Influence of Bioselector Processes on 17α-Ethinylestradiol Biodegradation in Activated Sludge Wastewater Treatment Systems

摘要

The removal of the potent endocrine-disrupting estrogen hormone, 17α-ethinylestradiol (EE2), in municipal wastewater treatment plant (WWTP) activated sludge (AS) processes can occur through biodegradation by heterotrophic bacteria growing on other organic wastewater substrates. Different kinetic and metabolic substrate utilization conditions created with AS bioselector processes can affect the heterotrophic population composition in AS. The primary goal of this research was to determine if these changes also affect specific EE2 biodegradation kinetics. A series of experiments were conducted with parallel bench-scale AS reactors treating municipal waste-water with estrogens at 100-300 ng/L concentrations to evaluate the effect of bioselector designs on pseudo first-order EE2 biodegradation kinetics normalized to mixed liquor volatile suspended solids (VSS). Kinetic rate coefficient (k_b) values for EE2 biodegradation ranged from 5.0 to 18.9 L/g VSS/d at temperatures of 18 ℃ to 24 ℃. EE2 k_b values for aerobic biomass growth at low initial food to mass ratio feeding conditions (F/M_f) were 1.4 to 2.2 times greater than that from growth at high initial F/M_f. Anoxic/aerobic and anaerobic/aerobic metabolic bioselector reactors achieving biological nutrient removal had similar EE2 k_b values, which were lower than that in aerobic AS reactors with biomass growth at low initial F/M_f. These results provide evidence that population selection with growth at low organic substrate concentrations can lead to improved EE2 biodegradation kinetics in AS treatment.