Ballast Water: What’s the best method of treatment?

A Ballast Water Treatment System is a crucial and necessary piece of equipment for globally trading commercial vessels but not all use the same method or are made equal.

Today, there are numerous available solutions and implementations that have been developed over the last 15 years. Considering the variety of available land-based water treatment technologies, it is no surprise that a few of these have been adapted and transferred to the marine environment.

At the bottom of it

A recent research by SGS found that one in five BWMS installed on commercial vessels might not be treating water to a compliant standard when they are delivered. Moreover the study shows that 21% of systems failed even from their commissioning testing – meaning they might had been installed/ operated incorrectly and that owners would be liable for fines or other enforcement action should the issues not be rectified.

Right now, most regulators do not require commissioning testing with these systems remaining non-compliant and representing a compliance risk for the entire lifespan of the system. MEPC 75 is planning to change this with new commissioning testing standards on the agenda for their 16-20 November 2020 meeting. These will ensure that systems are tested quickly after they are installed, and any faults found and rectified prior to delivery.

What is the most effective method?

According to another research made by Clarksons in October 2020, 46% of ships have installed electro-chlorination and 24% UV disinfection BWTS. Are these considered the best methods out there?

Electro-chlorination (EC) is the process during which a disinfectant TRO (total residual oxidant) is produced by an EC cell module, comprising of electrolytic cells, specifically designed to generate sodium hypochlorite from sea water. The sodium hypochlorite generated is then pumped into the main ballast line, mixed with filtered ballast water for efficient disinfection, and pumped into the ballast tanks.

Manufacturer ERMA FIRST has published a detailed research comparing the effectiveness of its Full-Flow Electro-Chlorination technology with ultra-violet (UV) technologies, side-stream ballast water systems and systems without filters.

The ERMA FIRST report, Ballast Water Treatment Systems Performance Analysis and Review, compares ballast water treatment technologies focusing on the needs of the spot trading cargo fleet, which trades in a range of waters and may be subject to both US Coast Guard and IMO standards. 

As stated by ERMA First, a company that has been developing BWMS since 2007 and has successfully installed systems on all vessel types and sizes, electro-chlorination systems have set the standard for effective ballast water treatment. The report also shows the importance of proper filtration and the UV design limitation.


Different ships will require different methods. While some ships, for operational reasons will need to ballast and de-ballast high quantities of sea water on a daily basis, high, other vessels only require ballasting operations occasionally and with minimum qualities for trim and draft adjustments. Efficiency also involves having proper trained crew and prompt technical support available to ships. It is not enough after all to have the latest equipment if you don’t know how to properly operate and maintain it.

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