Trend for ballast water treatment system retrofits

Ballast water plays a crucial role in maintaining ship stability, yet it remains a major pathway for the spread of invasive marine species. Regulations introduced by the International Maritime Organization (IMO) now require vessels to treat ballast water before discharge, prompting widespread retrofitting of treatment systems. A broad review of research highlights the diverse adoption of prominent technologies, such as electrolysis and ozonation, alongside significant attention on ultraviolet (UV) treatment methods. The overall trend in ballast water management emphasizes greater system stability, lower operational costs, and improved ease of operation and maintenance over a single dominant technology. Publication trends show growing international collaboration and increasing focus on regulatory compliance, cost analysis, and environmental impact. Evaluations across various studies point to seven key aspects in retrofit planning, including system selection, spatial layout, compliance with international standards, and integration of advanced modeling tools. While many retrofit projects prioritize efficiency and cost, fewer have addressed long-term monitoring or biological risk mitigation. Differences in regulatory frameworks across countries create compliance gaps, while newer risks, such as persistent microorganisms and radioactive discharge, remain difficult to control with current systems. Emerging tools, including real-time monitoring devices and genetic testing methods, offer promise for improving system performance and post-installation validation. Retrofit planning increasingly incorporates digital engineering, helping to reduce installation time and minimize costs. Global cooperation remains essential, especially when managing compliance in international waters. Addressing both known and emerging challenges requires a combination of strong technical planning, legal harmonization, and environmental awareness. A more integrated approach will support sustainable marine operations and help safeguard ocean ecosystems from the long-term effects of untreated ballast water. ------------------------------------------------------------------------------Cite this article: Sari, W. R., Gunawan, & Muzhoffar, D. A. F. (2026). Trend for ballast water treatment system retrofits. Maritime Technology and Research, 8(1), 281429. https://doi.org/10.33175/mtr.2026.281429 ------------------------------------------------------------------------------ Highlights The study uses an integrated, three-stage framework comprising descriptive, bibliometric, and systematic analysis to comprehensively assess the landscape of BWTS retrofit research. This multi-faceted approach goes beyond a simple summary to generate new insights into the interplay of technological, regulatory, and operational factors. Ultraviolet (UV) treatment is the most dominant and cost-effective BWTS technology, with 72 publications in the abstract, reflecting its prominence in research. However, UV efficiency is highly dependent on water quality, and studies found system failures in waters with high Total Suspended Solids (TSS). In addition to UV, electrolysis and ozonation are also widely adopted, with electrolysis showing growing research interest, as evidenced by 74 publications by abstract. Seven key stages for retrofitting BWTS are defined, including assessment and planning, space selection, regulatory compliance, BWTS method selection, engineering drawing and 3D modeling, installation planning, and commissioning and integration. Global research trends show that the United States and China are the leaders in BWTS research. China has the highest number of documents with 61 and citations with 800. The United States, while having fewer documents, shows a stronger collaboration link strength about 117 compared to China's about 67, indicating a more prominent role in shaping research directions through its collaborative network. The use of advanced tools like 3D scanning and CAD modeling is increasing to improve retrofit efficiency and reduce costs. These methodologies have been shown to cut project time by approximately 25 % and total costs by about 15 %. Furthermore, frameworks like fuzzy logic and life-cycle costing are used to help ship operators make optimal decisions based on various criteria, including cost and operational constraints.