AOX removal from industrial wastewaters using advanced oxidation processes: assessment of a combined chemical-biological oxidation

In this paper, the abatement of adsorbable halogenated organic compounds (AOX) from an industrial wastewater containing relatively high chloride concentrations by a combined chemical and biological oxidation is assessed. For chemical oxidation, the O-3/UV, H2O2/UV and photo-Fenton processes are evaluated on pilot scale. Biological oxidation is simulated in a 4 h respirometry experiment with periodic aeration. The results show that a selective degradation of AOX with respect to the matrix compounds (expressed as chemical oxygen demand) could be achieved. For O-3/UV, lowering the ratio of O-3 dosage to UV intensity leads to a better selectivity for AOX. During O-3-based experiments, the AOX removal is generally less than during the H2O2-based experiments. However, after biological oxidation, the AOX levels are comparable. For H2O2/UV, optimal operating parameters for UV and H2O2 dosage are next determined in a second run with another wastewater sample.