Download Phosphorus Removal from Dairy Wastewater: Technologies and Economics and more Lab Reports Engineering in PDF only on Docsity! 1 Phosphorus Removal from Dairy Wastewater Montessa Young December 2, 2003 Ag Waste Management Why Remove Phosphorus? • Nitrogen: Phosphorus uptake in plants – Corn Silage 4.4:1 – Alfalfa 10.2:1 – Tall Fescue 9.85 :1 • Nitrogen: Phosphorus in dairy manure – 6.4:1 as produced, 3.2:1 after losses • Application of manure to nitrogen rates will over apply phosphorus. • Idaho regulation based on phosphorus Where is this technology needed? • Large dairies with a limited land base – Flush facilities – Areas with high density of dairies – Field attributes that prevent liquid application – Fields that have had phosphorus over applied to in the past. Methods to Remove Phosphorus • Mechanical or gravity separation • Lime (Calcium) • Liquid Alum (Aluminum) • Iron Compounds • Biological processes • Magnesium, Struvite precipitation Phosphorus Cycle Comparing Methods • Most numbers based on laboratory conditions and not full scale farm operations • All work with different wastewater with varying concentrations of phosphorus and solids. • Difference in number reporting – Capture Efficiency – Removal Efficiency – Total Phosphorus (TP) vs. Soluble Phosphorus (SP) • Varying dosage rates of each chemical 2 Mechanical or Gravity Separation • Theory: Removing solids from wastewater will remove the phosphorus • How it Works: Gravity separation in cement or earthen separators. Mechanical separation by screw press, slope screen, centrifuge. • Removal Efficiency: – Slope screen mechanical : 5% – Screw press mechanical: decreased TP by 65%, increased SP – Gravity separation: 25%-75% Lime (Calcium) • Theory: Lime acts as a coagulant to settle out phosphorus • How it Works: Calcium reacts with the natural bicarbonate alkalinity to form calcium carbonate, which raises the pH. At ph>10 hydroxylapatite forms. • Removal Efficiency: Low dosage (1.3 g/L): 39% SP in one hour High dosage (6.6 g/L): 78% SP in one hour Liquid Alum (Aluminum) • Theory: Aluminum acts a coagulant to settle out phosphorus • How it Works: Soluble P combines with aluminum to form insoluble phosphates or adsorbs onto oxides. Performs in neutral to acidic range. • Removal Efficiency: – Low dosage (.8 g/L): 41% SP in one hour – High dosage (8 g/L): 100% SP in one hour 82% TP in one hour Iron Compounds • Theory: Iron acts a coagulant to settle out phosphorus • How it Works: Soluble P combines with ferric chloride or ferric sulfate to form insoluble oxides. Performs in acidic range. • Removal Efficiency: – Low dosage (0.8 g/L): 42% SP in one hour – High dosage (8 g/L): 100% SP in one hour 74% TP in one hour Biological Processes • Theory: Biomass will consume phosphorus, die and be settled out. • How it Works: Waste goes through alternating periods of low aeration/low growth and high aeration/ high growth in which the biomass luxury consume phosphorus. • Removal Efficiency: – 31% to 91% (swine) range due to pH, phosphorus species, and metal ions. Magnesium, Struvite Precipitation • Theory: Magnesium acts as a coagulant to settle out phosphorus. • How it Works: Magnesium, ammonium and phosphate ions when at a pH of 7 to 11 will combine to form struvite (MgNH4PO4*6 H2O) • Removal Efficiency: – 90% reduction in SP (swine)
