Pretreatment of 2,4-dinitroanisole (DNAN) producing wastewater using a combined zero-valent iron (ZVI) reduction and Fenton oxidation process

A combined zero-valent iron (ZVI) reduction and Fenton oxidation process was tested for the pretreatment of 2,4-dinitroanisole (DNAN) producing wastewater. Operating conditions were optimized and overall performance of the combined process was evaluated. For ZVI process, almost complete reduction of nitroaromatic compounds was observed at empty bed contact time (EBCT) of 8h. For Fenton process, the optimal pH, H₂O₂ to Fe(II) molar ratio, H₂O₂ dosage and hydraulic retention time (HRT) were found to be 3.0, 15, 0.216mol/L and 5h, respectively. After pretreatment by the combined ZVI-Fenton process under the optimal conditions, aromatic organic compound removal was as high as 77.2%, while the majority of COD remained to be further treated by sequent biological process. The combined anaerobic-aerobic process consisted of an anaerobic baffled reactor (ABR) and a moving-bed biofilm reactor (MBBR) was operated for 3 months, fed with ZVI-Fenton effluent. The results revealed that the coupled ZVI-Fenton-ABR-MBBR system was significantly efficient in terms of correcting the effluent's main parameters of relevance, mainly aromatic compounds concentration, COD concentration, color and acute toxicity. These results indicate that the combined ZVI-Fenton process offers bright prospects for the pretreatment of wastewater containing nitroaromatic compounds.