The Finnish Transport Safety Agency (Trafi) has published a review of methods available for analysing treated ballast water, concluding that Adenosine Triphosphate (ATP) or Pulse Amplitude-Modulation (PAM) technologies should be used to detect the effect of ballast water treatment in “a simple, quick, portable and relatively cheap manner”.
Although the study focused primarily on the water conditions and characteristics of the Baltic Sea, it evaluated the efficiency of various test kits to assess their reliability in waters of low salinity and temperature and high turbidity. The objective was to compare the advantages and disadvantages of various methods and to provide recommendations as to the most suitable systems available.
Researchers found that the use of these methods – both indicative methods that provide a direct measurement of a representative sample from the ballast water tank – increased the reliability of ballast water sampling where different types and sizes of organisms were detected.
However, while both methods were considered reliable indicative monitoring tools, the Trafi study found that ATP technologies had the “essential benefit” of being able to measure and detect all organism categories (bacteria, >10 to <50µm and > 50 µm) listed in regulation D2 of the BWM Convention. PAM measurements were found “somewhat limited” to detecting only the presence of phytoplankton.
“The benefit of ATP method over PAM fluorometry is the ability to evaluate the concentration of all organism size categories including autotrophic and heterotrophic organisms,” cited the report.
Carine Magdo, Business Development Manager at aqua-tools, a supplier of advanced second-generation ATP-type ballast water monitoring systems, said: “The research verifies the reliability of indicative ballast water sampling methods in determining whether a vessel is compliant with the discharge requirements of the Ballast Water Management Convention. It also found that test results are not affected by turbid water, which is especially important to vessels operating ballast water treatment systems in the Baltic.”
The Trafi study, titled Literature Review of the Indicative Ballast Water Analysis Methods, also provided important recommendations on how best to prevent the over- and under-estimation of organism concentrations during sampling; a problem that can result in an incorrect evaluation of ballast water treatment systems efficiency.
“This can be achieved simply by ensuring samples are not taken within the first and last five minutes of deballasting operations,” Magdo explained. “Trafi recommends that the usual ten-minute sampling time be revised to take 0.5l samples every minute. At least two random samples in a ten-minute period should be taken, rather than a single ten-minute sequential sample as this can under- or overestimate the concentration of organisms present.”
Other than reliability and performance efficiency, user-friendliness, training, and procurements costs were also assessed in the study, with Trafi suggesting “indicative analysis sampling devices should cost less than $100,000, with a maximum analysis time of two hours.”
Aqua-tools ATP-based monitoring kit was costs below $5000 and less than $100 per sample analysis for the three factions. The price range for those PAM sampling devices assessed, however, varied between $4,000 and $15,000.