Iron and Aluminum Compounds for Removing Phosphorus and Turbidity

from Pond Waters

Claude E. Boyd, Puan Pengseng and Suthira Soongsawang

Department of Fisheries and Allied AquaculturesAuburn University, Alabama 36849 USA

Turbidity Removal

_ Soil colloids + Al3+(Fe3+) _ Soil colloids

The neutral particles will flocculate and settle from the water.

Al3+

Al3+ Al3+

Phosphorus Removal

AL3+ + H2PO4- + 2H2O AlPO42H2O + 2H+

Fe3+ + H2PO4- + 2H2O FePO42H2O + 2H+

Effect on Total Alkalinity

Al3+ + 3H2O = Al(OH)3 + 3H+

CaCO3 + 2H+ = CO2 + H2O + Ca2+

1 mg/L Al3+ = 5.6 mg/L CaCO3

Same reaction for iron, but

1 mg/L Fe3+ = 2.7 mg/L CaCO3

Kemira products for removing phosphorus and suspended solids from aquaculture pond water.

Product name

Specific gravity(g/cm3)

Ferric chloride, liquid, 11.1% Fe 1.38

Ferix-3, granular ferric sulfate, 21% Fe N/A

Aluminum chloride, liquid, 5.6% Al 1.27

Ferrous chloride, 25% solution 1.24

Ferric chloride, liquid, 13.5% Fe 1.43

Ferric sulfate, 13.5% Fe solution 1.55

Kemira products for removing phosphorus and suspended solids from aquaculture pond water.

Product name Specific gravity(g/cm3)

PAX-18, liquid polyaluminum chloride, 9% Al 1.37

Aluminum sulfate (alum) solution, liquid, % Al (?) 1.33

Ferrous sulfate, 5-7% Fe solution 1.15

Clear PASS 1000, liquid, 13% Fe 1.27

Polyferric sulfate, 12% Fe solution 1.5

Effect of Kemira products at 10 mg/L on total phosphorus concentration and turbidity in laboratory tests.

TP (mg/L) Turbidity (NTU)

Product Control Treated Control Treated

Ferric chloride, 11.1% Fe 0.30 0.03 23 1.6

Ferric chloride, 13.5% Fe 0.30 0.03 25 2.4

Granular ferric sulfate, 21% Fe

0.29 0.24 24 20

Ferric sulfate, 13.5% Fe 0.34 0.05 22 4.0

Polyferric sulfate, 12% Fe 0.40 0.23 17 12

Ferrous chloride, 25% Fe 0.33 0.25 28 30

Effect of Kemira products at 10 mg/L on total phosphorus concentration and turbidity in laboratory tests.

TP (mg/L) Turbidity (NTU)

Product Control Treated Control Treated

Ferrous sulfate, 5-7% Fe 0.30 0.26 12 10

Clear PASS 1000, liquid, 13% Fe 0.30 0.25 19 17

Aluminum chloride, 5.6% Al 0.32 0.03 19 1.4

Aluminum sulfate, % Al (?) 0.30 0.25 19 17

Polyaluminum chloride, 9% Al 0.29 0.22 19 15

Effects of liquid ferric chloride (13.5% Fe) on water quality in laboratory tests.

Product concentration

(mg/L)SRP (g/L)

TP (mg/L)

Turbidity (NTU) pH

Total alkalinity

(mg/L)

0 208 0.35 10.1 7.6 80.1

2 75 --- --- --- ---

4 8 --- --- --- ---

6 9 0.08 2.2 7.1 58.7

8 8 0.07 1.6 7.0 52.1

10 8 0.05 1.0 6.8 44.1

Effects of liquid ferric sulfate (13.5% Fe) on water quality in laboratory tests.

Product concentration

(mg/L)

SRP (g/L)

TP (mg/L)

Turbidity (NTU) pH

Total alkalinity

(mg/L)

0 183 0.33 6.9 7.5 81.4

2 12 --- --- --- ---

4 17 --- --- --- ---

6 8 0.12 3.2 7.2 60.1

8 9 0.09 2.2 7.0 54.7

10 9 0.06 1.6 6.8 47.4

Average concentrations of soluble reactive phosphorus (mg/L) in control ponds and in ponds treated at 10 mg/L with ferric chloride and ferric sulfate.

Before Days after application

Treatment application 1 7 14

Ferric chloride 0.011 0.005 0.009 0.010

Ferric sulfate 0.010 0.006 0.012 0.009

Control 0.018 0.014 0.012 0.012

Average concentrations of total phosphorus (mg/L) in control ponds and in ponds treated at 10 mg/L with ferric chloride and ferric sulfate.

Before Days after application

Treatment application 1 7 14

Ferric chloride 0.09 0.03 0.04 0.04

Ferric sulfate 0.11 0.05 0.05 0.05

Control 0.13 0.12 0.04 0.06

Average concentrations of turbidity (NTU) in control ponds and in ponds treated at 10 mg/L with ferric chloride and ferric sulfate.

Before Days after application

Treatment application 1 7 14

Ferric chloride 218 189 219 243

Ferric sulfate 143 127 155 162

Control 200 228 238 214

Average concentrations of water quality variables in control ponds and in ponds treated at 10 mg/L with ferric chloride and ferric sulfate (continued).

Before Days after application

Treatment application 1 7 14

Total alkalinity (mg/L)

Ferric chloride 33.7 30.7 30.6 32.3

Ferric sulfate 30.6 29.2 29.1 28.1

Control 35.2 33.3 38.9 33.1

pH

Ferric chloride 7.8 7.8 7.8 7.8

Ferric sulfate 7.9 7.8 7.9 7.8

Control 7.9 7.8 7.8 7.9

Average fish survival and production in ponds treated eight times during the production period with 10 mg/L of ferric chloride and ferric sulfate. Treatments and control were replicated three times.Variable Ferric chloride Ferric sulfate Control

Survival (%)

Channel catfish 76.5 81.1 80.7

Grass carp 100 95 92

Production (kg/ha)

Channel catfish 4,572 4,867 4,551

Grass carp 264 328 401