Modern Treatment Plants Strip Hormone from Sewage. (Extracting Estrogens)
Harder, B., Science News
Reproductive hormones, both natural and the synthetic ones in contraceptive drugs, sometimes survive sewage treatment and turn up in the environment where they can affect wildlife. Modern sewage-treatment facilities, about half of those used in Europe, break down these sex hormones more effectively than older plants do.
A new study shows why: Only the modern, multiple-chamber treatment plants subject the sewage to the gamut of chemical and biological conditions required to break down different hormones.
Sewage often contains two natural estrogens, estrone (E1) and 17-beta-estradiol (E2), as well as the synthetic estrogen 17-alpha-ethinylestradiol (EE2), used in birth-control pills and patches. Scientists have determined that some estrogen passes through U.S. water-treatment plants and reaches waterways (SN: 6/17/00, p. 388), where it can cause fish to develop sexual abnormalities (SN: 1/8/94, p. 24).
Older plants have a single tank designed to remove phosphate and nitrate from sludge, but newer facilities use several such tanks and retain sludge considerably longer, says environmental chemist Thomas A. Ternes of Bundesanstalt fur Gewasserkunde in Koblenz, Germany. At a recently updated plant in Wiesbaden, Germany, for example, sludge spends 11 to 13 days in a trio of tanks rather than the 4 days or less it took in a single tank before the renovation.
Different kinds of bacteria populate the various tanks because some tanks expose sludge to oxygen and others don't. …