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Safe and efficient maritime transport would hardly be conceivable without the targeted use of ballast water as additional weight for stabilisation. However, the global scale of this practice is enormous. According to figures from the International Maritime Organization (IMO) and the Canadian organisation Clear Seas, between five and ten billion tonnes of ballast water are transferred internationally each year. However, these vast volumes of water also carry stowaways: microorganisms, bacteria, small invertebrates, as well as eggs and larvae of a wide variety of species. They are taken up with the water, transported across the world’s oceans in ballast tanks, and released again in foreign ports.
Put simply, it is water – usually seawater, brackish water or fresh water – that ships carry in special tanks. This water is stored on board in ballast water tanks or ballast tanks, which are integrated deep within the ship’s hull or along its sides. Carrying ballast in the form of water is therefore an indispensable aspect of ship design. It serves to adjust the draught, improve stability at sea and reduce the structural load on the hull. Particularly when cargo ships are travelling unloaded or only partially loaded, maintaining this weight balance is essential for manoeuvrability and safety.
A cargo ship is exposed to significant physical forces at sea. The weight of the cargo varies depending on the loading status at each port. Containers are unloaded, new goods are taken on board, or the ship sails completely empty. Ballast water is required to compensate for these variations. It is a physical necessity to safely adapt the ship to the different operating conditions.
The process of taking on and discharging ballast water poses ecological risks: invasive species can enter foreign ecosystems, displace native species and severely disrupt the delicate balance of the marine environment.
To mitigate these negative impacts on marine ecosystems, the handling of ballast water is subject to strict international regulations. For modern shipbuilding, this presents a technical challenge: the integration of water treatment systems and the design of reliable, durable piping systems are key factors in the successful planning of seagoing vessels.
The International Maritime Organization (IMO) has established binding rules to protect the sensitive marine environment from the uncontrolled spread of invasive species. At the heart of this regulation is the Ballast Water Management Convention (the International Convention for the Control and Management of Ships’ Ballast Water and Sediments). The Convention entered into force on 8 September 2017.
Under its provisions, almost all commercially operated ships on international routes are required to treat their ballast water before discharging it into the ocean or a port. Simply exchanging ballast water at sea (the Ballast Water Exchange Standard D-1) was intended as a temporary measure. Today, the stricter D-2 standard applies. This defines clear limits for the maximum number of viable organisms and bacteria (such as Vibrio cholerae or E. coli) that may remain in the water before discharge from the ballast water system.
To reliably comply with these strict D-2 limits at sea, the installation of a certified ballast water treatment system is essential on a modern ship. In Germany, for example, the Federal Maritime and Hydrographic Agency (BSH) plays a central role in the approval of these systems. The BSH tests and certifies ballast water treatment systems (BWMS) for vessels sailing the German flag and ensures that the installed technology complies with the strict IMO guidelines.
For shipbuilding and shipyards, an efficient water treatment system is a key component for certification. The practical implementation of IMO requirements presents designers with complex challenges. A ballast water treatment system (Ballast Water Management System, BWMS) must handle large flow rates depending on the size of the vessel.
The technical challenge lies in efficiently filtering and disinfecting this water whilst the ship is in operation. Multi-stage processes are generally used: mechanical pre-filtration separates out sediments, followed by disinfection via UV irradiation or chemical processes such as electrolysis.
Overview of ballast water treatment systems Übersicht Ballastwasser-Behandlungssysteme
|
Process |
Function |
Advantages |
Challenges |
|
Filtration |
Separating particles/organisms |
Simple, low maintenance |
Only effective for particles >10 µm |
|
UV irradiation |
Inactivates microorganisms |
No chemicals |
Difficult with turbid water |
|
Electrolysis |
Generates chlorine, disinfects |
Effective in brackish water |
Risk of corrosion |
|
Active substances |
Chemical disinfection |
High effectiveness |
Complex approval |
The reliability and cost-effectiveness of ballast water treatment systems depend largely on the peripheral systems. This is because large volumes of seawater must be safely pumped through filters, UV or chemical reactors. Corrosion-resistant piping systems are required here to keep the lifetime costs of the entire system low.
As the piping system is constantly in contact with aggressive seawater and brackish water, which also has an additional oxidising effect due to disinfection processes (e.g. chlorination in electrolytic processes), metallic materials often reach their limits. Corrosion and pitting therefore represent significant safety risks.
The use of polypropylene (PP-RCT) piping systems therefore offers major advantages in shipbuilding. The aquatherm blue system is a prime example of this. Thanks to its material properties, it is ideally suited for maritime applications.
Further advantages of aquatherm include digital pipework planning and intelligent prefabrication. Together, these enable the complex BWMS systems to be precisely fitted into the often confined spaces on board even before the sections are built.
|
Property |
PP-RCT |
Conventional steel
|
|
Corrosion resistance |
Excellent (immune to seawater corrosion) |
Low (risk of pitting corrosion) |
|
Weight |
Very low (up to 80% lighter) |
High |
|
Service life |
Very high (>50 years) |
Limited (high maintenance required) |
In summary, ballast water management goes far beyond a purely operational solution. Ballast water is indispensable for safe ship operation (stability, trim, and draught) under varying loading conditions. Due to the IMO Convention and national regulations (e.g. by the BSH), the treatment of ballast water is now a prerequisite for operating permits on international routes.
The success of protective measures depends on a well-considered technical implementation on board that leaves no room for weaknesses. Solutions that are both fully compliant with regulations and cost-effective are achieved where ballast water management and the associated piping systems are designed together in an integral manner. Only if peripheral systems are as robust as the treatment plant itself can the high demands of the maritime environment be met in the long term.
aquatherm supports you with specialist expertise in the design and implementation of suitable piping systems. Our corrosion-free solutions are specifically tailored to the harsh conditions at sea and the requirements of modern ballast water systems.
Arrange a consultation with our experts now.
