PRETREATMENT FOR THICKENING OF WASTE ZINC WATER

摘要

PURPOSE:To decrease an alkali agent to be used by adjusting the pH of waste strong acidic zinc water contg. aluminum ion to 5.5-6.5, and adjusting the pH to 3.5-5.5 after removal of the generated flocs thereby thickening the zinc component. CONSTITUTION:Original water having <=4.0pH is introduced through an inflow pipe 1 into a stirring tank where sodium hydroxide is added to the water to adjust the pH thereof to 5.5-6.5. The water is then stirred with a stirrer 3 to flocculate and deposit the hydroxide of iron and aluminum. The flocculated floc- contg. original water is admitted through a conduit 4 into a settling tank where the flocs are settled and the supernatant water is separated. The supernatant water is introduced through a conduit 6 into an intermediate storage tank 7 and is thereafter introduced into a filter tank 11, where the water is filtered with filter media 12. The filtrate stored in a filtrate tank 14 is supplied through a conduit 15 and a conduit 17 to a precision filter 18. An acid such as hydrochloric acid is added to the conduit 17 to readjust the pH to 3.5-5.5 and thereafter the water is supplied to a module 22.