We compared two H 2 O 2 oxidation methods for the treatment of industrial wastewater: oxidation using Fenton's reagent [H 2 O 2 /Fe(II)] and microwave irradiation. Both methods were applied to the treatment of synthetic phenol solutions (100 mg L −1 ) and of an industrial effluent containing a mixture of ionic and non-ionic surfactants at high load (20 g L −1 of COD). The effects of initial pH, initial H 2 O 2 concentration, Fenton catalyst amount and irradiation time were assessed. According to the oxidation of phenol, it has been found that the oxidation by Fenton's reagent is dependent on the pH, contrary to the microwave system, which is not influenced by this parameter. For both systems, a limiting amount of oxidant has been found; above this point the oxidation of phenol is not improved by a further addition of peroxide. The oxidation of the industrial surfactant effluent has only been successful with the Fenton's reagent. In this case, large amounts of ferrous ions are necessary for the precipitation of the ionic surfactants of the effluent, followed by the oxidation of the non-ionic constituents of the solution.

This study investigates the environmental quality of water treatments by evaluating the effectiveness of advanced oxidation technologies, such as H2O2/Fe(II) and H2O2/UV, in treating phenol-contaminated effluents. Toxicity measurements complement the chemical analyses used to evaluate the environmental quality of a treated effluent and are an additional method for interpreting the effects of chemicals not directly measured. This study proposes an estimation model for toxicity based on the Microtox test that is adaptable to the contaminant concentration of each case. The model allows for analysis of the contribution of the different components of the treated effluent: hydrogen peroxide, phenolics, colored compounds, and others. In the second part of this work, a study was conducted of the toxicity of samples treated with the aforementioned oxidative systems. In the Fenton system, the sample after oxidation was analyzed, and it was observed that the toxicity was due to intermediate oxidation compounds, such as carboxylic acids, which rejects the influence of compounds of color and other phenolics. The H2O2/UV system tracks the progress of toxicity. This parameter quickly reaches minimum values (within about 15 min) from the start of the reaction and is a representation of the final values of primary degradation. Therefore, it is not recommended to extend the oxidation beyond this point to minimize the toxicity.

This paper describes a laboratory study conducted to elucidate the possibility of treating high loaded solutions of surfactants through an Advanced Oxidation Process. Synthetic solutions of linear alkylbenzene sulfonates are treated in this work as this is a model compound commonly used in the formulation of detergents, with a great presence in urban and industrial waste-waters. The application of UV combined with hydrogen peroxide to oxidise a surfactant effluent is shown to be suitable as a primary oxidation step since conversions of around 50% of the original compound are achieved in the most favourable cases. Initially, the influence of the operating variables on the degradation levels is analysed in this work. A kinetic model that takes into account both the contributions of direct photolysis and radical attack is also worked out. Direct photolysis is performed to determine the quantum yield in the single photodecomposition reaction. Additionally, the rate constant of the reaction between hydroxyl radicals and LAS in the oxidising system H2O2/UV is determined for different operational conditions. Finally, the contribution of each oxidation pathway is quantified; a higher contribution of the radical reaction than that of the direct photolysis was found in all cases.