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

Natural steroidal estrogens, such as 17 -estradiol (E2), as well as antimicrobials such as doxycycline and norfloxacin, 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 respiration and E2 mineralization in sewage sludge, biosolid, and soil in the presence and the absence of doxycycline and norfloxacin. The antimicrobials were applied to the media either alone or in combination at total rates of 4 and 40mg 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 418days in sewage sludge, from 721 to 869days in soil, and from 2,258 to 14,146days in biosolid. E2 mineralization followed first-order and the presence of antimicrobials had no significant effect on mineralization half-lives, except for some antimicrobial applications to the human waste products. At 189day, total E2 mineralization was significantly greater in sewage sludge (38 +/- 0.7%) > soil (23 +/- 0.7%) > biosolid (3 +/- 0.7%), while total respiration was significantly greater in biosolid (1,258mg CO2) > sewage sludge (253mg CO2) soil (131mg CO2). Strong sorption of E2 to the organic fraction in biosolid may have resulted in reduced E2 mineralization despite the high microbial activity in this media. Total E2 mineralization at 189day was not significantly influenced by the presence of doxycycline and/or norfloxacin in the media. Antimicrobial additions also did not significantly influence total respiration in media, except that total CO2 respiration at 189day was significantly greater for biosolid with 40mg kg(-1) doxycycline added, relative to biosolid without antimicrobials. We conclude that it is unlikely for doxycycline and norfloxacin, 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.