Advanced treatment method for arsenic-containing wastewater

Abstract

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.

Description

technical field [0001] The invention relates to an advanced treatment method for arsenic-containing wastewater and arsenic-contaminated groundwater or drinking water, in particular to a new pre-oxidation-composite coagulation sedimentation-filtration method applied to the advanced treatment of arsenic-containing wastewater. Background technique [0002] Arsenic and its compounds are highly toxic, among which trivalent arsenic is more toxic than pentavalent arsenic, and has been identified as a first-class carcinogen by the International Agency for Anti-Cancer Research. Arsenic pollution mainly comes from waste water and waste residues produced by mining, metallurgy, chemical industry, chemical pharmaceuticals, pesticide production, glass processing, and tanning industries. Because arsenic is mainly harmful to human health through drinking water, countries such as Europe, America, Japan and China have listed arsenic as one of the priority water pollutants for control. The U....

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Problems solved by technology

Among them, the extraction method has the problem of secondary pollution from the residual extractant; the regeneration and desorption process of the ion exchange and adsorption methods are complex, the cost is high, and it is difficult to apply on a large scale; the iron salt precipitation method is relatively simple in process and has better practical application effect

Chinese patent (authorization number: CN1100008C) proposes a method for the harmless treatment of arsenic-containing wastewater by oxidation-calcium salt precipitation-iron salt flocculation precipitation. The separation time is long, and a large amount of sludge is generated. It is difficult to guarantee the arsenic content in the treated water to meet the drinking water standard required by the World Health Organization.

Chinese patent (publication number: CN101475252A) proposes a method for treating arsenic-containing wastewater with iron salt combined with bentonite, which can realize the removal of pentavalent arsenic in water through various mechanisms such as iron arsenate precipitation, hydroxyl iron coagulation and bentonite adsorption, but still It is difficult to meet the requirements of my country and the World Health Organization for the content of arsenic in drinking water

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