Study on treatment of high-salt printing and dyeing wastewater by electroflocculation-micro-nano-bubble ozone oxidation process

High-salt printing and dyeing wastewater has the characteristics of high chromaticity, poor biodegradability and unstable water quality, which makes it difficult to be treated efficiently by traditional biochemical methods. Micro-nano-bubble ozone (O₃) advanced oxidation process and electric flocculation (EC) process were combined to treat high-salt printing and dyeing wastewater, the coupling effect of the two processes was explored, and the influence of current density, salt concentration, pH and other factors on the treatment effect of the combined process was studied. The experimental results showed that EC alone could decolorize dyeing wastewater and remove organic matter to a certain extent, but the efficiency was low. Under the same conditions, the treatment efficiency of printing and dyeing wastewater by EC+O₃ process was higher than that by EC→O₃ process (EC treatment for 30 min→O₃ treatment for 120 min), and the ozone consumed by removing 1 mg COD was 0.46-1.39 mg. With the increase of current density and pH, the decolorization rate, UV₂₅₄, COD and TOC removal rate increased. With the increase of salt concentration, the decolorization rate, UV₂₅₄, COD and TOC removal rate increased slightly. The effects of ozone micro-nano-bubble process, H₂O₂/O₃ of advanced oxidation process and EC+O₃ processes on the treatment of actual printing and dyeing wastewater in Xinjiang and Zhejiang were compared, and the economic analysis was carried out. The electrical energy per order (EE/O) value of each stage of the three micro-nano-bubble treatment processes was EC+O₃ < H₂O₂/O₃ < O₃ from low to high.