Type Approval of ballast water treatment system (BWTS) is virtually in a dual structure between the International Maritime Organization (IMO) and the United States Coast Guard (USCG). For that reason, all oceangoing vessels are required to install a type-approved system by both IMO and USCG. It is recognized that obtaining USCG type approval in UV-type systems are assumed to be practically difficult because it entails a specific requirement which states that counting organisms be conducted by the Fluorescein diacetate (FDA) method. Under such situation, the elimination performance for test water was evaluated by simulating UV transmittance (UVT) to verify the capability of the ECOMARINE® UV system.
Although test water at 82% of UVT was within the discharge standard in case of TRC: 250m3/h, test water at 43% of UVT exceeded the discharge standard when the flow rate was reduced to 50m3/h. In addition, it could be assumed that the removal performance of S-sized plankton by the RC filter contributed to the reduction of UVT and based on which, it was estimated that UVT can be reduced by 2.6% and 11.1% if S-sized plankton is removed by 50% and 90%, respectively. Since the 10% reduction of UVT is equal to one-third reduction of treatment flow rate, this difference may be operationally indispensable.
Based on these results, it is highly likely that USCG Type Approval is granted to the ECOMARINE® UV system at practical treatment flow rates and UVTs by FDA method.
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