Characteristics of Steroid Estrogen Loss, Degradation and Residues during Open-Air Dairy Manure Disposal

Abstract

Steroid estrogens (SEs) are mainly derived from livestock manure, and composting is the common method of bioresource utilization. In this study, an open-air composting experiment with dairy manure was conducted to observe the degradation and loss of five SEs under the influence of different precipitation intensities and additional mixed fermentation strains. SE determination results for dairy manure after 30 days of composting indicated that the average removal rates of 17α-estradiol (E2α), estrone (E1), 17β-estradiol (E2β), 17α-ethinyl estradiol (EE2), estriol (E3), and estradiol equivalent (EEQ) were 76.67%, 71.07%, 73.88%, 92.02%, 98.77%, and 88.11%, respectively, partly due to SE runoff. The rates of SEs leaching from the open-air composting dairy manure ranged from 0.05% to 4.75% after 10 rounds of 5–60 mm/d simulated rainfall. The total leaching amount of SEs was positively correlated with rainfall, but the leaching concentrations of SEs were just the opposite. As a result of its role as a degradation intermediate of other SEs, E3 was the most prone to run off. By strengthening the action of microorganisms, the total leaching amount of EEQ increased by 5%, E3 increased by five times, and E2β also underwent a transition from a conjugated form to free. However, there were also fewer final SEs remaining in the composted product, as well as the environmental risks of conjugated SEs. These conclusions can provide beneficial suggestions and references for controlling the environmental risks of SEs in the process of composting livestock and poultry manure.