Compost Biofilters for Highway Stormwater Runoff Treatment

Water quality concerns of urban streams, coupled with increased construction activities in Ontario have prompted government agencies and academia to research new stormwater treatment technologies. In particular, stormwater runoff from highways often has high concentrations of deleterious substances such as fine sediments, heavy metals, chlorides and petroleum hydrocarbons that discharge through storm sewers and open ditches into nearby urban streams and rivers. Silt-laden runoff from highways has potential adverse effects on stream water quality and aquatic habitat and is a perpetual problem on highway construction contracts. To date, the use of compost as a filter media has been limited to mulch covers and compost blankets with little focus on the use of compost within a filter. Recently, the application of biofilters made from a mesh photodegradable tubular sock in combination with a compost filter media has been found to also be an effective method of stormwater treatment. In the summer of 2007 a site was selected in Kitchener, Ontario for the monitoring program. A biofilter was assembled by initially blowing a filter bag frame and base, then blowing raw compost into the middle, and covering the raw compost with more biofilter bags. The compost biofilters were found to significantly reduce sediments, heavy metals and petroleum hydrocarbons in highway stormwater runoff.