Zero liquid discharge means that after reuse of industrial water, the wastewater containing salt and pollutants is further concentrated and further recycled so that finally no waste liquid is discharged from the factory. The salt and contaminants in the water are discharged into the waste treatment plant after being concentrated or crystallized or the filter press residue is discharged into the waste treatment plant in the solid form or recycled as the useful chemical raw material. There are many menu process route combinations for zero liquid discharge, which can be selected according to the end customers’ needs.