Research On Arsenic Removal With The Coordination Of Iron, Manganese And Calcium For Groundwater

Groundwater with arsenic pollution, usually at the same time has a lot of iron, manganese and calcium. Iron salts and calcium salts are commonly used as coagulant and precipitant and iron ions and calcium ions have the effect of coagulation and precipitation; manganese oxide has some of the arsenic adsorption function.Simultaneously, iron, manganese, calcium ions are indicators of water quality pollution control, therefore, effective removal of arsenic in groundwater, including iron, manganese, calcium, to achieve synergy target, is the purpose of the research. The research expounds on arsenic removal efficiency and its data variation at various conditions by stimulating underground water and by process of pre-oxidation and sedimentation while there exist iron, manganese and calcium. By means of pre-oxidation process, changing coagulant dosage, the relationship between manganese interaction and calcium is explored, and during the research the characteristics of related ions, inclusive of their interaction and role are all demonstrated.The research demonstrates the following conclusions: pre-oxidation process is a very important step in the removal of arsenic, and arsenic removal efficiency is above 80% through pretreatment of ozone or potassium permanganate, while through the process of air aeration of the water, the arsenic removal is basically less than 50%. Iron ions, in the course of the coagulation, have a dual role, on the other hand the formation of ferric hydroxide removal the some of arsenic through adsorption which enhances the efficiency of arsenic removal. the removal rate of arsenic by coagulation method is basically up to 90% at a dosage of 5 mg/L. Calcium ions in the solution can promote the precipitation of arsenic separation and together with iron does better. The main function of manganese ion is its role of its oxide adsorption, manganese ions during coagulation can promote the removal rate of arsenic. When iron and manganese coexist, the manganese ions will promote the formation of ferric hydroxide, but it may reduce ferric arsenate formation rate, resulting in slightly lower efficiency of arsenic removal by coagulation. The actual existence of a large number of sulfate and nitrate and other anions in groundwater can cause a competitive adsorption against coagulant. Therefore the actual removal rate will be slightly lower than the theoretical results.Based on these results, combined with the water quality conditions and put forward the oxidation treatment options and the coagulation sedimentation filtration equipment in the original basis of pre-oxidation steps to add the improvement program, and conducted technical and economic comparison. Program can be seen from the comparison with traditional oxidation than coagulation for arsenic removal filter to improve the pre-oxidation on the removal of arsenic in slightly lower upfront investment. Later, after a program operating costs are lower, and the high degree of automation, easy operation, small-scale drinking water treatment in rural areas is more easily spread, but the water treatment effect needs further examination.