Liquid purification or separation – Processes – Including geographic feature
Reexamination Certificate
2001-11-06
2004-08-10
Hruskoci, Peter A. (Department: 1724)
Liquid purification or separation
Processes
Including geographic feature
C114S125000, C210S752000, C210S754000, C210S756000, C210S757000, C210S758000, C210S764000, C422S037000
Reexamination Certificate
active
06773607
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to water treatment systems and methods and, more particularly, to systems and methods for treating ship ballast water to eliminate non-indigenous marine animals in the ballast water.
BACKGROUND OF THE INVENTION
Global shipping moves 80 percent of world commodities. When ships load and/or remove their cargo, it is necessary to counteract the weight imbalance with ballast water in order for the ship to load and travel safely. In addition to maintaining a ship's weight balance and stability, ballast water is carried by ships to adjust a vessel's trim for optimal steering, propulsion, and safety. Ballasting fulfills many other functions including: reducing stresses on the hull of the ship, providing for transverse stability, aiding propulsion by controlling the submergence of the propeller, assisting maneuverability by submerging the rudder and reducing the amount of exposed hull surface (freeboard or windage), and compensating for weight lost from fuel and water consumption. (
Stemming the Tide: Controlling Introductions of non-indigenous Species by Ship's Ballast Water,
1996). The use of ballast water varies among vessel types, among port systems, and according to cargo and sea conditions. Ballast water often originates from ports and other coastal regions, which are rich in planktonic and other organisms. It is variously released at sea, along coastlines, and in port systems. As a result, a diverse mix of non-native or exotic organisms is transported and released around the world with the ballast water of ships.
Generally, many of the species of organisms contained in ballast water are either non-native or potentially pathogenic when they are released into the receiving water of the port. The transfer of organisms in ballast water has resulted in the unintentional introduction of tens to hundreds of nonindigenous freshwater and marine species to ports around the world. The invasion of these non-indigenous aquatic organisms has had tremendous detrimental impacts on native ecosystems and continues to cost billions of dollars in remedial actions. For example, the ballast-mediated introduction of the zebra mussel in the U.S. Great Lakes during the 1980s is expected to cost that region over $5 billion. Other examples include the introduction of toxic dinoflagellates in Australia and that of the Asian claim (Potamocorbula Amurensis) in the San Francisco Bay-Delta region. According to the U.S. Coast Guard, “ . . . ballast water from ships is one of the largest pathways for the intercontinental introduction and spread of aquatic nuisance species.” (http://www.uscg.mil/hq/g-m/mso/mso4/bwm.html, July 2000).
Ballast water amounts are extremely large, especially for non-cargo ships. For example, large tankers can carry in excess of 200,000 m
3
of ballast water and rates of pumping can be as high as 15,000 to 20,000 m
3
/h. It is estimated that more than 3,000 species of plants and animals are transported daily in ballast water. (Office of Technology Assessment, 1993). The most common plants carried in ballast water are phytoplankton, especially diatoms and dinoflagellates, and floating detached plants, including seaweed (algae) and seagrasses (eelgrass or turtlegrass). Zooplankton found in ballast is diverse and dense.
TABLE 1
Average Water Ballast Carried by Ships Average amount
of ballast water (in gallons per ship) in ships arriving at
United States and San Francisco Estuary ports from foreign ports
Ship Type
U.S. Average (gals)
SFBD Estuary Average (gals)
Ships in Ballast
Bulk Carriers
3,800,000
1,670,000
Container Ships
—*
—*
Tankers
3,170,000
2,370,000
All 3 Ship Types
2,720,000
1,840,000
Ships in Cargo
Bulk Carriers
—
1,670,000
Container Ships
1,380,000
1,380,000
Tankers
—
640,000
All 3 Ship Types
—
1,380,000
All Ships
Bulk Carriers
All Ships 3,000,000
1,670,000**
Container Ships
1,380,000
1,380,000**
Tankers
900,000
1,000,000**
All 3 Ship Types
1,580,000
1,410,000**
Unpumpable Ballast
Bulk Carriers
18,000
—
Container Ships
38,000
—
Tankers
22,700
All 3 Ship Types
24,500
—
Source: Carlton et al. 1995, page 77
*Container ships rarely sail without cargo, and thus do not arrive in ballast
**The quantities of ballast water discharged by these types of ships entering the Estuary, calculated from data in US Coast Guard 1996 are as follows:
Bulk Carriers
1,730,000 gallons
Container Carriers
1,270,000 gallons
Tankers
2,760,000 gallons
All 3 ship types
1,520,000 gallons
Differences in volume are due to available data used in the calculations.
Presently, open ocean ballast water exchange (BWE) is the only method in use for reducing exotic introductions via ballast water. Ballast water exchange involves replacing coastal water with open-ocean water that is located at least 200 miles offshore during a voyage. This process may reduce the density of coastal organisms in ballast tanks that may be able to invade a recipient port, replacing them with oceanic organisms with a lower probability of survival in nearshore waters.
Ballast water exchange is recommended as a voluntary measure by the International Maritime Organization (IMO). In addition, the Nonindigenous Aquatic Nuisance Prevention and Control Act of 1990 (P.L. 101-646) required that all vessels entering Great Lakes Ports from beyond the exclusive economic zone (EEZ—out to 200 miles from shore) undergo ballast exchange or some comparably effective ballast treatment which conforms to discharge requirements of the Federal Water Pollution Control Act (33 U.S.C. 1251). These requirements were extended to vessels arriving in ports of the upper Hudson River, north of the George Washington Bridge on Nov. 4, 1992, and now apply to all vessels entering U.S. waters.
The National Invasive Species Act (NISA) of 1996 (P.L. 104-332) reauthorized and amended the Nonindigenous Aquatic Nuisance Prevention and Control Act of 1990. NISA issued mandatory ballast management reporting and voluntary ballast exchange guidelines to all vessels that enter U.S. waters from outside the EEZ, with the exception of military vessels, crude oil tankers that carry out coastwise trade, and some passenger ships that are equipped with ballast water treatment systems.
There are two approved methods of open-ocean exchange: empty/refill and flow through. The empty/refill method consists of the ballast tanks being emptied and subsequently refilled. This process compromises the stability of the ship; therefore ships traveling in rough seas will not be able to use this method. Stability can be managed more easily with ships that have a higher number of small volume ballast tanks, rather than a low number of large volume ballast tanks, although the ability to safely conduct ballast water exchange still depends upon weather and sea surface conditions. The flow through method consists of pumping ballast water (three times the capacity of the ballast tank) through the tanks, allowing it to overflow through air vents of deck hatches. Stability is less of an issue during this process, but the integrity of the ship is still compromised. Additional safety hazards associated with this method include potential tank over pressurization and water overflowing on the deck. Thus, it is not always possible to perform an exchange. Furthermore, both of the approved ballast water exchange methods only reduce the density of coastal organisms in ballast tanks following an exchange. There are still some residual coastal organisms in the tanks, so these methods are only partly effective.
The exchange efficiency for both methods has been estimated to range from 75-95 percent in a variety of studies on specific biological species, usually depending on the structure of the ballast tanks (e.g., placement of intake and outflow pipes, shape of tanks, size of baffles in tanks, etc.). Although open-ocean exchange significantly reduces the risk of invasion, the remaining 5-25 percent still posses a significant threat. Another disadvantage is that open-oc
Hruskoci Peter A.
Law Offices of Karry W. Wang
Wang Karry W.
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