LAND-BASED EVALUATION OF THE 7.5 HP NANO BUBBLE OZONE/OXYGEN WATER CLEANING SYSTEM (2021 VERSION)

Abstract

This technical report presents the land-based evaluation of the Nanobubble Ozone/Oxygen Water Cleaning System (NBOT 2x7.5 HP-60 units) developed by the NanoClear Group Inc. of Rockville, Maryland, USA. This evaluation was a follow-up to work done previously at the Montreal Pier Facility using one 7.5 HP Nanobubble Ozone/Oxygen Water Cleaning System. The work was conducted to evaluate the potential of the system to be used as an in-tank, recirculating ballast water treatment method for the Laurentian Great Lakes. The evaluation began in June 2021 and ended in July 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, Wisconsin, USA. The NBOT 2x7.5-HP uses cavitation to create ultrafine microbubbles (nanobubbles) containing ozone (O3) generated by the system. According to the developer, the resulting ozone and hydroxyl radical byproducts destroy all chemicals containing activated functional groups (aldehydes, ketones, amines, nitrates, etc.), RNA, DNA, peptides, steroids, as well as activated organic compounds (herbicides and pesticides), and microbial toxins. Biological effectiveness was examined during the course of a commissioning trial plus three trials ranging from 96 to 120 hours treatment using ambient water conditions at the Montreal Pier Facility. Effectiveness was assessed in terms of live organisms in three size classes per unit volume: organisms ≥50 µm in minimum dimension (i.e., nominally zooplankton), organism entities ≥10 µm in any dimension and with cell sizes <50 µm in minimum dimension (i.e., nominally protists), and organisms <10 µm in minimum dimension (i.e., total culturable heterotrophic bacteria, 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 treated water versus control water. The NBOT 2x7.5 HP 60 system was found to be effective at reducing the densities of organisms in all three regulated size classes, although the system was not presented with water meeting ETV challenge conditions.