Research On Treatment For Tannery Wastewater By Fenton-fluidized Bed

Tannery wastewater was one of the main industrial pollution sources for its high contaminant concentrations. Since the pollutions in tannery wastewater were hardly bio-degraded, the common biochemical treatment cannot meet the increasingly stringent emission criterion. Therefore, it was necessary to develop a new advanced treatment for tannery wastewater.In our study, the real tannery wastewater was sampled at a working tannery wastewater treatment station. The station had a novel oxidation ditch combined with A/O process, while the effluent was still out of limits. Thus the removal efficiencies of Fenton reaction as advanced treatment were investigated. A laboratory scale study was carried out to study the effect of H2O2 dose, mol ratio of Fe SO4 and H2O2, reaction time and initial p H on the chemical oxygen demand(COD) removal by traditional Fenton reaction and Fenton-Fluidized Bed. The optimal conditions were determined by orthogonal test combined with single factor test. The results of traditional Fenton reaction showed that mol ratio of Fe SO4 and H2O2 played a significant role on COD removal followed by initial p H and H2O2 dose,while the effect of reaction time was minor. Under the optimal condition: H2O2 of 0.8 m L/L, mol ratio of Fe SO4 and H2O2 was 0.8, reaction of 20 min, initial p H 3, PAM(0.1%) of 2 m L/L and aeration of 30 min, the COD removal reached 59.8%.However, in the test of Fenton-Fluidized Bed, the H2O2 dose played a significant role on the COD removal and the initial p H and the reaction time followed, while the ratio of Fe SO4 and H2O2 was non-significant. The COD removal by Fenton-Fluidized Bed was higher(64.8%) under the optimal condition: H2O2 of 0.8 m L/L, mol ratio of Fe SO4 and H2O2 was 0.1, reaction of 60 min, initial p H 3, PAM(0.1%) of 2 m L/L and aeration of 30 min.Compared to those of traditional Fenton reaction, the COD removal of Fenton-Fluidized Bed was 5% higher, the reaction time was 40 min longer, the Fe SO4 dose was 87.5% less and the productivity of iron mud was 64% less. Overall, the Fenton-Fluidized Bed had higher treatment efficiencies than traditional Fenton reaction. Furthermore, pilot tests were also established to verify the effect of Fenton-fluidized bed in the real treatment station and the optimum parameters were determined according to the lab trial.Moreover, this study assessed the influence of newly-built A/O on the original oxidation ditch and the co-treatment effect of A/O combined with Fenton-fluidized bed on tannery wastewater was investigated.