Anaerobic biodegradation characteristics of estrone, estradiol, and 17α-ethinylestradiol in activated sludge batch tests

Abstract

The anaerobic degradation characteristics of estrone (E1), estradiol (E2), and 17α-ethinylestradiol (EE2) under single and combined conditions were investigated in batch tests and the influence of initial estrogen and sludge concentrations on the biodegradation process was studied. The results indicated that the degradation process of three estrogens was biphasic. The first phase was fast and the second phase was slow. The two phases could be described by the first-order degradation kinetics. In the single degradation experiments, at the fast stage, E2 degradation rate was the highest for the three estrogens, which was 2 and 5.17 times higher than E1 and EE2, respectively. However, at the slow stage, EE2 almost could not be biodegraded, and the degradation rate constant of E1 and E2 was 0.18 and 0.34 times lower than that at fast degradation phase, respectively. Meanwhile, E1 was accumulated in the process of E2 degradation, which indicated that E1 was a main intermediate product of the E2 anaerobic biodegradation. In the combined degradation experiments, the degradation rate constants of estrogens had the order of E1 ##xgt; E2 ##xgt; EE2, and the contribution of fast degradation stage was crucial to the removal of estrogens under anaerobic conditions. The degradation rate constant of estrogens decreased linearly with the initial estrogen concentrations and increased linearly with the sludge concentrations, which indicated that the higher sludge concentrations benefited the removal of estrogens under anaerobic conditions in the real wastewater treatment practice.