Biological Machine to Clean Farm Runoff
Published on by Water Network Research, Official research team of The Water Network in Academic
Watershed Institute Researching Better Ways to Filter the Pollutants out of Agricultural Runoff
Flowers and oceanscapes cover the exterior of Building 42, the humble headquarters of CSU Monterey Bay'sWatershed Institute. In the lot behind it, a geometric contraption has taken shape beside the greenhouses. A round plastic water tank balances on stilts, another tank is sunk into the ground, and a grid of PVC pipes runs through a compartmentalized box between them.
This is the field laboratory of CSUMB environmental science lecturersJohn SkardonandJohn Silveusand their six students. They're trying to find better ways to filter the pollutants out of agricultural runoff.
When farmers apply fertilizer to their crops,excess nitrates can flow into the watershed, contaminating groundwater and polluting aquatic habitats - contributing to hazards like "blue-baby syndrome" in humans and dead zones in oceans.
"Once it gets out of the fields, it becomes a real booger," Skardon says.
The low-tech treatment: wood-chip bioreactors. They're basically just mulch-filled trenches in the ground. Farmers pipe their runoff through them, and bacteria colonizing the wood chips consume some of the nitrate. But the systems often don't improve water quality enough to comply with regulations, Skardon says. More sophisticated systems are often too expensive to use on a large scale.
"I am really concerned we have to solve this problem in order to keep the ag industry here in California," he says. "With the lower level of rainfall, we're going to have to up our game a little bit."
The problem with today's bioreactors, Skardon says, is that wood chips don't provide enough carbon to feed the bacteria that break down nitrates. By adding more carbon to the system, his lab is cultivating the kind of low-oxygen bacteria that are really hungry for nitrates. (You may recognize these sorts of microbes as the snotty stuff plumbers clear out of kitchen drains.)
Hunter Burnham, a marine science undergrad, is researching alternatives - like ceramic pumice stones and grooved "bio-balls" - with more surface area than wood chips for bacteria to grow on.
Molecular biology student Alexandra Walling is studying how bacteria react to different carbon sources, an effort to nail the perfect nitrate-removing recipe.
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