Performance evaluation of sulfide-based autotrophic denitrification for petrochemical industry wastewater

Abstract Oil refineries generate wastewater pollutants such as sulfide and nitrate from gasoline sweetening and other concomitant processes, respectively. However, the concentration of biodegradable organic substrate in the industrial wastewater is insufficient for the complete denitrification process. Thus, this study investigated sulfide-based denitrification treatment for real sulfide-rich industrial wastewater, with a low C/N molar ratio, produced in the oil refinery. The performance of two continuous laboratory packed-bed reactors (PBRs) packed with different biomass carriers was evaluated. PBRs were denoted as R1 (polyester type carriers) and R2n (polyester type carriers coated with nanofibers) and operated at 24 °C with the fixed S/N molar ratio at 0.28, respectively. The maximum sulfide and nitrate-nitrogen applied loading rate was 0.17 kg/(m3⋅d) and 0.25 kg/(m3⋅d), respectively. Results showed nitrate removal efficiency was 94.8 % and 95.3 % in R1 and R2n, respectively. Sulfide was almost completely removed in both PBRs, achieving the sulfide removal efficiency of 99 % throughout the entire experiment. The R2n achieved a higher specific volumetric denitrification rate then R1 since nanofiber carriers enhanced bacterial attachment. This study indicated great potential for further application in petrochemical wastewater treatment.