Chemical and biological phosphorus removal and recovery

Phosphorus (P) is a fundamental nutrient sustaining all forms of life on Earth. According to the United Nations Sustainable Development Goal 2.3, aimed at doubling small-holder farm productivity, P use in agriculture could rise by 39% by 2030. Consequently, strategies for properly removing and recovering P from wastewater and sewage sludge are essential to sustain food production, meet future P demands, and protect the environment. P is usually removed from diluted solutions (wastewater) and recovered from concentrated solutions (or sludge) in the form of precipitated phosphate salts. This chapter begins by discussing the two main techniques for removing P from wastewater: chemical precipitation and enhanced biological P removal. Later, it details the processes used to concentrate P prior to precipitation, as well as the treatments required to extract P from sludge. Finally, it discusses the procedures for recovering P as a precipitate, such as calcium-based phosphate, magnesium ammonium phosphate, or iron phosphate.