Study On Degradatation Of Steroid Estrogens By Activated Sludge And A Sphingo.multivorum Bacterium

Aerobic batch degradation of estradiol (E2) spiked into the activated sludge liquor from a sewage treatment plant was studied, including the removal effect of common environmental factors. We also isolated a steroid estrogen-degadation strains, named ED4, which had a high efficiency of degradation. Finally, we draw the following conclusions:(1) The removal of estradiol (E2) in aerobic activated sludge process is strongly dependent on the influent E2 concentrations, MLVSS and temperatures. In the batch experiments conducted, E2 was eliminated from the aqueous phase in a faster pace at higher MLVSS and temperature levels, with the role of sorption by biomass seemed to be less significant. By fitting observed concentration data with a first-order rate expression, the degradation rate constants (k) under different initial E2 concentrations was 3.52h-1. The temperature parameters (θ) determined for the rate constant k over 5-20℃and 20-35℃fell in the range of 1.069-1.030, with the temperature impact being more significant for operations with lower MLSS.(2) Several novel bacteria capable of degrading E2 were isolated from activated sludge According to their morphology, physiochemical characteristics,these strains were identified as different bacterias in Sphingobacterium, Rhodococcus and Achromobacte. Four strains could degrade E2, but only one had further degradation ability of E1, which is Sphingo. Multivorum and named ED4.(3) In the process of E2 degradation with hunger effect, the accumulation of E1 phenomenon apperred and had slow degradation rate. When the hunger time increased, strains needed more time to resume E2 degradation ability. The optimum temperature for Strains ED4 is 30℃and the optimal initial pH is 8. In a certain concentration range in water, the impacts by Fe3+, Ca2+ to the E2 degradation were not big, but Sn2+, Zn2+, Al3+, Ba2+had certain inhibitions to Strains ED4 growth. The heavy metal ions Pb2+, fully inhibited the growth of Strains ED4. Along with the increase of E2 concentration in substrate, the growth of Strains ED4 were restrained. Lower concentration of the range of E2 had better removal efficiency. The degradation process fit the Monod model, which Km was 1.8 mg/L, and qmax was 0.32mg/mgVSS h.(4) According to production analysis by MS, it could be concluded that E2 was oxidized to E1 firstly, then 2-hydroxy-2,4-dienevaleric acid was produced and finally degraded to CO2 and H2O by TCA-cycle.