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Introduction
[edit]An oil water separator (OWS) is a piece of shipboard or in general waste water treatment equipment that separates oil from oily waste water such as bilge water before the waste water is discharged over board. Oily Water Systems also filter out other contaminates such as heavy metals, cleaners, glycol, solvents, phosphates and nitrates.[1] Bilge Water is an unavoidable product of ship board operations. Oil leaks from running machinery such as Ship Service Diesel Generators, Air Compressors, and the main propulsion engine which is most likely medium speed or slow speed diesel. OWS are designed with an alarm devices and an automatic closure device which is activated when the full oil storage capacity of the oil water separator has been reached.
Some manufacturers of oil water separator equipment are: Mercer International (USA), San Dizier Environment (France), Conder Environmental Solutions (UK), and Sulzer Chemtec (Switzerland).
Regulations for treated water discharge
[edit]Due to the regulations set forth by the Clean Water Act amended Section 312, regulates which discharge will be required to be treated with marine polling control divides such as an oily water separator. If a vessel doesn’t have an oily water separator contaminated water must be discarded to a shoreside treatment facility. When an oily water separator is on board a vessel discharges are subject to change depending on how far away the vessel is from land. If a vessel is twelve nautical miles or less from shore treated water can be discharged only if it contains less than 15 parts per million of contaminates.[2].Regulations vary from country to country, some regulations are more strict than others. Some European countries and Canada have stricter rules on discharge, since the beginning of 2005 vessel’s must have 5 part per million of contaminate or less.[3] Once a vessel has traveled more than twelve nautical miles away from land discharge of water containing less than 100ppm of contaminates is allowed.[2]
The discharge of oil contaminated waters are also under compliance with other organizations other than the Environmental Protection Agency, such as the International Convention for the Prevention of Pollution from Ships (MARPOL), and International Maritime Organization (IMO).These organizations also committed to strict adherence of the regulations set forth to protect marine life and coastal environments. To make sure sea goers and companies abide by these regulations, these agency require logs to be taken of when processed water is discharged. [4]
Types Of Oily Water Separators
[edit]Plate Gravity Separator
[edit]Inside of the treatment camber of Plate Gavity separators, there are sets of oleophilic plates where contaminated water flows through. The oil contaminates in the water coalesce on the underside of the plate. As more oil contaminates congregate on the plate they form droplets of oil. Once a sufficient amount of oil has accumulated on the underside of the plate, the mass of oil flows through the plate and head to the top of the treatment camber. The oil moves to the top since it’s specific gravity is less than water. The oil accumulating at the top is then transferred to waste oil tank on the vessel were it is later discharged to a treatment facility shoreside. This type of Oily Water Separator is very common in ships it has some flaws that decrease efficiency. Oil particles that are twenty microns or smaller do not get separated since they raise throughout the treatment champed very slowly. Bilge water isn’t contaminated with one type of oil, it is a contaminated with a variation of oils. Some of these oils like gross oil can stop the ability of the plates to let oil pass which significantly stunt efficiency of the Oil Water separator. Plates must be replaced when fouled, which in turn could increase annual costs of operation.[1]
Electrochemical
[edit]Wastewater purification of oils and contaminates by electrochemical emulsification is actively in research and development. Electrochemical emulsification involves the generation of electrolytic bubbles that attract pollutants such as sludge and carry them to the top of the treatment chamber. Once at the top of the treatment chamber the oil and other pollutants are transferred to a waste oil tank. [5]
Bioremediation
[edit]Bioremediation is the use of microorganisms to treat contaminated water. A sustained environment is needed for the microorganisms which includes nutrients and hydrocarbons such as oil or other contaminates, and oxygen. The process of bio remediation, is a common in nature and is very easy to install. Bio remediation would mostly like be used with a plate gravity system as a second means a purification. Bio remediation is able to treat pollutants that may not be detectable, or detectable under set limits. Bio remediation is also helpful for treating organic contaminates such as glycerol, solvents, jet fuel, detergents, nitrogen and phosphates. Bio remediation doesn't produce toxic or unpleasant odors. After treatment of contaminated water, carbon dioxide and water are the only product of the Bio remediation [1]
References
[edit]- ^ a b c Caplan, J. A., Newton, C., & Kelemen, D. (2000). Technical report: Novel oil/water separator for treatment of oily bilge water. Marine Technology and SNAME News, 37(2), 111.
- ^ a b EPA. Phase one final rule and technical development document of uniform national discharge standards: surface vessel bilgewater/ oil water separator: nature of discharge. Retrieved from http://water.epa.gov/lawsregs/lawsguidance/cwa/vessel/unds/upload/2007_07_10_oceans_regulatory_unds_TDDdocuments_appAsurface.pdf
- ^ Ghidossi, R. , Veyret, D. , Scotto, J. , Jalabert, T. , & Moulin, P. (2009). Ferry oily wastewater treatment. Separation and Purification Technology, 64(3), 296-303.
- ^ GARD AS. (December, 2013). Prevention of pollution of oil. Retrieved from http://www.gard.no/ikbViewer/Content/72338/pollution
- ^ Yang, C. (2007). Electrochemical coagulation for oily water demulsification. Separation and Purification Technology, 54(3), 388-395.