Oriented bio-feeding control of the anaerobic biodegradation of ethinyl estradiol

Up to 95% of hormones are excreted into domestic wastewater with urine or feces, but their macromolecules are difficult to biodegrade. This project studies the treatment of Ethinyl Estradiol (EE₂) in swine wastewater in an Upstream Solids Reactor (USR), and explores a new method for oriented bio-feeding to regulate the anaerobic biodegradation process. It was found that the metabolism of lactic acid and propionic acid was accompanied by changes in EE₂ content, but lactic acid molecules were not readily bioavailable, so adding propionic acid was more suitable. However, controlling the pH to lower (4.73) and higher (8.73) values inhibited further fermentation of acetic acid and propionic acid, which was not favorable for the removal of EE₂. This is simply due to the fact that propionic acid as a carbon source changes the preference of the microbes for consuming EE₂. The order of the effect of addition of propionic acid on the removal of EE₂ was as follows: P₄₀₀>P₈₀₀>P₀>P₂₀₀ (addition of propionic acid). The P₄₀₀ removal efficiency increased from 60% to 85%. In the metabolism of EE₂, after oxidation, hydrolysis, ketosis, hydroxylation and enzymatic action, dienoic acid and oleic acid were generated, and there was no secondary pollution from EE₂ metabolites. In conclusion, feeding microorganisms with propionic acid can enhance the anaerobic biodegradation of EE₂, providing a new strategy for the anaerobic biodegradation and bioremediation of refractory pollutants.