Removal behaviors of aerobic granular sludge on estrogens: Adsorption kinetics and removal mechanism

Aerobic granular sludge (AGS) has the advantages of high biomass and compact structure for withstanding the shocks and toxins. In this study, the removal behaviors of two typical endocrine disrupting chemicals (EDCs), 1713-estradiol (E2) and 17 alpha-ethinylestradiol (EE2), by AGS were investigated. 93.5% of E2 and 84.8% of EE2 were removed at a concentration of 10 mu g/L during 120 d operation, with the removal efficiencies of COD, NH4+-N and TP reaching the same level as those in the control group. Batch experimental results showed that the biodegradation was the dominant mechanism of E2 removal, while EE2 was more bio-refractory and mainly removed via adsorption. The adsorption of E2 and EE2 followed heterogeneous multilayer and chemical processes, owing to the active adsorption sites provided by amides, carboxylic groups, hydroxyl groups and polysaccharides on AGS. At the same time, Zoogloea, Sphingomonas, Pseudomonas and Brevundinomas were highly enriched under the pressure of estrogens, which assisted in the stability of AGS reactors by EPS secretion and estrogens degradation.