Ballast water management (BWM) and biofouling

Type approval

The IMO BWM Convention entered into force in September 2017 and applies to all ships and offshore structures that carry ballast water and are engaged in international voyages. Furthermore, the revised USCG BWM regulations came into force in 2012. Both will require ships to treat ballast water to ensure compliance with the D-2 standard (IMO) and the discharge standard (USCG). With our extensive knowledge of BWM and treatment technologies, we are ready to assist with type approval of BWM systems according to the latest requirements.

DNV is the worldwide leading body in type approval of ballast water management systems (BWMS) according to the IMO Guidelines. Furthermore, we were the first classification society accepted by the United States Coast Guard (USCG ) as an independent laboratory (IL) to evaluate and test technologies designed to treat ballast water on ships according to USCG regulations. We have developed a type approval programme for assessing BWMS during type approval according to the IMO and USCG regime. 

In addition to type approval of BWMS, DNV also performs approval of test facilities engaged in environmental, land-based and shipboard testing of BWMS. We are leading a partnership with several biological and environmental test facilities worldwide to test and evaluate BWMS to the USCG regulations. For further details, please contact us or visit our FAQ page. 

Overview of different technologies

There are a variety of treatment options for ballast water. Systems using UV, electrolysis or other chemical injection technologies have the largest market share today.

Some of these technologies are described below:

Technology Short description

Technology

Filter and UV

Short description

These systems filter the particulates and bigger organisms before UV disinfection. Usually, filters automatically back flush when a certain differential pressure is exceeded. The UV light kills or inactivates the organisms by disrupting their DNA, leaving them unable to perform vital cellular functions. During ballasting, the seawater is filtered and UV-treated, and during discharge the water is UV-treated a second time.
These systems do not produce any harmful by-products and they are independent of temperature and salinity. Low UV transmittance in the seawater will imply higher energy demand to meet the same UV target dose.
Technology Short description

Technology

Filter and electrolysis

Short description

These systems filter the particulates and the bigger organisms before active substances generated from the electrolysis are injected into the ballast water. The electrolysis can be installed inline or in a side stream, where the disinfectant breaks down the cell membranes of the organism. Some system uses a higher dose of active substance without filter.
The active substances are produced through oxidation of seawater in the electrolysis chamber. Electrolysis also produces hydrogen gas which shall be correctly handled for safety of the ship. During ballasting, the seawater is filtered, and active substances are injected. During de-ballasting, the active substance is neutralized prior to discharge overboard.
Technology Short description

Technology

Ozone

Short description

These systems disinfect by injecting O3 generated from ambient air. The O3 oxidizes and neutralizes aquatic species by reacting with seawater to produce effective disinfectants. Salinity and temperature are not obvious factors affecting the efficiency of these BWMS, however longer holding time may be required.
Residual by-products are required to be neutralized prior discharge. Since ozone is toxic, additional safety measures and crew training are necessary.
Technology Short description

Technology

Chemical injection

Short description

These systems are often used in combination with filtration, not always. A chemical solution is injected into the ballast water to ensure disinfection. The disinfectant may be liquid or granular and will require neutralization prior to discharge overboard.

Chemicals used are trademarked, and supply might be limited to specific ports. The chemicals must be stored on board in closed containers and may be hazardous. The use of chemicals requires implementation of strict safety provisions and crew training. These BWMS have a higher operational cost than other ballast water technologies.

Related downloads and links

 

BWMS Code MEPC.300(72)

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Type Approval Certificates

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USCG Regulations for BWMS

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