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Environmental Science and Technology (Revised version January 2005): note also CORRECTION published in EST 39(18): 7344* Corresponding author: Phone +61 2 9385 5082, fax: +61 2 9313 8624, email: andrew.feitz@unsw.edu.au AbstractA comparison of estrone (E1), 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) removal at a coastal enhanced primary and inland advanced sewage treatment plant (STP) is reported. The average concentration of estrogens in the raw sewage is similar to reports in other studies. The sequential batch reactor at the advanced STP removed on average 85% of the incoming E1 and 96% of the E2. Further removal was observed during later microfiltration with the estrogen concentration below detection (<0.1 ng.L -1 ) after reverse osmosis. Some 6% of the influent E1+E2 was removed in the waste activated sludge. The detection of EE2 in the waste activated sludge (0.42 ng.g -1 solids dry weight), undetectable in the raw sewage, suggests that EE2 is resistant to biological treatment in the sequential batch reactor and is primarily removed due to sorption. Little estrogen removal was observed at the enhanced primary with only 7% of E1 and 0% of E2 removed. Low removal is expected based on the degree of estrogens partitioning in the organic fraction given the relatively low solids concentration, but surprisingly, some 43% of E2, 24% of E1 and 100% of EE2 remains associated with the solids fraction in the treated effluent. Further research is necessary to determine whether the low level of estrogen removal for the coastal treatment plant will adversely affect the receiving marine environment. 2 IntroductionThere are increasing concerns that the release of steroid estrogens post wastewater treatment is leading to abnormal reproductive systems in freshwater and marine dwelling animals (1-3). Human excretion is considered to be the primary source of steroid estrogens from the urban environment and are is released by individuals into sewerage system in both conjugated and unconjugated forms at µg levels per day (4-6). Johnson and Williams (6) recently developed a model to estimate the quantities of estrogens by the human population, taking in consideration conjugation and metabolism of natural and synthetic hormones in the body and the different quantities released by different population groups. The average human excretion of estrogens per head is reported to be 10.5 µg.d -1 for estrone (E1), 6.6 µg.d -1 for 17β-estradiol (E2), with an additional 3.3 µg.d -1 transformation of the E1 to E2 in the sewer (6). The population normalized concentration of the synthetic steroid 17α-ethinylestradiol, an active agent in the contraceptive pill, is 1 µg.d -1 per head (6).

Ocean sediment samples were taken adjacent and 7km from a deep ocean outfall (average depth 80m), the discharge point of an enhanced primary sewage treatment plant. All samples contained steroid estrogens at nanogram per gram levels with higher concentrations at the 7km sampling site. The concentration of estrone ranged from (0.16 -1.17 ng/g), 17β-estradiol (0.22 -2.48 ng/g) and the synthetic 17α-ethinylestradiol (<0.1 -0.5 ng/g). The values detected correspond with estimates based on the proportion of estrogens sorbed to particles in the effluent and the expected proportion of sewage origin particles in the ocean sediments. The results suggest that estrogens associated with the particulate fraction aggregate on contact with high ionic strength seawater and settle to the seafloor after discharge through deep ocean outfalls.

The concentrations of two natural estrogens (estrone (E1) and Estradiol (E2)) and one synthetic progestin (Ethinylestradiol (EE2)) were measured for different unit operations in an advanced sewage treatment plant and in a large coastal enhanced primary sewage treatment plant. The average influent concentration to both plants was similar: 55 and 53 ng/L for E1 and 22 and 12 ng/L for E2 for the advanced and enhanced primary STPs, respectively. The activated sludge process at the advanced STP removed up to 85% and 96% of E1 and E2, respectively. The enhanced primary sewage treatment plant was mostly ineffective at removing the steroids with only 14% of E1 and 5% of E2 being removed during the treatment process. EE2 was not been detected during the study period in the influent or effluent of either STP. The difference in the observed removal between the two plants is primarily linked to plant performance but the extent to which removal of steroid estrogens is due to bacterial metabolism (i.e. the advanced STP) rather than adsorption to the bacterial biomass remains unclear. The poor removal observed for the coastal enhanced primary STP may have implications for the receiving environment in terms of a greater potential for abnormal reproductive systems in marine animals, particularly if discharges are into large bays or harbours where flushing is limited.