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