Alien plant and animal species that spread to the ecosystems in which they were not previously existent can cause major problems. Some plants and animals find opportunities in their new environment and can expand quickly. The result may be that the existing ecosystem and biodiversity is disturbed or breaks down. Species that aggressively and permanently establish themselves in new areas are known as invasive alien species.
To be an alien species should be described as invasive, and should fulfil a number of criteria. They will for example be carried from their area of origin to a new area, something that can be done deliberately by people for various reasons. There are also many opportunities for invasive species to become aggressive. Examples: oceangoing vessel ballast water, plants and animals that show up on boats and aircraft, or different organisms unintentionally transported from country to country, via live plant material.
There are many species, but it’s only a few who manage to both establish themselves and spread to surrounding environments. Of these, only a few can be classified as invasive and cause major problems. An example in Sweden is the Spanish slug that causes great concern in many home gardens.
In a global perspective, the problem of invasive species is very large and the EU environmental fund, LIFE, estimates the number of alien species in Europe to about 12,000. Some species add to ecosystems but others cause problems. According to LIFE, these species are a threat to biodiversity and the total within Europe is in the vicinity of 1,500 species.
Aquatic species – a notable problem area
In the sea and in freshwater, there are many invasive species that can spread across the world. Here we find such plants as algae, fungi, and protozoa. One of shipping’s major environmental problems is that species are moved to new areas through ships’ ballast water. Large oceangoing freighters can move tens of thousands of cubic meters of ballast water. Clearly, the intention is not to spread invasive species, but to give stability to the ship by balancing how heavy the load is, and compensate for different salinity and water temperatures. An example of an unwelcome bug is the American comb jelly (Mnemiopsis leidyi), which can hitchhike to the Baltic Sea from the United States.
The UN maritime body (IMO: International Maritime Organization) has drawn attention to the problem of invasive species and adopted a convention for handling ballast water (IMO’s International Convention for the Control and Management of Ships’ Ballast Water and Sediments). The Convention will enter into force one year after ratification by 30 countries, representing 35 per cent of world tonnage. Today, 36 countries have ratified, which corresponds to 29 percent of the world’s fleet. The Convention requires all ships in international traffic to treat all ballast water by 2016.
There are currently several different techniques to clean ballast water from foreign organisms. Chemicals, ultrasound, heat and ozone are some means. In addition, there is research to construct vessels that do not need ballast. The IMO has approved 30 water purification systems, and one of them is Swedish. The system is called PureBallast 3.0 and has been developed in collaboration between Wallenius Water and Alfa Laval.
“We are launching the third generation of our ballast water treatment system. It is called PureBallast 3.0,” said Peter Torstensson, communications director at Alfa Laval. “The system purifies ballast water to a level that is both consistent with the IMO Convention and U.S. Coast Guard Law (USCG). The plan is for us to obtain approval for USGC PureBallast 3.0 in 2014. The purification system is the first in the world to meet the IMO standard without the use of chemical pesticides or other chemical treatments, “says Torstensson.
“Another advantage of the new system is that it only takes up half as much space as their predecessors, and that we have managed to reduce energy consumption by up to 60 percent. For us, it is gratifying that the interest among ship owners has increased and when the IMO Convention is fully ratified, we expect 15,000 new and 20,000 existing vessels will be equipped with some type of system for cleaning ballast water over the next 10 years.”
UV light deactivates growth
UV light damages DNA and cells and makes it impossible for many organisms to reproduce. In the PureBallast 3.0 system, UV light is amplified through a process called Advanced Oxidation Technology (AOT). AOT allows the formation of “free radicals” and these cause irreversible damage to the organisms’ cell membranes.
When ballast water is filled, it passes the first mechanical filter that removes particles and organisms that are larger than 50 microns. Then the water passes through the AOT reactor and the UV light neutralises the biological activity. The amount of energy needed in the process is adapted to how clear the water is. If the water is relatively clean and clear, the amount of UV light is reduced which can provide significant energy savings. Before the ballast water is discharged at another location, the same treatment is done. Renewed UV irradiation kills the organisms that may have survived the first treatment and who have grown up during the sea voyage.
The PureBallast 3.0 system can process between 250 and 3,000 m3 of ballast water per hour. If a dual system is installed, up to 6,000 m3/hr can be treated. To irradiate 1,000 m3 of water / hour requires about 100 kW, corresponding to 30 percent less energy than previous systems. The “Dimming” function provides additional opportunities for lower energy consumption.
The article was published in May 2013