Ballast Water Treatment, the Current Challenges.


Andrew Marshall, Chief Executive Officer of Coldharbour Marine, reviews the challenges facing ship owners and operators as they plan the implementation of the IMO Ballast Water Treatment Convention.


Andrew believes that, as the concerns of the International Chamber of Shipping (ICS) have begun to be allayed and as the more robust procedures that now under- pin IMO ratification become accepted, it is likely that the convention will come into force this year or early 2016. The IMO implementation timetable has reduced the risk of a bottleneck as ship owners and operators need only to place retrofit orders to ensure their vessels achieve the standard by the next renewal survey following the convention launch. But what is guaranteed is that there will be many a furrowed brow as owners, operators and agents try to decide exactly which system is best for their fleet.


Before Coldharbour Marine designed its patented ballast water management system, (BWMS) Andrew ordered an audit of customers’ views. “Customers told us they were thinking beyond installation costs but were also working to identify the best option for their particular fleet. They were worried about staff training, about system reliability and functionality, about running costs and about the impact of a newly installed system on the rest of their vessel especially when managing port operations.”


Andrew Marshal sympathises, he believes that there is no simple solution to preventing foreign organisms being transported thousands of miles in ballast water to contaminate virgin environments. Vessels vary in size and capacity so the space available for a new installation varies too. Ships cross waters that physically vary; they may travel to collect or discharge from a fresh water port, salinity circa 15 psu and travel to a port with salinity levels in excess of 38 psu ; they may start in the warm, transparent waters of the Indian Ocean and sail into turbid environments like the Yangtze, they may start in near freezing waters of the Capes and have to discharge in the warmth of the Pacific. In short, Andrew says, “One size does not, and never can, fit everything.”


In discussions with customers, Coldharbour identified 14 criteria that an ideal BWMS must achieve:

  • It must not disrupt normal operations, especially ballasting and de-ballasting

  • It must allow for gravity ballasting and de-ballasting

  • It must not require upgrades to ballast pumps or pipes

  • There must be no ballast water filtration requirement

  • It must not require upgrades to on-board power generation capacity

  • It must have a small footprint

  • It must have low running costs

  • It must be robust, reliable and suitable for life on-board

  • There must be no specialist maintenance requirement

  • It must be simple to use

  • It must be safe for crew and the environment, particularly in the event of accidental misuse

  • It ideally must not use chemicals or active substances – G8 approval preferred

  • It must be able to deal with any regrowth in the ballast tanks

  • It must be future proof and able to respond to tightening regulations worldwide

    Coldharbour Marine’s development of a new BWMS was based upon these criteria.


    The company has a long history in the manufacture and supply of inert gas generators producing super-clean, very low oxygen inert gases used to blanket cargoes in tankers, LNG and LPG carriers and floating production, storage and off-loading vessels (FPSOs). Coldharbour decided to focus on the needs of the market in which it was expert and to design and develop an in-tank solution to serve their needs.  Coldharbour’s design engineers then set down a set of challenges that their system had to overcome:-


  • The BWMS had to cope with high ballast water volumes and flow rates depended upon by tanker operators, with a minimum of 6,000 – 8,000 m/hr of water being pumped; testing volumes and flow rates for systems relying on filtration. It must avoid equipment which would cause pressure drops or impede ballasting.


  • The system had to handle very large volumes of ballast water, with 100,000m 3 or greater volumes being utilized. With these large volumes issues of regrowth on longer voyages had to be eliminated.


  • The critical time for any ship operator is in port, when personnel are busy managing ballasting and deballasting, taking on stores, transferring cargo, liaising with Customs etc. Power demands are high as is the pressure on crews. Avoiding the need to manage ballast on top of everything else happening during port time has obvious appeal.


  • The final design demand was the need to minimise the footprint of any equipment that needed to be installed, the smaller the footprint the better.


With the design challenges established, Coldharbour Marine developed its Ballast Water Management System using an Inert Gas Generator linked to simple Gas Lift Diffusion (GLD™) units mounted inside the ballast tanks. All is engineered to 100% reliability.


The Gas Lift Diffuser within the ballast tank uses natural fluid dynamics to stir inert gases through the ballast water and ensure thorough treatment. The inert gases reduce the oxygen content of the ballast water while the elevated CO2 levels in the inert gas reduce its pH. The gases leaving the Gas Lift Diffusion device generate an ultrasonic frequency which physically disrupts the cell walls of any organism living in the water while gas micro-bubbles amplify and enhance these in-tank ultrasonics. Organisms are killed in three ways: by hypoxia, caused by low levels of O2, by hypercapnia caused by the low pH / dissolved CO2, and by ultrasonic cell wall disruption.


By starting by identifying the challenges, the Coldharbour system delivers a number of benefits. The IGG has no burner cone, no demister pads and no steam injector. The BWMS has no filters, no membranes, no active substances and no electrical connections. There are no filters to block and pump sizes are as irrelevant as are flow rates. The system can be operated when the ship is underway, meaning staff can focus when in port. With the units inside the ballast tanks having no power demand, the overall system has a small footprint meaning ancillary equipment can be installed anywhere. The IGG element of the BWMS can double up, producing inert gases for blanketing cargo.  Being based upon well understood marine inert gas technology and with a minimum of moving parts, the Coldharbour system requires minimal maintenance or staff training. 


IMO system certification is under the UK Maritime and Coastguard Agency supervised by Lloyds Register delivering an option, which, from the ship operator’s perspective, has very real benefits. The Coldharbour BWMS was retrofitted onto a VLCC during a normal dry-docking period. During the 24 months since installation, the operator reported no disruption to normal ballasting / deballasting. The system proved immune to changes in water salinity and temperature. No additional power generation was needed and the ballast water was cleaned in voyage when power demands were a minimum. There were no problems with regrowth since the organisms had been killed in the tanks, meaning it was always safe to deballast.


The GLD system handled silts, sediments and turbid water as easily as clean water. Finally, since there are no active ingredients nor chemicals involved, there was no damage nor corrosion in the ballast tanks themselves. Indeed Jotun and International Paints both independently verified reduced ballast tank corrosion tests bringing savings in tank repair costs and vessel downtime.


Asking Andrew whether or not Coldharbour’s BWMS is the solution for all operators, his answer was surprising, “Not necessarily. The in-tank system is not the cheapest option. It works very well and offers particular advantages to tanker owners operating large vessels with significant ballast flows and water volumes. Owners of vessels using smaller volumes of ballast should balance the cost savings gained from specifying an alternative system against the difficulties of managing a power-hungry system relying on UV, active agents, filters and maintenance. As I said at the beginning, one size does not fit all!” 





For more information contact Rosie Featherstone

Tel  01332 862073  or 07788 592314













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