PHOSPHORUS REMOVAL ON DAIRIES IN THE
PACIFIC NORTHWEST
Applying a Cone Shaped Fluidized Bed Phosphorus Crystallizer
Ron Sheffield – U of IdahoKeith Bowers – Multiform Harvest Inc.
Joe Harrison – U of Washington
Magnesium, Struvite Precipitation
Magnesium ammonia phosphate crystal Similar to a Kidney Stone
Equilimolar concentrations of Mg, NH3 and PO4
Naturally occurring in waste systems Overflow pipes, recycle elbows, pump impeller Very common in municipal and swine waste systems
Historically produced slow release fertilizer
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 from a swine anaerobic
treatment lagoon in NC
Laboratory Crystallizer
Crystallizer Cone
Mg Dissolving Cone (optional)
Anhydrous Ammonia
Mg
Wastewater In
Harvested Struvite4-20-0.25
Treated Effluent
Fluidized-Bed Struvite (MgNH4PO4) Crystallizer
Pilot Scale Crystallizer2 gpm
Si-Ellen Farm
4,000 cow open lot Flush feeding alleys Primary Solids Removal – Slope Screen Secondary Solids Removal – Gravity Basin 3 Wastewater Storage Ponds - 18M gallons
Werkhoven Dairy
600 cow freestall Flush manure handling Primary Solids Removal – Gravity Basin 3 Wastewater Storage Ponds - 18M gallons
Wastewater Analysis TP = 85 mg/l PO4 = 25.4 mg/l pH = 7.8
Results
PARAMETERBowers and
Westerman, 2003Idaho Dairy
Washington Dairy
TP (ppm) 88 93 83
OP (ppm) 42 27 39
Mg (ppm) 60 155 241
TAN (ppm as N) 178 332 662
pH 7.7 7.5 7.8
TP removal (%) 66 19(0 – 55)
6(-41 – 63)
PO4 removal (%) 80 56(-59 – 89)
4(-55 – 38)
Crystalline Product
Advantages Non-sludgy Crystalline structure Easily dried and handled Concentrated Fertilizer -
4:20:0.25 Average ID analysis
Organic Product??? Limitations
Slow Release Low Nitrogen
Wastewater Solubility vs Equilibrium - Ohlinger et al. 1998
Conclusions
Cone shaped fluidized bed crystallizer was successful in removing P from dairy wastewater
TP removal was observed to be lower than as demonstrated with swine lagoon wastewater
PNW dairies showed higher Mg and TAN: possibly reducing TP removal via struvite harvesting
Next Steps…..Struvite Crystallization
Acidification Pre-Treatment pH, retention time
Portable Struvite Crystallizer Trailer mounted Evaluate various wastewaters
Full-Scale Crystallizer: >10M gallons/year Organic Certification Crop Response
Next Steps…..Anaerobic Digestion
Phosphorus Pretreatment Digester not for energy production
rather as P removal systems Investigate lowest Hydraulic
Retention Time (HRT) to achieve highest PO4:TP
Smaller & Cheaper digester Follow with Struvite Crystallization