title: Conditions influencing the precipitation of magnesium ammonium phosphate.
abstract: Struvite precipitation in wastewater treatment works has caused substantial operational problems since the early 1960s. Struvite, magnesium ammonium phosphate hexahydrate (MgNH4PO4 6H2O), is a white inorganic crystalline mineral that precipitates in places with increased turbulence such as pumps, aerators and pipe bends. Batch experiments were conducted to examine the influence of a number of physical and chemical parameters on struvite crystallisation. This was undertaken by dosing a medium of de-ionised water with varying concentrations of Mg2+, NH4+ and PO4(3-) ions. Preliminary experiments found that struvite could be precipitated out of solution at pH 10 and increasing the ion concentration stoichiometrically could increase crystal yield. Increasing the NH4+ concentration increased purity of the precipitate. As reaction time was increased from 1 to 180 min, crystal size was found to increase from 0.1 to 3mm.
authors.affiliation: Environmental Processes and Water Technology Group, T.H. Huxley School of the Environment, Earth Sciences and Engineering, Imperial College of Science, Technology and Medicine, London, UK.
authors.forename: I
authors.initials: I
authors.lastname: Stratful
authors.forename: M D
authors.initials: MD
authors.lastname: Scrimshaw
authors.forename: J N
authors.initials: JN
authors.lastname: Lester
mesh_terms: D011232:Chemical Precipitation; D006490:Hemostatics / Q000737:chemistry*; D017616:Magnesium Compounds / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry*; D012995:Solubility; D000069877:Struvite; D014865:Waste Disposal, Fluid; D014872:Water Movements
chemical_list: D006490:Hemostatics; D017616:Magnesium Compounds; D010710:Phosphates; D000069877:Struvite