Integrated co-cultured bacterial strains capabilities to aqueous sulfide and chemical oxygen demand mitigation from high-strength petroleum refinery wastewater

Abstract

The heterogeneous nature of petroleum refinery based wastewater (PRW) couple with the documented paucity of the classical physicochemical mitigation approaches were behind the quest for a cost-effective and ecofriendly alternative with minimum negative effects. The toxic and inhibitory substances contained in PRW have made its treatment strenuous using a simple pure culture. A novel integrated bacterial mixed culture (BMC), Pseudomonas putida (ATCC 49128) and Bacillus cereus (ATCC 14579) with traceable imprints in biodegradation of high-strength PRW was proposed as a suitable alternative for sulfide oxidation and COD reduction with a potential alternative to classical physicochemical mitigation approaches. Comparative biodegradation potential of two acclaimed bacteria mixed-culture regimen was evaluated. The degree of inhibition cast was assessed based on the effectiveness of BMC to remove the targeted compounds (aqueous hydrogen sulfide and COD) within the assigned period of 8 hours hydraulic retention time (HRT). The PRW was found to contained initial concentration of 8,155 ppm COD, and 500 ppm sulfide, coupled with other refractory substances. The experiment was repeated batch-wise under defined optimal conditions of 0.25 L/min O₂, the temperature of 30^oC, agitation of 140 rpm at 8 hours retention time. The results obtained indicated 97.47±1.7 % (mg/L) COD reduction and 99.75±1.8 (ppm) sulfide removal efficiency (RE). In addition, the SEM analysis revealed further the potential of BMC to degrade sulfide from PRW to economically feasible elemental sulfur species, while EDXS demonstrated a proportionate elemental composition revealing appreciable sulfur content and high organic carbon accumulation. Despite the expected toxicity and inhibitory effect of the medium, an overwhelming biodegradation was achieved disproportionately, hence the model can be suggested for further research of repulsive wastewaters.

Keywords: Biodegradation, petroleum refinery wastewater, mixed-culture, Batch culture