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The BWT system – from start to finish
During uptake the sea water passes through the filtration unit where the larger organisms and sediments are removed.
To allow for different water qualities, a sample of sea water is taken before it reaches the UV chambers and measured using a UVT sensor. The sensor measures the UV light transmittance of the sample – the amount of UV light actually passing through the water. The power to the lamps is automatically raised or lowered, optimising the power usage.
At regular intervals the retained material in the filter is automatically back flushed and discharged at the original ballasting site, with very minimal reduction of the ballast water flow during the back flushing process. The sea water continues to UV treatment where smaller organisms, bacteria and pathogens, are rendered harmless before the water passes to the ballast tanks.
The performance of the lamps is constantly monitored by UV intensity meters indicating when cleaning, replacement or refurbishment is necessary.
During ballast discharge the sea water by passes the filter unit and goes directly to the UV chambers where it is treated for a second time. This avoids the risk of any contamination due to re-growth in the ballast tank.
Located on pipework before and after the BWT unit, the sampling points enable laboratory specimens of sea water to be taken by the Port State Authority, if required.