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Problems ballast water can bring to our shores


 
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Peter Cochrane, who works for the Australian Quarantine Inspection Service (AQIS) in Broome, outlines the problems that ballast water can bring to our shores.    
Many ships come to Australia to pick up goods such as iron ore, coal, grain and salt. These ships are specifically designed to carry heavy cargoes. For the ship to efficiently travel through the water, both rudder and propeller must be below the waterline. A ship that left Australia with 200,000 tons of iron ore, for instance, would unload its cargo at its destination. This would make it rise in the water so it must re- ballast (be made heavier) and this is done using local water, which can be suspect in many ports.

 
There is an Australian requirement that all ballast water must be managed prior to entry to protect our pristine coastal environment. Foreign marine plant life, seeds, crustacea, dinoflagellates are all unwanted organisms, so quarantine officers board these vessels to ensure they comply with the AQIS ballast water management plan.

Exchanges are conducted at positions greater than 200 metres depth offshore and involves removing the ballast water and replacing it with deep sea ocean water. This water is then discharged at port before they take on more cargo. One vessel alone can discharge 71,000 cubic metres of ballast water. At the present time there could be 60 vessels in a queue at Newcastle with a similar number at Gladstone and Dampier. The quantity of ballast water discharged in Australia is staggering but it is well managed by AQIS.

 
Bulk carriers have a number of classes dependent on size  -  large to small: Cape size, Panamax, Handimax.
Images one and three are of Cape size vessels loading iron ore in the Pilbara WA. Image two is of a Panamax loading at Koolan Island and image four shows the Be Hai (Handimax) loading at Cockatoo Island. Both islands are north of Broome in Yampi Sound.

 
AQIS has a marine program in Canberra that has tested these exchange methods of ballast water. Organisms are specific to depths of water that they survive in, so no port environment organism will survive the deep sea ballast exchange. The ballast exchange is part of a world wide system under the auspices of the International Maritime Organisation, but Australia has a few added stipulations.

 
Vessels that ply the shallow waters around The Philippines and Indonesia pose another problem if they subsequently sail to Australia. There are only a few opportunities for deep sea exchange so AQIS is very aware of ensuring that the ballast exchanges are done correctly at sea.
A few years ago the black-striped mussel was found at Cullen Bay Marina, Darwin, causing authorities to close the area off (as it was designed to do), keeping the water at a particular depth. The water was then super chlorinated, wiping out the mussel.

 
It was thought that a yacht was the most likely culprit, acting as the vector for the mussel to reach Darwin. Yachts, as with other boats, are all checked by AQIS officers. They look for any pets on board, remove any food products that are a risk and check the hull using a remote camera. If these vessels are made of timber, they must be fumigated, a mandatory requirement.

On the larger vessels the ballast tanks have strainers which can trap organisms, so AQIS asks for all those strainers to be cleaned, requesting photographs if needed. Other countries have other requirements for specific reasons. On the east coast of South America, for instance, ballast water has to be treated for cholera if the vessel is sailing between two ports in that region.

 
There are two methods of ballast refill. In one, the empty - refill, the tank is emptied down to 5% of its capacity before refilling with ocean water. In another, the tanks are opened and the water floods out on to the decks while it is replaced. This is done three times to ensure the proper dilution.
Ballast refills can be a hazardous operation at sea, so from 2010 on, ships being constructed must have ballast water treatment facilities on board. This is a series of water treatment plants meaning that the ballast water can be recycled, saving a lot of time and energy all round.

 

AQIS certainly knows how to keep vessels ship shape.

Text: V.B. September 2009
Images from Peter Cochrane


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Introducing AQIS, Broome WA AQIS has a program of Indigenous engagement across Australia's Top End

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