The Phenol-degradation Properties Of Mixed Culture And Its Immobilization

Phenol is a degradable pollutant, which mainly relies upon biodegradation. At the present time, the polluted waters containing phenol are mainly degraded only by a single microbial strain. The degradation method is high cost in the culture of the microbial strain with the light load on phenol. But, the method by mixed strains could provide a way to remedy the defect in that by the microbial strain. Two strains with highly-effective phenol-degradation, Flavobacterium sp.and Acetobacter sp., were found by screening and isolating in the thesis. The binary mixed strains with high-effective phenol-degradation were obtained through mixing the two strains.The effect of the parameters such as dissolved oxygen, temperature, pH and inoculum size on the phenol-degradation rate and biomass of the mixed strains was studied in the single factor experiment, and put forward the ranges of the values of the parameters. Response Surface Methodology experimental design was carried out in order to optimize the phenol-degradation conditions. The optimum conditions are recommended that the phenol degradation rate and biomass of the binary mixed strains were 96.97%and 410.78 mg/L when temperature was 33℃, pH 6.00 and inoculum size 13%, respectively.The growth dynamics behavior of the binary mixed strains followed Haldane model, and the dynamics parameters were μmax=0.30041/h, Ks=74.5334 mg/L, Ki= 981.2239 mg/L. When the concentration of phenol in the synthetic wastewater was under 270.43 mg/L, it is suitable for the growth of the strains. The phenol-degradation of the mixed strains could be described by Andrews model, and the kinetics parameters were qmax=0.51281/h, Ks=79.4395 mg/L, Ki=974.0619 mg/L. The inhibitory effect of substrate phenol on the mixed strains was negligible when the concentration of phenol was lower than 278.17 mg/L. The kinetic experimental data were fitted well with the corresponding kinetic model data in the growth and phenol-degradation of the mixed strains.The optimized conditions were Mg/Fe molar ratio of 3:1 and carrier dosing 4 g/L for 12 h, when the binary mixed strains were immobilized on the Mg-Fe hydrotalcite. The surface of the Mg-Fe hydrotalcite particle was the major adsorption area of the mixed strains.The processing parameters were carried out in the phenol-degradation of immobilized mixed strains. The phenol-degradation rate was up to 90% under the conditions of 30～37℃ and pH 5.0～7.0. The immobilized mixed strains kept high activity after three times used. In order to keep the immobilized mixed strains high active, it was good to preserve it dry in the air at constant temperature.