October 17-18 2002 in Lakeland, FL

Excerpts on Pond Water and Double Liming from an IMC Technology Dep’t Presentation:

Phosphate Plant Pond Water Treatment using Reverse Osmosis

Pond Water – SourcePond Water – Source

Phosphoric Acid Plant

Gypsum Stacks

Pond System

Phosphoric Acid ProcessPhosphoric Acid ProcessOrigin of Pond WaterOrigin of Pond Water

Phosphate Rock

Sulfuric Acid

Phosphoric AcidPlant

Pond Water

Pond System

Gypsum Slurry

Other Water Water From Stack

Rain

GypsumStack

PhosphoricAcid

Fresh Water

““Typical” Pond WaterTypical” Pond WaterCHEMICAL COMPONENT RANGE OF CONCENTRATION

P 1700-12,000 ppm

SO4 4300-9600 ppm

F 200-15,000 ppm

Si 100-4100 ppm

(ammoniacal) N 40-1500 ppm

Na 1200-2500 ppm

Mg 160-510 ppm

Ca 450-3500 ppm

K 80-370 ppm

Fe 5-350 ppm

Al 10-430 ppm

Cl 10-300 ppm

Traditional TreatmentTraditional Treatment“Double Liming”“Double Liming”

Lime Slurry Addition to pH ~5.5Settling and Sludge Separation2nd Lime Addition to pH 12-12.5Settling and Sludge SeparationAir Stripping for NH3 Removal

Sulfuric Acid Addition to pH 8

Double LimingDouble LimingLimitationsLimitations

Clear Water Recovery Only 50-60%Remaining Sludge Difficult to Dewater

– Large Impoundment Ponds

Precipitated Phosphate Difficult to RecoverDifficulty Meeting Ammonia LimitsHigh Cost

Cost EstimateCost EstimateDouble LimingDouble Liming

$/Month $/1000 Gal. DischargedDouble Liming Double Liming

Fixed Costs

Labor/OH 65,000$ 0.97$

Maintenance/CS 141,000$ 2.11$

Laboratory 11,000$ 0.17$

Total Fixed Costs 217,000$ 3.25$

Variable Costs

Lime 750,000$ 11.22$

Caustic/Ammonia

Flocculent 42,000$ 0.63$

Sulfuric Acid

R.O. Chemicals

Electricity 52,000$ 0.78$

Total Variable Costs 844,000$ 12.62$

Total 1,061,000$ 15.87$

Credits (Rock, Acid, NH3) 3.07$ Net Cost 12.80$

Basis 2.2MM GPD Discharge Flow