Great Ships Initiative: Final Report of Land-Based Freshwater Testing of a Ballast Water Treatment Involving Sodium Hypochlorite (NaOCl)

This Great Ships Initiative (GSI) technical report describes outcomes from land-based status tests of a ballast water treatment system (BWTS) developed by researchers from the National Parks of Lake Superior Foundation (NPLSF) and the Michigan Technological University (MTU) involving sodium hypochlorite (NaOCl), in the same formulation used for household bleach. The BWTS is proposed for emergency treatment of ballast water in tanks of Great Lakes vessels passing through the Welland Canal system of the St. Lawrence Seaway into the upstream lakes. Tests took place at GSI’s Land-Based Facility in Superior, Wisconsin, in October 2011 during which time GSI evaluated the BWTS for its ability to: (1) deliver a target concentration of chlorine (above natural chlorine demand) using a 6.15% NaOCl solution, and deliver the target concentration of neutralizer; (2) reduce densities of live organisms in intake water from prescribed threshold densities to below densities allowed by the Ballast Water Performance Standard of the International Maritime Organization (IMO) Convention; and (3) result in treatment water safe to discharge in terms of residual chlorine concentration and whole effluent toxicity (WET). Disinfection by products (DBPs) were also measured and reported. Overall, tests yielded mixed results. In terms of operational performance, GSI was able to accurately dose a sampled volume of water with 6.15 % NaOCl solution to a predetermined chlorine concentration by factoring in the natural chlorine demand. The neutralization process recommended by the BWTS developer did require additional neutralizer additions, which could be problematic in an actual shipboard situation. More research is needed on the effect of temperature and water quality on the ability of sodium bisulfite (NaHSO3) or a neutralization substitute to successfully neutralize NaOCl-treated water for BWTS application in the real-world. Second, the BWTS reduced live densities of organisms ? 50 ?m relative to control discharge. But BWTS live discharge densities were well above the IMO benchmark. The BWTS did reduce live densities of organisms > 10 and < 50 ?m minimum dimension to below benchmark levels within the IMO Convention, but intake densities of these organisms also were below IMO testing guidelines due to the late season timing of the tests. Finally, the treated and neutralized discharge water was found to be safe to discharge (though, in some cases only after multiple neutralization steps) and free from toxicity in WET tests. Measurable concentrations of DBP were found in the treatment discharge, specifically trihalomethanes and haloacetic acids. Overall, the GSI results show that the NaOCl BWTS both warrants and would benefit from further research and development on its potential as an emergency BWTS with relevancy in the Great Lakes.

2012 GSI Land Based Testing of Sodium Hypochlorite