The ballast water challenge

Transcription

1 The ballast water challenge The movement of organisms via the transport of water from one ecological system or part of the world to another can pose serious ecological and health threats in the host environment. An effective solution to the problem is on its way. When ballast water is taken in by ships, microscopic organisms and the larval stages of larger organisms can be taken in as well. These organisms are then transported far beyond their natural habitat and released at the deballasting site, where they may cause massive problems in their new environment. The International Marine Organization (IMO) has identified the introduction of invasive marine species into new environments via ships ballast water, attached to ships hulls and via other vectors as one of the four greatest threats to the world s oceans. The other three threats are land-based sources of marine pollution, the overexploitation of living marine resources and the physical alteration/destruction of marine habitat. Despite general agreement as to the importance of the ballast water problem, arriving at a solution has proven to be a difficult challenge. Any ballast water treatment system must be not only economical and effective, but also safe and practicable for both ship and crew. Up to now, such considerations have severely limited the practices available for avoiding ballast water contamination. IMO s ballast water division has emphasized this complexity in its guidelines for achieving a ballast water solution. A successful system must maintain a delicate balance in which biological effectiveness is only one consideration. Not only must the system work, it must do so without environmental compromises, and it must avoid putting the user s safety and profitability at risk. Few but hazardous survivors At least 7000 different species, comprising anything small enough to pass through ballast intakes and pumps, are carried in the ballast tanks of ships worldwide. Naturally these include bacteria and other microbes, but they also include small invertebrates and the eggs, cysts and larvae of various species. Since almost all marine species have life cycles involving a plankton stage, even species with large adults or which live anchored to the sea floor can be transported. Fortunately, most of the species carried in ballast water do not survive the journey. The ballasting and deballasting processes themselves are often fatal to the organisms, and the environment inside the ballast tanks can be extremely hostile. Moreover, those organisms still living at journey s end are faced with a new environment in which temperature and salinity differences, as well as competition from native species, will most likely hinder their survival. In a few cases, however, organisms are able to beat the odds and establish a reproductive population in the host environment. This may mark the establishment of a harmless new species, or it may be the start of a troublesome invasion, in which native species are out competed and populations of the new species become unmanageable. Some of the most striking examples of this occur when ships transport species from one temperate zone to another, providing passage across the tropical zones that otherwise form a natural barrier.

2 Severe impacts Unfortunately, the introduction of species is not like oil spills and other forms of marine pollution, for which action can be taken to help the environment recover. Hundreds of catastrophic introductions have been documented around the world, and in most cases the effects are irreversible. Invasive species can have a severe ecological and economic impact on their host environments. One of the most famous examples is the European zebra mussel, which by infesting 40% of US internal waterways may have cost between 750 million and one billion USD in control measures between 1989 and Another dramatic example is the filter-feeding North American jellyfish mnemiopsis leidyi, which has reached biomass densities of up to 1 kg/m2 in the Black Sea. This has in turn led to the depletion of native plankton stocks, thereby contributing to the collapse of entire commercial fisheries. Even more disturbing are the potential health effects of introducing a non-native species. Red tide algae (toxic dinoflagellates) can be absorbed by oysters and other filterfeeding shellfish, causing paralysis and death when eaten by humans. Likewise, it is suspected that diseases can be transported in ballast water, causing incidents like the South American cholera outbreak in the 1990s which was responsible for the deaths of more than people. Stricter laws in the pipeline Legislative attempts to deal with the ballast water problem have been ongoing for several years at an international level. In February of this year, IMO adopted an International Convention for the Control and Management of Ships Ballast Water and Sediments. The IMO convention adopted in 2004 will require ships constructed in 2009 or later to meet ballast water treatment standards. By 2014, existing ships must also start to meet these standards. In addition, national restrictions are already in place in a number of countries. These include Argentina, Australia, Canada, Chile, Israel and New Zealand, as well as the United Kingdom and USA. Alfa Laval s ballast water solution Alfa Laval has announced that it will meet the urgent need for ballast water treatment well before IMO regulations for ballast water take effect in A complete system, already undergoing full-scale trials aboard a Wallenius Marine transoceanic car carrier, will be commercially available in It is based on the patented Benrad AOT (Advanced Oxidation Technology), developed in cooperation between Alfa Laval and the Swedish company Benrad AB. This technology has been found extremely potent in the treatment of water and removal of all kinds of micro organisms and bacteria. Key benefits with the Alfa Laval Ballast Water Treatment System - No chemicals added or unwanted residuals remaining from the process - Low operating cost - The operating cost for electricity and cleaning is below 0,01 /m3 with consumables included. - Automated and marine adapted - Sales, local presence and service worldwide

3 Concept Working Principles The in-line Ballast Water Treatment (BWT) system consist of the following main components: -Benrad AOT unit (modular) chemicals - treatment without additives or chemicals - Filter - for removal of larger organisms and particles - Cleaning system for Benrad AOT units - Control system for automatic operation of the complete BWT system The water is treated at intake and once again at discharge. The treatment on intake ensures that minimal amount of viable organisms enter into the tanks and reduces de sediment built-up in the tanks, witch is a potential area for survival of organisms. The water is treated again at discharge to ensure that any potential growth of organisms in the tanks is neutralized.(fig 1) The system is fully automatic and can be adapted for different system requirements (different vessel types). The filter is automatic self-c1eaning and will be installed on the discharge side of the ballast water pumps. At ballasting, the back-flushing water from the filter is returned to the ocean. During deballasting, the filter is bypassed. This way there is no risk of contamination at the deballasting site. The Benrad AOT unit is cleaned regularly to prevent reduced performance due to sealing from seawater contaminants. The cleaning system uses an environmental friendly cleaning solution, which is reused until it is consumed. The cleaning solution is biodegradable and can be disposed either into the tanks or into the sea without any environmental concerns. The treatment system is robust and well prepared for the harsh practicalities of the marine environment The lifetime of the system corresponds to the lifetime of the ship, years. The system will not need any special skill for service and maintenance compared to other standard marine equipment. The treatment process will not affect corrosion rates in the ballast water system

4 The Benrad AOT treatment process The Benrad AOT utilises the synergy effect created by using several photo catalytic redox processes with the sole purpose of producing hydroxyl (OH) radicals. Special UV light wavelength is used in combination with catalyst for generation of OH radicals, which are ex1remely potent in breaking down micro-organisms and bacteria The cell-membrane of the micro organism is the first site of attack, see figure 2 below. Hydroxyl radicals efficiently break down the cell membrane, while traditional UV requires more energy to destroy the DNA. This is the main reason why Benrad AOT is superior to traditional UV. There are no substances added to the process and there are no residuals created. The levels of hydroxyl radicals are enough to sterilize the water but will not change the properties of the water. Treatment efficiency (%) The IMO convention regulates the maximum number of viable organism per volume of released ballast water. An organism is ecologically dead and hence not viable if the reproduction is inhibited. IMO class Efficacy (%) sd Date Zooplankton (>50μm) 99,7 0, Phytoplankton (10-50μm) 99,5 0, Bacteria, E. coli 99,9 0, Fig 3. Test results on natural seawater in shore based tests The sampled water needs to be stored in order to ensure confident results with viability and reproduction taken into account. The results above simulate the treatment at ballasting. With the results above together with the principle of treatment at both ballasting and deballasting, the treatment system will meet the IMO requirements.

5 Fig 4: Two Planktonic dinoflagellates before and directly (20 min) after passage trough the Benrad system. From top: Ceratium tripos and Protoperidinium sp. According to results from several test methods there is no remaining toxicity or other unwanted residuals in the treated water after passage through the system. Figure 5. The Wallenius lines vessel MIV Don Quijote where the Ballast Water Treatment System is installed. Onboard installation A full-sca1e prototype system is in operation on boart the Wallenius vessel MN Don Quijote since September The system is integrated with the ship' s ordinary ballast water system and can be operated at all ballast and deballast operations without affecting the ballast operation procedure. The onboard system installation bas, from a very early stage, been planned together with technical management of the shipowner, the crew, installation personnel and contributing partners. The installation bas been completed during full operation of the vessel, which is encouraging for future retrofitting of the existing fleet.

6 Figure 6. Benrad AOT Unit, onboard MN Don Quijote. An initial onboard test program was performed in August 2004 during an European route. The tests were performed both with and without treatment system in operation. The system treated the water both on ballasting as well as on deballasting. The system efficacy was more than 99% with regards to both phyto- and zooplankton at these initial tests. These results were achieved even though the system was not fully optimized at the time for the tests. System vs. Types of vessels Different vessel types will have different requirements on a ballast water treatment system. Tankers, Container vessels, Bulk carriers, Car Carriers or Cruise vessels a1l have very different environments and requirements on an installation. The system components are easy to separate for installation with limited space and have no critical requirement in terms of electrical power, space needed or control system interfaces. Figuur 7. Self-cleaning automatic filter. It is obvious that the system will be easier to insta1l on a new building than on an existing vessel. However the experience with the full-scale installation during full operation of MN Don Quijote is encouraging. We thank ALFA LAVAL for the authorisation to reproduce this article.