The Evolution system is currently being tested to the ‘live/dead’ standard demanded by the U.S. Coast Guard with the aim of gaining Type Approval by the 3rd Qtr of 2017.

The new system will supersede the Cathelco Mk 1 system which already holds IMO Approval and AMS Certification. The independent laboratory appointed to supervise the USCG Type Approval testing programme for the Evolution is Lloyds Register.

Shipboard testing commenced in August 2017 and it is anticipated that all of the test results will be submitted to the U.S. Coast Guard for approval by the end of the 1st Qtr 2017.

Major features

  • Based on a combination of filtration and UV technology.
  • Operates in salt, brackish and fresh water.
  • Precise adjustment to different water qualities.
  • Effective in challenging water conditions.
  • Stepless power control – saving energy.
  • Capacities from 34m3/h to 1,500m3/h in a single unit.

System Overview


During uptake the sea water passes through the filtration unit where the larger organisms and sediments are removed. At regular intervals the retained material 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 seawater continues to UV treatment where smaller organisms, bacteria and pathogens are rendered harmless before the water passes to the ballast tank in compliance with IMO regulations. During ballast discharge the sea water by-passes the filter unit and goes directly to the UV chambers where it is sterilized for a second time. This avoids the risk of any contamination due to re-growth in the ballast tank.

6 reasons for choosing the Cathelco BWT system

1 Enhanced UV chamber design

The chamber has been re-designed to increase the level of irradiation to meet the ‘live/dead’ standard, whilst other improvements extend the exposure time with the sea water. In addition to creating a helix flow as the water enters the chamber, its path is interrupted by baffles to cause a lateral movement. This brings organisms from the edge of the flow closer to the light emitted from the UV lamps in a repeating cycle as the water passes along the chambers.

2 Precise adjustment to different sea water qualities

The unique Cathelco UVT sensor system has already proved its value in precisely adjusting the UV dose to different water qualities. This is achieved by taking a sample of sea water before it reaches the UV chamber and measuring the amount of UV light  actually passing through it. This works in conjunction with UV intensity meters which are mounted on the chamber and measure the intensity of light which is received.

Combined with stepless power control, all of these features ensure that power is not used excessively, only the amount needed to meet the ‘live/dead’ standard.

Cathelco are the only manufacturers to supply the UVT system as standard. With other suppliers it must be purchased as an extra.

3 Less pressure demand on pumps

The pressure loss with the Evolution it is just 0.6 bar at 250m3, resulting in less pressure demand on the ballast pumps.

4 Easy switch over – IMO to US waters

When vessels are sailing towards US waters or within them, crew simply have to press the ‘US button’ when ballasting/de-ballasting and the system automatically reconfigures to meet the U.S. Coast Guard regulations.

5 Footprint 50% smaller

The footprints of the skid mounted systems are more than 50% smaller than their predecessors even when the control panels are included. The reduction in size has been achieved by mounting the UV chamber vertically, simplifying the pipework arrangement and introducing the CIP wiper system.

6 Easy, intuitive control system

The control system on the Mk I system has proved popular with ships’ engineers and will be carried over to the Evolution. With easy to read schematics showing sea water routing, read outs showing the transition state of valves as well as instant information from sensors, engineers can easily see how the system is performing.