Integrated anaerobic‐aerobic process for the biodegradation of chlorinated aromatic compounds

An integrated anaerobic‐aerobic process for the complete mineralization of 2,4,6‐trichlorophenol (used in this work as the model toxic halogenated aromatic compound to degrade) was successfully tested and operated. The sludge obtained from the anaerobic digester of a commercial treatment plant was used to obtain an anaerobic consortium capable of partially dechlorinating 2,4,6‐trichlorophenol (2,4,6‐TCP). The clarified and sterilized effluent from the same anaerobic digester was used as the medium for the anaerobic consortium. During the anaerobic process 2,4,6‐TCP was first dechlorinated to 2,4‐dichlorophenol and then to 4‐chlorophenol (4‐CP). Stoichiometric amounts of 4‐CP were recovered. Similar results were obtained when the anaerobic microorganisms were immobilized on Manville R‐635 silica beads. After immobilization, the consortium was able to dechlorinate 150 μM of 2,4,6‐TCP in four days. Pseudomonas Glathei and an indigenous culture obtained from same sludge used to produce the anaerobic enrichment culture were shown to be able to degrade the 4‐CP produced from the anaerobic dechlorination of 2,4,6‐TCP. However, for the aerobic 4‐CP mineralization to occur the medium had to be buffered with phosphate, since high pH would inhibit the aerobic bacterial activity. It is expected that the proposed approach will be used to treat recalcitrant halogenated compounds that are not amenable to conventional biological treatment.