Sediment management practices for ports and shipyards - applicable approach

The management of ballast water sediment has not so far been extensively researched. Although it was not analysed as often as ballast water itself, the ballast water sediment has been also recognized as a significant vector for transfer of alien invasive species (AIS), harmful organisms and pathogens (HAOP). Additionally, ballast water sediment is identified as a matter that may also contain toxic chemical compounds or heavy metals. So far, the sediment management procedures are not yet harmonized among stakeholders, in particular those involved in maritime transport such as port and shipyard managements and maritime administrations. Therefore, development and implementation of such harmonized procedures shall decrease risks associated with transfer of HAOPs, toxic elements and compounds. At the procedural level, ballast water sediment management should include at least sampling procedures, collecting and disposal procedures as well as information dissemination. The responsibility to implement measures is primarily on ships’ crews and secondary, on national maritime administrations responsible for the implementation of the Ballast Water Management Convention.

pdf10 trang | Chia sẻ: thanhuyen291 | Ngày: 10/06/2022 | Lượt xem: 228 | Lượt tải: 0download
Bạn đang xem nội dung tài liệu Sediment management practices for ports and shipyards - applicable approach, để tải tài liệu về máy bạn click vào nút DOWNLOAD ở trên
225 Sediment management practices for ports and shipyards – applicable approach Vlado Frančić, Assistant professor, Lovro Maglić, Assistant professor, Marija Šimić Hlača, Ph.D. student Faculty of Maritime Studies Rijeka, Croatia, vfrancic@pfri.hr, Studentska 2, Rijeka, Croatia Faculty of Maritime Studies, Rijeka, Croatia, maglic@pfri.hr Faculty of Maritime Studies, Rijeka, Croatia, marija@pfri.hr Abstract The management of ballast water sediment has not so far been extensively researched. Although it was not analysed as often as ballast water itself, the ballast water sediment has been also recognized as a significant vector for transfer of alien invasive species (AIS), harmful organisms and pathogens (HAOP). Additionally, ballast water sediment is identified as a matter that may also contain toxic chemical compounds or heavy metals. So far, the sediment management procedures are not yet harmonized among stakeholders, in particular those involved in maritime transport such as port and shipyard managements and maritime administrations. Therefore, development and implementation of such harmonized procedures shall decrease risks associated with transfer of HAOPs, toxic elements and compounds. At the procedural level, ballast water sediment management should include at least sampling procedures, collecting and disposal procedures as well as information dissemination. The responsibility to implement measures is primarily on ships’ crews and secondary, on national maritime administrations responsible for the implementation of the Ballast Water Management Convention. Generally, sediment management comprises of on-board and on-shore sediment removal and disposal procedures. Although very similar, the responsibilities for those procedures are very different: in case of removal and disposal of ballast water sediment in shipyards, only national legislation is applied, while on-board removal procedures are strictly regulated by the BWM Convention and related guidelines. In any case, the operation should not cause delays or unduly costs to ships, port operators or any other person or entity operating within port areas and shipyards, unless such delay or cost is reasonable and can clearly prevent or minimise transfer of alien invasive species or HAOP. This paper analyses best practices of sediment management for ports and shipyards, including relevant legal issues and applicable training requirements for personnel. The disposal options by using innovative technologies are analysed and presented considering their technical aspects, application requirements, safety aspects, training needs and the need to keep operational costs within acceptable ranges. Furthermore, detailed analysis for the existing sediment management procedures in the Adriatic Sea is presented. Finally, knowledge, understanding and proficiencies that may or should be considered as a part of the STCW Convention (once the BWM Convention enters into force) are discussed. Key words: ballast water sediment, ports, shipyards, best management practices, BWM Convention. 1. Introduction Ballast water transfer by ships as a vector for the movement of HAOP through different ecosystems can be considered as a significant threat to the world’s seas, human health, property and resources 0. Ballast water transfer was regulated by the International Convention for the Control and Management of Ship’s 226 Ballast Water and Sediments, 2004 (BWM Convention) which defines the global standards on ballast water and sediment management requirements.2 Sediments in ballast water tanks and their management, although mentioned in numerous different documents, have not been extensively researched [2].3 Before adopting BWM Convention, the accent was on evaluating possibilities and the extent of transfer of HAOPs via ballast water. Internationally available sources do not deal much with sediment management. The majority of the documents and scientific papers on ballast water sediments deal with presence of organisms and their identification proving that sediment is a significant vector for the transfer of organisms [2]. Another group of papers deals with ship design, management and new treatment techniques for reducing the build-up of sediments and sediment sampling methods from the ballast water tanks [10-12]. The research on the physical and chemical properties including the presence of heavy metals in ballast tank sediments is presented in the study created by Macdonald and Davidson in 1997 [13] and Maglic in 2016 [14]. The first study was based on an extensive number of samples taken from ships visiting Scottish ports. The results showed that the levels of heavy metal in ballast tank sediment build-up are frequently higher than those detected in the natural environment. In the second paper, the analysis of samples from three ships visiting the port of Rijeka (Croatia) revealed no significant abundance of heavy or toxic metals. However, high concentrations of detected metals may endanger humans or environment. The Contracting States are responsible for deciding on best sediment management and disposal practices for ports and shipyards taking into account technical aspects, application requirements, safety aspects, and the related costs. Sediment management should take into account three main issues: whether a sediment accumulation which is about to be unloaded from a ship may endanger human health and/or the environment, how to treat the unloaded sediments, and where it may be disposed. Policies and regulations that will be proposed should be in accordance with principles and requirements outlined in guidelines adopted by the International Maritime Organization, notably in line with Resolution MEPC.152(55) Guidelines for Sediment Reception Facilities (G1) [15] and Resolution MEPC.150(55) Guidelines on Design and Construction to Facilitate Sediment Control on Ships (G12) [16]. New regulations should cause no delays or unduly costs to the ships or port operators or any other person or entity operating within port areas and shipyards, unless such delay or cost is reasonable and clearly prevents or minimises the transfer of alien invasive species or influence of the toxic or heavy metals to humans and environment. 2. Ballast water tanks sediments Ballast water sediment builds up in ballast tanks from water containing different solid particles either sucked or being produced by different processes in tanks and associated pipelines. Soil sediment drawn consists mostly of clay, silt and sand and sometimes includes even larger granular particles. Clay is a natural earthy material consisting mainly of fine particles of hydrated silicates of aluminium and other minerals. In most cases, clay soil shows plastic behaviour due to water content. However, 2 BWM Convention is still not in force. Presently 50 countries have ratified the Convention. However these 50 countries represent 34,8% of the GT of the world’s merchant fleet, less than the 35% that is required. 3 A “search by title” in Web of Science revealed 1.850 publications with the term ‘ballast water’ as opposed to only 338 with ‘ballast sediment’ (May 2016). However, a significant increase of interest in the topic is noted because the number of results increased approximately 3 times for ‘ballast water’ and 10 times for ‘ballast sediment’ term within one year. 227 after being dried, clay usually becomes hard and brittle. Depending on additional substances, it may appear in various colours, including white, grey, brown or red. The size of clay particles is usually considered to be 2 m or less. As such, it is easily sucked and deposited in ballast tanks. If homogenous structure is formed in tank, clay removal may be quite a demanding task. Silt may occur as soil (low water content) or as sediment mixed with water. On board ships it is almost always found as a suspended load in a body of water. It may be found also as soil deposited at the bottom. Silt, when dry, usually has a floury feel, and may give a slippery feel when wet. Silt particles are much larger then clay but smaller than sand particles, usually in range between 2 m and 63 m. It can be found across the world. Sand is a naturally occurring granular material composed of finely divided rock and mineral particles. It is finer than gravel and coarser than silt. Sand particles range in diameter from 63 m to 2 mm. The composition of sand varies, depending on the local sources and conditions, but the most common constituent is silicon dioxide, usually in the form of quartz, or calcium carbonate. Colour can be different, depending on other constituents, and vary from white to yellow, orange and even red. Larger particles may occasionally be found in ballast tanks. They may be found in tanks if suction point is quite close to the sea bottom and/or external forces upheld larger particles in the water column (for example, in river estuaries where tidal currents meet fresh water flow). Beside sediment in the ballast tanks, there also may be found particles produced by different processes in tanks or in associated pipelines. These particles include the corrosion products, parts of protective coatings, and organic material. Finally, there is sea water. Pumping out the complete volume of ballast water is rarely possible. The quantity that persistently remains in a tank mostly depends on design of the suction line(s) and efficiency of the ballast pumps. Usually, in the area around suction bell it remains up to 5 centimetres of water, assuming that sediment build-up does not block the free water flow. The quantity of water depends on sediment content; sediment actually prevents free water flaw, thus decreasing the capability of the ballast pumps to suck out maximum quantity of water. The water may contain up to 70% of content of the tank that cannot be pumped out. Deposited sediments are not removed by themselves from the ballast tanks, even though the tanks are repeatedly filled and emptied. In fact, the quantity of deposited sediments may increase gradually as ballast water is loaded and discharged because pumps cannot extract sediments that have already settled down. Sometimes, particularly when mud-based sediments prevail, deposits on the bottoms of the ballast tanks gradually harden and become denser under pressure. This hardening is caused by repelling of water. Such hardened, mud-based dense sediments from the ballast tanks are usually difficult to remove, requiring lot of manual work. A layer of sediment in a ballast tank may reach up to 10-15 centimetres. It may occur in tanks that are not easily accessible (low water dynamics and/or restricted movement of water between different compartments made of athwart ship floors and bottom longitudinals). For example, a Panamax-type bulk carrier, with a length over all of 220 m and a breadth of 32.20 m, typically contains ballast tanks that encompass a joint area of about 150 m length and about 30 m width, rendering an area of approximately 4,500 m². A layer of 0.10 m of sediment over such bottom would result in a mean volume of 450 m³. With an estimated average sediment density of 1.5 kg/ dm³, the sediment may reach 675 tons. However, such build-up is relatively rare. Usually, the height of the deposited sediment reaches up to few centimetres, rarely more. Density of sediment may vary between 228 1.2 up to 2.0 kg/dm³, mostly depending on the water content. For the most mid-sized ocean-going ships the weight of accumulated sediments typically varies between 10 to 15 tons. 3. Sediment disposal options While ballast water can be easily pumped out, the removal of sediment accumulated in the tanks requires additional efforts. Since the sediment structure is solidified and firm, the removal requires manual collection and safe disposal. The main goal of the sediment disposal management is to ensure that sediment is not disposed into sea, neither in wet nor in dry condition. Accordingly, sediment disposal management must include: on- board sediment removal and disposal, and on-shore sediment reception facilities. On-board sediment removal implies collection of sediments while vessel is underway or in port. It is initiated when sediment build-up on tank bottoms and other tank surfaces is such that in some way impacts ship’s operations. After being collected, the sediment is either disposed overboard, or delivered to the shore reception facilities. If decided to dispose sediment overboard, the BWM Convention provisions should be followed, in particular procedure outlined in the vessel’s Ballast Water Management Plan (discharge of sediments has to be carried out when vessel is in areas sufficiently distant from the shore and with minimum depth as it is required for ballast water exchange standards). If decided to deliver sediment to shore reception facilities, it has to be properly packed and secured. In this case, the main obstacle is possible water content (wet sediment). If handed over as ordinary ship’s waste, the additional fee will be charged for excessive mass to be handled. Therefore, delivery of sediment as ship’s waste in ports is rarely carried out. It is much easier to dispose it overboard. In case of sediment removal in shipyards, two distinctive phases can be recognized:  collection of the sediment and its temporary storage within shipyard area, and  transfer of sediments to permanent storage facility. The main reasons for favouring removal during vessels’ dry-docking are:  need to survey hull,  need to repair ballast tanks,  need to refurbish damage of the ship hull or any damage to ship’s structural elements. Tank repair is usually the outcome of the ballast tank survey process. If the tank condition requires repair and maintenance, it has to be clean and free of water and any kind of sediments or material. Generally, on-shore removal methods include:  mechanical collection of sediments,  sediments’ unloading by using industrial vacuum cleaner equipment. Mechanical collection of sediments is very similar to the process carried out by shipboard crew. The only difference is that it is usually carried out while ship is alongside in shipyard or in dry-dock and is carried out by the shore based manpower. After being removed from tanks, sediments have to be disposed in appropriate impermeable containers (Figure 1) and then transported to dedicated landfills within the shipyard or port. Landfills (Figure 2) are used as temporary storage facility. There sediment has to be drained before being moved to permanent reception facility, usually land waste disposal area outside port or shipyard area. 229 Figure 1 Containers for sediment collection Figure 2 Landfill for temporary sediment disposal If there are expected big quantities of sediment, vacuum cleaning equipment is normally used. The sediments are sucked up in provided containers. As far as it is learned in the ports and shipyards in the Adriatic Sea region, aforementioned sediment disposal options are regularly used in repairing shipyards during vessels’ dry-docking. The other option i.e. to collect by crew members and dispose in ports occurs quite rarely. It has to be emphasized that some national regulations clearly prohibit sediment disposal overboard.4 4. Sediment disposal management 4.1 Legal framework Existing legal framework dealing with ballast sediment disposal management and implementation of the associated plan for sediment disposal management follows the BWM Convention regulations and relevant guidelines adopted by the Organization. In addition, several national and local regulations outline procedures related to sediment management. The BWM Convention clearly gives specific details on sediment management in two articles and in one regulation [2]. In Article 1 sediment is defined as matter settled out of ballast water within ships. Article 5 sets up rules on sediment reception facilities which are complemented with the guidelines developed by the Organization. Finally, Regulation B-5 of the BWM Convention provides requirements for sediment management on ships. According to the aforementioned provisions of the BWM Convention, the following should be taken into consideration:  In ports and terminals where cleaning and repairing of ballast tanks occur, adequate sediment reception facilities should be provided.  Reception facilities should operate in a way not causing unnecessary delays to ships, providing environmentally safe sediment disposal.  Each state shall report to the Organization on availability and location of any reception facilities for the environmentally safe disposal of sediments, and any inadequacy of the reception facility. In addition, the Convention gives detailed requirements for sediment management for ships (Regulation B-5). The ships shall remove and dispose sediments from spaces designated to carry ballast water in accordance with the ships’ BWM Plan. Accordingly, ships shall be designed and constructed in a way 4 For example, Croatian “Ordinance on ballast water management and control” in Article 20 clearly prohibits disposal of sediments into sea: “It is prohibited to discharge sediments into sea”. 230 that minimizes the uptake and undesirable entrapment of sediments, facilitates removal of sediments, and provides safe access that allow sediment removal and sampling. Coastal states are obliged to report any requirements and procedures relating to the Ballast Water Management, including laws, regulations, and guidelines implementing the BWM Convention. Accordingly, any provisions related to the implementation plan for sediment disposal management should be adequately reported. The guidelines (G1) contain provisions that refer to:  Provision of sediment reception facilities,  Treatment, handling and disposal of received sediment,  Capabilities of a reception facility, and  Training of personnel engaged in sediment management disposal. According to the guidelines, any sediment disposal measure shall avoid unwanted side effects to environment, human health or damage to property or resources. Adequate information on available facility should be made available to ships wishing to use facility. Employed personnel should receive adequate instructions and training on sediment disposal management. Based on the BWM Convention rules and regulations, several countries have already adopted their national requirements in addition to the internationally recognized legal framework. For example, the United States Code of Federal Regulation (CFR) provides comprehensive requirements on Ballast Water Management where specific regulations are set up for particular navigable areas. Title 33 of the CFR “Navigation and navigable area” in part 151 – “Vessels carrying oil, noxious liquid substances, garbage, municipal or commercial waste, and ballast water” separately prescribes ballast water management for Control of Nonindigenous Species in waters of the United States (Subpart D) and in the Great Lakes and Hudson River (Subpart D). The rule gives detailed explanation on ballast management control options, including requirements for ballast water management, ballast water discharge standards (BWDS), instructions for ballast water management methods and reporting as well as recording requirements for sediment management. Transport Canada provides “A Guide to Canada’s Ballast Water Control and Management Regulations” – Transport Publication TP 13617 E. Part A of the guide – “Guidelines for Ballast Water Management” under paragraph 1.3 gives details on Sediment Management. According to the guidelines, removal of sediment from ballast tanks should preferably be undertaken under controlled conditions in port, at a repair facility or in dry-dock. A
Tài liệu liên quan