common type of distillation used on ships. The ships typically operate MSF with two- to six-stage flash distillers. The ratio of product water to feed water is about 1 gal of product water per 10–20 gal of feed water. MSF distillation units on Navy surface ships range from 6,000 to 100,000 gal/day (Rankin et al., 1975). Distillation will reject almost all dissolved species, but distillers are sensitive to volatile contaminants that may evaporate from the feed stream. Few or no data exist to verify the contaminant load in the potable water onboard Navy ships; if there is a need to understand the concentration of contaminants in potable water, experiments or models would have to be used to reconstruct the distillation process and offer some clarity.

AUSTRALIAN STUDY

In 2002, researchers at the National Research Centre for Environmental Toxicology (NRCET) and the Queensland Health Scientific Services in Australia conducted a study designed to investigate the potential for exposure of Australian sailors to phenoxy herbicides (such as Agent Orange) contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and dimethylarsinic acid (DMA) through potable water (Muller et al., 2002). The goal of the study, titled “Examination of the Potential Exposure of Royal Australian Navy (RAN) Personnel to Polychlorinated Dibenzodioxins and Polychlorinated Dibenzofurans via Drinking Water” (hereafter the NRCET study), was to determine whether polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were codistilled during distillation of estuarine waters to produce potable water. Experiments were designed to mimic distillation procedures aboard RAN ships and used a simple rotary evaporator to simulate MSF.

The distillation portion of the study comprised three different stages: (1) reverse osmosis1 (RO) water spiked with PCDD/Fs (polychlorinated dibenzodioxins and furans; TCDD was spiked at 40 ng/L) and DMA, (2) RO water spiked with contaminants and salt (15 g/L and 30 g/L, respectively), and (3) RO water spiked with total suspended solids (TSS) (0–1.44 g/L TSS). Results were generally presented as percentages of distilled water versus relative retention time of

1

Reverse osmosis is a filtration method that removes many types of large molecules and ions from solution by applying pressure to the solution when it is on one side of a selective membrane.



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