Microbiological oxidation of sulfides present in refinery sour waters by fixed bed reactors

Abstract

Agroup of native bacteria with a sulfide oxidation capacity was isolated at the Instituto Colombiano del Petróleo (ICP). The bacteria were immobilized in an inert inorganic support of sintered glass that was used to evaluate a fixed packed column system working in batches as well as in a continuous mode. The experiments carried out in real wastewater and in refinery sour water show high sulfide removal percentages (over 90%) both in low and high sulfide concentrations. The appropriate operation pH is in the alkaline range (8.0 to 9.0) and it decreases as the reaction proceeds. The ability of the microbial consortium to take in the ammonia nitrogen required for their metabolic activity and a possible heterotrofic nitrification, and the phenol present in the stream as a carbon source for some of the formulated strains, is demonstrated. Sulfur mass balances are carried out quantifying it as sulfates, tiosulfates, sulfide, and elementary sulfur. The effect of operational changes on the sulfide removal percentage is evaluated obtaining a quick response of the system. A kinetic analysis was carried out and the corresponding constants derived from the Michaelis-Menten equation were calculated. The maximum removal velocity and the saturation constant are V_m = 6.03-1 0 kg S/m s and K_s = 2.1325-10-⁴ kgS/m³.