The main source of fluorine-containing wastewater is the fluorine-containing "three wastes" discharged from industrial production. The industries involved mainly include aluminum electrolysis, steel, cement, bricks and tiles, ceramics, phosphate fertilizer, glass, semiconductors, pharmaceuticals, etc. The common feature of these industries is that fluorine-containing minerals are the main raw materials or auxiliary raw materials. In the process of smelting and production, fluorine is decomposed from minerals to produce fluorine-containing wastewater.

At present, there are many researches on the treatment of fluorine-containing wastewater at home and abroad. The main treatment methods are: chemical precipitation, flocculation precipitation, adsorption, seed addition, ion exchange, reverse osmosis, activated carbon fluoride removal, electrodialysis and electrocoagulation. There are many fluoride treatment methods, but most of them have problems such as unstable water quality, excessive use of chemicals, or secondary pollution, which makes these fluoride removal methods have certain limitations. For the above method, ion exchange has high requirements on the water quality of the incoming water, the treatment cost of activated carbon defluoridation is high, the reverse osmosis and electrocoagulation process is complex, the power consumption is large, and the cost is high. At present, the industrial treatment goal of fluorine-containing wastewater is only to achieve the discharge standard of effluent, and the treatment methods widely used on this basis are mainly chemical precipitation and flocculation precipitation.

Chemical precipitation method, adding calcium salt, using the chemical reaction of calcium ions and fluoride ions to generate calcium fluoride precipitation to remove fluoride ions in fluoride-containing wastewater. The price of calcium salt is cheaper and the operating cost is low, but the amount of slag produced is large, and if the water contains other salts, the solubility of calcium fluoride will increase, resulting in a decrease in the removal efficiency of fluorine in fluorine-containing wastewater;

Flocculation and precipitation method, which uses the adsorption, ion exchange, complexing sedimentation and other effects of alum flowers produced by aluminum salt in water to remove fluoride ions, uses flocculation and precipitation method to treat fluoride-containing wastewater with small dosage, large treatment capacity and obvious effect, and can realize one-time fluoride-containing industrial wastewater treatment and discharge up to standard. After the treatment, the adsorption method has better effect, but compared with the above two methods, because the adsorption carrier needs to be replaced, the operating cost is high.

The chemical precipitation method can treat high-concentration fluorine-containing wastewater, so that the final concentration of COD in wastewater is reduced to 20-30mg/l, while the flocculation precipitation method can deeply treat the low-concentration fluorine-containing wastewater, and can also use the process of combining the two methods of chemical precipitation flocculation precipitation, so that the treated wastewater can be discharged up to the standard.