The total phosphorus in the sewage plant exceeded the standard. What chemicals are used to treat it?

Biological phosphorus removal method can also be used to treat total phosphorus in sewage, but if chemical agents are used, it is usually chemical method. With the increasing requirements of environmental protection, chemical phosphorus removal is more and more widely used, fast and effective.

1. Iron-based phosphorus remover

Iron-based dephosphorization agent is mainly polymeric ferric sulfate, which is the most common dephosphorization agent in the market. The principle is that ferric sulfate will hydrolyze in water to form ferric hydroxide colloid, which has adsorption effect and will adsorb a lot of phosphate, and further phosphate will form colloidal precipitation with iron ions, thus removing it. However, iron ions can be dissolved in water after combining with hypophosphite, and the solubility is very high. Therefore, it is ineffective to treat hypophosphite with iron salt.

2. Calcium phosphate remover

The calcium phosphate remover is mainly composed of calcium chloride and lime. In the phosphorus removal effect, calcium salt is not as good as iron salt, because calcium salt will not hydrolyze in water to form colloid, thus reducing the adsorption effect of macromolecules. The function of calcium phosphate remover mainly depends on calcium phosphate precipitation. Calcium-based dephosphorization agent is similar to iron-based dephosphorization agent, and will not precipitate with hypophosphite, so it cannot remove phosphorus.

3. Aluminum dephosphorization agent

Aluminum salts commonly used in aluminum-based dephosphorization agents are polyaluminum chloride and aluminum sulfate. Its principle is that when aluminum salt is dispersed in water, colloidal precipitation of aluminum hydroxide is generated, which promotes the rapid instability, coagulation and precipitation of colloid and suspended matter, showing good phosphorus removal effect. Aluminum salt and iron salt have obvious phosphorus removal effect and good flocculation and sedimentation performance, but aluminum salt will lead to excessive aluminum ions in water due to excessive phosphorus removal, and aluminum ions are more toxic to human body.

4. Phosphate remover P3

The hypophosphite remover is a heterogeneous inorganic compound salt. Different from single iron-based dephosphorization agent and calcium-based dephosphorization agent, hypophosphite dephosphorization agent P3 has a complex microstructure and can combine with hypophosphite in wastewater to form a stable coordination bond, so it can combine under acidic conditions to form a precipitate. In electroless nickel plating wastewater, the traditional iron-based dephosphorization agent and calcium-based dephosphorization agent can not play a role, while dephosphorization agent P3 can effectively remove phosphorus, reaching below 0.5ppm.

5. Compound dephosphorizing agent

Compound dephosphorizing agent is developed for domestic sewage, anodic oxidation, pretreatment before painting, phosphating and other phosphorus-containing wastewater. It can effectively remove all kinds of orthophosphates and most organic phosphines, and has the advantages of small dosage, wide pH range, good coagulation effect and clear and transparent effluent.