APPLICATION OF IMMOBILIZED MIXED BACTERIAL CULTURE FOR THE DEGRADATION OF PHENOL PRESENT IN OIL REFINERY EFFLUENT

Free and calcium alginate entrapped cells of four microorganisms namel y Pseudomonas aeruginosa, Pseudomonas fluorescens, Serratia sp., and Y ersinia sp.. have been examined for degradation of phenol, present in oil refinery effluent by observing growth and tolerance capacity again st toxic effects of phenol. The study of tolerance capacity of all the four microorganisms for different sublethal concentrations have shown that phenol concentrations above 200 mg/l was toxic to Pseudomonas fl uorescens while other three microorganisms tolerated phenol upto 400 m g/l. These four microorganisms were mixed for the formulation of micro bial consortia and further used for the biodegradation of phenol prese nt in oil refinery effluent. At bacteriostatic concentrations of pheno l, toxicity effect has been found to be significantly lower in the cas e of immobilized bacteria in comparison to free cells. The immobilized microorganisms have been found to degrade 100% of phenol in 96 hrs., while the free cells degraded 80% phenol in 96 hrs. The oil refinery e ffluent's pollutional strength has been determined on the basis of Che mical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD) tests be sides the determination of phenol contents in various layers of oil re finery effluent. The immobilized mixed bacterial cells were able to de grade 37% of phenol present in oil refinery effluent within 6 hrs. The viability of the system is discussed in terms of its industrial appli cation.