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A skimmer is a machine that separates oil or particles floating on a liquid surface. A common application is removing oil floating on water using an oily water skimmer. These technologies are commonly used for oil spill remediation but are also commonly found in industrial applications such as removing oil from machine tool coolant and removing oil from aqueous parts washers. They were used to great effect to assist in the remediation of the Exxon Valdez spill in 1989.
The use of skimmers in industrial applications is often required to remove oils, grease and fats prior to further treatment for environmental discharge compliance. By removing the top layer of oils, water stagnation, smell and unsightly surface scum can be reduced. Placed before a oily water treatment system may give greater oil separation efficiency for improved wastewater quality. It should be noted that all oil skimmers will pick up a percentage of water with the oil which will need to be decanted to obtain concentrated oil
Oil skimmers are commonly found in three types: weir and oleophilic and non-oleophilic (disc, drum, belt, tube, brush,mop, grooved disc, grooved drum):
Weir skimmers function by allowing the oil floating on the surface of the water to flow over a weir. The height of the weir may be manually adjustable. These devices will collect water when oil is no longer present. Weir skimmers are also available in floating, self-adjusting variations. These models allow them to be effectively used even in changing water levels.
Oleophilic skimmers function by using a rotating element such as a drum, to which the oil adheres. The oil is wiped from the surface of the drum and collected. They are very efficient and do not pick up any appreciable amounts of water even when oil is not present. Oleophilic skimmers are distinguished not by their operation but by the component used to collect the oil. Ropes, discs, or drums are treated with a substance or otherwise manufactured to adhere to oil.
Non-oleophilic skimmers are distinguished by the component used to collect the oil. A metal disc, belt or drum is used in applications where an oleophilic material is inappropriate, such as in a hot alkaline aqueous parts washer. The skimmer is generally turned off whenever there is no oil to skim thus minimizing the amount of water collected. Metal skimming elements are nearly as efficient as oleophilic skimmers when oil is present.
Oil skimming designs were entered in the The Wendy Schmidt Oil Cleanup X CHALLENGE in 2011. The winning technology utilized Grooves placed on the surface of rotating discs.
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