Fenton and electro-Fenton treatment for industrial textile wastewater recycling. Comparison of by-products removal, biodegradability, toxicity, and re-dyeing

A comparative study of the results obtained from using Fenton and electro-Fenton processes in textile wastewater treatment is presented. Global indicators, color, COD, TOC, and BOD5 were employed to investigate the treatments. Examination of the representative by-products gave new insights into Fenton. Even though the color removal was higher for classical Fenton (almost 100% color removal) than for electro-Fenton, the overall purification effect was not directly advantageous for Fenton. We found that electro-Fenton removed COD and TOC more efficiently. The biodegradability BI (BOD5/COD) parameter was investigated, where the textile wastewater was hardly biodegradable (BI was 0.12 +/- 0.007). BI of Fenton was also low (0.044 +/- 0.006). ElectroFenton yielded a considerably more promising result, where BI was 0.83 +/- 0.15, and proved more bio-friendly than classical Fenton. Additionally, electro-Fenton was more efficient in by-product removal, especially the naphthalic component, with 90% removal (while Fenton removed 50%). The by-products influenced the after-treatment toxicity assessment of V. fischeri. The EC50 values were below 2% and even lower for electro-Fenton. The results of the color matching parameters (DECMC) of re-dyeing were unacceptable using after-Fenton water at 8.66. DECMC results were between 1.01 and 2.71 after electro-Fenton treatment and had a recycling perspective.