Restoration of an urban creek water quality using sand and biochar filtration galleries

Stormwater runoff from parking lots often contains a variety of elements and compounds in different forms and concentrations that may pose risks to biota in receiving aquatic systems. Heavy metals including copper (Cu) and zinc (Zn), and polycyclic aromatic hydrocarbons (PAHs) are of particular concern in such runoff due to their prevalence, toxicity to aquatic organisms and persistence in the environment. The ability of a commercially available biochar to remove pollutants of concern through column treatments was assessed in this research. Factors including the pollutant’s concentration, total organic carbon (TOC), pH, and biochar particle size were considered. The biochar used in this study showed a significant heavy metals and PAH removal ability compared to sand, qualifying it as a potential substitute for sand in urban structural best management practices. Maximum percentage removal using biochar followed the order of naphthalene (NAP) > Zn > Cu. Regarding Cu and Zn removal, small biochar exhibited higher removal efficiency compared to medium biochar. In terms of NAP removal, both small and medium biochar exceeded sand with a five-fold percentage removal. However, biochar of different particle sizes had the same removal percentage.