Phosphorelimination

Phosphorelimination is the process of removing phosphorus from a water or process stream to prevent eutrophication, reduce scaling, or recover phosphorus as a usable resource. In environmental engineering and process chemistry, phosphorelimination encompasses chemical, biological, and physical methods designed to lower dissolved phosphate concentrations and/or remove phosphorus-bearing solids.

Chemical methods include precipitation with iron(III) or aluminum salts, lime, or other coagulants to form insoluble phosphate minerals that can be settled and removed. pH and chemical dose are critical to optimize performance and minimize sludge production. A parallel approach is struvite precipitation, where magnesium and ammonium react with phosphate to form magnesium ammonium phosphate crystals that can be harvested as fertilizer.

Physical and adsorptive methods involve media-based adsorption or ion exchange using activated alumina, iron-oxide coatings, or other phosphate-selective materials, often as polishing steps after primary treatment or in industrial streams with low phosphorus concentrations.

Biological methods rely on phosphorus-accumulating organisms in activated sludge systems, enabling enhanced biological phosphorus removal (EBPR). These organisms uptake phosphorus under anaerobic conditions and release it under aerobic conditions, allowing separation with waste sludge when the process is operated to accumulate phosphorus inside cells for later removal.

Applications include municipal wastewater treatment to meet regulatory limits, industrial effluent treatment, and resource recovery strategies. Considerations include cost, sludge handling, regeneration of media, and the potential for phosphorus rebound in effluent if process control is not maintained.

See also: phosphorus removal, phosphorus recovery, struvite.