Some sewage treatments more effective than others, fish show.

Filby, AL, JA Shears, BE Drage, JH Churchley and CR Tyler. 2010. Effects of advanced treatments of wastewater effluents on estrogenic and reproductive health impacts in fish. Environmental Science and Technology 44(11):4348-4354.

Some wastewater treatments are more effective than others at removing estrogens and minimizing reproductive effects on fish exposed to them in sewage effluent, reports researchers from the United Kingdom. All three of the treatments tested in the study did so, but each influenced different reproductive endpoints that were measured in the fish.

The study is important because it more fully evaluates which water treatment technologies are best at removing estrogens from the wastewater and thus minimizing health and population effects in the fish. It is unique in that it combined two different ways of measuring the reproductive impacts: physical markers that change with estrogen exposures, and for the first time, breeding success in the fish. Prior studies simply monitored the chemical changes in the endocrine disrupting compounds in the water following different treatments.

Exposure to estrogenic compounds found in wastewater can impact fish and other wildlife, especially certain sexual development traits and overall reproduction. The estrogens most likely to be found in effluent include the natural estrogen 17beta-estradiol (E2), the synthetic estrogen – 17alpha-ethinylestradiol (EE2) – used in birth control pills, and perhaps, their degradation products.

Conventional sewage treatment does not usually remove all of these compounds. Fish are then exposed when the estrogens are released into waterways. It is not well documented if costly advanced treatments would be effective in removing the hormones.

To conduct this study, researchers exposed fathead minnows to either treated or untreated wastewater effluent for 21 days. They used three types of treatment systems: granular activated carbon (GAC), ozone (O3) and chlorine dioxide (ClO2). After the exposures, the fish were evaluated for specific indicators – or markers – of environmental estrogen exposure: plasma vitellogenin (an egg yolk precursor and a biomarker of endocrine disruption), secondary sex characteristics in male fish and egg production in mating pairs.

All three treatments reduced estrogen levels in the water between 70 and 100 percent for total estrogens and between 53 and 100 percent for individual types of estrogens. ClO2 removed the most, while ozone the least.

The authors found that even though all three treatment processes reduced the biological impacts of the standard wastewater effluent, each treatment method affected the fish differently. Effluent treated with GAC and ClO2, but not ozone, reduced the induction of vitellogenin in exposed fish. However, ozone was best at reducing adverse impacts on secondary sex characteristics in male fish.

They also found that while exposure to the effluent impacted the number of eggs produced in mating pairs, treating the water did not minimize this effect. The finding indicates that the changes to egg production are most likely not mediated by estrogens.