Evaluation of operational risks and treatment performance in ship ballast water treatment systems

Ship-induced marine pollution has become a significant environmental concern that can no longer be overlooked, primarily due to the increasing volume of maritime trade. One of the main sources of this pollution is the uncontrolled discharge of ship ballast water into the sea. To address this problem, the International Maritime Organization (IMO) implemented the International Convention for the Control and Management of Ships' Ballast Water and Sediments (BWM-2004), requiring ships operating in the waters of member states to use ballast water treatment systems. This thesis comprises two separate field studies aimed at evaluating the operational risks and treatment performance of ballast water treatment systems. In the first chapter, surveys were administered to maritime personnel on 30 different ships to identify operational problems associated with these systems. The identified issues were analyzed using traditional Failure Modes and Effects Analysis (FMEA), enhanced with Fuzzy Logic-based FMEA (F-FMEA). The data enabled prioritization of failure types, revealing critical risk areas such as system malfunctions, filter blockages, and lack of audits. Furthermore, a sensitivity analysis based on expert weighting was conducted to evaluate the impact of expert judgment on the decision-making process. In the second chapter, certified ballast water test reports from 59 ships of varying types and sizes were analyzed to assess the performance of the treatment systems. Structural Equation Modeling (SEM) was employed to examine the relationships between ship characteristics, treatment system parameters, and microbiological outcomes. The findings indicate that treatment capacity plays a decisive role in reducing organisms sized 10–50 µm, while its impact on larger organisms (≥50 µm) is relatively limited. In conclusion, the effectiveness of ballast water treatment systems (BWTS) is not solely determined by the technology used but is also directly influenced by ship characteristics, operational conditions, and human factors. This comprehensive approach not only provides a framework for regulatory compliance in ballast water management but also offers a holistic evaluation of system selection, design, and operation. The findings clearly demonstrate the need for treatment strategies tailored to ship-specific operations to support the protection of the marine environment.