Fenton oxidation for the treatment of liquid waste with high COD and anionic-non-ionic surfactants

In the present work, liquid wastes from different kinds of industrial plants, characterized by high COD (up to 100,000 mg/L) and surfactants (up to 16,000 and 3,800 mg/L for non-ionic and anionic respectively) concentrations were treated by means of Fenton oxidation. During the experimental research 28 tests at laboratory scale were performed. Each test was characterized by specific dosage of reagents (Fe2+ and H2O2 ) and contact time. In particular, Fe2+/H2O ratio varied from 0.25 to 0.50, H2O2/COD ratio from 0.72 to 1.5 while the contact time increased from 30 to 120 minutes. The main objective of this work was to define the dosage of reagents and the reaction contact time able to optimize the process performance in terms of removal yields of COD and surfactants. The results showed that the optimal treatment conditions could be obtained with a Fe2+/H2O2 ratio equal to 0.25, a H2O2/COD ratio of 1 and a reaction time of 30 minutes. An average removal yield of 70% for AS (non-ionic surfactants) and COD and 95% for MBAS (anionic surfactants) respectively was obtained.