UF+RO or MBR+RO double membrane combination technology is adopted to make the effluent from the final system be partially returned to production. UF and MBR were used as pretreatment systems for RO membrane technology to remove suspended solids, colloids, particles, bacteria and some organic matter from wastewater. In addition, MBR technology can further improve the removal rate of organic matter. Then the RO membrane technology is used to remove the dissolved salts and most of the organic matter in the wastewater.