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The Phosphate Filter: Which Type of Soil?

This study examines the ability of organic and inorganic soils to remove phosphorus from water. It also investigates the impact of iron oxide levels on phosphorus removal. The findings provide insights for designing effective phosphate filtration systems.

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The Phosphate Filter: Which Type of Soil?

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  1. The Phosphate Filter:Which Type of Soil? Noah Haibach Central Catholic HS 2007-2008

  2. Phosphorus Pollution • Phosphorus can cause problems in the human digestive tract. • It is a growth-limiting factor. Causes overgrowth in streams and ponds; can destroy aquatic ecosystems. • Comes from human waste, fertilizer, detergents, and industry point sources.

  3. Phosphorus Treatment • Water treatment plants cannot efficiently remove phosphorus from water. • Marshes can effectively remove the phosphorus. They prevent excess nutrients from causing overgrowth in bodies of water. • Some marshes are constructed to treat water with high levels of phosphorus. • Ex: Florida Everglades

  4. Acceler8 Florida Everglades • $8 billion project currently under way. • Add 6,000 acres to State’s current 36,000 acres of treatment marshes. • Lower P levels to 10-15g/L or ppb. • P levels above this limit can cause imbalances in algae, plant and small animal communities.

  5. Phosphorus Absorption 1. Incorporation into Biomass a. locked away into organic compounds by plants. 2. Retention by Soil* a. physical precipitation b. chemical absorption, where P binds to Al, Fe, or Ca. Fe must be in the fully oxidized form of iron (III) oxide. * Both soil removal techniques sensitive to DO level.

  6. PurposeIn Light of Previous Experimentation • Soil removed much more P from a water sample than did cattails. • Soil removed about 500 g from 1 L solution in 2 days. • Chemical absorption appears to be quickest method of P removal. • Soil was mixture of organic & inorganic. • Which type of soil (organic or inorganic) removes the most P? • Do iron oxide levels affect P removal?

  7. Hypotheses • Organic soil will be richer in P, Ca, and Fe than the inorganic soil (sand). • Organic soil will remove more P than sand, due to chemical absorption of P. • Treatments with added iron oxide will also remove more P than treatments without.

  8. 20 clear 2-Liter pop bottles 3 3.78 bottles distilled water Anhydrous KH2PO4 Reagents for the molybdenum blue ascorbic acid method (4500-P E. method) Ocean Optics USB 2000 spectrophotometer 120 10mL test tubes w/lids 10% organic content soil Sand High-grade iron (III) oxide Graduated cylinders Automatic pipettes; micro and macro Materials

  9. Soil Soil & Fe Sand Sand & Fe Control 1 P ppm 1 P ppm 1 P ppm 1 P ppm 1 P ppm Soil Soil Sand Sand Iron Oxide Iron Oxide Procedure • First, gather the materials needed. Then, prepare a stock solution of 100 P mg/L (ppm). Add stock solution to each of the distilled water containers, so that they have a concentration of 1 P mg/L. • Prepare cakes of soil. Mix 240mL soil/sand with 60mL water. If called for, add iron oxide so that iron oxide content is 4%. Freeze the cakes. • Follow the below diagram for setup, with 4 reps for each treatment. • Take 10mL samples over a period of time. • Prepare the reagents for the molybdenum blue ascorbic acid method, and react the samples. This colorimetric test turns them blue. • Determine the phosphorus content of samples, using a standard curve. 1 P ppm

  10. Experimental Corrections • Too much initial P: 5 mg/L • P concentration outside of range of colorimetric test: 1 cm cuvette range of 0.15 – 1.30 P mg/L • Too little soil: 120mL/treatment • After 1 week, very little P absorbed Corrective Steps • Lower initial P to 1 mg/L • Double size of soil cake Extremely Dark Samples

  11. Data 4 replicates/treatment Arithmetic Standard Mean Deviation

  12. Chart

  13. Anova Results Day 4 Treatments • P Values • Chart Observations • The soil-containing samples varied from the control. • The sand did not vary from the control, but the sand & Fe did vary. • The sand varied from the soil. • The Fe made a difference: sand varied from sand & Fe. • soil varied from soil & Fe.

  14. Conclusions • Treatments with added iron oxide did remove more P than those without. • Organic soil removed more P than the sand, which removed no P in comparison to the control. • Sand & Iron removed more P than Organic Soil & Iron. Due to the high amount of P already present in the organic soil: Organic soil: 9 P mg/L* sand: 1 P mg/L* Dissolved oxygen levels in the soil were 4.9mg/L. DO in the control was 7mg/L; anaerobic conditions may have caused release of P from the organic soil. *Data obtained from Penn State Agricultural Analytical Services Laboratory

  15. Accreditations • Special Thanks to… Dr. Ron Ripper and Carnegie Mellon University Dr. Carrie Doonan Dr. John Stolz of Duquesne University • Sources Standard Method for the Treatment of Water and Wastewater, 18th ed. (Washington D.C.: American Public Health Association, 1992), pp. 4-115 & 4-116. University of Florida, “Wastewater Treatment Wetlands: Applications and Treatment Efficiency,” http://edis.ifas.ufl.edu/SS294 Science Daily, “Everglades Phosphorus Limits On The Right Track, But More Is Needed”, http://www.sciencedaily.com/releases/2007/10/071024092417.htm

  16. Sand Sand + Fe Org. soil Org. soil + Fe Control

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