Treatment of Highway Stormwater Runoff Using Sustainable Biochar: A Review

Human activities and atmospheric deposits on highways have led to an increase of pollutants in highway stormwater runoff. The reduction of these pollutants to a minimum acceptance level has been a great subject of concern for the US Department of Transportation and US Environment Protection Agency. Researchers have investigated several methods; however, biochar utilization, an environmentally and economically favorable way for pollutant removal from highway stormwater runoff, has not been studied extensively. Biochar has been intensively used for soil improvement and water treatment. Its unique carbon structure, large surface area, and higher pore structure have made it a potential candidate for water retention and contaminant removal. This literature review focused on the removal of highway stormwater runoff pollutants such as suspended solids (dust, sludge, and leaves), heavy metals (Ni, Zn, Pb, Cr, Cd, and Cu), nutrients (nitrate and phosphate), and organic contaminants (paraffin, nitrobenzene, and p-nitrotoluene) using biomass-derived biochar. This comprehensive literature review introduces biochar production and the effect of the production process operating temperature on biochar's structure and performance. It also analyzes the impact and efficiency of biochar on pollutant removal and illustrates its potential in the treatment of highway stormwater runoff.