Estrogen Biodegradation Kinetics and Estrogenic Activity Reduction for Two Biological Wastewater Treatment Methods

摘要

Estrogens from anthropogenic and livestock sources are a serious concern for aquatic ecosystems at concentrations less than 1 ng/L. Fundamental process parameters to reduce estrogenic activity were investigated for two biotreatment methods: heterotrophic bacterial degradation in municipal activated sludge (AS) and a nitration process that is applicable to high NH_4-N wastewaters. Batch tests with estrogen and nitro-estrogen compounds were conducted at nanogram per liter concentrations with mixed liquor from an AS wastewater treatment facility (WWTF) operating at a 3 day solids retention time (SRT) and a membrane bioreactor (MBR) WWTF operating at a 30-40 day SRT. The estrogenic activities of estrone (E1), 17β-estradiol (E2),and 17α-ethinylestradiol (EE2)were reduced 80-97% following nitration. First-order biological degradation rate coefficients (k_b) of the nitrated estrogens were 10-50% lower than the parent estrogen compounds. The k_b values for EE2 in MBR and AS mixed liquors were similar, 1.67 and 1.63 L/gVSS-day respectively, indicating that the bacteria responsible for EE2 degradation were present at long and short SRTs. The k_b values for E1 and E2 were 2 orders of magnitude greater than for EE2. EE2 degradation was 7.5 times faster in the presence of E1 and E2, and no effect was observed with other estrogen mixtures.