An integrated chemical-biological treatment process for aniline using green oxidation and simultaneous nitrification-denitrification (SND) bacteria

Aniline is widely used in chemical industries, producing wastewater that poses significant risks to our environment. However, developing an efficient, cost-effective and sustainable solution for treating aniline wastewater remains a significant challenge. In this study, we present an integrated chemical-biological approach that combines advanced oxidation processes (AOPs) with a simultaneous nitrification-denitrification (SND) process to treat high-strength aniline wastewater with nearly 100% removal efficiency. In the first step, aniline is oxidized by using H 2 O 2 in the presence of a green catalyst, iron tetra amido macrocyclic ligand (Fe-TAML). This reaction produces insoluble aniline oligomers (as solid precipitates) and soluble inorganic nitrogen species such as ammonium (NH₄ + ) and nitrate (NO₃ − ). Microscopic analysis reveals that the solid precipitate consists of uniform colloidal particles with an average size of 893 nm. The precipitate can be separated from the solution easily by decantation. The remaining nitrogen species in the solution can be denitrified by using Thauera sp. strain SND5, provided that sodium acetate is added as a carbon source at a carbon-to‑nitrogen (C/N) ratio of 8. After 48 h of incubation, the NH 4 + and NO 3 − concentrations decreased from 28.5 mg/L and 40.2 mg/L to 1.6 mg/L and 3.4 mg/L, respectively. As a proof of concept, the process was also applied to treat a real industrial wastewater sample containing 950 mg/L of aniline. At the end, 100% of aniline and 82.8% of total nitrogen (TN) were removed. This integrated chemical-biological process is potentially useful for the treatment of high-strength aniline wastewater which cannot be treated by using traditional chemical or biological methods. It also demonstrates the possibility of combining AOPs with a denitrification process which does not require an anaerobic condition. • The integrated chemical/biological process achieved nearly 100% aniline removal from wastewater. • Oxidation of aniline produces insoluble aniline oligomers and inorganic nitrogen species (NH 4 + and NO 3 − ) at pH 8. • Thauera sp. SND5 removes NH 4 + and NO 3 − with the addition of acetate. • The integrated process was successfully applied to real industrial wastewater.