Fenton and Photo-Fenton for Treatment of Red Water Containing Trinitrotoluene: A Comparative Study

Wastewater originating from the production of TNT explosives (red water) contains special hazardous substances that must be treated before discharging into the water environment. In this study, we applied both conventional Fenton and photo-Fenton (UV-Fenton) processes to treat COD and color in red water. In the Fenton process, the COD and color removal efficiencies were 75.5 and 92.4%, respectively, under optimal operating conditions of pH = 3, [Fe2+] = 0.3 g L-1, H2O2/Fe(Ⅱ) ratio = 10:1, reaction time = 120 min. In the UV-Fenton process, the efficiencies were 76.1 and 94.2%, respectively, under optimal operating conditions of pH = 3, [Fe2+] = 0.21 g L-1, H2O2/Fe(Ⅱ) ratio = 7:1, reaction time = 90 min. These results indicate that the use of ultraviolet could reduce not only the reaction time but also the chemical use (i.e. H2O2 and Fe2+), thus reducing the sludge production. Importantly, the UV-Fenton process significantly increased the BOD5/COD ratio from 0.13 to 0.58, which greatly enhanced the biodegradability of the wastewater for biological treatment. Therefore, UV-Fenton can be applied as an effective pretreatment in the treatment of red water with high color and organic pollutants.