title: Overcoming challenges to struvite recovery from anaerobically digested dairy manure.
abstract: Recovering struvite from dairy manure has consistently posed problems for researchers. This study separated solids from anaerobically digested dairy manure using a filtration system. Filtrate was rich in free magnesium (160 to 423 mg/L), ammonium (320 to 1800 mg N/L) and orthophosphate (93 to 332 mg P/L). High concentrations of free calcium (128 to 361 mg/L) and alkalinity (3309 to 6567 mg/L as CaCO3), however, may hinder struvite precipitation. Batch precipitation tests were conducted to identify and overcome factors that interfere with struvite formation. Precipitation tests at pH 9 identified calcium and ionic strength as most probable interferences. Calcium addition did not significantly change phosphorus removal efficiency, but decreased struvite purity because of formation of calcium phosphates when Ca:P activity ratio was greater than 0.5 to 1. Batch tests demonstrated effective calcium removal from anaerobically digested dairy manure through precipitation of calcium carbonate at pH 9 to 10 while retaining magnesium and orthophosphate, lessening hindrance to struvite formation.
authors.affiliation: Department of Environmental Resources Engineering, State University of New York College of Environmental Science and Forestry, Syracuse, New York, USA. mphuchze@syr.edu
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Huchzermeier
authors.forename: Wendong
authors.initials: W
authors.lastname: Tao
mesh_terms: D000693:Anaerobiosis; D000818:Animals; D002118:Calcium / Q000737:chemistry; D002417:Cattle; D003612:Dairying; D017616:Magnesium Compounds / Q000302:isolation & purification*; D008372:Manure; D008855:Microscopy, Electron, Scanning; D010710:Phosphates / Q000302:isolation & purification*; D000069877:Struvite
chemical_list: D017616:Magnesium Compounds; D008372:Manure; D010710:Phosphates; D000069877:Struvite; D002118:Calcium