Enhanced Phenol and Chlorinated Phenols Removal by Combining Ozonation and Biodegradation

Water treatment for wastewater containing phenols and their chlorinated variations has attracted important research efforts. Phenol's high toxicity makes them a good model to test possible water treatment based on biological and/or chemical methods. High concentrations of phenols may be treated by pure biological schemes. However, chlorinated phenols are very toxic for many microorganisms. Therefore, mixed treatment trains can be proposed to solve the treatment of this class of organics. In this study, the ozonation was used as pretreatment to decompose chlorinated phenols. Besides, this study describes how the microbial consortiums were adapted to handle ozonation by-products. The biodegradation of different phenol concentrations from 50 to 1,500 mg/L was evaluated using preadapted microbial consortia in batch and in a trickling packed-bed reactor (TPBR). Under batch conditions, phenol was efficiently removed up to 500 mg/L. For every phenol concentration evaluated, higher degradation rates were obtained in TPBR. The chlorophenols were found to be poorly degraded by the pure biological treatment, 4-CPh was not degraded during the biological process and 2,4-DCPh was only 40 % degraded after 250 h of culture. By combining the chemical (as pretreatment) and the biological processes, 85 % of 4-CPh was removed, while the degradation of the 2,4-DCPh was enhanced from 40 to 87 %. The predominant bacteria found in the preadapted cultures were Xanthomonas sp., Ancylobacter sp., and Rhodopseudomonas. Total treatment period was reduced from several weeks to some days. This information reflects the benefits offered by the mixed water treatment train proposed in this paper.