A Pilot-scale Filtration Device using Polymeric Media for Control of Heavy Metals and Alkylphenols in Urban Storm Runoff

Abstract

A pilot-scale filtration device for urban storm runoff control was operated to investigate the removal characteristics of heavy metals (Pb, Zn, Cu) and alkylphenols (APs) species, including 4-t-butylphenol(4tBP), 4-n-butylphenol (4nBP), 4-t-octylphenol (4tOP), 4- nonylphenol (NP) and bisphenol A (BPA). The filtration device in this study had a novel structure to alleviate the fluctuation in the infiltration rate through media. As a result, effluent heavy metal concentration was largely determined by the influent concentration, not by the influent flow rate. The average removal efficiencies for heavy metals were 41.5~73.4% for Pb, 50.7~83.6% for Zn, and 13.3~34.5% for Cu. The large portion of dissolved phase contributed to the Cu concentration, resulting to the least removal efficiency. Efficient removal of Pb and Zn occurred, since they were distinctly associated with suspended solids smaller than 100 μm. The concentration of APs in the influent storm runoff averaged from 0.136~ 5.408 μg/L, depending on AP species, with higher concentration for NP and BPA by an order of magnitude. In the case of dissolved-phase APs (32~59% of total APs), apparent removal could be observed only for NP and BPA. More distinct removal occurred for particulate APs except 4tBP. Weak relationship between particulate APs and SS concentration suggested that APs would be carried by colloidal particles, an insignificant fraction of suspended solids by mass. The results of this study demonstrated the effectiveness of filtration device to alleviate the loads of toxic micro-pollutants discharged to surface water. The importance of this study could be stressed further, since the behavior of alkylphenol in the storm runoff has been rarely reported.