Synchronous complete COD reduction for persistent chemical-industrial organic wastewater using the integrated treatment system

Chemical-industrial organic wastewater often contains organic contaminants with low biodegradability. One challenge of chemical-industrial organic wastewater treatment is to select suitable pre-treatment combined with biological wastewater treatment. On the other hand, most wastewater treatment systems are open to the atmosphere, and the emission of gaseous organic matters usually occurs during the wastewater treatment processes. Thus, this work provided a conception of synchronous complete COD reduction during chemical wastewater treatment. Real p-Aminodiphenylamine (RT-Base) wastewater, a kind of typical chemical-industrial organic wastewater, was selected to verify the feasibility of the conception. An integrated closed system was utilized which involving a tourmaline-based Fenton-like process and Activated sludge (AS) process. The results showed that trimethylamine emitted after the wastewater pH adjustment and the emitted gaseous matter could be effectively removed by AS process. Additionally, the biodegradability of the wastewater was enhanced after the tourmaline-based Fenton-like pretreatment. Furthermore, the combination of Fenton oxidation with AS process provided a high total removal efficiency (COD removal rate = 98.87%). The emitted gaseous organic matter could be effectively captured and treated by another independent AS process, and there was no longer emitted gaseous organic matter in the off-gas. Microbial DNA analysis showed that the most dominant phyla in the activated sludge were bacteroidetes, proteobacteria, actinobacteria, and firmicutes. Carbohydrate metabolism was the most abundant pathway and its abundance increased 0.03%-1.19% after the treatment. Consequently, the conception of synchronous complete COD reduction in real chemical-industrial wastewater has been verified.