|dc.description.abstract||This thesis presents the potential of integrating chemical and biological treatment technologies for the removal of high concentrations of phenol in a bioremediation medium. High concentrations of phenol in wastewater are difficult to remove by purely biological methods. Chemical oxidation is one way to treat high concentrations of phenol but complete oxidation is not always possible or will make the treatment process uneconomical. An experimental design approach, based on central composite rotatable design (CCRD) was used to evaluate the effects of process parameters on phenol oxidation by Fenton’s reagent and chlorine dioxide. Performance of the chemical oxidation was evaluated by determining the percentage of phenol oxidized at equilibrium. The reaction mechanism for the oxidation of phenol by Fenton’s reagent was proposed based on identification of the intermediate compounds.
The effects of H2O2 concentration (2000 to 5000 mg L-1) and FeSO4.7H2O concentration (500 to 2000 mg L-1) were investigated on phenol oxidation and optimal concentrations of H2O2 and FeSO4.7H2O for complete oxidation of 2000 mg L-1 phenol in medium were found to be 4340 mg L-1 and 1616 mg L-1, respectively, at 25°C and pH 3. The main oxidation products were identified as catechol, hydroquinone and maleic acid.
In the case of phenol oxidation by chlorine dioxide, the effects of chlorine dioxide concentration (500 to 2000 mg L-1), temperature (10 to 40°C) and pH (3 to 7) on the oxidation of 2000 mg L-1 of phenol were determined. The optimal concentration of chlorine dioxide to completely oxidize 2000 mg L-1 of phenol was 2000 mg L-1. The other parameters did not significantly affect the oxidation over the ranges studied. The main oxidation products were identified as 1,4-benzoquinone and 2-chloro-1,4-benzoquinone.
Finally, the biodegradation of 1,4-benzoquinone, the main oxidation product of phenol oxidation by chlorine dioxide, was studied in batch and continuous systems using Pseudomonas putida 17484 in two dose McKinney’s medium. The effects of 1,4-benzoquinone concentration and temperature were studied on biodegradation of 1,4-benzoquinone in batch reactors. Under optimal conditions, it was found that 150 mg L-1 1,4-benzoquinone could be successfully biodegraded at 15°C. In a continuous reactor operating at 15°C the highest removal rate with 500 mg L-1 of 1,4-benzoquinone was found to be 246 mg L-1 h-1. The values of µmax, Ks and yield were also determined as 0.74±0.03 h-1 and 14.17±3.21 mg L-1 and 2x1013 cell mg-1, respectively.||en_US