In its third guide 'Operational and commercial risks' the Club discusses the challenges arising from a BWMS for a shipowner and operator, and how they can deal with potential risks.
Namely, there is a variety of ballast water treatment systems (BWTS), that they either work on the principles of one or a combination of mechanical, physical and chemical. The majority of these systems use a two-step process, usually mechanical filtration followed by disinfection.
- Common methods:
#1 Filter and ultraviolet (UV): systems filter the particulates and bigger organisms followed by UV disinfection.
#2 Filter and electrolysis: systems filter the particulates and the bigger organisms followed by injection of active substances1 generated from the electrolysis.
#3 Filter and chemical injection: systems filter the particulates and the bigger organisms followed by injection of a chemical solution.
#4 Ozone: disinfection through injection of O3.
#5 Inert gas and ultrasonic: diffusing inert gas directly into the ballast tank to deoxygenate the water and using ultrasonic shockwaves to treat anaerobic organisms and bacteria.
- The operation of a BWMS includes:
The intake part, when the ballast water is filtered before passing through disinfection unit, typically chemical injection, electrochlorination or UV.
Upon the discharge, the filter is bypassed and, depending on type, the ballast water will be pumped directly overboard. Chemical and electro-chlorination systems cannot provide secondary treatment.
A common message from experts in the industry is that there is no “one size fits all” or a “plug and play” solution.
Selecting the right plant and system for retrofitting on a particular vessel takes careful consideration. Thus, below the Club stresses some factors that play a crucial role when opting for a BWMS to be in line with the vessel's operation.
- Factors to match the system to the operational demands : (all the factors can be found on the PDF below)
- Will the vessel be trading in US waters and therefore need to comply with Federal and State requirements as well as satisfying the IMO BWM Convention?
- Will the vessel operate in freshwater, seawater or brackish water?
- Will pumping rates be adversely affected when using the treatment system for both ballasting and deballasting operations?
- Can the vessel’s existing electrical generation capacity meet the demands of the treatment system?
- Is there enough space on the vessel to fit the treatment system and associated pipework.
- Are the materials and components used for the system and pipework up to a satisfactory quality and resistant to corrosion?
- Are spare parts and consumables readily available?
- What training is required to competently and confidently use and maintain the system?
- What are the limitations of the treatment system? These operational limitations are listed on the Type Approval certificate and include water condition, temperature and minimum holding times.
Concluding, when it comes to sampling, EMSA proposes that samples should be taken from the discharge line through designated sampling points. The sampling should be from a straight part of the discharge line as near to the ballast water discharge overboard as practicable.
But there might be instances where this is not possible and samples are taken directly from the ballast tanks, such as gravity discharge of top side tanks.
To explore more, click on the PDF herebelow