Comparative Study on Phytoplankton Treatment Effectiveness of the Ballast Water Management System with Four Different Processes

Abstract

Ballast water (BW) poses the risk of introducing species. Therefore, ships install the ballast water management system (BWMS) to reduce the risks caused by BW. To gain a deeper understanding of the treatment effectiveness of the BWMS, in this study we compared the effectiveness of four different treatment processes of BWMSs on seawater phytoplankton, which were electrochlorination treatment, hydroxyl radical oxidation treatment, membrane separation and deoxygenation treatments, and UV irradiation treatment. The results showed that all four BWMSs had a reduction in phytoplankton density of over 99%. In terms of phytoplankton taxa, the effectiveness of the four BWMSs was different. The taxa removal rates of the four BWMSs were 81.25%, 39.58%, 59.31%, and 74.49%, respectively. Electrochlorination treatment and UV irradiation treatment were significantly more effective than hydroxyl radical oxidation treatment and membrane separation and deoxygenation treatments. The residual phytoplankton taxa were mainly dinoflagellate and diatoms, such as Cucumeridinium, Prorocentrum, Navicula, and Skeletonema. Taxa that can tolerate treatment may be more likely to survive and reproduce. There is still a need to continue to strengthen the development and research on the BWMS in the future to promote the development of BW management.