Pilot-scale microaerobic hydrolysis-acidification and anoxic-oxic processes for the treatment of petrochemical wastewater

Abstract

Microaerobic hydrolysis and acidification (MHA), as a promising pre-treatment method of industrial wastewater, is drawing increasing attention to enhance the hydrolysis-acidification rate and inhibit the production of toxic gas H₂S. In the present work, a pilot-scale MHA reactor coupled with anoxic-oxic (A/O) processes for treating the petrochemical wastewater was established and the mechanism and application of the MHA reaction were explored. The results showed that the ratio of VFA/COD was increased by 43–90% and low effluent S²⁻ concentration (less than 0.2 mg/L) was obtained after MHA treatment with 5.5–13.8 L air m⁻³ h⁻¹ supply. The MHA sludge exhibited a good settleability, a higher protease activity and plentiful community diversity. In addition to the dominant anaerobic bacteria responsible for hydrolysis and acidification such as Clostridiales uncultured, Anaerovorax, Anaerolineaceae uncultured and Fastidiosipila, the sulfate reducing bacteria involving Desulfobacter, Desulfomicrobium and Desulfobulbus, the sulphur oxidizing bacteria involving Thiobacillus, Arcobacter and Limnobacter, the nitrifies such as Nitrosomonadaceae uncultured and Nitrospira, and denitrifies Thauera were also identified. MHA pre-treatment guaranteed the efficacy and stability of the following A/O treatment. The removal efficiency of COD and ammonium of the MHA-A/O system remained at around 78.3% and 80.8%, respectively, although the organic load fluctuated greatly in the influent. Graphical abstract