Detoxification of Olive Mill Wastewaters by Fenton’s Process

Abstract

Olive mill wastewaters (OMW) constitute an environmental problem affecting mainly Mediterranean Sea area countries where the olive mill industry is a very important economic sector. The strong impact and management issues of these effluents are mainly due to their seasonality, localized production, and high organic load with high toxic features and low biodegradability. As the olive oil industry is highly water demanding, the search for suitable water recovery strategies requires the development and optimization of advanced treatment technologies. The classical Fenton’s process is an interesting alternative, as it operates at room conditions of pressure and temperature. However, it shows some drawbacks, such as the generation of iron sludges, which require further management. Nevertheless, because of its features that make it industrially desirable, overcoming these limitations has been the focus of researchers in the last years. Bearing this in mind, this paper focuses on the recent research regarding OMW treatment using Fenton’s process. The use of Fenton’s peroxidation treatment at homogenous, heterogeneous, and photo-aided conditions is analysed. The use of solid catalysts may be an interesting way to avoid sludge formation. Light-driven Fenton can also reduce the amount of iron needed for effective degradation. Moreover, Fenton’s process integration in combined treatment schemes is discussed. Finally, remarks regarding its application at full scale are given.

Catalytic Efficiency of Red Mud for the Degradation of Olive Mill Wastewater through Heterogeneous Fenton’s Process

“…On the other hand, 3,4-dihydroxybenzoic acid has two hydroxide groups which unprotect the benzene ring making it readily reactive with hydroxyl radicals. In fact, at the beginning of the reaction, a high amount of hydrogen peroxide and iron (II) should be available to react and produce hydroxyl radical, according to Equation (4) [4].…”

“…In this sense, the optimization of the quantity used must be carefully carried out. Above the optimum concentration, hydrogen peroxide can scavenge hydroxyl radicals leading to the reduction of the process efficiency [4].…”

“…OMW can be characterized by high pollutant load (g L −1 ): chemical oxygen demand(COD) 45-180, biochemical oxygen demand (BOD 5 ) 25-100, total solids 24-120, mineral solids 5-15, total phenolics 2-15, fat 0.5-1.0 and pH 4.0-5.2 [3]. The treatment of those effluents is a priority to environmental preservation and water recovery [4]. The most common treatments are based on biological reactors, but they are not efficient when applied to OMW due to the presence of toxic compounds [5,6].…”

Study of the Degradation of Trimethoprim Using Photo-Fenton Oxidation Technology

“…The main disadvantage of photo-Fenton technology is the need for removing the dissolved iron from the treated sewage. At present, after oxidation treatment, the wastewater is treated by alkalization to form insoluble Fe(OH) 3 , which is precipitated in the form of iron sludge [11,12].…”

Decreasing COD in Sugarcane Vinasse Using the Fenton Reaction: The Effect of Processing Parameters

“…The Fenton oxidation mechanism generates hydroxyl radicals ( • OH) from the catalyzing reaction between ferrous or ferric ion (Fe 2+ /Fe 3+ ) and hydrogen peroxide (H 2 O 2 ) under acidic conditions (pH 2-6). The overall reactions of the Fenton process are as presented in the following equations [11,12]: •OH + organics → products (8) The Fenton reaction has been used to reduce the organic load or toxicity of different wastewaters, for example, from the chemical industry, textile, pharmaceutical, paper pulp, and olive mills [13][14][15][16]. Some researchers also have applied the Fenton reaction for vinasse treatment in their experiments, such as de Heredia [2] and Guerreiro [17].…”