A zero-liquid discharge air pollution control system, comprising: a boiler that combusts fuel; a heat recovery device that is provided on a main flue gas duct (L 11) discharging a boiler flue gas from the boiler and recovers heat of the boiler flue gas; a precipitator that removes soot dust in the boiler flue gas after the heat recovery device; a desulfurization device that removes sulfur oxides contained in the boiler flue gas after the precipitator with a desulfurization absorbent; a solid-liquid separator that removes solid material from desulfurized effluent discharged from the desulfurization device; a spray drying device that sprays separated water from the solid-liquid separator; a gas introduction line (L 12) that introduces into the spray drying device a drying gas for evaporating and drying the separated water; a discharged-gas supply line (L 13) that returns to the main flue gas duct (L 11) a discharged gas after evaporating and drying the separated water by the spray drying device; an evaporated salt separator that is provided on the discharged-gas supply line (L 13) and separates an evaporated waste salt containing harmful substances and deliquescent compounds in the discharged gas; and a slurrying vessel that dissolves and slurries the waste containing harmful substances and deliquescent compounds in solvent water to obtain slurried material; a cement kneading vessel that adds a cement solidifying agent to slurried material in which an iron-based additive is mixed to obtain a cement kneaded product; an iron-based additive supply unit that adds the iron-based additive to either one or both of the slurrying vessel and the cement kneading vessel; and a cement solidification unit that cures the cement kneaded product to form a cement solidified product.. a boiler that combusts fuel; a heat recovery device that is provided on a main flue gas duct (L 11) discharging a boiler flue gas from the boiler and recovers heat of the boiler flue gas; a precipitator that removes soot dust in the boiler flue gas after the heat recovery device; a desulfurization device that removes sulfur oxides contained in the boiler flue gas after the precipitator with a desulfurization absorbent; a solid-liquid separator that removes solid material from desulfurized effluent discharged from the desulfurization device; a spray drying device that sprays separated water from the solid-liquid separator; a gas introduction line (L 12) that introduces into the spray drying device a drying gas for evaporating and drying the separated water; a discharged-gas supply line (L 13) that returns to the main flue gas duct (L 11) a discharged gas after evaporating and drying the separated water by the spray drying device; an evaporated salt separator that is provided on the discharged-gas supply line (L 13) and separates an evaporated waste salt containing harmful substances and deliquescent compounds in the discharged gas; and a slurrying vessel that dissolves and slurries the waste containing harmful substances and deliquescent compounds in solvent water to obtain slurried material; a cement kneading vessel that adds a cement solidifying agent to slurried material in which an iron-based additive is mixed to obtain a cement kneaded product; an iron-based additive supply unit that adds the iron-based additive to either one or both of the slurrying vessel and the cement kneading vessel; and a cement solidification unit that cures the cement kneaded product to form a cement solidified product..