Degradation of di-, tri-, tetra-, and pentachlorophenol mixtures in an aerobic biofilter

Chlorophenols are highly toxic xenobiotic compounds, normally found in the effluents of many industries. Due to the high toxicity of these compounds, it is difficult to treat effluent streams containing high concentrations of chlorophenols. The aim of this work is to demonstrate the capabilities of an aerobic submerged filter previously characterized in the degradation of phenol and chlorophenols in the treatment of highly toxic di-, tri-, tetra- and penta- chlorophenols mixtures (200 - 800 mgL ^-1 as total phenols concentration). It is shown that the system is capable of treating up to 600 mgL ^-1 of total chlorophenols with excellent reduction values, and biodegradation rates (BDRs) between 87 - 97%, and 34 - 157 mgL ^-1 day ^-1, respectively (total organic carbon, TOC degradations up to 80%). In the case of the 800 mgL ^-1, a strong inhibition due to the high toxicity of the mixture was observed. The system reduced the influent toxicity (EC50 or toxic units) by 48 - 76%, even when the initial toxicities of the mixtures were in the range of 40 - 358 toxic units (classified as very toxic). The kinetics of the phenol and TOC degradation were characterized through a first order kinetic expression. The values of TPh _o, TOC _o, k ₁ and k ₂ are reported for the biodegradation of the total phenols and for the TOC, respectively. A system with powerful capabilities in the treatment of industrial streams, contaminated aquifers or accidentally contaminated municipal wastewaters containing high quantities of chlorophenols, is described.