Electro-Ionization Technology as a Treatment for Ballast Water with a Review of Methods Used to Determine Treatment Effectiveness.

• Main Author: Arena, Courtney Campbell
• Format: Others
• Published: NSUWorks 2005
• Subjects: Marine Biology; Oceanography and Atmospheric Sciences and Meteorology
• Online Access: http://nsuworks.nova.edu/occ_stuetd/128; http://nsuworks.nova.edu/cgi/viewcontent.cgi?article=1274&context=occ_stuetd

This study addresses the topical issue of ballast water discharge. There is a need for best management practices to minimize the release of non-indigenous (or exotic) organisms contained in ballast tanks. The release of such biota originating from foreign ports has been shown to have significant health, ecological and economic impacts on receiving waters. One hope for the future is to develop effective treatment systems to disinfect the water prior to discharge. A preliminary study of cruise ship ballast water was conducted to assess the concentrations of in situ microorganisms (bacteria and protists) and macroinvertebrates contained in a typical ballast tank. Chemical and physical parameters were also monitored as part of this investigation. This was the first reported study of the constituents of ballast water from a cruise ship and provided valuable baseline information about the scale of treatment that would be required to reduce the number of organisms to acceptable discharge levels. A local company (Marine Environmental Partners [MEP] Inc., Florida) embarked on the development of a novel ballast water treatment system. Research reported here focused on assessing the effectiveness (in terms of biotic kill or inactivation) of various configurations of treatment components. In this way, the company was guided towards the most effective full-scale system. Treatment options investigated included chlorination/bromination, gas ionization, filtration and coagulation in either a closed, recycling system, or via a one-pass system. The bacterial and protistan (algae and protozoa) counts in both control and treated water samples were routinely monitored by laboratory enrichment cultivation methods. Techniques appropriate for viruses and macroinvertebrates were also investigated. Since these enumeration methods are all time consuming, indirect counting methods were also investigated in an attempt to identify useful rapid detection methods for ballast treatment assessment. Methods evaluated included ATP analysis, Biological Oxygen Demand studies and epifluorescence microscopy using a commercially available fluorescent stains to distinguish live from dead bacteria. After laboratory trials identified the most promising combination of system components, a pilot ballast water treatment system was constructed (by MEP) and installed on-board a Carnival Cruise ship, the Elation. Using enumeration methods similar to those used in the laboratory experiments, the efficacy of this novel treatment system was assessed. These shipboard tests, which were conducted over a 5 d period, showed that the complete system was capable of killing or inactivating around 95% of the indigenous bacteria in a ballast tank and slightly less of the protists (90%). Perhaps more importantly, this testing highlighted the difficulties of assessing treatment systems on board a ship. Accurate assessment of treatment technologies may require land-based testing, and discussion of this option is included.