Testing Ballast Water Management Systems: Challenge Water Conditions During More Than 100 Test Voyages

Ballast water management systems (BWMS) are rigorously tested in land-based and shipboard settings, according to requirements outlined in the former G8 Guidelines of the International Maritime Organization (IMO). Noting doubts that the water conditions to challenge BWMS as stated in G8 may not be challenging enough to represent all port water conditions worldwide, this guideline was revised at IMO in 2016 to make G8 better fit for purpose, and the instrument was made mandatory as BWMS Code in 2018. This contribution summarizes the intake water conditions we observed during >300 samples taken during >100 shipboard BWMS performance tests during 12 years. The data presented include the abiotic water conditions (i.e., temperature, salinity, TSS and POC) and the counts of viable organisms in the two size classes addressed by the Ballast Water Performance Standard (Regulation D-2) of the IMO Ballast Water Management Convention. Our data showed how close IMO challenge water requirements are to what was observed in nature. In addition, we compared our results with the test requirements of the US BWMS test protocol. Based on our results, further recommendations for BWMS Code improvements were included. These recommendations refer to the challenge water conditions in performance tests of BWMS, which were kept unchanged during the G8/BWMS Code revision(s). One of our recommendations is to increase the required concentration of zooplankton organisms in the challenge water during shipboard tests to better reflect the natural zooplankton concentrations.