Combined ozone oxidation and biological aerated filter processes for treatment of cyanide containing electroplating wastewater

• The combined process of BAF–O3–BAF was suitable for treating cyanide containing EPWW.
• BAF can tolerate higher cyanide toxicity than some other bioreactor.
• High removal efficiencies were obtained with low influent BOD5/TN in BAF.
• The addition of glucose into raw EPWW could increase the efficiencies of BAF.
• Cyanide compounds of EPWW could be used as the nitrogen source for the microbes.

In this study, combined ozone oxidation and biological aerated filter (BAF) processes treating cyanide containing electroplating wastewater was investigated. The combined process of first BAF–ozone–second BAF (BAF1–O3–BAF2) was proved the optimal combined way. Under the optimal condition of 100 mg/L ozone dosage, BAF1 HRT (hydraulic retention time) 9 h and BAF2 HRT 6 h, the CN−, COD (chemical oxygen demand), Cu2+ and Ni2+ removal efficiencies were 99.7%, 81.7%, 97.8% and 95.3%, respectively and the effluent CN−, COD, Cu2+ and Ni2+ concentrations of 0.16 mg/L, 55.0 mg/L, 0.38 mg/L and 0.41 mg/L, respectively satisfied the discharge standard for electroplating (China). The results show that BAF1 can tolerate higher cyanide toxicity than some other bioreactors. Furthermore, the addition of glucose into raw electroplating wastewater (EPWW) could increase contaminants removal efficiencies of BAF1. Cyanide compounds of EPWW could be used as the nitrogen source for the microorganisms.