SYSTEM AND METHOD FOR TREATING SELENIUM-CONTAINING DRAINAGE

摘要

PROBLEM TO BE SOLVED: To provide a system for treating selenium-containing drainage which can reduce costs by utilizing the iron content used in selenium removal when the selenium concentration of the drainage is high.SOLUTION: A system for treating selenium-containing drainage comprises: sulfuric acid removal means 1 of removing mainly sulfate ion (SO) from the drainage; COD ingredient removal means 2 of removing mainly dithionate ion (SO) from the drainage; and selenium removal means 3 of removing selenium from the drainage. In selenium removal in the selenium removal means 3, iron reduces hexavalent selenium to form tetravalent selenium, and the tetravalent selenium co-precipitates with iron sludge when oxidized iron precipitates as sludge of iron hydroxide. A part of the sludge is circulated to COD ingredient removal means 2 and charged into the selenium-containing drainage for utilization of iron.