Decay model for biocide treatment of unballasted vessels: Application for the Laurentian Great Lakes

摘要

A biocide decay model was developed to assess the potential efficacy and environmental impacts associated with using glutaral-dehyde to treat unballasted overseas vessels trading on the Laurentian Great Lakes. The results of Monte Carlo simulations indicate that effective glutaraldehyde concentrations can be maintained for the duration of a vessel's oceanic transit (approximately 9-12 days): During this transit, glutaraldehyde concentrations were predicted to decrease by approximately 10% from initial treatment levels (e.g., 500 mg L~(-1)). In terms of environmental impacts, mean glutaraldehyde concentrations released at Duluth-Superior Harbor, MN were predicted to be 100-fold lower than initial treatment concentrations, and ranged from 3.2 mg L~(-1) (2 SD: 2.74) in April to 0.7 mg L~(-1) (2 SD: 1.28) in August. Sensitivity analyses indicated that the reballasting dilution factor was the major variable governing final glutaraldehyde concentrations; however, lake surface temperatures became increasingly important during the warmer summer months.