Retrofit Risks of Ballast Water Treatment Systems


The IMO Ballast Water Management (BWM) Convention entered into force in 2017 but at that time it applied only to new vessels. A new milestone is now upon us – the Convention will apply to existing vessels from 8 September 2019.

From this date, existing vessels have up until its next IOPP Certificate renewal survey to comply. This effectively means that vessels whose keel were laid before 8 September 2017 are likely to need to install an approved ballast water treatment system (BWTS) at some point between 8 September 2019 and 8 September 2024, depending the date of IOPP certificate renewal.

You may ask ‘what’s the big deal’? New vessels have been complying with the ballast water regulations for the last two years with little fuss. There is a big difference, however, between installing a BWTS during newbuild and retrofitting a system on an existing vessel. On an existing vessel, such a system would not have been considered at time of original build and no dedicated space would have been allocated.

What could go wrong?

Both the IMO BWM Convention and United States federal legislation (the USA are not signatories to the Convention and have their own rules) impose a discharge performance standard. This means that having a ‘type approved’ BWTS is not enough. If during deballasting operations the water is found to fail the discharge quality criteria, the vessel could be in violation of the applicable rules.

So, it is clearly important that the BWTS is fully operational, reliable and effective.

A 2019 report issued by ABS highlighted significant concerns in the operability and reliability of ballast water treatment systems. ABS reported, worryingly, that over half of the vessels participating in their survey experienced problems.

Some of the common problems included unstable sensors, frequent failing of UV lamps, filter clogging and issues when operating in low-salinity waters. The ABS report also states that most IMO and USCG type-approved systems are, to date, not suitable for use when gravity-discharging topside tanks.

Regrowth – a real risk?

Aside from the findings of the ABS report, the subject of ‘regrowth’ has not gone away. Organisms that survive the treatment process on intake (i.e. ballasting) can find themselves in an environment with an abundance of food, free from predators and can lead to a surge in their population. Concerns on the potential for regrowth within the ballast tank have been raised by a number of parties. This is particularly relevant to those systems without secondary disinfection (i.e. those that treat the water again during deballasting), where the scale of regrowth during a voyage could result in discharged ballast water failing the regulatory discharge performance standard.

Got the power

A vessel is fitted with a power generation plant matched to its expected demand.

So, it is possible that the generating capacity of an existing vessel might struggle with the increase in power demand created by the addition of a power-hungry BWTS. Or, the generating capacity may have diminished over time as wear or poor combustion affects the ship’s auxiliary engines.

It is therefore vital that the vessel can cope with the power demands of a BWTS and that it does not require the shutting down of other important electrical consumers, such as cargo gear or reefer containers. If it cannot cope, then this can result in delays to cargo operations and lead to disputes.

Commercial impact of failure

The obvious consequence of a treatment system failing to perform as expected is a regulatory violation picked up by Port State control (PSC) during an inspection. The punishment depends on the jurisdiction, but PSC deficiencies, detentions and financial penalties can be expected.

However, there are other commercial impacts to consider. Some are outlined below:

The vessel is not considered to be seaworthy on delivery or cannot later complete a voyage: The types of substantial damages that may result could include extra expenses to fix an alternative performing vessel, cargo transhipment to deliver to final destination, etc. There is evidently some variance in BWM regulations around the world which could be problematic.

A voyage cannot proceed promptly after delivery: This may cause other sizeable disputes for wasted expenses, fuel consumed, and over who pays for other delay consequences. For time charters, the vessel may be expected to be treated as off-hire if the full working of the vessel is not immediately available which can vary on the case circumstances. For voyage charters, the vessel may be unable to commence laytime (or after commenced, time may not count as laytime or as demurrage) if lost due to delay through non-compliance.

Reduction in vessel’s ballasting performance: There is a risk of reduction in a vessel’s ballasting capacity following the retrofit of a BWTS, potentially delaying cargo operations. This drop in performance could be due to the system being unreliable or being a poor match for the throughput of the vessel’s ballast pumps or additional pipework and filters introducing pressure drops in the system.

Increased fuel consumption: The greater power demands of a treatment system may result in an increased fuel consumption.

If a vessel’s performance is impacted following the retrofit of a treatment system, it is therefore recommended that the vessel’s description (and any associated performance warranties) is amended accordingly. If the charterparty remains unamended, a shipowner may be exposed to a charterer’s allegations of breach of warranty if delays are experienced as a result of the longer time needed for ballasting and deballasting.

No Plug and Play

To ensure a BWTS is reliable and performs to the required standard, it must be right for the vessel. A common message from experts in the industry is that there is no “one size fits all” or a “plug and play” solution.

Just as importantly, treatment plant installation projects must be properly planned. A typical project timescale from initiation to commissioning is several months. This requires careful planning of the selection process of treatment plants, lead times of equipment and workforce (or dry dock) availability and system designs for pipelines and electrical power. Selecting the right plant and system for retrofitting on a particular vessel takes careful consideration. The system must be matched to the operational demands and trading pattern of the vessel.


Alvin Forster: Deputy Director (Loss Prevention)

Jim Leighton: Senior Solicitor, England & Wales (FD&D)

Find out more
See our new guidance on complying with ballast water regulations here. Part 1 looks at the regulatory landscape, Part 2 on the different treatment systems available and Part 3 on the potential operational and commercial impacts.