A zero-liquid discharge air pollution control system , comprising: a boiler that combusts fuel (F); a heat recovery device (AH) 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 (AH); 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 (F); a heat recovery device (AH) 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 (AH); 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 .. <EOS>