9. The process requires that the moisture content of raw materials for preparation and screening should not exceed 20%, the screening area required for raw materials (air-drying) should not be less than 0.25m2/kg/min, and the opening rate should not be less than 30%. Sludge residue drying Sludge residue is preferably dehydrated by mechanical pressing, with a solid content of not less than 35%. The initial temperature of the evaporation concentrated waste liquid entering the evaporation concentration system shall not be lower than 70°C, the suspended solids shall not be greater than 100 mg/kg, the solid content shall be 15% to 18%, and the solid content of the final concentrated waste liquid shall not be less than 45%. The pH value of production dilute waste liquid and concentrated waste liquid is not greater than 9.0.