Transporting non-native species in ballast tanks has been a major challenge over the years. The number of surviving species in the host environment is quite small compared to those of all introduced. However, even a single species can cause great harm to the environment, economy, and public health. Ballast water treatment issues are difficult and complex as the performance of the treatment is highly affected by the variable characteristics of the seawater. In addition, targeted organisms are in a wide spectrum. The International Convention on the Control and Management of Ship Ballast Water and Sediments requires ships to manage ballast water with a Type Approved System in compliance with the Ballast water discharge standard defined in the Convention. The Ballast Water Management Systems Approval (G8) Guide was revised in 2016 and accepted as the BWMS Code (Ballast Water Management Systems Approval Code) as the mandatory regime in 2018. According to the implementation schedule of this mandatory approval regime, the ballast water management system installed on or after 28 October 2020 must be type-approved according to the IMO’s revised G8 requirements. Several systems use different methods with their limitations. However, the ballast water problem does not seem to end only with the installation of the systems on ships. Although substantial international progress has been made in ballast water management (both technically and regulatory), there are still several issues regarding effectiveness, compliance monitoring, and the environment.
A B S T R A C TThe transportation of exotic species in ballast tanks is one of the most important global environmental problems facing the shipping industry. Electrochemical techniques offer one of the most viable solutions for ballast water problems. This work reports laboratory experiments conducted by Istanbul Technical University (ITU) for the best and optimal electrochemical cell design for EU Project BaWaPla (Contract 031529), in which a new hybrid ballast water treatment system has been developed. The capability of an electrochemical system to effectively eliminate these organisms depends on various internal and external parameters. Five different electrochemical cells were assessed for the BaWaPla system. The variable parameters of the cell design were the geometry and dimensions of the electrodes. In additional to cell design, the effects of Ca 2+ and Mg 2+ concentrations, along with ammonia, were also investigated as external parameters for system capability. The results show that the enlargement of electrode surfaces result in increased chlorine concentrations in the disinfectant. On the other hand, suitable electrode and coating materials are essential for "reverse polarity" operation in order to avoid scaling of Ca 2+ and Mg 2+ ions on electrodes and clogging the membrane. Ammonia, if present in ballast water, has a negative effect on disinfection quality. Experiments show that presence of 7.8 mg/L ammonia in electrolyte may cause up to 73% loss of free available chlorine and 38% loss of total available chlorine concentrations. Measures should be considered, both in the design stage and during the disinfection process, to reduce the negative effect of ammonia.
SummaryBallast tank sediments may cause several problems in a wide range changing from environmental to economical. Its contribution to biological invasion is an important concern. Thus, the sediment management is included as an integral component of the "The International Convention on the Control and Management of Ships' Ballast Water and Sediments". The reduction of the amount of the sediment to be removed is of great importance for management issues. Therefore, the convention underlines that ships should be designed and constructed with a view to minimize the uptake and undesirable entrapment of sediments and facilitate removal of sediments. Design and construction solutions can effectively be developed after determination of the problem areas. In this study, sediment accumulation pattern and problem areas in the ballast tank model of a longitudinally framed double bottom tanker is determined. The problem areas are found to be at the mid-section of the tank closer to the centre girder.
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