New BWTS for Big Bulk Carriers Unveiled

A new ballast water treatment system (BWTS) specifically designed for large dry bulk and ore carriers has been launched. 

Developed by the UK-based Coldharbour Marine, the system uses the company’s existing inert gas based GLDTM treatment plant to meet the needs of large bulk carriers, which often ship large volumes of ballast water in upper wing tanks and discharge it directly into the sea.

The IMO International Convention for the Control and Management of Ships’ Ballast Water and Sediments presents specific challenges for operators of bulk carriers by setting out specific discharge standards which must be met, according to Coldharbour Marine.

Most system technologies work by treating the ballast water at the point it is taken on board at the cargo discharge port and usually incorporate a filtration process and chemical dosing. Delays during ballast loading due to filtration issues or system breakdown are only one of the potential pitfalls, as explained by Andrew Marshall, Coldharbour Marine’s Chief Executive.

“Big bulk carriers are usually deployed on long-haul routes and lengthy ballast voyages can lead to significant organism regrowth. Ships fitted with in-line BWTS technologies cannot guarantee full compliance with discharge standards at the end of a long ballast voyage,” Marshall said.

In contrast, the newly launched system is not an in-line process and does not treat ballast water at uptake. Instead, it is an in-voyage process, so there are no filters and no potential problems relating to flow rates, pressure drops, or power consumption during ballasting.

“Some try to ignore the regrowth issue, but the fact is that no BWTS technology is 100% kill effective. If treatment is only undertaken during uptake, the few organisms that survive will thrive and multiply over a long ballast voyage in the food rich, benign environment of the ballast tank. The longer the ballast leg, the greater the risk of significant regrowth, meaning that ballast water could easily fail to meet discharge standards several weeks later,” Marshall continued.

Bulkers sometimes load extra ‘heavy weather’ ballast water in cargo holds, which inevitably faces contamination by cargo residues. In-line systems would find this water hard to process and could be damaged by it. In this case, the company has developed a pipe circuit to allow ballast to be pumped from the various tanks through robust gas lift diffusion (GLD) units mounted in the machinery space – instead of in-tank, meaning that water can be returned to the tanks via multiple outlets to ensure that contents are stirred and treated.

“Now that the IMO’s Ballast Water Convention has entered force, vigilant port states will be watching bulk carrier operators closely. Operators of these vessels have no time to lose in assessing how they will meet convention requirements,” Marshall concluded.