Discoloration and Organic Matter Removal from Coffee Wastewater by Electrochemical Advanced Oxidation Processes

Abstract

The coffee agro-industry generates a large volume of wastewater that is notable for its high organic strength as well as its color content. Due to the seasonal nature of the harvest (3-4 months per year), this particular industrial waste needs a treatment method that is both reliable and fast (in terms of start-up time). As part of investigating a system capable of treating a coffee wastewater, this research evaluated four electrochemical advanced oxidation processes (EAOPs) using boron-doped diamond (BDD) electrodes. The processes were anodic oxidation (AO), anodic oxidation with electrogenerated H 2 O 2 (AO-H 2 O 2 ), electro-Fenton (EF), and photoelectro-Fenton (PEF). Experimental conditions were as follows: 40 mA cm −2 current density (all EAOPs), 0.3 mmol Fe 2+ L −1 (Fenton systems), 300 mL air min −1 (AO-H 2 O 2 , EF, PEF), and 500 μW cm −2 UV irradiation (photo-Fenton systems). The performance of the four EAOP treatment methods (in terms of color and organic carbon removal) was compared against two conventional chemical oxidation methods, namely, Fenton and photo-Fenton. The research indicated that the four EAOPs were better at removing color (89-93 %) and total organic carbon (TOC) (73-84 %) than the respective chemical Fenton (58 and 4.8 %) and photo-Fenton (61 and 7 %) methods. The trend in performance was as follows: AO-H 2 O 2 >AO>PEF≈EF. It appeared that the ferrous iron reagent formed a dark-colored complex with some coffee components, diminishing the effect of Fenton reactions. In addition, the dark color of the wastewater limited the effect of light in the UV-Fenton processes. Analysis showed that acceptable levels of Fe 2+ (0.3 mmol L −1 ) and energy (0.082-0.098 kWh g −1 TOC) were required by the EAOPs after 4-h treatment time. In conclusion, the use of electrochemical methods (equipped with BDD electrodes) seems a promising method for the effective treatment of coffee wastewaters.

Coffee processing wastewater treatment: a critical review on current treatment technologies with a proposed alternative

“…Although the photo-Fenton reaction is very effective for decolorization of coffee eluent, the additional supply of hydrogen peroxide consumed in the process and the control of optimal pH at around 3.0 are drawbacks (Tokumura et al 2006(Tokumura et al , 2008Yamal-Turbay et al 2012;Villanueva-Rodríguez et al 2014).…”

Performance Evaluation of Fenton Based Processes in Reducing COD of the Petroleum Effluents Using the Waste of Steel Slag

“…shown their high potential in removing various contaminants (Villanueva-Rodríguez et al, 2014;Brillas and Martínez-Huitle, 2015;Flores et al, 2016;Steter, Brillas and Sirés, 2016;Komtchou et al, 2017;Moreira et al, 2017;Aveiro et al, 2018;Guelfi et al, 2019;Thiam and Salazar, 2019;Ye et al, 2019). Some studies have investigated the effect of the similar cathode and anode electrode (such as identical electrodes of Na 2 SO 4 (Babuponnusami and Muthukumar, 2012b); graphite electrodes (Nidheesh and Gandhimathi, 2014) and identical BBD electrodes (Villanueva-Rodríguez et al, 2014) in the Fenton based processes and achieved good results.…”

Tratamiento de aguas residuales de la industria del café soluble vía Electrocoagulación - Oxidación Anódica. Selección de los electrodos

“…Recientemente, el proceso de OA ha demostrado alta capacidad para el tratamiento de aguas residuales de diferentes orígenes. Algunos de estos estudios (Subba Rao y Venkatarangaiah, 2018; Fernandes et al, 2015;Villanueva et al, 2014;Cañizares et al, 2009b) han aplicado esta tecnología para oxidar aguas residuales con alto contenido de color, para degradar específicamente alguna de las sustancias constitutivas del efluente proveniente de la producción de café (v.g., melanoidinas, cafeína y polifenoles) o para aguas relacionadas con otros procesos de producción del café (v.g., lavado y despulpado). Sin embargo, en la literatura abierta, hasta el momento no existe reportada una evaluación de la OA como tratamiento específico para las aguas residuales provenientes de la industria de café soluble.…”