Last winter was so wet for so long that we could hardly get rid of all that water fast enough, as jaw-dropping volumes of stormwater rushed along gutters, into stormdrains, and ultimately out to sea. Even so, people were hard-hit in flood-prone regions, particularly central Sonoma County. In late February, the Russian River ran high enough to turn the towns of Guerneville and Monte Vista into islands. Now that we’re deep into the dry season, though, it would be great to have some of that water back. The need to use stormwater as a resource will likely intensify with climate change, which is projected to trigger droughts that hit more often and last longer.

A major barrier to using urban stormwater is that it’s dirty. Rain starts picking up contaminants the moment it hits rooftops, streets, and other hard surfaces, as well as landscapes laden with fertilizer and herbicides. Pollutants include nutrients, heavy metals such as copper and lead, and a host of pesticides, flame retardants, and other toxicants collectively known as trace organic compounds. Stormwater typically gushes directly down drains with little treatment, apart from grates that help block trash and debris.

New research shows that a cost-effective, low-tech approach can go a long way toward cleaning up urban stormwater. Researchers collected runoff from Fryer Creek, which drains the City of Sonoma, and treated it with a combination of woodchips and biochar. “The system worked really well,” said Richard Luthy, a Stanford environmental engineer who led the study, which was recently published in the journal Water Research, in partnership with the Sonoma County Water Agency. “It removed all the nitrates and trace organics,” Luthy said. With the exception of zinc, the system also did a good job removing heavy metals from stormwater.

Read full article here.