Compost Biofilters For Highway Stormwater Runoff Treatment.

Stormwater runoff containing pollutants deposited on highways from vehicular traffic and urban activities has been identified as a serious threat to aquatic habitats. Although many urban stormwater management technologies serve to reduce the concentrations of pollutants from being transported to larger bodies of water, these stormwater management installations do not always meet the provincial water quality guidelines. In summer 2007, a compost biofilter was installed in a ditch near Highway 8 in Kitchener, Ontario and monitored for 18 storm events spanned over two years for both flow rate and water quality. The main objectives of the study were to determine highway runoff quality and biofilter pollutant removal efficiency. This study shows that the key factors that affect the build-up of the pollutants on a highway are the average annual daily traffic (AADT) and the antecedent dry days (ADD), and the main factors that affect the wash-off of pollutants, include total rainfall depth and rainfall intensity. Before filtration, highway runoff contaminant levels often exceeded the Ontario Provincial Water Quality Objectives (PWQO). However, the biofilter reduced the total suspended solids, zinc, copper and polycyclic aromatic hydrocarbons by 42, 32, 29, and 66%. [ABSTRACT FROM AUTHOR]