Agricultural Research Service scientists and their collaborators have improved on an existing method for removing contaminants from storm water runoff from point sources such as construction sites and urban landscapes. By using "filter socks" containing compost tucked into mesh tubes researches have been able to capture some of the silt, heavy metals, fertilizers and petroleum products washed from compacted surface areas into nearby streams and rivers.
The work was based on how wastewater treatment plants use flocculation agents to help sediments and pollutants form clumps large enough to be filtered out of the water even when the substances are in a dissolved state. The team added flocculation agents to the compost socks and then ran laboratory tests to see how well the socks trapped.
The ARS researchers found that the compost socks with flocculation agents removed 10% more of the ammonium nitrogen; 24% more of the E. coli bacteria; 15% more of the motor oil; and 11% more of the available gasoline.