Toxicity reduction in an industrial nitro-aromatic wastewater plant: an assessment and a proposed improvement

In this study, the performance of a typical Chinese industrial nitro-aromatic wastewater project (operational capacity: 3,000 m(3) d(-1)) was evaluated using chemical properties and toxicity data. Additionally, the relationship between the removal of organic pollutants and toxicity reduction was investigated throughout the whole-process wastewater treatment. Current advanced treatment reduced the dissolved organic carbon by 40% compared with biologically treated wastewater effluent (BTWE), but the acute toxicity and early life-stage toxicity increased significantly. For instance, the acute toxicity of the current advanced treated wastewater was 450% greater than that of the untreated BTWE. With the aim of effectively decreasing the toxicity of the effluent, several efficient adsorption technologies were assessed and compared for further treatment of BTWE. Coagulation and/or oxidation coupled with activated carbon adsorption, hypercrosslinked resin adsorption, or MIEX(R) technology was helpful for improving chemical indices and reducing toxicity. Among these adsorption treatment technologies, hypercrosslinked resin adsorption was more effective at removing most of the toxicants than MIEX(R) technology, and it also had better regeneration efficiency and mechanical properties compared with activated carbon. Therefore, hypercrosslinked resin adsorption may be a promising technology for enhancing organic pollutant removal and toxicity reduction of BTWE from nitro-aromatic factories.