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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.
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 1 2 3 4 5 6
alum sample
phos
phor
us c
once
ntra
tion
(mg/
L)
Results: First experiment cont.Results: First experiment cont.
0
0.5
1
1.5
2
2.5
3
3.5
4
0 1 2 3 4 5 6
ferric chloride sample
ph
osp
ho
rus
con
cen
trat
ion
(m
g/L
)
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.
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
8 10 12 14 16 18 20 22 24 26
concentration alum added (mg/L)
conc
entr
atio
n of
ph
osph
orus
in e
fflu
ent
(mg/
L)
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!