ballast water treatment  sytem
ballast water treatment sytem

Choosing a ballast water treatment system

The 11 points below are key issues that should be discussed with any supplier. For more detailed information on considerations in choosing a treatment system, explore Alfa Laval’s extensive resources on ballast water management.

1. Is the system type approved by both IMO and the U.S. Coast Guard?

The IMO Ballast Water Management (BWM) Convention, which has now been ratified, serves as the main international guideline for ballast water treatment systems. Compliance with the BWM Convention is a must.

Moreover, it is important to look for a relatively recent IMO type approval certificate. The evaluation of systems has developed since the BWM Convention was adopted in 2004. Certificates issued by authorized third-party bodies now provide more details about the testing, as well as information concerning the system operating limitations.

In addition, a range of national and regional regulations have now come into play, most notably the U.S. Coast Guard (USCG) Ballast Water Discharge Standard. In order to deballast in United States waters, a vessel’s ballast water treatment system must be type approved by the USCG or an AMS approved system can be used up to five years from the vessels compliance date (either original or extended). If the AMS operation meets a vessel's operational needs, whereas the type approval does not (example given the 72 hours hold-time is a restriction), then the AMS can be used (i.e. system can be operated in IMO mode)

Compliance with USCG legislation is important even for vessels that are not affected by it directly, because it affects their potential resale value. If a vessel’s ballast water treatment system does not have USCG approval, it will be difficult to sell to any buyer who wants to operate in this key market.

In examining both IMO and USCG type approvals, it is important to look for certificates that are issued by an authorized third party. This will ensure greater validity and increased transparency. (See question 2).

2. Has water with naturally occurring organisms been used in certification?

It is important that any type approval certificate is issued by an authorized third party, so as to ensure a controlled testing environment and realistic test conditions. Without third-party transparency, the door may be opened for technological shortcuts.

For example, organisms that live close to the water surface are more resistant to UV light and therefore best treated by means of medium-pressure UV lamps. By using a uniform mixture of selected and cultivated organisms, these difficult organisms can simply be removed from the equation. In the real world, however, water is not regulated and the organisms are both tougher and more varied.

Serious suppliers, who understand the real-world implications of non-compliance, choose robust UV technology, seek third-party transparency and pro-actively stress their systems. Natural water with non-cultivated organisms like polychaetes, rotifers and shrimp should be used, ideally in the presence of difficulties such as algae blooms.

3. Is the system specifically designed for marine use?

Surprising as it may seem, most ballast water treatment systems have their roots in drinking water treatment on land. Their technology has thus been adapted to the marine environment, rather than developed for it.

In contrast to land-based UV treatment systems, which are preceded by other cleaning processes, ballast water treatment systems face difficult organisms, irregular water quality, higher temperatures and long periods of standstill with saline water inside them. A system specifically designed for marine conditions will be better equipped for these challenges.

4. Will the system’s key components resist corrosion in seawater?

The key components of many ballast water treatment systems are made of lower-grade materials, such as 316L steel. While 316L is a common engineering material, it is also one that corrodes in contact with seawater. A UV treatment reactor, which is filled with seawater throughout the treatment process, may corrode in as little as five years if made of 316L – thus necessitating an expensive replacement.

If built with a material like 254 SMO or AL6XN Super austenitic stainless steel, which effectively resists seawater corrosion, a treatment system’s key components can be expected to last much longer. UV reactors of AL6-XN, for example, can last up to 20 years or more.

5. Does the system make maximum use of produced UV light?

Part of making UV treatment biologically effective and energy efficient is ensuring that all UV light produced by the lamps actually reaches the targeted organisms. The reactor’s internal construction should ensure a high and even distribution of the UV light, as well as high turbulence in the water passing through it. This will make certain that all organisms receive a concentrated dose.

In low-clarity waters, where UV transmittance is lower, even stronger measures are required. The use of specially designed lamp sleeves of synthetic quartz will support transmission of a broader wavelength spectrum and provide more UV light for disinfection. (See question 6).

6. Does the system offer effective power management?

Power management is partly a question of energy efficiency. Naturally, a ballast water treatment system should use the least possible amount of power to ensure compliance.

However, power management is also a matter of biological disinfection performance. While the system should operate efficiently, it should also have a significant amount of power in reserve. This will allow it to ramp up for the most difficult scenarios, e.g. waters with extremely low UV transmittance (see question 5).

Without ramp-up capabilities, a system may compromise vessel operations in difficult waters. At best, it may slow ballast operations by substantially reducing the ballast water flow rate. At worst, it may prevent entry into these waters at all.

7. Does the system have an automatic Cleaning-In-Place (CIP) cycle?

Without some form of cleaning, deposits of calcium carbonate and metal ions will build up on the quartz sleeves of the UV lamps in a ballast water treatment system. This will impair treatment, since less of the UV light produced by the lamps will be able to pass through.

Mechanical wiping is an alternative to CIP, but wipers are ineffective against the build-up of metal ions, which must be removed with a low-pH fluid. Nor do they clean the UV sensor within the reactor, which measures the UV transmittance. If the sensor is dirty, the system may use more power than necessary or be otherwise poorly controlled.

Any form of mechanical cleaning – including manual cleaning – will also lead to sleeve scratches. Eventually, these too will degrade the treatment performance.

Simply put, tests have shown that CIP has a valuable role in maintaining the biological disinfection performance of a ballast water treatment system. In a UV-based system, the effects are noticeable after a single cleaning operation.

Without ramp-up capabilities, a system may compromise vessel operations in difficult waters. At best, it may slow ballast operations by substantially reducing the ballast water flow rate. At worst, it may prevent entry into these waters at all.

8. Are comprehensive monitoring and hardwired safety functions present?

Safety is paramount on board. This is one reason for choosing a UV-based ballast water treatment system, rather than one reliant on chemicals. Even a UV treatment system, however, must be built with safety in mind.

Monitoring of all major components is a must. For example, the position of all valves should be indicated via feedback. The reactor itself should have both temperature and level sensors (preferably in a double setup), and there should be a hardwired shutdown function in the event of overheating or low water level. The latter can prevent serious damage to the equipment in the event of a malfunction.

9. Is the system automatic and easy for an operator to understand?

Though the number and complexity of onboard systems is increasing, the available time and overall competence of crews is not. This makes automatic operation essential for any ballast water treatment system. One-button starts and stops, without manual intervention during operation, are the ideal.

A graphical user interface, rather than a text-based interface, can provide a clearer overview that facilitates correct decisions and use by international crews. For maximum overview and flexibility, the control system should be possible to incorporate into the vessel’s Integrated Ship Control System.

10. Does the system’s supplier have demonstrated capabilities?

As with any major installation, the supplier’s ability to deliver on time is critical to avoiding additional costs. Installing a ballast water treatment system is an especially complex undertaking, especially when done as a retrofit. Multiple parties are often involved, which means the supplier must be able to work with many partners and to provide strong project management when needed.

These capabilities are even more important now that the BWM Convention has been ratified. Since all vessels will need a ballast water treatment system within just a few years, thousands of vessels will be competing for the few resources that exist.

Many suppliers have delivered only a handful of systems to date, and thus lack the production strength to scale up in the coming years. Others lack the hands-on experience to ensure smooth installation with the many parties involved. To secure a compliant system in time, it is important to look carefully at the supplier’s installed base and track record.

11. Is the system accompanied by a strong global service offering?

The choice of a ballast water treatment system has long-term implications, since the equipment is intended to last the lifetime of the vessel. There will be a need not only for parts, but also for expertise in optimizing the system over many years of operation.

Having easy access to support will make a positive difference in peace of mind and lifecycle cost. Not having it, on the other hand, may affect the vessel’s ability to comply if service cannot be arranged in time. Choosing a supplier with a global service network is critical, and the supplier should ideally have a well-developed service offering specifically for ballast water treatment.

If the vessel is sold down the road, having a system from a recognized supplier with worldwide support may also positively influence the sale price and the number of potential buyers.