Disinfection of Water by Ultrasound: Application to Ballast Water Treatment

摘要

Ultrasound has potential application in disinfecting a variety of water streams, including shipboard ballast water to avoid transfer of non- indigenous species between geographic locations. Two approaches for improving the performance of ultrasound in disinfecting bacteria were examined: (1) optimizing the ultrasonic intensity by varying the treatment cell diameter, and (2) using ultrasound in conjunction with a second treatment. A contact time for one log kill of an E. coli pure culture of 0.6 minutes was measured when using higher average intensities resulting from reduced treatment cell diameters, a substantial improvement over previous work. Combined treatment consisting of ultrasonic and thermal treatment resulted in a reduction of about 40% in contact time for one log kill of E. coli. Since a contact time of 0.6 minutes per log kill is still likely to be too long for a flow-through treatment system for ballast water, the applicability of ultrasound to ballast water treatment is expected to focus on zooplankton, for which ultrasound is very effective. A second treatment that targets the bacteria could also be employed. Additionally, ultrasound is effective in disinfecting both bacteria and zooplankton in lower flow rates and may have application to other water treatment applications. Additional experimentation is recommended using ultrasound to disinfect natural seawater.