Advanced treatment of dye manufacturing wastewater by electrocoagulation and electro-Fenton processes: Effect on COD fractions, energy consumption, and sludge analysis

Abstract

This study investigated chemical oxygen demand (COD), color number (CN), and UV254 removal from dye manufacturing wastewater via electrocoagulation (EC) and electro-Fenton (EF) processes. The effects of current density, initial pH, reaction time, and H2O2/COD ratio on the EC and EF processes were evaluated and optimum operating conditions were determined. The effects of EC and EF processes on COD fractions and the specific energy consumption of both processes were evaluated. Sludge analyses were conducted by organic removal to sludge ratio (ORSR) and Fourier Transform Infrared Spectroscopy spectra were assessed for characterization of generated sludge. Optimum operation conditions for the EC process were 21 mA/cm2 current density, 7.3 initial pH, and 25 min reaction time while they were 21 mA/cm2 current density, 3.5 initial pH, 1.25 H2O2/COD ratio, and 35 min reaction time for EF process. Under optimum conditions COD, CN, and UV254 removal efficiencies were 38.5%, 90.1%, and 52.5%, respectively in EC process and 54.8%, 94.2%, and 88.1%, respectively in EF process. Both processes have a positive effect on the increase of biodegradable and soluble COD fractions. Higher ORSR and lower specific energy consumption were provided by the EF process under optimum conditions. The EF process is more effective when pollutant removal efficiencies, ORSR, and specific energy consumption are considered.