Heavy metal removal from stormwater runoff by sorption

In this study, several sorbents (i.e. alumina, activated bauxsol coated sand (ABCS), bark,bauxsol coated sand (BCS), fly ash (FA), granulated activated carbon (GAC), iron oxidecoated sand (IOCS), natural zeolite (NZ), sand, and spine!) are investigated with the longterm goal of developing a feasible technology for heavy metal removal during secondarytreatment of storm water. The sorbents are tested in batch tests for their As, Cd, Cr, Cu, Ni andZn removal efficiency from synthetic stormwater samples, where all of these metals coexisted at a starting pH of 6.5. It is found that each sorbent has different affinity to the heavymetals, with heavy metal cations (i.e. Cd, Cu, Ni and Zn) removed more effectively thanheavy metal anions (i.e. As and Cr) by all sorbents except IOCS, which has a high affinitytowards As. The results further indicated that alumina and BCS outperform the other sorbents,possibly due to high surface area of alumina and the favourable sorption sites of BCS;whereas NZ, sand and bark were the least efficient. On the other hand, although FAeffectively retained Cd, Ni and Zn, the leaching of As, Cr, and Cu is a concern.