Detoxification of waters contaminated with phenol, formaldehyde and phenol-formaldehyde mixtures using a combination of biological treatments and advanced oxidation techniques

摘要

The detoxification process of waters contaminated with phenol, formaldehyde and phenol-formaldehyde mixtures was studied using advanced oxidation treatments (heterogeneous photocatalysis and Fen-ton), biological techniques (aerated biological and wetland reactors) and combinations of the two. It is shown that photocatalysis was efficient in the detoxification of concentrations below 50 mg L~(-1) of those compounds. Sample toxicity increased at higher concentrations due to the generated intermediates. Phenol-formaldehyde mixtures were impossible to detoxify by heterogeneous photocatalysis at any of the studied concentrations. Treatments using the Fenton reaction were able to degrade concentrations above 1000mg L~(-1), though the use of a reagent such as peroxide makes it a costly technique. The efficiency of the biological aerated filter (BAF) mainly depended on initial concentration and toxicity, with removal rates of 3.08 and 0.26 g L~(-1) d~(-1) obtained for phenol and formaldehyde, respectively. Taking into account the results obtained for the treatment of complex phenol-formaldehyde mixtures, the best combination of techniques for the treatment of concentrations found in the industrial wastewater studied in this paper was the Fenton + BAF technique which was able to detoxify phenol-formaldehyde concentrations (1:1) of 1000 mg L~(-1).