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

Abstract

This technical report represents the land-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 be used as a flow-through water treatment method for the Laurentian Great Lakes, treating via heat treatment with one pass of water through the treatment system. The evaluation began in September 2021 and ended October 2021. All analyses were conducted at either the Montreal Pier Facility or the Lake Superior Research Institute (LSRI) at the University of Wisconsin-Superior (UWS), both located in Superior, WI, USA. Biological effectiveness was examined at the Montreal Pier Facility during a commissioning trial and four efficacy trials with a single pass of harbor water through the Bawat BWMS Mk2 – Mobile Treatment Unit. Harbor water was amended to achieve ETV Protocol challenge conditions. Effectiveness was assessed in terms of remaining live organisms in three size classes per unit volume: organisms ≥50 µm in minimum dimension (nominally zooplankton), organism entities ≥10 µm in any dimension and with cell sizes <50 µm in minimum dimension (nominally protists), and organisms <10 µm in minimum dimension (e.g., total culturable heterotrophic bacteria, total coliform bacteria, Escherichia coli, Enterococcus spp., and toxigenic Vibrio cholerae O1 and O139). 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. E. coli and Enterococcus spp., and Vibrio cholerae densities on discharge were below the USCG ballast water discharge standard (BWDS) in all trials. Protist densities were below the USCG BWDS in all but the final trial. Temperature of discharge water was approximately 5°C higher than uptake water, but other water quality parameters were minimally impacted by treatment.