Pass the Salt

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Science  08 Jan 2010:
Vol. 327, Issue 5962, pp. 127
DOI: 10.1126/science.327.5962.127-a

As our global freshwater resources continue to be consumed at an unsustainable rate, the demand for new sources of abundant, clean water continues to rise. Desalinated seawater is an attractive option as a complement to natural freshwater sources, but it remains fraught with unresolved problems such as minimizing energy requirements for the process and improving the quality of the product stream. To further understand the latter concern, Agus and Sedlak analyzed the chemical by-products generated by the addition of disinfecting chlorine to seawater under pilot-scale as well as various bench-scale conditions. Although few harmful by-products exceeded the recommended drinking water thresholds, certain patterns emerged that may further improve water quality. Seasonal and geographic increases in seawater-dissolved organic matter correlated with increased levels of potentially toxic by-products such as brominated trihalomethanes. Blending common freshwater sources (e.g., river water) with desalinated seawater could reduce the potential for chlorinated by-product formation; however, because seawater is naturally rich in bromine, nontrivial levels of other harmful by-products, such as dihaloacetonitriles, may be produced. Ultimately, the quality of desalinated seawater should pose little threat to human health or aquatic ecosystems, thus increasing the likelihood that desalination will remain a viable option for meeting our freshwater demands.

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