The Phosphate Filter:

Which Type of Soil?

Noah HaibachCentral Catholic HS

2007-2008

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.

Phosphorus TreatmentWater 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

Acceler8

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

Florida Everglades

Phosphorus Absorption

1. Incorporation into Biomassa. 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.

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?

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.

Materials20 clear 2-Liter pop bottles3 3.78 bottles distilled waterAnhydrous KH2PO4

Reagents for the molybdenum blue ascorbic acid method (4500-P E. method)Ocean Optics USB 2000 spectrophotometer120 10mL test tubes w/lids10% organic content soilSandHigh-grade iron (III) oxide

Graduated cylindersAutomatic pipettes; micro and macro

Procedure1. 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.

2. 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.

3. Follow the below diagram for setup, with 4 reps for each treatment.

4. Take 10mL samples over a period of time.5. Prepare the reagents for the molybdenum blue ascorbic acid method,

and react the samples. This colorimetric test turns them blue.6. Determine the phosphorus content of samples, using a standard

curve.

1 P ppm

Soil Soil & Fe Sand Sand & Fe Control

1 P ppm

Soil Sand

1 P ppm1 P ppm1 P ppm

Soil Sand

Iron Oxide

Iron Oxide

1 P ppm

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

Experimental Corrections

Extremely Dark Samples

Data

  Day 0 Day 2 Day 4

Control 0.95 0.00 0.91 0.03 0.72 0.09

Sand 0.96 0.02 0.86 0.06 0.73 0.06

Soil 0.98 0.00 0.96 0.04 0.49 0.06

Sand & Fe 0.95 0.03 0.22 0.03 0.08 0.06

Soil & Fe 0.92 0.00 0.68 0.08 0.26 0.08

Arithmetic Standard Mean Deviation

4 replicates/treatment

Phosphorus Concentration (mg/L)

0.00

0.20

0.40

0.60

0.80

1.00

1.20

Day 0 Day 2 Day 4

Control

Sand

Soil

Sand + Fe

Soil + Fe

Chart

Anova Results Day 4 Treatments

P Values  Control Sand Soil Sand & Fe Soil & Fe

Control ----------- 0.801 6.41E-03 2.76E-05 1.07E-03

Sand ----------- ------------ 1.41E-03 5.95E-06 3.23E-04

Soil ----------- ------------ ------------- 6.85E-05 6.64E-03

Sand w/ Fe ----------- ------------ ------------- ------------ 0.021

Soil w/ Fe ----------- ------------ ------------- ------------ -------------

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.

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

Accreditations Special Thanks to…

Dr. Ron Ripper and Carnegie Mellon UniversityDr. Carrie DoonanDr. John Stolz of Duquesne University

SourcesStandard 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/SS294Science Daily, “Everglades Phosphorus Limits On The Right Track, But More Is Needed”,

http://www.sciencedaily.com/releases/2007/10/071024092417.htm

Sand

Sand + Fe

Org. soil

Org. soil + Fe

Control