Challenge of Ballast Water

Introduction of D-2 Standard


If a seagoing vessel takes on or discharges ballast water for stabilisation, microorganisms and tiny creatures living in the water are regularly conveyed from the ballast water tanks to coastal waters. This “invasion” leads to destruction of the ecological equilibrium. Due to the sharp increase in shipping traffic in the past, bigger and faster vessels and changes in climatic conditions, there is more than ever a persistent need of action regarding intake and discharge of ballast water. According to IMO estimates, ships annually carry over ten billion tons of ballast water worldwide that is pumped in and out on the open seas.

For this reason the IMO adopted a ballast water convention back in 2004. Germany wants to ratify it in 2010, but by 2013 at the latest. Once at least 30 countries with at least 35 percent of the gross tonnage of the world merchant shipping fleet have ratified this convention, the ballast water convention can go into force twelve months from the date of ratification. Currently 18 nations, and thus 15.27 percent of the world tonnage, have made this binding declaration under international law. As a consequence of the delay in the convention's coming into force, national regulations are increasingly created, such as in the case of the US coast, South America and the Ukraine.

As soon as it goes into effect, the convention requires as of 2004, but by 2016 at the latest, a ballast water management system that extensively does away with the previously customary uncontrolled water exchange during intake and discharge of ballast water. An exception to this rule is the presence of a safety risk. In this case the ballast water can be taken on board or pumped out anywhere. As of 2016 (for 1,000 TEU vessels as of 2014), the ballast water on board the Hansa Mare fleet has to be treated by means of appropriate ballast water treatment systems prior to discharge into the marine environment. This is specified by the so-called D-2 standard.

Ballast water exchange according to the IMO's D-1 Exchange Standard is only permitted on the high seas, and not in port in some countries. This exchange may take place via a sequential process in which the tanks are first 95 percent emptied and then filled again. The sediments are flushed by means of the continuous flow process, in which new water is constantly pumped in and old water constantly pumped out. At Hansa Mare the entire water exchange is documented in the ballast water management plan.

The D-2 standard, which becomes binding – if ratified – as of 2014 or 2016 respectively, provides for ballast water treatment directly on board so that a stipulated limit for microorganisms per cubic metre is not exceeded.

These figures shall be achieved by means of ballast water treatment systems installed on seagoing vessels and approved by the IMO. At the time of adoption of the convention there were no suitable technologies capable of meeting the strict D-2 standard. In the meantime industrial enterprises worldwide are developing and designing various innovative systems and technologies that are already going through the complex approval procedure at the IMO or at the national approval authorities. Eight systems have been approved worldwide thus far. New vessels can be equipped with them since 2009. An important prerequisite is their environmental compatibility. For example, the systems must decompose active substances in the ballast water tank like chlorine, which is used to disinfect the water, within a short time.

The ballast water treatment systems approved by the IMO function according to different methods. Pretreatment can be carried out by means of mechanical filters, such as a hydrocyclone – a centrifugal separator operated in the liquid phase such that gases are separated in liquid particles, filtration or flocculation. After that an environmentally sound cleaning process is activated during which the ballast water is disinfected either chemically or physically. The physical process is carried out using UV radiation or ultrasound. In the chemical process special substances, such as chlorine, ozone, peracetic acid or chlorine dioxide, are added to kill off microorganisms when ballast water is taken in. These are substances that can be degraded rapidly without residue before the water is pumped out.

The decision in favour of physically or chemically based systems depends, among other things, on the type of vessel and the ballast water volume on board. In the case of large volumes, a system with physical disinfection would require considerable space on board; the energy requirements of such a system would also be enormous. On the other hand, no chemicals would have to be additionally stored on board as would be necessary with a system for chemical disinfection.

Ballast water treatment systems on board mean further inspection work on the part of international authorities. Besides a transparent certification process, constant checks of the treatment facilities by Port State Control are necessary to effectively tackle the challenge posed by ballast water.

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