Biodegradation of Bromobenzene, Chlorobenzene, Iodobenzene and Fluorobenzene: Batch and Continuous Experiments

Abstract

Many pharmaceutical industry processes use halogenated aromatics, other than chlorinated, as solvents or starting materials, and these can often exhibit inhibitory effects affecting normal process operation of biological Wastewater Treatment Plants (WWTPs). A mixed culture, initially selected for growth at the expense of chlorobenzene as the sole source of carbon and energy, was enriched with a mixture containing bromobenzene, chlorobenzene, fluorobenzene and iodobenzene. After three weeks of continuousoperation in a stirred tank bioreactor, none of these halogenated compoundswere detected in the growth medium. The complete mineralization of each of the compounds with concomitant release of stoichiometric amounts of halide was then investigated individually in batch experiments. Mineralization of chlorobenzene, bromobenzene and iodobenzene up to their maximum solubility level (in minimal salts media) was achieved, while fluorobenzene was not biodegraded but simply volatilized.The complete mineralization of iodobenzene up to 150mg l −1 (in 18 hours) with complete recovery of iodide is particularly interesting since published literature shows no previous report of similar results. Preliminary characterization has shown that the cultures responsible for iodobenzene and bromobenzene biodegradation are strains of Pseudomonas putida .