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Feature Article

Quick-Response System For Harbor Oil Spills
Deployment of Disk-Type Oil Skimmer on Tank Truck To Enable Early Response to Shallow-Water Spills

Feature Author
Dr. Duck-Jong Jang
Associate Professor
Department of Maritime Police Science

Feature Author
Dr. Tae-Ho Kim
Associate Professor
School of Marine Technology
Chonnam National University
Yeosu, South Korea

Feature Author
Dr. Sun-Chol Na
Research and Education Manager
Korea Marine Environment Management Corp.
Pusan, South Korea

Marine accidents such as ship collision and stranding or careless handling of oil can cause spills, leading to marine pollution. A large-scale spill involving a big ship such as the Hebei Spirit, which spilled approximately 10,000 tons of crude oil from a collision in South Korea's Taean Coast in December 2007, could widely contaminate nearby coasts in a short time.

While accidents involving large ships at sea get a lot of attention, oil spills happen more often among small and medium ships in harbors. Small-scale oil spills caused by human error and negligence, for example, during oil transportation between mooring ships or the misoperation of valves during fueling, become a major cause of aggravation in the harbor marine environment. When spills occur in the open sea, a cleanup vessel is usually dispatched to install an oil fence to prevent the spread of oil, and various equipment such as oil skimmers are used to recover the oil.

However, if spills happen in shallow and narrow spaces, such as inland waters or harbors, it is difficult for a cleanup vessel to access the accident and put a large oil skimmer in such a small space. Thus, cleanup work should be done manually. If this work is delayed, the damage from pollution could increase and incur excessive cleanup expenses relative to the small amount of oil spilled.

A study was conducted in October 2010 at Yeosu, South Korea, to devise a system to recover spilled oil from a narrow space using an onshore tank truck with good accessibility to the site and equipped with a high-suction vacuum pump. The designed system comprises a tank truck, an inflatable oil fence that prevents oil spread and condenses the spilled oil, and an electronic oil skimmer. The system uses the vacuum pump and power source mounted on the tank truck to inflate the fence and operate the skimmer.

This is essentially a one-step cleanup system that responds quickly to the early stages of a spill, as it does not change the structure of the tank truck and does not need an additional power source to operate an oil fence and skimmer because it uses the power source and vacuum pump already on the truck.

The tank-truck cleanup system arrives at the site of an oil spill.

Oil Skimmer Disk Material
Weir- and suction-type oil skimmers use the specific gravity difference between water and oil, and absorption-type skimmers use the oil's adherence characteristics. A skimmer is chosen considering the type or characteristics of the spilled oil, sea conditions and location of the spill. Usually, weir- and suction-type skimmers need big storage tanks because oil is collected together with water, while an absorption-type skimmer that uses a disk, drum, belt and rope mop typically has a higher pure-oil recovery rate.

The oil recovery efficiency of the designed system is limited to the truck's tank capacity. The skimmer must have a high pure-oil recovery rate, with low water content. This system applies a disk-type oil skimmer, with multiple disks arranged vertically in a narrow space. The factors influencing the performance of disk-type skimmers are the kind of oil, viscosity, thickness, disk width, number of disk rotations and disk material. With the same oil characteristics and disk operation conditions, disk material may decide the recovery rate. The tank truck skimmer needed disk material that can absorb oil with low water content.

Several materials with oil-absorption capability, such as aluminum, stainless steel, acrylic, polypropylene, high-density polyethylene, acrylonitrile butadiene styrene and polyvinylchloride, were used to perform an oil recovery efficiency comparison experiment on Bunker A oil, which was chosen for its wide use on ships, in a circular water tank with a 200-centimeter diameter using various 120-millimeter-diameter disks. After 10 minutes of operation, the aluminim disk showed the same or higher pure-oil recovery rate compared to the other materials, with a strength greater than polyethylene, making it optimal for the system's skimmer.

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Dr. Duck-Jong Jang is an associate professor at the Department of Maritime Police Science of Chonnam National University in South Korea. He received a Ph.D. in fisheries physical from Pukyong National University. His research interests include marine safety, design and development of oil spill cleanup systems.

Dr. Tae-Ho Kim is an associate professor at the School of Marine Technology of Chonnam National University in South Korea. He received a Ph.D. in ocean engineering from Pukyong National University. His research interests involve design and development of fishery systems and facilities.

Dr. Sun-Chol Na is a research and education manager at the Korea Marine Environment Management Corp. He received a Ph.D. in fisheries engineering from Chonnam National University. His research interest is in the development of oil spill cleanup.

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