Treatment of Eucalyptus chemical-mechanical pulp wastewater by coupling system of advanced catalytic oxidation and biodegradation: Synergistic effect of ozonation photocatalytic-microbial

Abstract

In addressing the issues concerning the challenging treatment, extensive discharge, substantial organic pollution load, and the intricate composition of chemical-mechanical pulp (CMP) wastewater in the pulp and paper industry, an innovative coupled advanced oxidation and biodegradation techniques known as the intimate coupling of ozone oxidation and photocatalysis-biological treatment (ICOPB) was developed for CMP wastewater remediation. The focus of the present research was to explore the optimization of this system, to comprehend the degradation mechanisms, and to understand microbial reaction behavior. Moreover, the study evaluated the degradation efficiency of four potential mechanisms inherent to ICOPB, which include adsorption, photocatalysis, biological treatment, and coupled photocatalytic-biological indirect wastewater treatment. Under the optimal conditions, wherein the O3 concentration was maintained at 35 mg/min, the carrier filling rate was kept at 5 %, pH was held at 7, and aeration was kept at 0.6 L/min, the degradation efficiencies for COD, BOD, and TOC reached 80.7 %, 91.6 %, and 84.6 %, respectively. When compared with the ICOP (intimate coupling of ozone oxidation and photocatalysis) procedure, the ICOPB demonstrates a superior removal efficiency and more comprehensive mineralization. Microbial diversity results indicated that Proteobacteria actively contribute to the subsequent biodegradation of CMP wastewater treated with the ICOPB system. As revealed by the GC–MS analysis and toxicity assessments of intermediate products, ICOPB notably amplified the rate of organic matter degradation and concurrently reduced the toxicity of the effluents. In conclusion, the findings of this research offer an innovative method for the effective degradation of CMP wastewater, thereby addressing a significant environmental concern in the pulp and paper industry.