[Isolation, identification of methyl tert-butyl ether degradation strain and its degradation kinetics].

A methyl tert-butyl ether degradation strain A1 was isolated from the soil under an old Gingko tree. It was identified preliminarily as Comamonas testosterone by 16S rDNA sequence analysis. The main factors including inoculation amount of microbes, pH, temperature and MTBE concentration that may affect the degradation efficiency of MTBE were further studied. The results indicated that the optimum conditions were as following: pH 7.0, temperature 25 degrees C, inoculation amount of microbes was 2 mL (D600 = 2.523 A), initial MTBE concentration 50 mg/L. Under that condition, MTBE can be reduced by 98.89% with seven days (compared with the blank, the volatilization of MTBE was 46.55%). In addition, the biodegradation process of MTBE can be well described by enzymatic reaction of high concentration inhibition, with the maximum substrate utilization rate 0.872 d(-1), Michaelis-Menten constant 7.832 mg x L(-1), inhibitory constant 130.75 mg x L(-1) respectively.

[Degradation of methyl tert-butyl ether (MTBE) by O3/H2O2].

The degradation of methyl tert-butyl ether (MTBE) in water solution has been studied using the combination of ozone/hydrogen peroxide in a bubble column. Effects of air (containing O3) currents, quantities of H2O2, initial concentrations of MTBE, pH values and temperatures on the oxidation of MTBE have been tested, and it is implicated that under the conditions of initial MTBE concentration of 10 mg x L(-1), air current of 0.5 L x min(-1), pH 6.5, 293 K and 2.4 mg x L(-1) H2O2 addition, MTBE can be reduced by 75.5% and the removal rate of COD reaches 68.0% within 30 min. The main of degradation products identified are tert-butyl formate (TBF), tert-butyl alcohol (TBA), acetone (AC) and methyl acetate (MA). On the basis of that, the probable mechanism and pathway of the oxidation of MTBE by ozone/hydrogen peroxide have been proposed.

Of pH and Eh on release of nitrogen and phosphorus from sediments of West Lake.

The effects of pH and Eh on release of nitrogen and phosphorus from sediments of West Lake under different conditions were investigated by simulation test. Results showed that the net flux of NH4(+) -N release from sediments increased with pH, but NO3(-) -N showed negative-going release at all tested pH levels. The net flux of NH4(+) -N release from sediments was higher under anaerobic or aerobic condition of the overlying water, but only under aerobic condition would net release of NO3(-) -N occur. It was also shown that phosphorus released was mainly in its inorganic form, higher pH and anaerobic conditions of overlying water greatly stimulated release of phosphorus. In situ measurement at several West Lake locations indicated that sediment resuspension induced by boat propeller stimulated nutrients release from sediment into overlying water.