand Casablanca region.Casablanca is Morocco's largest city as well as its chief port. It is also the biggest city in the Maghreb. The 2004 census recorded a population of 2,949,805 in the prefecture...


  • Manila Bay
    Manila Bay
    Manila Bay is a natural harbor which serves the Port of Manila , in the Philippines.The bay is considered to be one of the best natural harbors in Southeast Asia and one of the finest in the world...

  • Mumbai
    Mumbai , formerly known as Bombay in English, is the capital of the Indian state of Maharashtra. It is the most populous city in India, and the fourth most populous city in the world, with a total metropolitan area population of approximately 20.5 million...


  • Sydney
    Sydney is the most populous city in Australia and the state capital of New South Wales. Sydney is located on Australia's south-east coast of the Tasman Sea. As of June 2010, the greater metropolitan area had an approximate population of 4.6 million people...


  • Barcelona
    Barcelona is the second largest city in Spain after Madrid, and the capital of Catalonia, with a population of 1,621,537 within its administrative limits on a land area of...

    , Spain
  • Costa do Estoril (Portugal),
  • the Marmara Sea near Istanbul (Turkey),
  • San Sebastián
    San Sebastián
    Donostia-San Sebastián is a city and municipality located in the north of Spain, in the coast of the Bay of Biscay and 20 km away from the French border. The city is the capital of Gipuzkoa, in the autonomous community of the Basque Country. The municipality’s population is 186,122 , and its...

  • Split
    Split (city)
    Split is a Mediterranean city on the eastern shores of the Adriatic Sea, centered around the ancient Roman Palace of the Emperor Diocletian and its wide port bay. With a population of 178,192 citizens, and a metropolitan area numbering up to 467,899, Split is by far the largest Dalmatian city and...

  • the Thames Estuary
    Thames Estuary
    The Thames Mouth is the estuary in which the River Thames meets the waters of the North Sea.It is not easy to define the limits of the estuary, although physically the head of Sea Reach, near Canvey Island on the Essex shore is probably the western boundary...

     downstream of London (UK), and
  • Edinburgh, Scotland.

North America
  • Honolulu (USA),
  • the New York Bight
    New York Bight
    The New York Bight is a slight indentation along the Atlantic coast of the United States, extending northeasterly from Cape May Inlet in New Jersey to Montauk Point on the eastern tip of Long Island...

  • the Southern California Bight
    Southern California Bight
    The Southern California Bight includes coastal southern California, the Channel Islands and part of the Pacific Ocean.Within the Southern California bight lie the traditional territories of the Chumash and the Gabrieliño. These two cultures are considered the epitome of hunter-gatherer complexity...

     (USA), and
  • Victoria, British Columbia
    Victoria, British Columbia
    Victoria is the capital city of British Columbia, Canada and is located on the southern tip of Vancouver Island off Canada's Pacific coast. The city has a population of about 78,000 within the metropolitan area of Greater Victoria, which has a population of 360,063, the 15th most populous Canadian...

    , (Canada).

Latin America and the Caribbean
  • Cartagena, Colombia
    Cartagena, Colombia
    Cartagena de Indias , is a large Caribbean beach resort city on the northern coast of Colombia in the Caribbean Coast Region and capital of Bolívar Department...

  • Ipanema
    For other uses, see Ipanema . For the British rock band, see Ipanema .Ipanema is a neighborhood located in the southern region of the city of Rio de Janeiro, Brazil, between Leblon and Arpoador...

    A beach is a geological landform along the shoreline of an ocean, sea, lake or river. It usually consists of loose particles which are often composed of rock, such as sand, gravel, shingle, pebbles or cobblestones...

     from Rio de Janeiro
    Rio de Janeiro
    Rio de Janeiro , commonly referred to simply as Rio, is the capital city of the State of Rio de Janeiro, the second largest city of Brazil, and the third largest metropolitan area and agglomeration in South America, boasting approximately 6.3 million people within the city proper, making it the 6th...

    Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

    ). This outfall, built in 1975, discharges untreated wastewater through a pipe with a diameter of 2.4m and a length of 4,775m at a depth of 27m.
  • Sosua
    Sosúa is a small town in the Puerto Plata province of the Dominican Republic. Located approximately from the Puerto Plata International Airport , the town is accessed primarily by Camino Cinco, or Highway 5, which runs much of the length of the country's North coastline...

     (Dominican Republic).


In the 1960s the city of Sydney
Sydney is the most populous city in Australia and the state capital of New South Wales. Sydney is located on Australia's south-east coast of the Tasman Sea. As of June 2010, the greater metropolitan area had an approximate population of 4.6 million people...

 decided to build ocean sewage outfalls to discharge partially treated sewage 2-4 km offshore at a cost of US$ 300 million. In the late 1980s, however, the government promised to upgrade the coastal treatment plants so that sewage would be treated to at least secondary treatment standards before discharge into the ocean.

The submarine outfall in Cartagena, Colombia
Cartagena, Colombia
Cartagena de Indias , is a large Caribbean beach resort city on the northern coast of Colombia in the Caribbean Coast Region and capital of Bolívar Department...

 was financed with a loan by the World Bank
World Bank
The World Bank is an international financial institution that provides loans to developing countries for capital programmes.The World Bank's official goal is the reduction of poverty...

. It was subsequently challenged by residents claiming that the wastewater caused damage to the marine environment and to fisheries. The case was taken up by the World Bank's Inspection Panel
World Bank's Inspection Panel
The Inspection Panel is an independent accountability mechanism of the World Bank. It was established in September 1993 by the World Bank Board of Directors, and started operations on August 1, 1994. The Panel provides a forum for people who believe that they may be adversely affected by...

, which contracted two independent three-dimensional modeling efforts in 2006. Both "confirmed that the 2.85km long submarine outfall (was) adequate."


The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.