Ballast water management

The Evac Evolution ballast water management system (BWMS) is based on a combination of filtration and UV technology. A key aspect of the system is precise adjustment to different seawater qualities ensuring effective disinfection, but saving on power whenever possible using an advanced UVT ‘feedback’ loop.

The Evac Evolution ballast water management system is available with capacities from 34m3/h to 1,500m3/h in a single unit. The equipment can be provided skid mounted or in modular form simplifying retrofit installations where there is the need to make the best use of available space.

The Evac Evolution ballast water management system (BWMS), designed by Cathelco, complies with the revised IMO G8 standard and the U.S. Coast Guard regulations.

View our BWMS brochure

Key features of the Evac Evolution ballast water management system

  • Saving space – economizing on power
  • Precise adjustment to different water qualities
  • Helix flow through UV chambers
  • Easy, intuitive control systems.

The Evac Evolution technology description

The Evac Evolution ballast water management system (BWMS), developed over 10 years by Cathelco (part of the Evac Group),  is based on a combination of filtration and UV technology.

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 UV Transmission 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 BWMS, the sampling points enable laboratory specimens of sea water to be taken by the Port State Authority, if required.

Enhanced UV chamber design

The UV reactor is designed to increase the level of irradiation to meet the U.S. Coast Guard ‘live/dead’ standard, whilst other features extend the exposure time with the sea water. In addition to creating a helix flow as the water enters the reactor, its path is interrupted to cause a lateral movement. This brings organisms from the edge of the flow into closer contact with the light emitted from the UV lamps in a repeating cycle as the water passes along the chambers.

Precise adjustment to different water qualities – saving power

Maximum power is only used when the circumstances demand such as when the ship is operating in heavily silted waters within harbours and estuaries.

A UV Transmission sensor measures a sample of sea water before it reaches the UV chamber and registers the amount of UV light actually passing through it – a very accurate way of calculating the correct UV dose. This works in conjunction with UV intensity meters which are mounted on the chamber wall and measure the intensity of light which is received. As soon as the water quality improves, the power to the lamps is reduced saving on overall power consumption.

Your ships can go anywhere without restriction

Because the Evac Evolution system is effective in marine, brackish and fresh water there is no limitation on the areas where your vessel can trade. It can operate in the Great Lakes, inland waterways and estuaries, whilst also remaining effective in seawater temperatures down to minus 2 degrees C.

Effective in challenging water conditions

Some BWMS struggle to work effectively in the heavily silted water found in harbours. The Cathelco system has proved to be effective in waters where UV light transmittance is as low as 55%. This compares with normal seawater UVT levels of 75%.

Stepless power control – saving energy

In many BWMS, power to the lamps is increased in large incremental steps with inevitable wastage. In contrast, the Evac Evolution system uses the latest switchmode technology to provide a ‘linear’ power supply. This means that the demand from the lamps is met in much smaller steps without excessive and unnecessary use of power. As the power output is linked to data from the UV Transmission and UV intensity meter feed-back loop, the optimum amount of power is used at all times.

Easy, intuitive controls

The control system is easy and intuitive to use. Schematics show the routing of the water through the pipework and readings are immediately available from all of the sensors. It is also shows the transition state of valves, giving engineers a complete picture of how the system is performing.