The invention relates to a method for treating
arsenic-containing
wastewater by a process of preoxidation-composite coagulation deposition-filtering, and belongs to the technical field of
wastewater treatment. The method comprises the steps of adding a certain amount of an
oxidizing agent in a reaction tank for preoxidation in a condition that the
wastewater contains trivalent
arsenic so as to transform the trivalent
arsenic into pentavalent arsenic completely, while for the wastewater only contains the pentavalent arsenic, the preoxidation process is not needed; adding a certain amount of a
ferrous salt water solution; controlling a
molar ration of Fe to As being 5-50; adding acid or alkali to adjust a pH value being 6-8; stirring for 0.1-1 min rapidly, so that a
ferric arsenate precipitate is formed, at the same time, the
ferrous salt is hydrolyzed into
ferrous carbonyl to promote coagulation deposition of the
ferric arsenate; adding a solution of 0.1-10 mg / L
organic polymer flocculant; stirring for 0.1-1 min rapidly; stirring for 5-10 min slowly, precipitating for 10-30 min, discharging
sludge from the bottom, introducing supernatant into a
sand filter tank, a filter film or a filter bag, filtering and discharging the
effluent.
Arsenic content in water
after treatment is lower than that of a drinking water standard (less than 10 [mu]g / L) regulated by the
world health organization. The method has low
sludge production and low cost, and can be used for advanced treatment of the arsenic-containing industrial wastewater and treatment of arsenic polluted underground water and drinking water.