TESTS OF THE NANO BUBBLE OZONE TECHNOLOGY (2.5 HP UNIT)
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This technical report presents the bench-scale evaluation of the Nano Bubble Ozone Technology 2.5-horsepower unit (NBOT 2.5-HP) developed by NanoClear Group Inc. of Rockville, Maryland. This evaluation was the first to assess NBOT 2.5-HP as a potential in-tank, recirculating ballast water treatment method for the Laurentian Great Lakes. The evaluation began in September 2019 and ended in March 2020. All analyses occurred at the Lake Superior Research Institute (LSRI) at the University of Wisconsin-Superior (UWS) in Superior, Wisconsin, USA. The NBOT 2.5-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 biproducts 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. The ability of NBOT 2.5-HP to increase dissolved ozone in a 1,000-L treatment tank was tested at two water temperatures (~15°C and ~25°C) using both dechlorinated laboratory water (LW) and the more challenging amended dechlorinated laboratory water (LW-TMH). In LW, NBOT 2.5-HP increased ozone (<15 minutes) upon treatment and reached equilibrium after approximately 2 hours of treatment under both temperature conditions. In LW-TMH, no increase in ozone was observed initially upon treatment. Instead, ozone increased after approximately 2 hours and reached equilibrium after 5 to 7 hours under both temperature conditions. Degradation rates of dissolved ozone in LW and LW-TMH were examined at two water temperatures (~15°C and ~25°C). In general, ozone degradation rates were lower at 15°C than at 25°C while degradation occurred more rapidly in LW-TMH than in LW. Biological effectiveness tests examined the ability of NBOT 2.5-HP to induce mortality in biological organisms over time in both LW and LW-TMH. Three classes of organisms were tested: bacteria (Escherichia coli and Enterococcus faecium), green algae (Selenastrum capricornutum), and zooplankton (D. magna neonates, D. magna ephippia, and Eucyclops spp.). In LW, the algae and bacteria experienced 100% mortality, or no live organisms (a count of <1 MPN/100 mL) after 30 minutes of treatment. In LW, D. magna neonates and Eucyclops spp. experienced 100% mortality after 30 – 60 minutes of treatment. In LW-TMH, the algae and E. coli experienced 100% mortality, or no live organisms (a count of <1 MPN/100 mL) after 240 minutes of treatment. In LW-TMH, only one sample replicate had an E. faecium count of 3 MPN/100 mL at 240 minutes and no live organisms were detected after 390 minutes of treatment. In LW-TMH, D. magna neonates and Eucyclops spp. experienced 100% mortality after 240 – 390 minutes of treatment. In both water types, the D. magna ephippia had a hatch rate of 22.5 - 36% following treatment. These results demonstrate that NBOT 2.5-HP is effective at inducing mortality in a wide range of organisms within size classes regulated in ballast water discharge in two different water qualities. Chronic Residual Toxicity (CRT) testing examined the potential for water treated with NBOT 2.5-HP to cause toxicity to organisms in receiving water upon discharge. This testing was conducted using LW treated with the NBOT 2.5-HP system. Three classes of organisms were tested: green algae (Selenastrum capricornutum), zooplankton (Ceriodaphnia dubia), and vertebrate (Pimephales promelas). No statistically significant effects on growth, survival or reproduction were seen.