Estrogen nitration kinetics and implications for wastewater treatment.
Understanding estrogen-removal mechanisms in wastewater treatment is imperative, as estrogens have environmental effects at trace concentrations. Previous research investigating co-metabolic degradation of 17alpha-ethinylestradiol (EE2) by ammonia-oxidizing bacteria (AOB) revealed that, in batch tests where high nitrite-nitrogen (NO2-N) concentrations occurred as a result of ammonia-nitrogen (NH4-N) oxidation by AOB, an abiotic estrogen nitration reaction actually was occurring--not co-metabolic degradation. This paper addresses nitration kinetics. A first-order abiotic nitration model was developed that predicts nitration of EE2, 17beta-estradiol (E2), and estrone (El) as a function of temperature, pH, estrogen (EE2, E2, and E1), and NO2-N concentration. A contact time of 3.6 to 4.1 days is required for 90% estrogen nitration at 500 mg/L NO2-N and pH 6.4. At 20 degrees C and pH 6.4, the threshold NO2-N concentration for nitration to occur is 9 mg/L; therefore, estrogen nitration is not likely in activated sludge treatment of domestic wastewater, but has potential for high-NH4-N-strength wastewaters.
Gaulke
Linda S
LS
University of Washington, Department of Civil and Environmental Engineering, Box 352700, Seattle, WA 98195-2700, USA. lsg@u.washington.edu
Strand
Stuart E
SE
Kalhorn
Thomas F
TF
Stensel
H David
HD
D004967:Estrogens / Q000032:analysis / Q000737:chemistry*; D007700:Kinetics; D009573:Nitrites / Q000737:chemistry; D009584:Nitrogen / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*; D018508:Water Purification
D004967:Estrogens; D009573:Nitrites; D014874:Water Pollutants, Chemical; D009584:Nitrogen