Coagulation-Fenton coupled treatment for ecotoxicity reduction in highly polluted industrial wastewater

A coupled coagulation-Fenton process was applied for the treatment of cosmetic industry effluents. In a first step, FeSO4 was used as coagulant and the non-precipitated Fe2+ remaining in dissolution was used as catalyst in the further Fenton process. In the coagulation process a huge decrease in total organic carbon (TOC) was achieved, but the high concentration of phenol derivatives was not diminished. The decrease in TOC in the coagulation step significantly reduces the amount of H2O2 required in the Fenton process for phenol depletion. The coupled process, using a H2O2 dose of only 2 g l−1, reduced TOC and total phenol to values lower than 40 and 0.10 mg l−1, respectively. The short reaction period (less than 15 min) in TOC and phenol degradation bodes well for improving treatment in a continuous regime. The combination of both processes significantly reduced the ecotoxicity of raw effluent and markedly increased its biodegradability, thus allowing easier treatment by the conventional biological units in conventional sewage treatment plants (STPs).