Electrochemical Oxidation of Effluents from Food Processing Industries: A Short Review and a Case-Study

Abstract

A short review on the treatment of effluents from food processing industries by electrochemical oxidation (EO) was performed. Olive mill wastewater (OMW) and boron-doped diamond (BDD) are the most reported effluent and anode material, respectively. The addition of NaCl or Na2SO4 as supporting electrolytes is common in these studies, and their influence on the EO performance depends, among other things, on the anode material, since the electrolyte oxidation mechanism is different when active and non-active anode materials are utilized. A case-study on the application of a pilot plant, working in batch mode with recirculation, equipped with a BDD anode, to treat 4 L of OMW, slaughterhouse (SW) and winery (WW) wastewaters, with initial chemical oxygen demands (COD) of 20.5, 3.6 and 0.26 g L−1, respectively, is presented and discussed. In 16 h assays, 94% COD removal was achieved for OMW, and for SW and WW the Portuguese COD legal discharge limit of 150 mg L−1 was accomplished. Process efficiency decreased for lower organic load. NaCl addition increased COD removal in SW and WW, but presented an adverse effect for OMW COD removal, when compared to Na2SO4 addition. Nevertheless, lower specific energy consumptions were attained in chloride medium (48 Wh (g COD)−1).

Reuse of Pretreated Agro-Industrial Wastewaters for Hydroponic Production of Lettuce

“…The CNS, formulated according to Almeida et al [20], was prepared with groundwater and the following commercial fertilizers: 510 mg L −1 Ca(NO 3 ) 2 , 480 mg L −1 KNO 3 , 300 mg L −1 KH 2 PO 4 , 80 mg L −1 MgSO 4 , and 1.5 mL L −1 of NPK 3-8-11 fertilizer solution (Tecnifol). The Larson-Skold index (LSI) was determined according to Equation (3). Although the microbial characterization of the diluted pretreated samples was not performed, it is known from previous studies that lime precipitation leads to the complete elimination of coliforms, and, thus, the treated wastewaters pose a low risk of pathogen contamination [6,21].…”

“…When considering AIWW treatment options, two determining factors must be considered: the AIWW composition and characteristics and the intended quality of the treated effluent. Several different treatment technologies have been applied to AIWWs, such as physicochemical and biological processes, constructed wetlands, advanced oxidation processes, including electrochemical processes, and membrane technologies [1,[3][4][5]. Among the different processes described in the literature for AIWW treatment, immediate onestep lime precipitation (IOSLP) is presented as a simple and economic process that can be used to obtain, in a fast and efficient way, a clarified and disinfected effluent, rich in nutrients and with very low content in heavy metals, apparently capable of being reutilized for agricultural purposes [6].…”

Electrochemical Recovery of Phosphorus from Simulated and Real Wastewater: Effect of Investigational Conditions on the Process Efficiency

“…A COD removal of 22% was attained. Although it is not a remarkable removal, the treatment time was just 1 h. Since the objective was to recover phosphorus, it was not worth extending the treatment time to reach higher COD removal, as this can be performed in a secondary electrochemical treatment, without magnesium consumable anodes [62]. A COD removal of 22% was attained.…”

Phytoremediation as a Sustainable Alternative for Organic Matter Removal From Slaughterhouse Wastewater Pretreated by Immediate One-Step Lime Precipitation

“…Activated sludges have considerable energy consumption and are poorly tolerant to load and flow variations [5]. In this way, different SWW treatment processes have been investigated, namely chemical (e.g., electrochemical oxidation [6],…”