Removing 17β-estradiol from drinking water in a biologically active carbon (BAC) reactor modified from a granular activated carbon (GAC) reactor

Estrogenic compounds in drinking water sources pose potential threats to human health. Treatment technologies are needed to effectively remove these compounds for the production of safe drinking water. In this study, GAC adsorption was first tested for its ability to remove a model estrogenic compound, 17β-estradiol (. E2). Although GAC showed a relatively high adsorption capacity for . E2 in isotherm experiments, it appeared to have a long mass transfer zone in a GAC column reactor, causing an early leakage of . E2 in the effluent. With an influent . E2 concentration of 20 μg/L, the GAC reactor was able to bring down effluent . E2 to ~200 ng/L. To further enhance . E2 removal, the GAC reactor was converted to a biologically active carbon (BAC) reactor by promoting biofilm growth in the reactor. Under optimal operating conditions, the BAC reactor had an effluent . E2 concentration of ~50 ng/L. With the empty bed contact times tested, the reactor exhibited more robust . E2 removal performance under the BAC operation than under the GAC operation. It is noted that estrone (. E1), an . E2 biodegradation intermediate, was frequently detected in reactor effluent during the BAC operation. Results from this study suggested that BAC could be an effective drinking water treatment process for . E2 removal and in the meantime . E1 accumulation needs to be addressed.