UV ballast water solutions gain favour

Ratification of IMO’s Ballast Water Management Convention is widely anticipated within the next 12 months and it could well be legally enforceable by the end of 2013. The intention is that almost all commercial vessels will have to be fitted with a ballast water management system (BWMS) by 2016. As a consequence, passenger ship owners and operators, along with the rest of the shipping industry, are having to evaluate which ballast water treatment technology is best suited to meet their requirements.

Many manufacturers are now competing to deliver technology suitable for various vessel types, including passenger ships, for both newbuildings and what is expected to prove to be a hugely lucrative market for BWMS retrofits. Not all BWMSs being developed are appropriate for the passenger shipping sector, however, as ferries and cruise ships will typically require ballast water treatment systems with capacities of 100m3 to 800m3 per hour. Several systems on the market are aimed at larger cargo vessels with much higher capacity requirements, up to 6,500m3 per hour, and so will not be well matched to the needs of passenger ship operators.

Severn Trent De Nora, for example, gained IMO type approval last year for its Balpure system, which uses electrolytic disinfection technology. Marketing manager, Joyce Teng, said, “We have decided not to focus on such small ballast-rate capacity ships. The smallest system in the Balpure range is currently 500m3 per hour and for most passenger ships this is a larger capacity than required. However we are studying the marketability of smaller Balpure designs, based on our offshore platform system, which may be attractive for these types of vessels.”

For those manufacturers targeting the passenger ship market, the cruise ship sector in particular has specific requirements to meet. For example, the itinerary of a typical cruise ship may include frequent port calls and this creates a need for a BWMS solution that can comply with short post-treatment ballast water residence times in the tanks. The wide range of environmental conditions that a cruise ship may encounter in undertaking different cruise itineraries also requires a high degree of design flexibility, so that the system is able to handle variable water quality over a wide range of water temperatures.

Several manufacturers point out that, in their discussions with cruise operators, it is made clear that adopting ballast treatments that make use of chemical agents is not desirable. As a result there seems to be a clear preference amongst cruise shipping companies to adopt ultraviolet (UV)-based solutions.

As a practical example, Sumitomo Electric Industries has recently agreed with NYK Cruises to install the UV-based Ecomarine BWMS on its cruise ship, Asuka II. The work was due to be completed by the end of January 2012.

Ecomarine incorporates filter units originally developed by Sumitomo Electric to separate large plankton and other aquatic organisms. The ballast water management system then eliminates any remaining small organisms with a medium-pressure UV system. When tested on land using an arrangement comparable to onboard conditions – with a water treatment rate of 200m3 per hour – Ecomarine is reported to have demonstrated reduced power consumption and a organism removal capacity in line with requirements. Sumitomo has now applied for IMO approval for its system and says it aims to secure full type approval for Ecomarine by the end of 2012.

Elsewhere, UK-based Hamworthy has recently introduced its Aquarius range, which includes both UV and chemical treatment options. The passenger ship market is expected to be an important target for the UV product especially. Dr Joe Thomas, managing director, Hamworthy Ballast Water Systems, commented, “We are currently the only original equipment manufacturer offering a choice of ballast water treatment solutions to both the newbuild and retrofit markets.”

The Aquarius-UV system is a two-stage approach with filtration followed by disinfection using ultraviolet light, and so does not use any active substance. As there is no detrimental effect on water quality, ballast water can be safely discharged from the ballast tank at any time. Furthermore, to ensure maximum disinfection, UV treatment is utilised during the discharge cycle, as well as on ballasting. In developing the Aquarius-UV system, Hamworthy has formed a strategic partnership with UK-based Hanovia, a specialist in UV system design and manufacturing. Hamworthy has, however, assumed overall responsibility for performance compliance against the required regulatory standards.

Hamworthy is also marketing the Aquarius-EC system, which similarly employs a two-stage approach, but in this case disinfection uses an active substance, generated using side stream electro-chlorination. Hamworthy is collaborating with Magneto Special Anodes to develop the advanced electrolysis technology. Upon de-ballasting, the system neutralises any remaining active substance using sodium bisulfite, ensuring that the ballast water can be safely discharged.

The Aquarius-UV system is currently being prototype tested on a 2,000 dwt LPG carrier, while the EC version is being tested on a 13,000 dwt roro ship. Although Hamworthy has not been engaged in any passenger ship BWMS installations to date, the company says it is actively engaged with a number of key cruise ship owners and operators.

Dr Thomas added, “BWMS for passenger ships must be modular to allow for retrofitting on the existing fleet. We believe the fact that we have adopted a modular approach to system design in both versions of Aquarius will prove a key selling point in this sector of the industry.”

Norway-based Optimarin is another company that has embraced UV-based ballast water technology with its Optimarin Ballast System (OBS). Birgir Nilsen, vice president, business development, said, “We think that the OBS is well-suited for the passenger industry because the system is simple, flexible, and has a small onboard footprint. Furthermore the low maintenance requirement for this technology will be a key factor.” He also pointed out that the capacity of the system is well matched to vessels in this segment. “Most relevant systems in the passenger industry will only require one UV lamp, [for] up to 167m3 per hour, while some will have two UV lamps in two chambers [for] up to 334m3 per hour.”

Optimarin continues to improve its OBS technology and over the past year has updated the software that regulates the power consumption of the UV lamps. Based on the UV intensity, which is measured and fed back to a control panel, Optimarin can automatically regulate power consumption. In particular the new approach can reduce power when the vessel is in clear water conditions and increase it to maximum when water conditions are poor. Experience to date has demonstrated that the software has reduced power consumption by up to 50 per cent.

Optimarin has no recent experience of installations in the passenger ship sector, although it is interested in this market. Mr Nilsen said, “We have in the past year installed our system on board a large number of platform support and other offshore vessels that have comparable ballast pump capacities, but less available space and power. This experience demonstrates its suitability for passenger ships, as it can be configured in a number of different ways.”

There are a number of other manufacturers offering UV-based ballast water treatment systems, including US company Hyde Marine, whose Hyde Guardian is a totally chemical-free process, based on an automatic backflushing disk filter and medium pressure UV treatment. The system has successfully been installed on two cruise vessels, Coral Princess and Celebrity Mercury, as well as vessels of other types.

Finland’s Wärtsilä has joined forces with US-based Trojan Technologies to develop a new ballast water treatment system. This technology, currently under development, promises to combine filtration and UV disinfection techniques into a single unit, making this compact and easy to install.

Not all manufacturers are confident that UV is best for the passenger shipping industry. Severn Trent De Nora’s Ms Teng said, for instance, “Ballast water treatment systems using UV-based technology seem to be meeting the needs of passenger vessels, and the combination of higher power consumption but irregular use appears to be acceptable in this market segment. However there may be a false sense of security with UV-based systems as, if they prove not to work well at sea, this may only manifest itself once the Convention is ratified and when system performance inspections are performed by port state control authorities.” She said that there are currently no guidelines for such inspections, although these are expected to be issued in draft during the IMO MEPC 63 meeting in March 2012.

One established player that believes non-UV systems can still have success in the passenger market is Veolia Water’s RWO division, which is continuing to focus on its tried and tested CleanBallast technology, combining a mechanical disk filter and electrolytic disinfection. “With over 20 CleanBallast units already commissioned, this is one of the few ballast water treatment systems that has operational experience including sea trials in very difficult environments. It is suitable for use on passenger vessels and we are in discussions with both shipyards and owners to install CleanBallast on passenger vessels,” said spokeswoman Saskia Skovdal.

During the past 12 months RWO has refined the design to reduce the footprint of the CleanBallast system by as much as 50 per cent and has cut capital expenditure costs by 30 per cent – improvements which should make it more attractive to passenger vessel operators. Ms Skovdal added, “CleanBallast is a system which is already in use, exceeds IMO test requirements and has very low power consumption.” PST