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Journal of Environmental Science and Health
Vol. 51 (10), 2016, Pages: 655 660

17 -estradiol mineralization in human waste products and soil in the presence and the absence of antimicrobials

Inoka Amarakoon, Annemieke Farenhorst, Karin Rose, Anne Claeys, and Bruna Ascef

Department of Soil Science, University of Manitoba, Winnipeg, Manitoba, Canada.


Natural steroidal estrogens, such as 17 -estradiol(E2),aswellasantimicrobialssuchasdoxycyclineand nor floxacin, are excreted by humans and hence detected in sewage sludge and biosolid. The disposal of human waste products on agricultural land results in estrogens and antibiotics being detected as mixtures in soils. The objective of this study was to examine microbial respira tion and E2 mineralization in sewage sludge, biosolid, and soil in the presence and the absence of doxycycline and nor fl oxacin. The antimicrobials were applied to the media either alone or in combination at total rates of 4 and 40 mg kg-1 ,with the 4mg kg-1 rate being an environmentally relevant concentration. The calculated time that half of the applied E2 was mineralized ranged from 294 to 418 days in sewage sludge, from 721 to 869 days in soil, and from 2,258 to 14,146 days in biosolid. E2 mineralization followed fi rst-order and the presence of a ntimicrobials had no signi fi cant effect on mineralization half-lives, except for some antimicrobial applications to the human waste products. At 189 day, total E2 mineralization was signi fi cantly greater in sewage sludge (38 0.7%) > soil (23 0.7%) > biosolid (3 0.7%), while total respiration was signi fi cantly greater in biosolid (1,258 mg CO2) > sewage sludge (253 mg CO2) soil (131 mg CO2). Strong sorption of E2 to the organic fracti on in biosolid may have resulted in reduced E2 mineralization despite the high microbial activity in this media. Total E2 mineralization at 189 day was not signi fi cantly in fluenced by the presence of doxycycline and/or nor floxacin in the media. Antimicrobial additions also did not signifcantly in fluence total respiration in m edia, except that total CO2 respiration at 189 day was signi ficantly greater for biosolid with 40 mg kg-1 doxycycline added, relative to biosolid without antimicrobials. We conclude that it is unlikely for doxycycline and nor floxacin, or their mixtures, to have a significant effect on E2 mineralization in human waste products and soil. However , the potential for E2 to be persistent in biosolids, with and without the presence of antimicrobials, is posing a challenge for biosolid disposal to agricultural lands.

Keywords: 17 -estradiol; antimicrobial; doxycycline; nor fl oxacin; sewage sludge; biosolid; soil; mineralization; respiration.

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