Ballast Water Treatment Systems 

Unique in-tank, in-voyage inert gas based ballast water treatment technology specifically designed and optimised for fitting to large tankers and ore carriers, LNG carriers and bulkers.

VLCC Installation

The system was retro-fitted to a VLCC for IMO [MEPC 174(58)] Type Approval testing 2012. ​Watch the video to find out how this was achieved. We were awarded the certificate in 2015.

Simple to operate and maintain

The Coldharbour Marine GLD™ ballast water treatment system is an in-tank system taking the inert gas output from the Coldharbour Inert Gas Generator (IGG) linked to specially designed Gas Lift Diffusion (GLD™) pipe assemblies mounted inside the ships ballast tanks. 

Sea Guardian™, our 3rd generation IGG produces very clean, very low oxygen inert gas and is compact, stable, reliable and largely maintenance free.   During the voyage, inert gas from the IGG is pumped (by standard marine type compressors) to the GLD™ units in the ballast tanks where the treatment takes place.​


In addition to killing the invasive aquatic species present in the ballast water in accordance with IMO and other regulatory requirements, our ballast water treatment system also offers the ship owner savings in maintenance costs through a reduction in ballast tank corrosion. This is achieved because the diffused reduced oxygen gas sits in the ullage space within the tank thereby suppressing the corrosive effect of sea water on the tank structure, even if the coating has been cracked or compromised in some way.

Tests have shown that corrosion may be reduced by as much as 65% in normal operation and this provides significant savings in dry dock maintenance time and repair costs, as well as offering an extension to the economic operating life of the vessel.


The Coldharbour Marine Sea Guardian Inert Gas Generator (IGG) has been designed to be easy to operate with a minimum requirement for servicing,  maintenance or consumables. The Coldharbour Marine in-tank Gas Lift Diffusion (GLD) units have no moving parts, are 100% reliable and have little requirement for servicing, maintenance or consumables.


The system is GUARANTEED not to disrupt any aspect of terminal operations, including gravity ballasting and de-ballasting. No part of the treatment process takes place at uptake or at discharge. There are no in-line filters and no changes to the standard ballast system are needed. Ballast water treatment takes place during part of the ballast voyage. On long ballast legs this means that the crew can select the optimal time to treat the water – and by treating in the tank in this way, the system completely removes the risk of organism regrowth taking place during long journeys.

The system automatically monitors water conditions inside every ballast tank – which means that the crew can have confidence that the ballast will always be fully treated and safe to discharge at the port of destination. System performance is not affected by silt levels, water temperature or salinity. 


In operation, as the inert gas diffuses into the ballast water through the GLDs, oxygen is stripped from the water while the elevated level of CO2 in the inert gas temporarily reduces the pH value of the water. This simultaneously induces hypoxia and a condition known as hypercapnia in marine life. These conditions are fatal to both aerobic and anaerobic organisms. Effective treatment of enteric bacteria (E.coli for example) is achieved by a patented method of gas-induced ultrasonic shock-waves produced inside the GLD. The ultrasonic generator requires no power and has no moving parts and is designed for years of reliable operation inside the harsh environment of the ballast tank.


The Coldharbour ballast water treatment system does not use active chemicals to treat the ballast water which means that when the treated water is discharged it poses no threat to the marine environment. The treated ballast water is re-oxygenated prior to discharge, ready to fully support marine life in the ocean.

The Coldharbour ballast water treatment system is one of the first systems to achieve Type Approval through the United Kingdom Maritime and Coastguard Agency (UK MCA) following extensive testing over 4 years in a wide range of conditions.