Adsorption and biodegradation of typical estrogens in activated sludge under aerobic conditions

Abstract

The adsorption and biodegradability of thefive estrogens, including estrone (E1), 17β-estradiol (E2), estriol (E3), 17α-estradiol and 17α-ethynylestradiol (EE2), by four kinds of activated sludge collected from sewage treatment plants in Hong Kong and Shenzhen are characterized. A pretreatment method of Liquid-liquid-extraction and the GC-MS measurement were applied for determining concentrations of residual estrogens. Adsorption equilibrium could be achieved in around 30 min-1 h and the residual estrogen in adsorption control sets kept relatively stable with no significant difference among different sludges. The average adsorption amount of EE2 and 17α-E2 were estimated at 2.6 and 2.5 μg per mg MLVSS, while E1, E2 and E3 had average adsorption amounts of 1.6, 1.7 and 0.9 μg·mg-1. The average biodegradation rate of E1, E2, E3, 17α-E2 and EE2 was 326, 252, 440, 275 and 13 μg·L-1·d-1, respectively under aerobic conditions. The half lives of E1, E2, E3, 17α-E2 and EE2 by the four sludges were estimated at 14.9 h, 0.9 h, 4.3 h, 4.7 h and 18.9 d in average. The adsorption amount of E3 was lower than other estrogens, which might be due to its polar structure. EE2 was the hardest to digest. The sludge AS2, nitrifying activated sludge (NAS), was more effective in transforming EE2 than that of other three sludges, which might be closely related to the nitrifiers in NAS.