Deep Treatment of Ammonia Nitrogen Tannery Wastewater by an Electro-Fenton System

Abstract

The effect of an Electro-Fenton system on the deep treatment of ammonia nitrogen (NH3-N) and corresponding removal rate was investigated in this article. By using simulated ammonia nitrogen wastewater, it included a Cl- concentration of 3000 mg/L, SO4 2- concentration of 100 mg/L according to conventional leather wastewater conditions. Furthermore, Cl- and SO4 2- can be used as supporting electrolyte. After pretreatment, the ammonia nitrogen concentration kept about 100 mg/L. The optimal treatment conditions of Electro-Fenton system were obtained throughout single factors experiments. The current density was 150 A/m2, the reaction time was 30 min, the plate spacing distance was 40 mm, and the reaction temperature was adjusted to 40°C. After flocculation treatment of leather wastewater, the ammonia nitrogen concentration was 142.11 mg/L, and the tanning wastewater was further treated with an Electro-Fenton system. The final ammonia nitrogen concentration was 11.23 mg/L, which meets the first-level wastewater discharge standard. The removal rate was 92.10%, which indicated that the Electro- Fenton system is one kind of clean, feasible and sustainable treatment method for the deep treatment of ammonia nitrogen in tannery wastewater.