Does chlorination remove cyanide from waste water?
Cyanide treatment consists of two reaction tanks. In the first tank, conditions are adjusted to oxidize cyanides to cyanates by the introduction of chlorine and caustic to maintain a pH range of 9.5 to 10.0. Chlorine is typically added as chlorine gas or sodium hypochlorite. In the second reaction tank, conditions are maintained to oxidize cyanate to carbon dioxide and nitrogen. Additional chlorine is added and adequate caustic is mixed in to maintain a pH of 8.0. An additional tank may be added for holding and treatment to meet discharge limitations. Detention times of 45 minutes for each reaction tank is sufficient. A common method for the oxidation of cyanide wastewater is chlorination at high pH. However, there are several disadvantages with this type of treatment: 1 – it is expensive especially in the case of concentrated solutions; 2 – it is not so effective for cyanide complex wastes; and 3 – it produces a large quantity of sludge, which contains heavy metal after chemical decom
