W&H Pacific conceived the idea of utilizing yard debris compost as a treatment and filtration medium for storm-water runoff. This medium removes organic and inorganic pollutants through adsorption, filtration, and biological processes (ion exchange and bioremediation). The Compost Storm Water Treatment System (CSF®) has been constructed at eight different sites throughout Oregon. Six of the eight systems are enclosed facilities, located below grade, while the remaining two are open channel systems retrofitted into existing swales. The technology is being tested and field modified.
The filtering capacity of the medium removes sediments from the runoff. Ion exchange and adsorption removes oils and greases, heavy metals, and non-dissolved nutrients. Following adsorption, organic material is further broken down into carbon dioxide and water by microbial action within the compost. Treated stormwater then passes through a 6 in to 8 in gravel layer underneath the filtering media, and is conveyed to a surface water body or to a storm drainage system by an underdrain system.
Prototype test results for nine events show good solids removal: 67% removal of COD, 40% removal of total phosphorous, 67% removal of copper, and better than
87% removal of zinc, aluminum and iron. The leaf compost has very good cation exchange capacity. However, like sand and enhanced filters, operating life depends on the frequency of preventive maintenance.
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