Biodegradability and toxicity assessment of a real textile wastewater effluent treated by an optimized electrocoagulation process

Abstract

In this work, the application of an iron electrode-based electrocoagulation (EC) process on the treatment of a real textile wastewater (RTW) was investigated. In order to perform an efficient integration of the EC process with a biological oxidation one, an enhancement in the biodegradability and low toxicity of final compounds was sought. Optimal values of EC reactor operation parameters (pH, current density and electrolysis time) were achieved by applying a full factorial 3³ experimental design. Biodegradability and toxicity assays were performed on treated RTW samples obtained at the optimal values of: pH of the solution (7.0), current density (142.9 A m⁻²) and different electrolysis times. As response variables for the biodegradability and toxicity assessment, the Zahn–Wellens test (D_t), the ratio values of dissolved organic carbon (DOC) relative to low-molecular-weight carboxylates anions (LMCA) and lethal concentration 50 (LC₅₀) were used. According to the D_t, the DOC/LMCA ratio and LC₅₀, an electrolysis time of 15 min along with the optimal values of pH and current density were suggested as suitable for a next stage of treatment based on a biological oxidation process.

Keywords:

• textile wastewater
• electrocoagulation
• experimental design
• biodegradability
• toxicity

Acknowledgments

This work was supported by projects PEst-C/EQB/LA0020/2013 and NORTE-07-0162-FEDER-000050, financed by FEDER through COMPETE - Programa Operacional Factores de Competitividade, by FCT – Fundação para a Ciência e a Tecnologia and by QREN and ON2. We also would like to thank the Araucaria Foundation-BR, CNPq-BR and CAPES-BR (BEX 9794/11-5 and 5512/10-7 processes) for financial support for this study. V.J.P. Vilar acknowledges the FCT Investigator 2013 Programme (IF/01501/2013).