Aerobic batch degradation of 17-β estradiol (E2) by activated sludge: Effects of spiking E2 concentrations, MLVSS and temperatures

Aerobic batch degradation of 17β estradiol (E2) spiked into the activated sludge liquor from a sewage treatment plant was studied; and the likely impacts of E2ʹs initial concentrations (C0), microbial population densities (MLVSS) and temperatures (TEMPT) were examined for a variety of combinations of these three factors: C0=10, 30 and 50 μg l−1; MLVSS=1750, 875 and 435 mg l−1; and TEMPT=5, 20 and 35 °C. The results, together with those obtained through two control runs performed using a killed sludge sample, demonstrated clearly that E2 was eliminated from the aqueous phase readily under appropriate MLVSS and temperature levels, with the role of sorption by biomass being less significant. By fitting observed concentration data with a first-order rate expression, the degradation rate constants (k) under all experimental conditions were estimated. The magnitude of k changed markedly in the range of 0.23–4.79 h−1, following a general order that the higher the MLVSS was, the higher the rate constant, and that the higher the temperature, the higher the rate constant. An obvious increasing trend of the biomass-modified average rate constant (k′) with increases in the temperature was also presented: the k′ values at 5, 20 and 35 °C were 0.79, 1.77 and 3.29 l MLVSS g−1 h−1, respectively. Furthermore, based upon the estimated k values, the temperature coefficients (θ) over the ranges of 5–20 and 20–35 °C were determined. In similarity with the magnitude of θ reported for ordinary BOD-based organic matrices in domestic wastewater, the θ values of E2 varied in the range of 1.026–1.09, suggesting that the temperature impacts on the degradation rates of E2 and BOD constituents are probably similar.