Pulse amplitude modulation as an indicative method for monitoring compliance of ballast water management – Walz Water PAM instrument test

Vessels are considered one of the primary pathways for the transfer of harmful aquatic organisms and pathogens. The D-2 Regulation of the Ballast Water Management Convention specifies the maximum number of organisms per unit volume in order to prevent their spread and transfer, and the introduction of harmful aquatic organisms and pathogens around the globe. The Convention also requires an inspection of every ship’s ballast water in order to verify compliance with the requirements. Inspectors take samples of ballast water and perform quick analyses on board using indicative instruments. We evaluated the appropriateness of the Walz Water PAM instrument for indicative analysis of ballast water. The instrument estimates the phytoplankton biomass and its photochemical efficiency. The instrument measurements were compared to the results of detailed laboratory analyses of samples for phytoplankton cells in the size range 10–50 µm and with minimum diameter, as addressed by the Regulation D-2. The instrument correctly evaluated all 19 compliant samples from the detailed analyses and 88 of 95 non-compliant samples from detailed analyses (93%). We can thus conclude that Walz Water PAM is a suitable tool for the indicative analysis of vessels’ ballast water.