Constructed wetlands for the treatment of highway runoff.

Highway surface runoff contains pollutants such as total suspended solids (TSS), hydrocarbons, de-icing salts, and heavy metals. Treatment methods for highway runoff include storage/treatment facilities, such as constructed wetlands (CWs), detention ponds, or sedimentation tanks; stormwater infiltration facilities, such as soakaways, trenches, or basins; and filter strips and swales. These facilities are commonly referred to as SuDS - Sustainable Drainage Systems.The treatment of highway runoff using CWs is widely used in America, Australia and most of Europe. CWs are a suitable choice for the treatment of highway runoff, due to their relative low cost and good efficiency in treating contaminants such as TSS, organic matter, heavy metals, as well as hydrocarbons and inorganic salts. This review paper aims to characterise highway surface runoff, quantify the removal mechanisms of influent pollutants, evaluate the performance of CWs in the treatment of highway runoff, discuss their design criteria, and compare their performance with other treatment methods.peer-reviewe