EURO-ECO 2008 Hanover 18 - 20 November 2008	Environmental and Engineering Aspects for sustainable living
	European Academy of Natural Sciences, Hanover European Scientific Society, Hanover University of Bremen, Bremen

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Oil and oil products are the most large scale contaminants for water basins. Over 13 – 14 mln tones of oil products pollute the World Ocean annually due to leakages, oil spills and other accidents. Oil contamination spreads out across the surface of the water basins and forms thin hydrophobic film, which keeps the water environment from free gases interchange with the atmosphere, resulting in negative effect on the living organisms. Due to strong molecular adhesion the oil film is only slightly destroyable and quickly “closes” when its integrity is damaged.

To remove the oil contamination spot from the surface of the water basin, slick bars, specialized oil sweepers, skimmer arrangements, various sorbing agents and germ cultures are used. One of the well-known skimmer arrangements (the Reinverft arrangement) represents a floating submerged chute hopper, out of which the water with oil film supplied from the surface is drained by means of a pump (Nilson-Smith. “Oil and Sea Ecology”. Publishing house: Progress. Moscow. 1977). This and other devices feature a certain disadvantage: their complex design and inability to work under conditions of sea disturbance.

We have developed a device intended for collecting oil contamination from water basin surfaces; this device employs renewable energy of the waves for operation (Patent of the Russian Federation, No. 6809) – the water-wave oil skimmer. The device is simple in design. It presents a reservoir open at both ends, its upper part equipped with a circular band from the inside; this circular band serves as the mounting seat for a light floating valve.

The reservoir is suspended from a fixed (relative to the waves) base (from the shore or berth) or from a movable base (awash, from a water craft, raft, buoy). When suspending the device both from a fixed base and from the awash foundation, the upper edge of the reservoir crosses the water boundary, covered with oil film, and appears now under the water and then above the water surface.

The device intended for collecting oil contamination from the water basin surface operates in the following manner. The device is placed in the water at the site where the oil contamination has spread, the upper edge of the reservoir is submerged into water, the floating valve presses against the circular band and closes the reservoir. The oil film destroyed while the device is being installed, recovers its integrity, closing above the reservoir. When the upper edge of the reservoir appears above the water basin surface, the valve affected by gravity departs from the circular band thus performing the opening action, and the water with the oil contamination spot enters the reservoir.

Light crude oil appears in the upper part of the reservoir under the valve, and the heavier water is released through the lower end of the reservoir. When the upper end of the reservoir submerges under the water surface again, the valve is pressed against the circular band again, closing the reservoir opening, not allowing the lighter oil to leave the reservoir. The oil film above the reservoir closes up again. When the reservoir lifts up above water surface again, the valve opens and the oil contamination spot enters the reservoir and is accumulated in its upper part under the valve; the water supplied from the surface is released through the lower end of the reservoir.

Multiple crossing action of the water boundary up and downwards allows the reservoir to collect the oil contamination. Given the period of wave, oil film thickness and volume of the reservoir one can calculate the time required to fill the reservoir with oil contamination and take timely actions to drain it by means of a pump into a special tank.

When the operation is complete, the device may be moved to another operation spot.

The water-wave oil skimmer may be used to collect oil contaminations both at sites, where such contamination is continuously supplied into the water basin (in ports, bulk plants), and in open water areas. The device may also be used to collect both the oil contamination and the floating wastes from the surface of the water basin. The device can also be used to collect the sorbent from the water surface, where it has been diffused for oil gathering.

Prototypes of the water-wave oil skimmer have been tested under laboratory conditions for proper operation. Our calculations have shown that the oil skimmer device with a reservoir 1 meter in diameter is capable of collecting oil contamination spot of the size 3-4 ha within 24 hours.