TREATMENT METHOD FOR WASTE LIQUID CONTAINING CADMIUM AND SELENIUM

摘要

PROBLEM TO BE SOLVED: To provide a technique of treating cadmium and selenium which are difficult in batch treatment of <=0.1 mg/L which is an effluent standard by one time of solid-liquid separation operation from a waste water liquid in which the cadmium and the selenium coexist and preventing the elution of cadmium and selenium from the treated sludge. SOLUTION: This method includes a first process step of stabilizing the cadmium and other heavy metals and reducing the hexad selenium to quadrivalent selenium by effecting ferritization treatment at a pH 9 to 10, a second process step of treating the selenium by subjecting the treating liquid undergoing the first process step to ferritization reaction again at the pH lower than the pH 9 or iron flocculation and precipitation reaction with an iron salt, and a third process step of subjecting the insoluble matter obtained in the first process step and the second process step to solid-liquid separation from the treating liquid.