선박 평형수관리장치 배출수의 해양생태위해성평가 연구

Abstract

The International Convention for Control and Management of Ship's Ballast Water and Sediments (BWM convention) has been adopted by the IMO (International Maritime Organization) in 2004 to prevent, minimize and ultimately eliminate transfer of non-indigenous species via the ship's ballast Water. The many BWMSs (Ballast Water Management Systems) have been developed thereafter. However, discharged water from the BWMS that uses active substances could have negative effect on marine life because the main aim for developing BWMS is to eliminate aquatic organisms in the ballast water. UV (Ultraviolet) and Electrolysis disinfection technologies have been mainly used in the BWMS development. Acute toxic effects on aquatic organisms and water quality changed by UV irradiation have been reported in the previous research. Electrolysis module can also produce active substances and relevant chemicals that may pose the residual toxic effect on the aquatic organisms. There was no information for negative effect by Plasma disinfection because of the first employment for BWMS development. To verify the unacceptable effect of discharged water from BWMS using UV, Plasma & UV and Electrolysis on marine ecosystem, WET (Whole Effluent Toxicity) test for assessing the integrated toxic effect of the discharged water from BWMS, chemical analysis for identifying substances produced by BWMS and ERA (Ecological Risk Assessment) using PBT property and PEC (Predicted Environmental Concentration) / PNEC (Predicted No Effect Concentration) ratio of produced substances were conducted. For the discharged water from the UV BWMS, Anthocidaris crassispina was the most sensitive test organism that gave the NOEC (No Observed Effect Concentration) value of 6.25%, LOEC (Lowest Observed Effect Concentration) value of 100.00% and 14d-LC50 (50% lethal concentration) value of >100.00% from WET test results for 34psu discharged water. There are no observations of substances produced by the UV BWMS due to the fact that the irradiation of UV and running time of ballast water in UV reactor are max. 390 mWs/cm2 and just several seconds (flow rate ca. 3 m/sec.), although possibility of photochemical water quality changes from UV irradiation is being discussed. Therefore, both results of WET test and the chemical analysis indicate that the discharged water from the UV BWMS will not cause an unacceptable effect on marine ecosystem. For the discharged water from the Plasma & UV BWMS, Paralichthys olivaceus was the most sensitive organism that gave the NOEC value of 50.00%, LOEC value of 100.00% and 7d-LC50 value of >100.00% from WET test result for 34psu discharged water. The concentration of chlorobenzene, bromobenzene and 4-chlorotoluene in 34psu discharged water from the UV & Plasma BWMS were 0.13, 0.18 and 0.10 μg/L, respectively which is higher than the original content of seawater. In addition, the chronic toxic effect on P. olivaceus is supposed to originate from the three substances. However, the three substances are not requisitely produced by Plasma and/or UV disinfection because the formation of the chlorobenzene, bromobenzene and 4-chlorotoluene in the discharged water were originated from toluene and/or benzene in the thinner for painting the inner wall of ballast water tank. Persistence of the three substances was not considered because its half-life does not exceed 60 days. Bioaccumulation of 4-chlorotoluene of three substances was considered because log Kow value was exceeded 3. Uncertainty of toxic property of the three substances was high. However, the PECs of chlorobenzene and bromobenzene calculated by MAMPEC were 2.10E-03 and 3.34E-03 μg/L, and PNECs of them were 0.5 and 1.6 μg/L respectively. The PEC/PNEC ratio of chlorobenzene and bromobenzene did not exceed 1. For 4-chlorotoluene that have bioaccumulative property, PECfish/PNECfish ratio did not exceed 1. Therefore, the results of WET test, chemical analysis and ERA for produced substances indicate that the discharged water from the Plasma & UV BWMS will not cause an unacceptable effect on marine ecosystem. For the discharged water from the Electrolysis BWMS, Skeletonema costatum was the most sensitive organism that gave the NOEC value of 25.00%, LOEC value of 50.00% and 72h-EC50 value of 69.97% from WET test result for 20psu discharged water. In the chemical analysis results, 18 substances were newly produced by the Electrolysis BWMS, composing a bromate, 6 volatile halogenated organic compounds, 7 halogenated acetic acids and 1 halogenated acetonitrile in the 34psu discharged water. In the 20psu discharged water substances produced by the Electrolysis BWMS were 5 volatile halogenated organic compounds, 6 HAAs, 4 HANs and chloropicrin. And correlation analysis using results of previous researches is indicated that the toxic effect on aquatic plant (S. costatum) is supposed to originate from the number and/or concentration of disinfection by-products, especially HAAs, and initial concentration of TRO. Eighteen substances does not consider as persistence and bioaccumulative chemicals because the half-life and log Kow value of 18 substances do not exceed 60 days and 3. Uncertainty of toxic property of the three substances was high. However, the PECs of 18 substances calculated by MAMPEC program were ranged from 4.58E-04 μg/L to 4.87E+00 μg/L and PNECs of them were ranged from 0.016 μg/L to 320.00 μg/L. The PEC/PNEC ratio of 18 substances did not exceed 1. Therefore, the results of WET test, chemical analysis and ERA for produced substances indicate that the discharged water from the Electrolysis BWMS does not predict an unacceptable effect on marine ecosystem. The results of WET test, chemical analysis, ERA and properties of substances produced by UV, Plasma & UV and Electrolysis BWMS indicate that the discharged water from these BWMS will not cause an unacceptable effect on marine ecosystem. However, WET test results for discharged water from Electrolysis BWMS were shown toxic effects, even though the toxicity of discharged water was low. These results suggest that Electrolysis BWMS still have connotations of potential risks to marine ecosystem when the BWMS is installed on the vessel. 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 systems.