Coupled continuous-flow ozonation and biodegradation system for the mineralization of a mixture of phenolic compounds

abstract

This study investigates the mineralization of a mixture of phenolic compounds¿phenol (Ph), 4-chlorophenol (4-CPh), and 2,4-dichlorophenol (2,4-DCPh)¿ using a combined ozonation¿biodegradation treatment in a continuous-flow multistage system. Each compound (at 120 mg L¿1) and its mixture (containing 40 mg L¿1 of each) were treated through continuous ozonation. Although the complete removal of phenols (Phs) was achieved, total organic carbon (TOC) removal ranged from 27 % to 47 %, with oxalic acid identified as the main by-product. Before establishing the final operational conditions, four ozone doses (between 4.3 and 34 mg O3 mg¿1 TOC) were tested as a pre-treatment to evaluate the effectiveness of ozonation in reducing the toxicity of the Phs mixture prior to subsequent biodegradation. A dose of 17 mg O3 mg¿1 TOC achieved 97 % global mineralization. The coupled system operated with a hydraulic retention time of 60 min (for the ozonation stage), an ozone dose of 16.3 mg O3 mg¿1 TOC, and a flow rate of 0.868 mL min¿1 (for the biodegradation stage) into a 4 L bioreactor, achieving 96 % overall mineralization. The high biodegradation efficiency was attributed to the microbial community within the pre-adapted consortium, which displayed cooperative interactions among genera capable of degrading halogenated compounds and organic acids. These included Afipia , Variovorax , Pseudomonas , Rhodopseudomonas , Achromobacter , Ochrobactrum , Shinella , Ancylobacter , and Mesorhizobium , among others. The reuse of the treated water as an influent diluent was also examined, showing TOC removal comparable to that of undiluted water. This integrated treatment approach demonstrates high potential for effective contaminant removal and water reuse, supporting sustainable water resource management. © 2025 Elsevier Ltd.