Special seminar by Dr. Yang Kun-Lin, National University of Singapore.

 

Advanced oxidation processes (AOPs) have been utilized for industrial wastewater treatment, but their high cost limits their application to high-strength wastewater. In addition, no biological treatment processes are currently available for high-strength wastewater due to its high toxicity. Recently, we demonstrated an integrated chemical-biological approach that combines oxidative oligomerization with a simultaneous nitrification-denitrification (SND) process to treat high-strength aniline wastewater, achieving nearly 100% removal efficiency. The process is also highly efficient and cost effective. In the first step, aniline is partially oxidized using hydrogen peroxide (H₂O₂) in the presence of a green catalyst, iron tetra amido macrocyclic ligand (Fe-TAML). This reaction produces insoluble aniline oligomers as well as soluble inorganic nitrogen species such as ammonium (NH₄⁺) and nitrate (NO₃⁻). Microscopic analysis shows that the insoluble aniline oligomer comprises of colloidal particles averaging 890 nm in size. They form a sticky precipitate layer which can be easily separated by decantation. The remaining nitrogen species are subsequently treated biologically using Thauera sp. strain SND5. Before inoculation, the solution contained 28.5 mg/L NH₄⁺ and 40.2 mg/L NO₃⁻. After 48 hours of incubation, these concentrations decreased to 1.6 mg/L and 3.4 mg/L, respectively. After further optimization, we demonstrated this process for the treatment of real high-strength industrial wastewater with great success. This integrated chemical-biological process is environmentally friendly and presents a promising solution for the treatment of high-strength wastewater.