Arsenic pollution mainly comes from the mining and smelting of arsenic compounds, the production and use of arsenic containing pesticides, raw materials for chemical industry, pottery, glass and leather making, and coal combustion. For arsenic wastewater treatment, enhanced coagulation technology is commonly used, which mainly uses ferric salt, aluminum salt, lime and polymerized ferric sulfate, activated carbon or ferrous sulfate as coagulants. In this way, the cost of arsenic removal is low and the effect is good, but the effect of lime on trivalent arsenic treatment is poor.

Arsenic pollution includes air arsenic pollution and water arsenic pollution. There are mainly two methods to deal with arsenic pollution in water.

1. Arsenic removal by ferrous sulfate

The method of removing arsenic by iron ion is to use iron ion or its compound to adsorb and co precipitate arsenic ion to achieve the purpose of removing arsenic. This method mainly uses ferrous sulfate to remove arsenic. The use of ferrous sulfate to remove arsenic has higher requirements on the pH value of water body, generally in the range of 5.5-8.5, adding ferrous sulfate and other ferric salt coagulants to arsenic containing sewage for acid-base adjustment (ferrous sulfate to treat alkaline wastewater), and increasing the content of iron in sewage. The content of iron ion in water is kept at or higher than 1.5mg/l. When the ratio of iron ion and arsenic ion in sewage is not less than 20:1, the removal rate can reach 80% - 95%.

2. Arsenic removal by adsorption with lime and ferrous sulfate

Arsenic removal by lime + ferrous sulfate is to use arsenate and arsenate to react with calcium ions in lime to produce calcium arsenate or calcium arsenite precipitation which is insoluble in water, and then through the complex formed by ferrous sulfate hydrolysis to adsorb and precipitate the remaining arsenic ions to remove arsenic. This method is used to treat the acid wastewater with arsenic content less than 150 mg / L or low arsenic content of 1.8 mg / L. the arsenic content can be reduced to 0.01 mg / L when the wastewater is close to neutral or weak alkaline. But it is difficult to filter arsenic residue. And lime and ferrous sulfate are coagulants that produce more sludge, so Lvyuan Environment Group Co.,Limited reminds that although this method has good effect, it will produce a lot of sludge.