Denim is a cotton fabric specifically used to manufacture jeans. Denim processing generates complex effluents with high levels of pumice stone, color and chemical oxygen demand (COD). There is therefore a need for advanced treatment methods to limit pollution of natural waters. Here, we hypothesized that Fenton oxidation, a method using Fe2+ and H2O2, could replace the traditional step of activated sludge treatment. We studied a daily composite sample at laboratory scale for preliminary settling, chemical settling and Fenton oxidation. We found that pumice stone can be effectively controlled by preliminary settling with partial COD removal and limited color removal. Chemical treatment improved COD removal, but color reduction still remained partial. Fenton oxidation decreased color below visual detection after 5 min and COD decreased to 110 mg/L after 30 min. These findings surpassed the performances of activated sludge treatment.