Nutrient Removal Project: Nutrient Removal Project: Chemical Phosphorus RemovalChemical Phosphorus Removal

Jill Crispell, Stephanie Wedekind, Sarah Rosenbaum

ObjectivesObjectives

Reduce the concentration of phosphorus in the effluent of the wastewater treatment plant by precipitating the phosphorus with varying concentrations of metallic salts

Total phosphates should not exceed a concentration of 50ug/L in a stream entering a lake or reservoir

HypothesisHypothesisAs the concentration of a metallic salt

added increases, the concentration of phosphorus in the effluent should decrease from 4 mg/L to a value less than 50 g/L.

The final phosphorus concentration will be independent from the concentration of metallic salts at high metallic salts concentrations.

Metallic salts conc.

PhosphorusConc.

SetupSetup

SetupSetup

Flow Rate:– 450 mL/min

Reagents:– Phosphorus solution: 200 mg/L KH2PO4

– Alum solution: 400 mg/L Al2(SO4)3 o 14H2O

– Ferric Chloride: 200 mg/L FeCl3

MethodsMethods

First experiment: Effect of flocs– In each cycle, phosphorus and water added to bring

concentration to 4 mg/L– Only in first cycle alum (12.5 mg/L) or ferric chloride

(6.8 mg/L)

Al2(SO4)3 o 14H2O + 2PO43- 2AlPO4 + 3SO4

2- +14H2O

FeCl3 + PO43- FePO4 + 3Cl-

Results: First experimentResults: First experiment

Alum was more effective than ferric chloride in removing phosphorus.

Discovered original influent water contained ferric chloride

Flocs remaining in tank continued to react with the phosphorus added

Results: First experiment cont.Results: First experiment cont.

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Results: First experiment cont.Results: First experiment cont.

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Results: First experiment cont.Results: First experiment cont.

Solutions to our Discoveries:– Decided to pump tap water into the plant

from a large jug.– Completely drain the tank.– Added two new states, rinse and rinse

effluent, to clean out the tank of all flocs.

Second experiment: Increasing Second experiment: Increasing concentration of alumconcentration of alum

Different concentrations, 10 mg/L, 12.5 mg/L, 15 mg/L and 25 mg/L, of alum were used to determine which concentration removes phosphorus most efficiently

All samples were analyzed using the spectrophotometer to determine the amount of phosphorus remaining in the effluent.

Results: Second experimentResults: Second experimentAs alum concentration in the plant

increased, phosphorus concentration decreased and percent removal increased based on samples with 10 mg/L, 12.5 mg/L, 15 mg/L and 25 mg/L of alum respectively

alum concentration (mg/L)

average effluent phosphorus conc. (mg/L)

percent removal

10 1.27 68.1712.5 1.10 72.4215 1.03 74.2025 0.70 82.57

Results: Second experiment Results: Second experiment cont.cont.

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Results: Second experiment Results: Second experiment cont.cont.

Although we did not meet our goal of 50 g/L, our high percent removal indicates that the alum is effective

Generally, the trend appears to be decreasing

Results: Second experiment Results: Second experiment cont.cont.

More testing is necessary to determine if the phosphorus reaches a minimum concentration

There cannot be 100% removal (and thus a linear solution) because there is a saturation level in which additional alum no longer effects phosphorus removal

Results: Second experiment Results: Second experiment cont.cont.

According to the stoichiometry of the equations, we should have only needed to use a concentration of 12.5 mg/L of alum to completely react with the 4 mg/L of phosphorus, but much more is needed.

Reasons: other reactants in water, more mixing time.

In the future we would…In the future we would…

Test higher concentrations of alumTry mixing alum and FeCl3

Adjust the pH to be in the optimum range of the coagulants (4.5-5 for FeCl3, 5.5-6.5 for Alum)– Our pH was between 8.3 and 8.4

THE ENDTHE ENDHave a great summer!Have a great summer!