PROBLEM TO BE SOLVED: To provide a treatment method capable of stably reducing the arsenic concentration to or less than a wastewater standard even in wastewater in which the Fe / As ratio fluctuates significantly in the treatment of wastewater containing arsenic. SOLUTION: In a treatment method in which acidic waste water containing arsenic is neutralized in the presence of iron to form arsenic into a starch to reduce the arsenic concentration, the weight ratio (Fe / As ratio) of iron to arsenic is high. With respect to the fluctuating wastewater, sludge containing arsenic starch produced by the neutralization treatment is recovered, and the Fe / As ratio of the wastewater is about 1.9 times the lower limit of the Fe / As ratio of the wastewater. By returning sludge having an Fe / As ratio in the range of about 0.6 times the upper limit of the above-mentioned neutralization treatment to the above-mentioned neutralization treatment and performing the neutralization treatment, fluctuations in the above-mentioned Fe / As ratio are alleviated and arsenic is formed into an arsenic starch. A method for treating arsenic-containing wastewater, which is characterized by advancing. [Selection diagram] Fig. 1
展开▼
