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Add carbon and stir

15th December 2007

Instead of "engineered burials," adding reactive carbon to polluted soils could actually keep toxic chemicals out of the food chain

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The same technology found in a Brita filter could soon be used to clean up San Francisco Bay. Stanford University’s Richard Luthy has designed a way to clean the bay’s sediment using “activated” carbon. The process involves mixing a couple of pounds of the stuff (imagine tiny bits of charcoal) into the top six inches of mud – which then soaks up polychlorinated biphenyls (PCBs), pesticides and other pollutants. This locks the pollution away from clams, worms and other creatures that live in the muck and ultimately prevents those chemicals from getting into fish (and us).

Traditionally there are two ways to deal with contaminated soils: Dig it all up and store it somewhere (or, for a much higher cost, clean it and return it to the site), or just cover up the whole mess and hope it doesn’t leak. In Hamilton Harbour, for example, a 9.5-hectare containment facility is being constructed around the bay’s sediment to keep it in place. But Prof. Luthy’s method takes a different tack. He leaves the mud in place, but makes it safer by adding an extra ingredient.

Prof. Luthy has done tests on about 400 square feet plots in the bay, and hopes that the U.S. Navy will adopt his method for the cleanup of the entire region. Most containment strategies “are like engineered burials,” he says. “But putting reactive material into the sediment is a new way of thinking.”

Published in The Green Report in The Globe and Mail

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• Tags:
• PCBs
• Research
• Science
• Water Quality

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