SHORE-BASED EVALUATION OF THE EFFECTIVENESS OF THE BAWAT BALLAST WATER MANAGEMENT SYSTEM MK2 – MOBILE TREATMENT UNIT

Abstract

This technical report represents the shore-based evaluation of the Bawat Ballast Water Management System (BWMS) Mk2 – Mobile Treatment Unit, developed by Bawat A/S Agern Alle, 2970 Horsholm, Denmark (www.bawat.com). This work was conducted to evaluate the potential of the system to kill living organisms in the ballast water of ships to reduce the risk of aquatic nuisance species migration in the Laurentian Great Lakes. The Bawat Mobile Treatment system is designed to heat water killing the organisms carried in the water in a single pass through the treatment system. The single pass can be filling or discharging a ships ballast water and requires no retention period. Biological effectiveness was examined October 22–24, 2023 at the AMI Consulting Engineers facility in Superior, WI during three efficacy trials with a single pass of harbor water through the Bawat BWMS Mk2 – Mobile Treatment Unit. Effectiveness was assessed in terms of reducing live organisms in three size classes per unit volume: organisms ≥50 µm in minimum dimension (nominally zooplankton), organisms ≥10 and <50 µm in minimum dimension (nominally protists), and organisms <10 µm in minimum dimension (e.g., total coliform bacteria, Escherichia coli, and Enterococcus spp.). Samples were compared to the United States Coast Guard’s (USCG) Standards for Living Organisms in Ships’ Ballast Water Discharged in U.S. Waters (USCG, 2012) with a focus on the reduction in the number of propagules in the treated water. The Bawat BWMS Mk2 was found to be highly effective at reducing the densities of organisms in all three regulated size classes. Protist, zooplankton, E. coli and Enterococcus spp. densities on discharge were below the USCG ballast water discharge standard (BWDS) in all trials. Temperature of discharge water was approximately 5°C higher than uptake water, but other water quality parameters were minimally impacted by treatment.