Pilot‐Scale Study on Salt Separation of Industrial High‐Salt Wastewater Based on Nanofiltration

Abstract

To explore the effect of nanofiltration on salt separation in high‐salt wastewater, a pilot plant of nanofiltration combined with a “sand filtration–carbon filtration–ultrafiltration–ozone” pretreatment process is designed. The water used in the pilot‐scale study is the sodium salt wastewater from a battery factory in Tianjin Binhai industrial park. Under the continuous and stable operation of the pilot plant, the key consideration is to investigate the retention rate of monovalent and divalent salt ions in high‐salt wastewater by nanofiltration membranes. The results show that the combined process has a good removal effect on pollutants in wastewater. Among them, the removal rates of conventional pollutants such as turbidity, chemical oxygen demand (COD), and total dissolved solids (TDS) are 97.5, 92.35, and 87.06%, respectively. The retention rate of SO42− is as high as 99.7%, but there is a negative retention phenomenon of Cl−. The main inorganic salts Na2SO4 and NaCl in high‐salt wastewater could be effectively separated. The efficiency of the combined process to remove pollutants and different salts mainly focuses on the nanofiltration part. The pretreatment has a specific removal effect on the turbidity and macromolecular organics of wastewater, reducing the pressure for the subsequent membrane process.