Abstract
The international Convention for Control and Management of the Ship''s Ballast Water and Sediments (BWM convention) has been adopted by the IMO (International Martime Organization) in 2004 to prevent transfer of exotic species by ballast water. Since then, many type of BWMSs (Ballast Water Management Systems) have been developed. However the processing method using Electrolysis makes active substances to remove the organisms, which generates relevant chemicals. Therefore, when treated ballast water is discharged into reciving water, it may cause toxic effects to marine organisms.
To verify the unacceptable effects of ship''s ballast water treated by Electrolysis on marine ecosystem, the WET (Whole Effluent Toxicity) test using diatom, Skeletonema costatum as primary producer, rotifer, Brachionus plicatilis as first consumer and olive flounder fish, Paralichthys olivaceus as predetor, chemical analysis for identifying substances produced by Electrolysis BWMS was conducted. In addition, Marine ERA (Ecological Risk Assessment) using PBT properties and PEC (Predicted Environmental Concentration) / PNEC (Predicted No Effect Concentration) ratios of produced substances was conducted.
S. costatum was the most sensitive organism that gave the NOEC (No Observed Effect Concentration), LOEC (Lowest Observed Effect Concentration) and EC50 (50% Effect Concentration) values of 12.50%, 25.00% and 83.32%, respectively from WET test results for 20psu of discharged water. In the chemical analysis results, 21 of the substances were newly produced by the Electorysis BWMS, composing of bromate, 9 volatile halogenated organic compounds, 2 halogenated acetonitriles, 8 halogenated acetic acids and chloropicrin. Twenty one substances was not considered as persistance and bioaccumulative chemicals because the half-life and log Kow value of substances did not exeed 60 days and 3 days, respectively. Uncertainty of toxic property of substances was high. However, the PECs of 21 substances calculated by the MAMPEC program ranged from 7.02×10-4 to 5.39×100 μg/L and PNECs of them ranged from 2.00×10-2 to 4.24×103 μg/L. The PEC/PNEC ratio of 20 substances did not exeed 1. Therefore, the results of the WET test with discharged water from Electrolysis BWMS and ERA for generated substances in the discharged water indicated that the ship''s ballast water treated by Electrolysis was not predicted an adverse effect on the marine ecosystem.
However, WET test results were shown that the ship''s ballast water treated by Electrolysis can have potential negative effects on the marine ecosystem. Therefore aquatic toxic effect of discharged water should not be overlooked and should be kept an eye out to prevent an adverse effect on marine ecosystem through continuous monitoring system.