Stemming the Tide Controlling Introductions of Nonindigenous Species by Ships' Ballast Water (1996) / Chapter Skim
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F CANDIDATE SHIPBOARD TREATMENT TECHNOLOGIES: SUPPLEMENTARY INFORMATION
F CANDIDATE SHIPBOARD TREATMENT TECHNOLOGIES: SUPPLEMENTARY INFORMATION
Pages 111-118
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From page 111... ...
The latest laboratory research indicates that exposure to temperatures of 35°C for approximately 12 hours may be sufficient to kill dinoflagellates. Controlled shipboard experiments were conducted on the Japanese vessel, Ondo Maru, to determine whether the water in ballast tanks may be sterilized over a long sea voyage by continuous flushing with ocean water heated to approximately 35°C.
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From page 112... ...
Current work focuses on destroying toxic dinoflagellates, and studies will be needed to determine the effectiveness of heat treatment in killing other specific target organisms. An advantage of the proposed flushing method is that the proportion of original sediment in the ballast tanks is reduced, thereby enhancing the overall effectiveness of the treatment.
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From page 113... ...
It may be possible to monitor temperature versus time as an indicator of treatment effectiveness. ELECTRIC PULSE AND PULSE PLASMA TECHNIQUES Pulsed electric field technology is being investigated as a means of preventing biofouling of water intake pipes on ships and at shore-based facilities.
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From page 114... ...
The pulse plasma arc discharge produces a short energy burst at very high power density across the electrode gap, generating an arc channel containing a highly ionized and pressurized plasma, which in turn transfers energy to the water via dissociation, excitation, and ionization; and a rapid temperature rise at the arc front. The discharge is an efficient method of promoting pyrolytic, hydroxyl radical, free electron and ultraviolet generated reactions in water.
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From page 115... ...
However, no chlorine has been detected in electric pulse experiments conducted to date. When in operation, pulse plasma systems vent gaseous decomposition products (primarily carbon dioxide)
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From page 116... ...
Treatment effectiveness decreases with increasing distance from the transducer as the energy density in the liquid decreases. The efficacy of ultrasonic treatment increases with exposure time and can also be influenced by resonance effects due to container geometry.
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From page 117... ...
A feasibility study was conducted in the mid 1970s using ultrasound for shipboard waste water treatment, but effective cavitation and resulting sterilization were not achieved for the volumes of water involved. Given the importance of the treatment chamber and geometry in determ~ning treatment effectiveness, it is clear that a large-scale shipboard system would need to be carefully designed.
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From page 118... ...
1995. Response to treatment options query received from the Center for Advanced Ship Repair and Maintenance, Old Dominion University, Norfolk, Virginia.
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