Removal of Estrogen From Water by Granular Activated Carbon Adsorption

Investigating the removal of estrogens in a natural water matrix using a granular activated carbon (GAC) sandwich biofiltration (GSBF) system, combined with the photolysis pretreatment process. To elucidate the main mechanisms of the decontamination process, the adsorption of estrogens onto GAC particles and photolysis of them under the irradiation of ultraviolet light (UV) in the batch experiment was studied firstly, in which the impacts induced by the presence of humic acid and matrix in natural water on the removal of estrogens was investigated, and corresponding kinetic models were adopted to explain the adsorption and photodegradation mechanisms. 

Then, a bench-scale GSBF system composed of fine sand and a GAC layer joining a photolysis reactor was installed for investigating elimination of free estrogens―estrone (E1), 17β-estradiol (E2), estriol (E3), and 17α-ethinyl estradiol (EE2) and estrogenic activity based on the adsorption and degradation models recorded earlier. Furthermore, the capacity of photolysis pretreatment for facilitating removal of estrogens was evaluated. The result showed that good removal for estrogens (96.2 % to 99.5 %) was constantly achieved by the GSBF over the eight weeks of the operation stage, while limited removal (20.95 % to 60.88 %) for both estrogens was observed in the slow sand filtration (SSF). Additionally, a significant reduction of estrogenic activity was achieved in GSBF, while a modest reduction was obtained for SSF. The involvement of photolysis was found to be effective to control the increase of head loss as a result of inhibiting the overgrowth of microorganisms. Therefore,  photolysis pretreatment, coupling with the GSBF, is a promising treatment system for removing estrogens and estrogenic activity sustainably.

Taking tap water as the raw water, the adsorption efficiency and kinetics of activated granular carbon in estrogen removal were studied by adding estrone (E1), 17β-estradiol (E2) and 17α-ethynylestradiol (EE2). Results indicated that estrogens in tap water could be removed by activated adsorption quickly and efficiently. Adsorption equilibration was reached after contact for 10 min. The adsorption equilibration was related to the estrogen initial concentration. At initial concentration of 500 ng/L, the removal efficiencies of E1, E2 and EE2 were 74.7%, 89.5% and 82.8%, respectively. In presence of E1, E2 and EE2 simultaneously, the adsorption of E2 by activated carbon was deteriorated significantly (at initial concentration of 500 ng/L, the adsorption equilibration concentration increased from 44.65 to 195.03 ng/L), however, the adsorption of E1 and EE2 was not affected. The adsorption isotherm data obtained from different initial concentrations could be well explained by the Freundlich isotherm equations.