EXHAUST GAS DESULFURIZATION WASTEWATER TREATMENT METHOD

摘要

PROBLEM TO BE SOLVED: To provide an exhaust gas desulfurization wastewater treatment method capable of forming sludge in which boron is hardly redissolved and enabling the reutilization of sludge to reduce the disposal amount of sludge. SOLUTION: Exhaust gas desulfurization wastewater 15 discharged from an exhaust gas desulfurization process is introduced into a reaction tank 5, and an aluminum compound 18, a calcium compound 19 and a pH control agent 20 are injected in the wastewater not only to adjust the pH thereof to 9 or more but also to be reacted with the wastewater to form an insoluble precipitate. The reaction liquid 23 is subjected to solid-liquid separation treatment in a solid-liquid separation tank 6 and a separated liquid is discharged as treated water 25. Separated sludge 27 containing boron is sent to a pH adjusting tank 7 and an acid 29 is added to the sludge to adjust the pH of the sludge to 5-8 to neutralize the sludge and a part or the whole of a gypsum slurry 13 concentrated in a solid-liquid separation part 2 is added as gypsum 33 discharged from the exhaust gas desulfurization process to form sludge in which boron is hardly dissolved. The gypsum added sludge 36 is introduced into a dehydrator 9 and the solid thereof is recovered as a dehydrated cake 37 to be reutilized.