Contribution of 17-ß estradiol to total estrogenicity in dairy manure subject to anaerobic digestion or separation and aeration

The contribution of 17s-estradiol (E2) to total estrogenicity was determined in two dairy manures. The first system was a full-scale manure handling system incorporating manure separation and surface aeration of separated liquid (Separation/Aeration). The second was an anaerobic digester receiving dairy manure on a commercial dairy farm (Anaerobic Digester). Manure samples were collected monthly from each system in April to June of 2007. A two-step base extraction method was used to extract estrogens from manure samples. E2 was analyzed using enzyme-linked immunosorbent assay (ELISA). Total estrogenicity was measured using yeast estrogen screen (YES) assay. All data were normalized based on the total solids (TS) content of the manure. In the Separation/Aeration system, the final aerated effluent had significantly lower E2 than did influent (88 vs. 175 ng/g TS). Total estrogenicity was lower in effluent than influent as well (115 vs. 225 ng/g TS). E2 as a proportion of total estrogenicity was similar in the influent (78%) and aerated effluent (74%). In the Anaerobic Digester, the effluent had significantly lower E2 than did influent (283 vs. 610 ng/g TS) and total estrogenicity was lower in effluent as well (1100 vs. 1423 ng/g TS). In the Anaerobic Digester, E2 was 43% of total estrogenicity in the influent, and 26% in the effluent. This difference may have resulted from different degradation rates of E2 and other estrogenic chemicals during anaerobic digestion. Alternatively, anaerobic digestion may have generated new estrogenic chemicals. More research is needed to examine the conversion and degradation of estrogens in dairy manure in manure storage and treatment systems.