Ballast water treatment system launched GREEN CRAFT TECHNOLOGY
W
HAT is claimed to be the first viable system for preventing the transport
of potentially invasive species via ballast water was launched towards the end of last year by Alfa Laval. PureBallast, whose technology was developed in cooperation with Wallenius Water, arrives more than two years in advance of International Maritime Organization (IMO) regulations to prevent the transport of potentially invasive species. The problem of invasive species has
long been a matter of international focus. Species transported via ballast water from one ecosystem to another have devastated marine life, collapsed local businesses and economies, and necessitated billions of dollars in control measures. IMO legislation designed to combat the
problem is set to take effect in 2009. Until now, however, no treatment system has been commercially viable or able to meet the proposed requirements without chemicals, Alfa Laval claims, and PureBallast’s chemical-free technology is thought to be unique. PureBallast is compact and designed for
real-life conditions at sea. While removing microorganisms to IMO-compl iant levels without the use of chemicals, it accommodates the short- and long-term needs of shipyards, owners, and operators. PureBallast, which has met the stringent
IMO ballast water requirements in pilot tests supervised by Det Norske Veritas, is well underway with the year-long official approval process. Moreover, its ability to perform at sea has been confirmed in three years of full-scale onboard tests.
Chemical-free Alfa Laval’s PureBallast system is based on advanced oxidation technology (AOT), which is a chemical-free process similar to that used in many of today’s ‘smart products’. The self-cleaning windows of skyscrapers and cars, for example, prevent the growth of organisms through an AOT reaction
The PureBallast system uses Wallenius AOT, here compared to UV-technology.
that occurs when sunlight strikes titanium dioxide. Such technology eliminates the need to stock or handle chemicals onboard vessels, which is especially important when dealing with large ballast water volumes. PureBallast’s patented version of this
technology, known as Wallenius AOT, has been industrialised by Alfa Laval in cooperation with Wallenius Water. In both pilot and onboard tests, the highly advanced method has proven an effective means of meeting the IMO requirements. Depending on a ship’s ballast water
volume, PureBallast involves one or more AOT units, which treat the water during ballasting and deballasting operations. These units contain titanium dioxide catalysts, which generate radicals when hit by light. The radicals, whose lifetime is only a few milliseconds, break down the cell membrane of microorganisms – without the use of chemicals or the creation of harmful residuals.
Installation and operation The PureBallast system is said to be compact and simple. The modular equipment fits
easily into the engineroom, due to a block- component structure that allows it to be installed between normal ballast water system components. This not only facilitates installation, but also simplifies day-to-day operations. There are no moving parts and few consumables, which means the system can be maintained with minimum effort. Treatment of water with PureBallast
occurs in two stages: pre-treatment and end- treatment. During ballasting, water passes through a pre-filter to remove any larger particles and organisms. The water then continues to the AOT unit, which produces radicals that effectively break down smaller organisms that have passed the filter. Sediment build-up in the ballasting tanks
is avoided thanks to the pre-filter stage, and any back-f lushing water is returned to the ocean directly at the ballasting site. During deballasting, water again passes
the AOT unit in order to destroy any organisms that might have re-grown in the tanks during the voyage. The filter, on the other hand, is bypassed, thus avoiding any filter backf lushing. This eliminates the risk of contamination via the filter at the deballasting site. The whole chain is fully automated, with
monitoring of alarms and possibilities for both local and remote operation. The system is started and stopped with the push of one button, and it involves no preparation, chemical dosing, or waste streams. To ensure that the performance of the AOT unit is not affected by scaling from seawater contaminants, an automatic cleaning unit has been integrated into the system.
The Alfa Laval PureBallast system, side view. 48
Proven biological efficiency Laboratory pilot tests of the PureBallast system, conducted by the Norwegian Institute for Water Research (NIVA) in 2006, have shown that PureBallast meets the IMO standards for ballast water treatment. Conducted under the supervision of DNV,
SHIP & BOAT INTERNATIONAL MAY/JUNE 2007
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