Pharmaceuticals, HPO production of caprolactam, starch processing, brewing, slaughterhouse, and other industries generate wastewater with high pollutant content, particularly with phosphorus levels often far exceeding those of most industrial wastewaters. The phosphorus composition is complex, including orthophosphorus, hypophosphorus, metaphosphorus, and organic phosphorus. Typically, the primary treatment processes for such wastewater involve: anaerobic/denitrifying tanks → aeration tanks → secondary clarifiers → chemical phosphorus removal agents → high-density settlers → filtration. After biological treatment, phosphorus-containing wastewater can have organic phosphorus, metaphosphorus, and polyphosphates absorbed by microorganisms and removed with microbial sludge. Some phosphorus is also decomposed into small orthophosphorus molecules.

Post-biological treatment effluent undergoes chemical phosphorus removal by adding aluminum or iron salts. Aluminum (Al3?) or iron (Fe3?) ions react with phosphate ions to convert dissolved phosphorus into particulate phosphorus precipitates. Metal salt phosphorus removal follows three steps:

1.Hydrolysis reaction: Al3? + H?O → Al(OH)?;

2.Surface complexation reaction: AlOO?-H + OH?-PO? → AlOO?-PO? + H?O (surface active sites, oxygen-containing functional groups covalently bond with phosphate ions);

3.Collision and aggregation: Al (OH)? → Al?(OH)? → Al?(OH)??, forming particulate phosphorus while coagulation occurs. Polyelectrolytes like PAM are added for electrostatic neutralization and bridging adsorption, flocculation suspended particles (including aluminum or iron phosphate colloids) into larger flocs, which are then separated in settlers and filtered through filters. However, effluent phosphorus levels often exceed limits because aluminum or iron phosphate precipitates are colloidal particles, extremely fine and difficult to settle, potentially penetrating filter layers.

For advanced chemical phosphorus removal in wastewater treatment, the M+FLO magnetic flocculation sedimentation tank system is recommended. It efficiently removes phosphorus and suspended solids (SS) by incorporating magnetic powder during flocculation, effectively adsorbing fine colloidal particles and rapidly settling with magnetic flocs. This enables deep phosphorus removal and concurrent SS reduction. The system process is as follows: [Diagram reference].

Typical application case - Xinhua Pharmaceutical (Shouguang) Factory, which generates 1,200 tons of industrial wastewater daily with a total phosphorus (TP) content of 100 mg/L, salt content of 60,000 mg/L, and chloride ion content of 4,000 mg/L. After treatment using the M+FLO magnetic coagulation sedimentation tank deep dephosphorization water purification system provided by Qingdao Pacific Chemical Equipment Co., Ltd., the effluent phosphorus content TP is reduced to <3 mg/L (fully meeting the TP <5 mg/L discharge standard for industrial park pipelines).

Chemical phosphorus removal in conventional magnetic flocculation sedimentation tanks can only remove inorganic phosphorus, such as orthophosphate. For organic phosphorus removal, pretreatment methods such as strong oxidation are required to convert organic phosphorus into orthophosphate, or alternatively, a powdered activated carbon magnetic flocculation sedimentation system can be employed for water purification.