Unit processes of stormwater pretreatment techniques (Adapted from WEF, 2008)
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Control Vegetated filter strips Vegetated swale Forebays Street/parking lot sweeping Proprietary settling/swirl chambers Oil/water separators Green roofs Cisterns Drain inlet inserts
Peak flow attenuation X X
Runoff volume reduction
Infiltration X X
Dispersion X X X
Evapotranspiration X
Runoff collection and usage X
Sedimentation X X X X X X
Flotation X X X
Laminar separation X
Swirl concentration X
Sorption X
Precipitation
Coagulation
Filtration X X X
Plant metabolism X X X
Nitrification/denitrification
Organic compound degradation
Pathogen die off
Temperature reduction X X X
Disinfection