Advanced treatment of pharmaceutical wastewater with combined micro-electrolysis, Fenton oxidation, and coagulation sedimentation method

Due to the inability of biochemical processes to remove refractory organic compounds from wastewater in pharmaceutical industrial parks, this research tried to find a new way to meet the requirement of the Discharge Standard in China. A combined process involving micro-electrolysis, Fenton oxidation, and coagulation was studied. Considering the removal efficiencies and operation costs, the reaction conditions were optimized. The COD concentration in the effluent after the combined treatment was less than the standard limit of 50mg/L. Molecular weight distribution of organic compounds in wastewater was analyzed by sequential filtration and ultrafiltration. When treated by the combined process, the particulate fraction (particle size>1,000nm) decreased, and the soluble portion (particle size<1nm) increased significantly. Composition of the refractory organics was investigated using GC-MS. A total of 34 types of low-molecular-weight organics were identified in the effluent, among which phthalates, amides, heterocyclic compounds, and PAHs were the main organic pollutants. All these results show that the proposed method is promising for refractory wastewater because it is efficient and easy to operate.