OPTIMIZATION OF THE SELF-BIOREMEDIATION PROCEDURE OF INDUSTRIAL CORK WASTEWATERS AND PRELIMINARY ASSESSMENT OF THE TOXICITY OF THE FINAL RESIDUE

Cork-boiling wastewaters are rich in phenolic compounds and have traditionally been remediated by chemical techniques. An alternative treatment, based on microbial bioremediation, is being developed. The objective of this work was to design and optimize an effective self-bioremediation system to treat polluted cork wastewater. Polyphenol tolerant cultivable bacteria were isolated from this effluent. The strains, identified by 16S rDNA, include Acinetobacter sp., Staphyloccocus sp., two Microbacterium spp. and Bacilllus sp., that were able to tolerate up to 15mM of phenol, and up to 1mM and 0.1mM of 4-chlorophenol and 2,4-dichlorophenol, respectively, using the pollutant as the sole carbon source. Degradation assays were performed using Acinetobacter sp. and the consortium formed by the five selected strains immobilized onto residual cork particles. Addition of low levels of carbon, together with micromolar concentrations of H2O2 in the presence of light were the optimal conditions for phenol removal. Under these conditions, the consortium was able to degrade more than 60% of initial phenol from cork wastewater in 10 days. The post-removal solution was tested for its toxicity applying a toxicity test based on the germination of Medicago sativa seeds. Results suggested that the treated solution was less toxic than the parent solution. Thus, self-bioremediation seems to be a promising eco-friendly technology that allows the treatment of cork boiling wastewater with low costs and the absence of collateral impacts.