Application of intensified Fenton oxidation to the treatment of sawmill wastewater Macarena Munoz ⇑ , Gema Pliego, Zahara M. de Pedro, Jose A. Casas, Juan J. Rodriguez Ingenieria Quimica, Universidad Autonoma de Madrid, Crta. Colmenar km 15, 28049 Madrid, Spain highlights  The intensified Fenton process represents a cost-effective alternative for sawmill wastewater treatment.  Increasing temperature to 120 °C and feeding H 2 O 2 in 3 additions improved the H 2 O 2 consumption efficiency.  High COD (80%) and TOC (70%) removal were achieved after 1 h reaction time.  Fungicides were completely removed obtaining short-chain organic acids as main products. graphical abstract article info Article history: Received 27 November 2013 Received in revised form 24 February 2014 Accepted 25 February 2014 Handling Editor: O. Hao Keywords: Fenton process intensification Sawmill wastewater Wood preservative Ecotoxicity abstract The application of the Fenton process for the treatment of sawmill wastewater has been investigated. The sawmill wastewater was characterized by a moderate COD load (3gL 1 ), high ecotoxicity (40 toxicity units) and almost negligible BOD/COD ratio (5  10 3 ) due to the presence of different fungicides such as propiconazole and 3-iodo-2-propynyl butyl carbamate, being the wastewater classified as non-biode- gradable. The effect of the key Fenton variables (temperature (50–120 °C), catalyst concentration (25–100 mg L 1 Fe 3+ ), H 2 O 2 dose (1 and 2 times the stoichiometric dose) and the mode of H 2 O 2 addition) on COD reduction and mineralization was investigated in order to fulfill the allowable local limits for industrial wastewater discharge and achieve an efficient consumption of H 2 O 2 in short reaction times (1 h). Increasing the temperature clearly improved the oxidation rate and mineralization degree, achiev- ing 60% COD reduction and 50% mineralization at 120 °C after 1 h with the stoichiometric H 2 O 2 dose and 25 mg L 1 Fe 3+ . The distribution of H 2 O 2 in multiple additions throughout the reaction time was clearly beneficial avoiding competitive scavenging reactions and thus, achieving higher efficiencies of H 2 O 2 consumption (X COD  80%). The main by-products were non-toxic short-chain organic acids (acetic, oxalic and formic). Thus, the application of the Fenton process allowed reaching the local limits for industrial wastewater discharge into local sewer system at a relatively low cost. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Wood is an important natural resource widely used as raw material for cellulose pulp, furniture and tools, among others. Sawmills generate relatively low amounts of wastewater (Taylor http://dx.doi.org/10.1016/j.chemosphere.2014.02.062 0045-6535/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +34 91 497 3991; fax: +34 91 497 3516. E-mail address: macarena.munnoz@uam.es (M. Munoz). Chemosphere 109 (2014) 34–41 Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere