Marine outfall
A marine outfall (or ocean outfall) is a pipeline or tunnel that discharges municipal or industrial
The world's first marine outfall was built in
Advantages
The main advantages of marine outfalls for the discharge of wastewater are:[8]
- the natural pathogensand other pollutants
- the ability to keep the sewage field submerged because of the depth at which the sewage 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.[9] Preliminary treatment also requires much less land than advanced wastewater treatment.
Disadvantages
Marine outfalls for partially treated or untreated wastewater remain controversial. 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
Technology
Outfalls vary in diameter from as narrow as 15 cm to as wide as 8 m; the widest registered outfall in the world with 8 m diameter is located in
Outfall materials include
Examples
Submarine outfalls exist, existed or have been considered in the following locations, among many others:
- Africa
- Casablanca (Morocco).
- Cape Town (South Africa).[10]
- Asia
- Manila Bay (Philippines).
- Mumbai (India).
- Mutwall ( Sri Lanka).
- Wellawaththa (Sri Lanka).
- Lunawa (Sri Lanka).
- Oceania
- Anglesea, Victoria.[11]
- Victoria.[12]
- Sydney (e.g., Bondi Ocean Outfall Sewer)
- Europe
- Barcelona, Spain
- Costa do Estoril(Portugal)
- Marmara Seanear Istanbul (Turkey)
- San Sebastián (Spain)
- Split(Croatia)
- Thames Estuary downstream of London (UK)
- Edinburgh, Scotland.
- North America
- Honolulu (USA)
- New York Bight (USA)
- Southern California Bight (USA).[13] and
- Victoria, British Columbia, (Canada).[14]
- Santa Monica, United States (world's first) [citation needed]
- Boston, United States (world's largest) [citation needed]
- The city of San Diego used Pacific Ocean dilution of primary treated effluent into the 21st century.[15]
- Latin America and the Caribbean
- Cartagena, Colombia
- Ipanema Beach beach from Rio de Janeiro (Brazil). 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.[2]
- Sosua(Dominican Republic).
Controversies
In the 1960s the city of Sydney 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.[16]
The submarine outfall in Cartagena, Colombia was financed with a loan by the World Bank. 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, which contracted two independent three-dimensional modeling efforts in 2006. Both "confirmed that the 2.85km long submarine outfall (was) adequate."[17]
For disposal into the ocean, environmental treaty requirements have to met. As international treaties often manage water over countries' borders, wastewater disposal is easier in bodies of water found entirely under the jurisdiction of one country.[citation needed]
References
- ISSN 0043-1354.
- ^ a b c d Outfalls Database Archived 2008-06-28 at the Wayback Machine Click on "Activities", then "Outfalls repository", then "database", then "Output"
- ^ "Combined Sewer Systems and Outfall Maps".
- ^ OUTFALLS DATABASE AND INFORMATION EXCHANGE Archived 2015-07-28 at the Wayback Machine
- ^ "Archived copy" (PDF). Archived from the original (PDF) on 2016-03-04. Retrieved 2015-08-24.
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: CS1 maint: archived copy as title (link) - ^ "Archived copy" (PDF). Archived from the original (PDF) on 2016-03-04. Retrieved 2015-08-24.
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: CS1 maint: archived copy as title (link) - ^ "Archived copy" (PDF). Archived from the original (PDF) on 2016-03-04. Retrieved 2015-08-24.
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: CS1 maint: archived copy as title (link) - ^ a b Beder, Sharon: From Pipe Dreams to Tunnel Vision: Engineering Decision-Making and Sydney's Sewerage System, Ph.D. Thesis, UNIVERSITY OF NEW SOUTH WALES, AUSTRALIA 1989, Chapter 8: The 'Science' and 'Metaphysics' of Submarine Outfalls
- ^ Philip JW Roberts:"Underwater and underused: The case of marine outfalls in wastewater disposal", in Water21, Magazine of the International Water Association, October 2010, pp. 22-26
- ^ "Error" (PDF).
- ^ "New Anglesea outfall towed into position". Barwon Water. Retrieved 2016-12-29.
- ^ Wong, Marcus (9 July 2015). "Where does Geelong's sewage go?". Waking Up In Geelong. Retrieved 2016-12-29.
- ^ Gunnerson, C.G., "Wastewater Management for Coastal Cities: The Ocean Disposal Option", World Bank Technical Paper Number 77, February 1988.
- ^ Rogers V.J.: Wastewater treatment utilizing submarine outfalls: the role of science, communications and public involvement in the decision-making process, Water Science and Technology, Volume 32, Number 2, 1995 , pp. 1-8(8)
- ^ "Point Loma Wastewater Treatment Plant". City of San Diego. Retrieved 5 January 2015.
- ^ Sharon Beder, 'Getting into Deep Water: Sydney's Extended Ocean Sewage Outfalls' in Pam Scott, ed., A Herd of White Elephants: Australia's Science & Technology Policy, Hale and Iremonger, Sydney, 1992, pp62-74.
- ^ World Bank Inspection Panel Progress Report on Cartagena Water Supply, Sewerage and Environmental Management Project
Sources
- IWA Committee on Marine Outfall Systems
- Salas, Henry J.:Submarine outfalls a viable alternative for sewage discharge of coastal cities in Latin America and the Caribbean, Lima; CEPIS, 2000