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Georgios Teriakidis*: When owners face the choice between one type of ballast water treatment system and another, there is no silver bullet

DNV GL has been working with owners and operators to ensure the safe installation of ballast water treatment systems (BWTS) on newbuilds and as part of retrofit projects for many years now.


Currently, the industry is under a lot of pressure to install ballast water management systems on time. To give you an idea of the scale of the task, we estimate that about 8,700 vessels (in DNV GL class) shall be issued with an International Ballast Water Management Certificate by 8 September 2017, which adds up to roughly 300 certifications per week up until the entry into force date. In addition, we estimate that about 5,000 ballast water management plans shall be approved by DNV GL over the same period. The installation of ballast water treatment systems will come in the next 6 years. DNV GL expects about 450 retrofit projects per year (this includes sister vessels).

In terms of system installations, retrofits are more complex than new-build installations. Due to the short time windows during dry docking, retrofits require very good planning and the classification society needs to be involved from an early stage. Some of the lessons learnt from previous retrofit projects include that every aspect of the installation needs approval by class, including any updates to the drawings and stability calculations. Also, the ballast water treatment system increases the vessel’s overall power requirement.

When owners face the choice between one type of ballast water treatment system and another, there is no silver bullet. Our recommendations for the type of system hinge on such questions as: What ship type is it? Does the vessel need to operate in fresh or brackish water? Does it operate in cold waters or in temperate conditions? Will the system have to work in high turbidity conditions, meaning water that contains a lot of clay, algae or silt? And of course, for existing vessels: is it worth it at all? Has the vessel reached such an age that a retrofit will involve a too high cost? Better to scrap the vessel now rather than retrofit? All these questions are very important for making the right choice. But a treatment system that is optimal for one ship may not be the best solution for another ship. There is no “one size fits all” solution. Careful selection of treatment systems can mitigate specific feasibility issues in terms of the individual ship. There are many factors, such as space constraints, electrical load limitations, the integration of control systems, optimization of performance and operational costs.
UV systems, which use a two-step process of filtration and ultraviolet (UV) irradiation to sterilize organisms and stop their reproduction, are among the prevalent options at present. UV systems are simple to operate and relatively easy to install. The electrolytic treatment systems are another popular option. By passing electric current through a small amount of seawater, they convert the salt, or sodium chloride (NaCl), into sodium hypochlorite, a disinfectant, which is then used to treat the ballast water. This is a proven method; the downside is that electrolytic systems are sensitive to low salinity and low temperatures. Salt or a heat must be added where necessary.

BWTS technologies may face challenges in specific water conditions, and neither the G8 nor the EVT protocol – the IMO and USCG protocols, respectively – guarantee treatment of all types of water in line with the D-2 standard. During the type approval process, the IMO and USCG protocols require that the system design limitations, water quality and operational parameters to which the BWTS is sensitive, are identified so that vessel operators can determine in which water conditions the system will function.
In case of doubt regarding treatment performance of the given water, or if the system fails during ballast intake, ballast water exchange with treatment when out of port may be an option, provided the vessel also has approval to perform ballast water exchange. However, once D-2 compliance is compulsory, shipowners will need to notify the port state if they need to perform exchange, and the port state will need to accept this as a solution.

Turbidity, opacity, temperature and salinity level of the intake water are challenges to which the treatment system is subjected. They will differ significantly between the different ports of intake of ballast water. Water in ports located in close vicinity to rivers may have high levels of particulate and organic matter carried out with the river water into the sea. Excessive levels of nutrients, such as nitrogen and phosphorus, may enrich the seawater that can generate algal blooms. If a vessel is trading in such areas, the BWTS is required to function adequately in water with high organic content. The filter will be susceptible to clogging, and reduced flow-rate may be expected due to the requirement for back-flushing. In water with high organic content, more disinfectants are required, and hence more chemicals need to be added to the system or produced by the system.

For ports located in fresh or brackish water, the salinity will subsequently be low; hence the BWTS is required to function adequately in fresh water and low salinity water. For some systems where the generated disinfectant is dependent on the salinity, such as electrolysis, the system cannot produce sufficient amounts of disinfectants when the availability of chlorine ions is low. Water temperature is also an important factor for some systems. The production of disinfectants by oxidation is a temperature-dependent process, and at low temperature, the system will have to produce more disinfectants, hence higher energy consumption.

The training needed for the crew will be dependent on the type of treatment system. For example, chemical injection systems will require crew training in handling chemical spills/ leakages. Electrolysis systems, both in-line and side-stream, create H2 gas as a by-product. Different manufacturers will have different systems for expelling the H2 gas. The crew must become familiar with the off-gassing system, as well as any alarms or shutdown procedures. Besides any hazards inherent to each technology type, the crew will need to receive training in operating the system, limitations of the system and any changes which may occur to the ballasting and de-ballasting procedures as a result of the new treatment system.

Bearing all of this in mind owners need to take their time to check the different solutions that exists and weigh all the possible options. A decision made in haste could have serious consequences if a sub-optimal solution is chosen. Specialised engineering services may be worth the investment when finalising this choice. For newbuilds, we advise that owners also bear in mind that if they do not fit a BWT system in the vessel initially, it may cost twice as much to install a system retroactively, not counting the potential loss of earnings from time spent in dry dock. If they do delay, they should ensure that the layout and equipment allows for fitting a BWTS at a later date. This entails looking at the piping system, the pump strength and capacity, and ensuring that a suitable BWTS is available for installation on the vessel by the compliance date.

DNV GL has developed a decision-making tool that helps shipowners choose the system most suitable for their ship and, most importantly, helps them avoid costly systems which are not compliant. The tool synthesizes information from shipowner experience and experience from advisory and class services. DNV GL can use this tool to perform quick assessments of treatment technologies for specific vessels on behalf of our customers. We have also developed a guide for retrofit installations of ballast water treatment systems. The description includes all approvals required when a BWMS is to be installed on board a ship classified by DNV GL in accordance with the BWM Convention.

In line with our policy of Greece been our 3rd home market, our Piraeus office is ready to assist the Greek Maritime community.
Our competent colleagues will be happy to assist either with the above mentioned tools and guideline or with the approval of the mandatory water ballast management plans.
* Regional Business Development Manager Region South East Europe & Middle East DNV GL – Maritime

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