Assessing the Potential Efficacy of Glutaraldehyde for Biocide Treatment of Un-ballasted Transoceanic Vessels

Treating the ballast water of oceanic vessels with a biocide is one potential management strategy to reduce the number of nonindigenous species released into the Laurentian Great Lakes from NOBOB ( no ballast on board) vessels. To evaluate biocide effectiveness, glutaraldehyde, a five-carbon dialdehyde widely used for its antimicrobial properties, was investigated. Biocide effectiveness was assessed for various organisms using 24 h acute toxicity bioassays in water-only and water-sediment environments. Acute studies indicate a 24 h LC 90 value of 100 mg glutaraldehyde L –1 or less for most of the freshwater organisms tested. The main exception was the freshwater amphipod, Hyalella azteca, which was much more resistant to glutaraldehyde (24 h LC 90 = 550 mg glutaraldehyde L −1; 95% CI: 476–681). Biocide efficacy was also evaluated in water-sediment exposures. The presence of a test sediment (3% organic carbon) greatly increased lethal concentration estimates for the oligochaete Lumbriculus variegatus, but not for H. azteca: The 24 h LC 90 for L. variegatus varied depending on the water-sediment ratio, and ranged from 61 mg glutaraldehyde L −1 (95% CI 52–78) for an 8:1 water-sediment ratio to 356 mg glutaraldehyde L −1 (95% CI 322–423) for a 2:1 water-sediment ratio. This indicates that the amount of sediments present in NOBOB vessels may have a significant impact on biocide efficacy. Experiments using material from actual NOBOB vessels generally corroborated data from the water-sediment experiments and suggest a potential treatment concentration of approximately 500 mg glutaraldehyde L −1 for short exposure periods (e.g., 24 h).