Evaluation of UV and electrochemical ballast water treatment systems from the perspective of expert seafarers working on the ship

Abstract

Ships need ballast water for stability, balance, and safe navigation. Ballast water transported by ships causes the displacement of millions of tons of seawater every year. In displaced seawater, approximately 10,000 living organisms are transported to different ecosystems every day. These transported living organisms can become dangerous and invasive when they can reproduce in the new ecosystem they go to. It is known that these invasive species, which are transported in ballast water and discharged to different ecosystems, cause serious ecological damage, economic losses, and negativities in human health in the marine environment. In order to prevent these harmful invasive species carried by ballast water, International Convention for the Control and Management of Ships' Ballast Water and Sediments was adopted by IMO in February 2004 and entered into force as of 8 September 2017. In the "D" part of this convention, the standards of the ballast water to be discharged into the sea are specified. D1 standard means "Balast water exchange standard" and D2 standard means "Balast water treatment standard". The D1 standard will expire on 8 September 2024 and from that date all ships will have to meet the D2 standard. Ships must be equipped with a type-approved ballast water treatment system in order to meet the D2 standard. Nowadays, there are many different producers and methods for ballast water treatment. Generally, UV and electrochemical type BWT system is used on ships. Within the scope of this study, the features that a BWT system should have were determined. A survey was created because the order of importance of the determined features is different for each seafarer. In the survey created, the seafarers were asked to rate the features in order of importance. According to the survey results, the most important features that seafarers want to have in a BWT system are; The BWT system has few alarms and malfunctions, is easy to maintain and use, and does not contain chemical handling. With the AHP technique based on the real data obtained, a selection was made between the two most used BWTS types on ships. According to the applied AHP method, the UV type BWT system was found to be 1.76 times more preferable than the El-Chem type BWT system. The maritime company, which has been actively using BWT systems on its ships since 2015, supplied El-Chem type BWT systems to twin tanker ships in 2015, UV-1 brand BWT systems to two different tanker ships of the same tonnage in 2019, and UV-B to two existing tankers of different tonnages in 2021. Equipped 2 brands of BWT systems. According to the applied AHP method, the BWTS type change made by the maritime company in 2019 was seen as positive by expert seafarers. In order to evaluate the UV-2 brand chosen by the maritime company in 2021, expert seafarers who worked in the UV-1 and UV-2 brands were interviewed. After evaluating the general opinions of the seafarers who have knowledge and experience in both brands, six different criteria were determined for the application of the AHP technique. The order of importance of the determined criteria has been determined by expert seafarers who have experience in both systems. According to the applied AHP method, the UV-1 brand BWT system was found to be 1.38 times more preferable than the UV-2 brand BWT system. The BWTS brand change made by the maritime company in 2021 was seen negatively by expert seafarers. In the bilateral meetings with the maritime company, the reasons for choosing the UV-2 brand in 2021 were asked. As the main reason, it was learned that the investment and operating cost of the UV-2 brand is 26% more economical than the UV-1 brand. If the ship owners act by considering the investment and operating costs in the selection of the BWT system, they may incur more financial losses in the long run because the disruptions that may occur in the ballast operations may directly affect the cargo operations and prevent the ship from staying in the port for too long or the cargo operation. Until recently, BWTS selection was based on a predetermined set of criteria. With the entry into force of the Ballast Water Management Convention, seafarers have gained sufficient knowledge and experience. With this study, which was implemented in the light of the available data, it was aimed to shed light on the selection of the best BWTS method and manufacturer by taking into account the new criteria determined during the BWTS selection stage.