Optimisation of Fe2+/H2O2 ratio in Fenton process to increase dewaterability and solubilisation of sludge

Fenton is one of the advanced oxidation processes that can oxide organic compounds efficiently increasing the dewaterability of sludge. This study reports the optimisation of two reagents, Fe2+ and H2O2, involved in the Fenton process in order to increase sludge dewaterability and solubilisation, which were evaluated in terms of SRF, CST and DS. The study was divided into two sets of tests. First the optimal ratio Fe2+/H2O2 was set varying from 0.5–2.0. Results showed that the best Fe2+/H2O2 was equal to 0.8 corresponding to 2.1 s of CST, 2.1·1013 m kg−1 of SRF and 3.1% of DS. In the second set of tests, the Fe2+/H2O2 ratio was maintained fixed to 0.8 while the concentration of reagents was decreased up to 98% in order to verify the efficiency of the process. Results showed that performing Fenton process with a concentration of H2O2 and Fe2+ of, respectively, 6000 and 5000 mg L−1 the SRF and CST could be reduced up to 88% and 76%, respectively, and a DS equal to 3.1% could be obtained. A reduction in the Fenton reagents down to 300 and 250 mg L−1, respectively, for H2O2 and Fe2+ showed a little decrease in efficiency of the process. However, the Fenton process could be still performed thus obtaining an economic saving.