Ocean Engineering 203 (2020) 107204 Available online 10 March 2020 0029-8018/© 2020 Elsevier Ltd. All rights reserved. Reduction of ballast tank sediment: Evaluating the effect of minor structural changes and developing a pneumatic cleaning system Ceren Bilgin Güney * , Devrim Bülent Danıs ¸man , S ¸ afak Nur Ertürk Bozkurto� glu Istanbul Technical University, Faculty of Naval Architecture and Ocean Engineering, 34469, Istanbul, Turkey A R T I C L E INFO Keywords: Ballast tank design Sediment reduction Pneumatic cleaning system Invasive species ABSTRACT Ballast tank sediments host organisms that pose invasion risk even if the ships are installed with ballast treatment systems. The bottom sediments also contribute to corrosion and cause cumulative deadweight loss over the years. This study presents the outcomes of the project “Conceptual Ballast Tank Design for Reducing Sediment Accumulation” (TUBITAK, Grant No: 115Y740). In the published frst phase of the project, sediment accumu- lation pattern was determined and the center girder was found to be critical. In this study, the fndings of the second and third phases are presented. In the second phase, the tank model design was revised aiming to reduce total sediment accumulation. The contribution of this revision was found to be is numerically insignifcant. However, this revision drove more sediment towards the center girder. Thus, in the third phase, a pneumatic cleaning system targeting the center girder was designed to mobilize water to suspend sediment and facilitate discharge from the tank. The pneumatic cleaning system reduced the total sediment deposition in the ballast tank up to 45%. Operating the pneumatic system before de-ballasting oper- ations on a regular basis would decrease the amount of sediment to be managed; reduce the invasion risk, tank corrosion, and cumulative deadweight loss. 1. Introduction Ballast water is an integral element of safe shipping. However, the living organisms in the ballast tanks have, in different aspects, been an important issue for the academic world and different stakeholders of marine transportation within the last four decades. Following the recognition of the translocation of organisms along with the ballast water (Carlton, 1985; Medcof, 1975), there have been great number of studies on identifying the organisms which are trans- located within the ballast tanks (Bailey, 2015; Chu, E Tam, Fung, & Chen, 1997; Davidson and Simkanin, 2012; Gollasch et al., 2015; Gon- çalves, 2013; Grigorovich et al., 2003; Hallegraeff, 2015; Hallegraeff and Bolch, 1991; Lavoie et al., 1999; Occhipinti-Ambrogi and Savini, 2003; Ojaveer et al., 2014; Wu et al., 2019). International Maritime Organization (IMO) has focused on the ballast water organism problem since the 1990s and fnally adopted The International Convention for The Control and Management of Ships Ballast Water and Sediments (BWM Convention) on 03 February 2004. The BWM requires all relevant vessels to manage their ballast water to meet either D-1 ballast water exchange standard or D-2 performance standard (for most of the ships, it can only be achieved through ballast water treat- ment) with a designated time table (IMO, 2004). However, the time table has been exceeded before the BWM Convention entered into force on September 8, 2017. Therefore, The BWM Convention’s imple- mentation timetable for existing ships has been postponed two years by the IMO Marine Environment Protection Committee (MEPC). According to the amendments, all existing vessels are required to comply with the D-2 standards on a date to be determined according to the age and In- ternational Oil Pollution Prevention (IOPP) renewal surveys, from 8 September 2019 to 8 September 2024 (MEPC, 2018a). On the other hand, certain requirements of The BWM Convention, including ballast water management for all ships and the D-2 standard for new ships, are now in force. The BWM Convention requires the treatment systems to be installed to have a Type Approval Certifcate in accordance with Guidelines for approval of ballast water management systems (Guidelines (G8)). The revised Guidelines (G8) have been converted into mandatory Code for Approval of Ballast Water Management Systems (BWMS Code) at the 72nd Session of MEPC (MEPC, 2018b). There are more than 70 type-approved systems which make use of * Corresponding author. E-mail addresses: bilgincer@itu.edu.tr, ceren.bilgin@itu.edu.tr (C.B. Güney). Contents lists available at ScienceDirect Ocean Engineering journal homepage: www.elsevier.com/locate/oceaneng https://doi.org/10.1016/j.oceaneng.2020.107204 Received 19 November 2019; Received in revised form 6 February 2020; Accepted 1 March 2020