Great Ships Initiative: Final Report of the Land-Based Freshwater Testing of the Lye (NaOH) Ballast Water Treatment System

This Great Ships Initiative (GSI) technical report describes outcomes from land-based tests conducted in July 2010 of a proposed ballast water treatment system (BWTS) developed by researchers from the US Geological Survey (USGS). The proposed system involved application of sodium hydroxide (NaOH, in the same formulation used for lye or caustic soda) to ballast water to raise pH to 12.0, followed by application of carbon dioxide (CO2) as a neutralization step prior to discharge of the ballast water to the receiving system. Over four trials, the NaOH BWTS was evaluated for its ability to: (a) successfully treat ballast water without interruption, (b) successfully neutralize treated ballast water after a two-day (Trial 1) or three-day (Trials 2 – 4) retention period to achieve Wisconsin Department of Natural Resources (WIDNR) permitting levels for harbor discharge (i.e., pH 6-9), (c) meet discharge target values for water chemistry/quality and biology that are approximately consistent with the International Maritime Organization (IMO) Convention’s Annex D-2 discharge standards, and (d) discharge water after a three-day retention period that is environmentally benign (i.e., no residual toxicity) pursuant to USEPA water quality criteria. Whole effluent toxicity testing was conducted on Trial 2 and 4 only. Overall, the NaOH BWTS performed very well operationally and well enough biologically to warrant additional testing at the bench, land and ship-based scales. The system successfully treated ballast water without interruption, and successfully neutralized treated ballast water to achieve WIDNR permitting levels for harbor discharge (i.e., pH 6-9). The BWTS also significantly reduced live organism densities in treated discharge relative to control discharge in all size classes of organisms. Finally, in these tests, the BWTS performance met discharge target values that were approximately consistent with the IMO Convention’s discharge standards, though precision in this estimate was not possible given the research and development testing parameters. The only possible problem that this testing revealed was that the water discharged after two- or three-day retention periods was not entirely environmentally benign (i.e., with no residual toxicity at the 100 % effluent dilution), though the level of residual toxicity in 100 % effluent evident from these tests may not be of regulatory concern.

2011 GSI Land Based Testing of Lye NaOH