Implementation of fluidized-bed Fenton as tertiary treatment of nitro-aromatic industrial wastewater

Abstract

In this study, the fluidized-bed Fenton (FBF) process was evaluated as a tertiary treatment of the second effluent from a nitro-aromatic industrial wastewater treatment plant. The soluble iron removal performances of four carriers, including quartz sand, construction sand, activated carbon, and zeolite, were examined. For the carriers, the results showed that a large surface area was available for the iron removal due to the heterogeneous nucleation, while a smooth surface contained less mesoporous seemed favorable for the consecutive iron removal because of the brittle iron oxide thickness and wash off effect. The essential variables for analysis include the initial pH and the molar ratio of [Fe2+]/[H2O2]. The results showed that the COD and SUVA254 removal efficiencies, including the utilization ratio of H2O2 on COD removal, had little difference with the increase of initial pH, suggesting that the adaptive pH range of FBF can extend from 2.5 to 7.4. However, high pH caused iron removal via homogeneous nucleation not by heterogeneous nucleation, resulting in the reduction. Under the sufficient H2O2 addition, the removal performances improved when the molar ratio of [Fe2+]/[H2O2] increased to 0.625, but a high iron addition led to a negative effect on iron removal due to the resolvable phenomenon by excess H2O2. An actual engineering project illustrated that FBF progress was a useful and cost-effective method for tertiary treatment.