|M.Sc Student||Massalha Nedal|
|Subject||Effect of Bacteria Immobilization on the Rate of|
Biodegradation of Phenol at High Concentration
|Department||Department of Civil and Environmental Engineering||Supervisors||Professor Emeritus Abraham Shaviv|
|Dr. Isam Sabbah|
|Full Thesis text - in Hebrew|
Phenol is an organic, aromatic compound that is found in natural environments. However, it rises to high concentrations in a wide spectrum of industrial and agricultural liquid wastes, including petroleum refineries, pulp and paper, plastic, dye, polymeric resins, pharmaceutical industry and olive mill wastewater. Phenol is water-soluble and highly mobile. Biodegradation of phenol is limited by the substrate delivery or bioavailability. High concentration inhibits microorganism's activity. Therefore meeting the challenge of controlling the phenol bioavailability at high concentration is the main purpose of this project. Modification of a well-known cell immobilization technique was done to enhance the biodegradation of phenol at high initial concentrations. This work focused on testing different low-cost mineral additives to a well-known cell immobilization technique while considering the diffusive internal mass transfer limitations.
The tested immobilization matrixes consisted of a combination between Ca-alginate polymer, Clay and Activated Carbon at different beads diameters 1-6 mm.
Biodegradation experiments of phenol were conducted by using isolated microorganism cells from a compost pile of agricultural wastes. The influence of different initial concentrations of phenol (200-2000 mg/l), on the rate of biodegradation, was tested in free and immobilized cells based systems. The experimental results of the free cells growth rate were described successfully by the “Haldane Model,” indicating a substrate inhibition effect. The results show that free and immobilized microorganisms in 4 mm beads of alginate biodegrade phenol only up to about 1300 mg/l. The bead size of 4 mm diameter and composition of clay and AC was found to be the optimal one for biodegradation of phenol at initial concentration of about 2000 mg/L. The bead size, significantly, affected the biodegradation rate of phenol, where the highest biodegradation rate was 4 3 mg/(g.h) for 1 mm beads diameter and the lowest value was 1 4 mg/(g.h) for the 6-mm beads diameter. Reuse of the same immobilized beads showed that the rate of biodegradation did not change compared to the performance in the first run. Gradual increasing of the initial phenol concentration in the system with immobilized microorganisms in 1 mm beads of alginate with clay and activated carbon increase the tolerance of the biomass up to 2600 mg phenol/l. However, biodegradation was not observed in the system with initial phenol concentration of 2000 mg/l.