Fe-Ni catalytic micro-electrolysis coupled with biological aerated filter for 2,4,6-trinitrotoluene production wastewater treatment

Abstract

Fe-Ni catalytic micro-electrolysis coupled with biological aerated filter was studied for 2,4,6-trinitrotoluene production wastewater treatment. In this study, Fe-Ni catalytic micro-electrolysis reactor and biological aerated filter were utilized as the possible pretreatment and secondary biological treatment process, respectively. The results reveal that the Fe-Ni catalytic micro-electrolysis reactor could effectively remove majority of nitroaromatics by catalytic reduction effect and some chemical oxygen demand in the wastewater by catalytic oxidation effect. Disappearance of both nitroaromatics and chemical oxygen demand followed first-order kinetics and 2,4,6-trinitrotoluene appeared to have a higher preference for the filler surface than 2,4-dinitrotoluene and 2,5-dinitrotoluene according to the rate constants k′ (h−1, 0.6379 for 2,4,6-trinitrotoluene, 0.4089 for 2,4-dinitrotoluene, and 0.3949 for 2,5-dinitrotoluene), and thereby was degraded first. Additionally, biological aerated filter could effectively degrade the chemical oxygen demand residue in effluent from the Fe-Ni catalytic micro-electrolysis reactor, suggesting great improvement of the wastewater biodegradability by the Fe-Ni catalytic micro-electrolysis pretreatment. Finally, about 98% of nitroaromatics, 93% of chemical oxygen demand and 97% of chroma could be removed by the coupled system of Fe-Ni catalytic micro-electrolysis and biological aerated filter at the optimum hydraulic retention time of 6.0 h for Fe-Ni catalytic micro-electrolysis reactor and 18.0 h for biological aerated filter, and the final effluent met the requirement of the national discharge standard (GB 14470.1–2002, nitroaromatics concentration ≤ 5.0 mg L−1, chemical oxygen demand ≤100 mg L−1, chroma ≤50).