Optimization of Fenton process for decoloration and COD removal in tobacco wastewater and toxicological evaluation of the effluent

Decoloration and chemical oxygen demand (COD) removal in tobacco wastewater by Fenton process has been optimized under 25 ± 2 °C. The results showed that the optimal range of conditions were pH 4.13–4.66, Fe2+ 0.29–0.34 g/L and H2O2 ≥ 2.73 g/L. Within this range, up to 95% of colour and 90% of COD was removed. In an enlarged system, setting the optimal conditions as pH 4.50, Fe2+ 0.34 g/L and H2O2 4.00 g/L, the colour removal rate was 96.03 ± 2.57%, with COD removal rate of 93.30 ± 2.92%. The residual COD of 73.67 ± 19.70 mg/L in effluent had hit the State's first-class standard for the industrial discharge in China (<100 mg/L COD, GB8978-1996). The ecological safety of Fenton process has also been evaluated. When reaction completed, the content of hydroxyl free radical (·OH) was 3.26 ± 0.44 mg/L. There was no inhibition of Fenton effluent in growth of Escherichia coli , Pseudomonas putida , Pseudomonas sp. HF-1, Acinetobacter sp. TW and Sphingomonas sp. TY. No oxidative stress was induced on strain HF-1 by Fenton effluent. Thus, Fenton process was one of high-efficiency and ecologically safe strategy for tobacco wastewater advanced treatment.