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Shipboard trials of an ozone-based ballast water treatment system |
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| Authors: | David A Wright Robert W Gensemer William A Stubblefield Rodger Dawson Jonathon S Bearr William J Cooper |
| Institution: | a University of Maryland, Center for Environmental Science (UMCES), Chesapeake Biological Laboratory, Solomons, MD 20688, USA b Parametrix Inc., 33972 Texas St. SW, Albany, OR 97321, USA c Environmental Research Services, Box 38349, Baltimore, MD 21231, USA d Maryland Department of Natural Resources, Tawes State Office Building, Annapolis, MD 21401, USA e Northeast Technical Services Co., Inc., P.O. Box 659, Columbia Station, OH 44028, USA f Urban Water Research Center, Department of Civil and Environmental Engineering, University of California, Irvine, CA 92697-2175, USA |
| Abstract: | Legislation introduced by the United Nations International Maritime Organization (IMO) has focused primarily on standards defining successful treatments designed to remove invasive species entrained in ballast water. An earlier shipboard study found that ozone introduced into salt water ballast resulted in the formation of bromine compounds, measured as total residual oxidants (TRO) that were toxic to both bacteria and plankton. However, the diffuser system employed to deliver ozone to the ballast water tanks resulted in patchiness in TRO distribution and toxicity to entrained organisms. In this follow-up study, the shipboard diffuser system was replaced by a single Venturi-type injection system designed to deliver a more homogeneous biocide distribution. Within-tank variability in TRO levels and associated toxicity to zooplankton, phytoplankton and marine bacteria was measured via a matrix of tubes deployed to sample different locations in treated and untreated (control) tanks. Three trials were conducted aboard the oil tanker S/T Prince William Sound in the Strait of Juan de Fuca off Port Angeles, Washington State, USA, between June and December 2007. Mortalities of plankton and bacteria and oxidant concentrations were recorded for treated and untreated ballast water up to 3 days following treatment, and residual toxicity beyond this period was measured by bioassay of standard test organisms. Results indicated uniform compliance with current IMO standards, but only partial compliance with other existing and pending ballast water legislation. |
| Keywords: | Ballast water Ozonation Invasive species |
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