SlideShare a Scribd company logo
1 of 43
Download to read offline
CHEMICAL PRECIPITATION
Practiced in water and wastewater treatment for
๏ƒ˜

Phosphorus removal (ww. treatment)
AlPO4 (s) , FePO4 (s) , Ca5(OH)(PO4)3

๏ƒ˜

Hardness removal, water softening
CaCO3 (s) , Mg(OH)2 (s)
๏ƒ˜

Iron and Manganese removal
Fe(OH)3 (s) ; MnO2 (s)

๏ƒ˜

Removal of heavy metals, radionuclei
As (V) or As (III), Ba, Cd, Hg, Zn, Ni, Cr (III)
precipitates in the form of As(V)

Mn+ + n OH-

M(OH)n (s)
If discharge limitations are lower S= ppt. is preferred
because solubility of sulfide salts is lower.
Mn+ + S2-

MS (s)
mostly in the form of H2S (g)
๏ƒ˜

Water conditioning
(To control scale formation or corrosion)

๏ƒ˜

Sulfate removal from wastewaters
CaSO4 (s) ; BaSO4 (s)
PHOSPHORUS REMOVAL
The Types of P
1.

Orthophosphate

H3PO4 , H2PO4- , HPO4= , PO43-

As a fertilizer, phosphorus must be in the form of
orthophosphate.
pKa1 = 2.1
pH
2.1
7.2
12.3

H3PO4

H2PO4-

HPO4=

PO43-

pKa2 = 7.2
pKa3 = 12.3
In the pH range of wastewaters (around 7), the
dominant forms of orthophosphate are H2PO4- and
HPO4=. As the pH increases, the equation moves
toward the formation of PO43-.
2. Condensed (polyphosphates)
When H3PO4 is heated, it decomposes, losing molecules of
water forming the P - O - P bonds. The process of losing water
is called condensation.
O

O

Hโ€“Oโ€“Pโ€“Oโ€“H + Hโ€“Oโ€“Pโ€“Oโ€“H

O

O

Hโ€“Oโ€“P โ€“Oโ€“Pโ€“Oโ€“H

O

O

O

O

H

H

H

H

Orthophosphoric acid

Dipolyphosphoric acid or
Pyrophosphoric acid

All of the hydrogen atoms are ionizable.
Properties of condensed phosphates
โ€ข Condensed phosphates are inorganic and contain
more than one P per molecule.
โ€ข They are used in corrosion control and in
detergents as complexation agents.
Ex. Pyrophosphate H4P2O7 and its ionization
products.

โ€ข They do not form precipitates. But they undergo
hydrolysis in aqueous solutions and transform
into the orthophosphates.
โ€ข Microorganisms convert polyphosphates into
orthophosphates.
3. Organic P : ATO, ADP, etc.
When organic compounds containing P are attacked by
microorganisms, they also undergo hydrolysis into the
orthophosphate forms.
๏ƒ˜ Typical municipal waste : 10 โ€“ 15 mg/L as P
30 % from human waste + 70 % from detergents (mostly in the
form of polyphosphates)
๏ƒ˜ P being a nutrient, causes algal blooms (eutrophication)
106 CO2 + 16 NO3- + HPO4= + 18 H+ + 122 H2O
C106H263O110N16P + 154 O2
๏ƒ˜ In most lakes P is the growth limiting nutrient for algae.
P > 0.01 mg/L stimulates algal growth.
๏ƒ˜ 80 % removal of P or a residual of 1 mg/L as P is
required in effluents discharged to streams which are
tributaries to lakes.

๏ƒ˜ Effluent concentrations are commonly specified to be 1
mg/L or less to minimize environmental effects.

Primary clarification removes 5 โ€“ 10 % of P.
Primary + secondary treatment removes 10 โ€“ 20 % of P.
Phosphorus Removal
The most common method to remove phosphorus from a
waste stream is chemical precipitation.
The common precipitating cations used are Ca, Al and Fe.
Removal of P by Chemical Precipitation

Salts of Al (III), Fe (III) and Ca(II)
Solubility Product Constants for Phosphate Precipitation
Precipitation Product

Ca5(PO3)3(OH)
Ca3(PO4)2
AlPO4
FePO4

Solubility Product , Ksp at 25 ยบC

10-55.9
10-25
10-21
10-21.9
Precipitation by Calcium
Calcium is usually added as lime (Ca(OH)2).
The reaction is represented as:
2๏€ซ

3๏€ญ
4

10Ca ๏€ซ 6PO ๏€ซ 2OH

๏€ญ

Ca10 (PO 4 ) 6 (OH) 2 (s)
Calcium
โ€ข Lime dosage is primarily a function of system
alkalinity.
โ€ข The key parameter here is pH.
โ€ข pH has to be elevated to somewhere between 10.5
and 11 to get effective P removal.
โ€ข As a rule of thumb, lime dose to attain this pH is about
1.5 times the alkalinity represented in mg/L as CaCO3
Disadvantages of lime addition

Lime addition is seldom practiced because
โ€ข it produces large amount of sludge, and
โ€ข the elevated pH has to be readjusted typically by

recarbonation.
Precipitation by Al and Fe

Phosphate precipitation of by Al
3๏€ซ

Al ๏€ซ H n PO

(3๏€ญ n ) ๏€ญ
4

๏‚ฎ AlPO 4 (s) ๏€ซ nH

๏€ซ

Phosphate precipitation of by Fe
3๏€ซ

Fe ๏€ซ H n PO

(3๏€ญ n ) ๏€ญ
4

๏‚ฎ FePO 4 (s) ๏€ซ nH

๏€ซ

1 mol of Al or Fe precipitates 1 mol of phosphate.
However, these reactions are simple and must be
considered in the light of many competing reactions.
In general, with Ca, Al or Fe addition to precipitate
PO43- higher pH is favorable (more PO43- as
opposed to HPO42- or H2PO4- ).
However, soluble Al-PO4-OH complexes begin to
form as pH increases.

For example, the following soluble species can form:
0
Al2 PO4 (OH)3 , Al2 PO4 (OH)๏€ซ , AlPO4 (OH)๏€ญ
2
Al2(SO4)3.XH2O

Al3+ , Al(OH)2+ , Al(OH)2+ , Al(OH)4- etc.
forms below pH 2
Al(OH)3 (s) according to pH.

tremendous waste of chemical.
๏‚ง The chemistry of phosphate precipitate formation
is complex because of complexes formed
between phosphate and metals, and between
metals and other ligands in the wastewater.
๏‚ง Side reactions of the metals with alkalinity to
form hydroxide precipitates are another factor to
be considered.
๏‚ง The amount of metal needed to remove
phosphorus exceeds the stoichiometric amount
at the low levels at which phosphorus is present
in a wastewater.
๏‚ง The common precipitates formed by the metals
are given in the following table.
Table 15.5 Phosphate Precipitates
Metal

Ca+2

Precipitates

Various calcium
phosphates ,
e.g. , Ca3(PO4)2 ,
Ca5(OH)(PO4)3 ,
CaHPO4,
CaCO3

pH range

โ‰ฅ10

โ‰ค9.5

Fe2+

Fe3(PO4)2 ,
Fex(OH)y(PO4)3
Fe(OH)2 , Fe(OH)3

6 โ€“ 8.5

Fe3+

Fex(OH)y(PO4)z , Fe(OH)3

6 โ€“ 8.5

Al3+

Alx(OH)y(PO4)3 , Al(OH)3

6 โ€“ 8.5

Comment

Produces lowest residual P
concentrations.
The alkalinity of the water
determines the dose because of
the formation of CaCO3.
Residual P in the range of 1 โ€“ 2
mg/L.
There will be some oxidation of
Fe2+ to Fe3+.
Purpose
Al3+ + PO4-

Al(PO4) (s)

So Al3+ required is more than 1:1 ratio.

Same for Fe (III)
Fe3+ + PO4-

Fe(PO4) (s)
โ€ข In order to determine the chemical requirement, site
specific experiments, which involve testing the amount
of phosphorus removal at different dosages, are
needed.
โ€ข Chemical requirement depends upon
๏ƒผ pH,
๏ƒผ Alkalinity,
๏ƒผ initial PT, and
๏ƒผ desired % P removal
โ€ข On-site tests under actual plant conditions are
preferred.
โ€ข A reasonably good correlation can be obtained by
plotting the log of the fraction of soluble phosphorus
remaining as a function of the weight ratio of metal to
soluble phosphorus.
โ€ข The required ratio of metal ion to influent soluble
phosphorus for a specified phosphorus removal can be
obtained from such a plot.
โ€ข This ratio is multiplied by the soluble influent
phosphorus concentration in mg/L to determine the
required chemical dose in mg/L.
Data are from several ferric chloride phosphorus removal studies conducted in
the Great Lakes region.

Ref: National Service Center for Environmental Publications (NSCEP)
Process Design Manual for Phosphorus Removal, April 1976
For iron and aluminum salts, without jar tests, the
general guideline for the metal dose to achieve total
soluble residual P concentrations of 1 to 2 mg P/L is

Typical Al or Fe
requirement per mole P

% P removal

1.5

75

1.7
2.3

85
95
Al3+ + PO43-

AlPO4

Ksp = [Al3+][PO43-]
Ksp = [Al3+](ฮฑ3.Ptotal)
[PO43- ]
ฮฑ3 =
[H3PO4 ] + [H 2 PO4- ] + [HPO4 = ] + [PO 43- ]

ฮฑ3 = fraction of PO43- in total P species.
PT =

K sp
ฮฑ3 . [Al3+ ]

[Al3+]

as pH

and

ฮฑ3 as pH
P solubility as a function of pH:
Pure metal phosphates are precipitated within the
shaded area. Mixed complex polynuclear species are
formed outside toward higher and lower pH values.

Figures : 6 โ€“ 12 a- b from Metcalf (pg:502)
Hydro-Complexes of Aluminum
Al
Al

Al

3๏€ซ

3๏€ซ

๏€ซ H 2O

๏€ซ 2 H 2O

Al (OH )

2๏€ซ

๏€ซH

๏€ซ

๏€ซ

Al (OH ) 2 ๏€ซ 2 H

๏€ซ

3๏€ซ

๏€ซ 3H 2O

Al (OH ) 3 ( s ) ๏€ซ 3H

3๏€ซ

๏€ซ 4 H 2O

Al (OH ) 4 ๏€ซ 4 H

Al

๏€ญ

๏€ซ

๏€ซ

โ€ข pH drops and alkalinity of water is reduced due to acid
formation.
โ€ข If Al(OH)3 precipitate is formed, 3 equivalents of alkalinity is
reduced per mole of Al3+ added.
A similar set of reactions can be written for Fe3+ .
โ€ข So there is a minimum point for Ptotal at about pH = 6โ€“7.
For FePO4, minimum Ptotal is at about pH = 5โ€“6.
โ€ข Use Fe salts if alkalinity is low.
โ€ข When salts are added, pH drops (hydrolysis reactions
and alkalinity consumption).

โ€ข This helps the precipitation, if the pH is above the
minimum solubility point.
โ€ข Otherwise, pH drop is detrimental.
Sodium Aluminate
NaAlO2

AlO2- + H2O

Na+ + AlO2-

Al3+ + Al(OH)2+ + Al(OH)2+ etc. + OH-

โ€ข NaAlO2 is more expensive than Alum but you generate
OH- instead of H+.
โ€ข OH- is released in the reaction. So, aluminate behaves as
a base and pH increases.
โ€ข If water is acidic, use NaAlO2 not Al2(SO4)3 or use a
mixture to adjust to the optimum pH.

โ€ข Higher Al (III) requirement with aluminate than alum.
Ref: National Service Center for Environmental Publications (NSCEP)
Process Design Manual for Phosphorus Removal, April 1976
Addition of Ca

โ€ข Lime is cheaper than alum, FeCl3 or Fe2(SO4)3.
โ€ข It can achieve the lowest residual phosphate
concentration because of the formation of apatites,
Ca5(OH)(PO4)3.
โ€ข Apatites are highly insoluble Ksp = 10-55.0, however a
high pH must be attained to realize their formation.
โ€ข Because calcium forms CaCO3 near pH 9.5 and pHs
higher than 9.5 are required for significant apatite
formation, the alkalinity of water is the governing
factor for the required dose of lime.
Very high doses of lime are required, which makes this
choice costly compared to other metal agents, although
the lowest residual P concentrations can be achieved.

Ca(OH)2, CaO : Both Ca++ and OH- source.
5 Ca2+ + OH- + 3 PO43Ca2+ + CO3=

Ca5(OH)(PO4)3 (s)

CaCO3 (s)

This reaction is not our purpose but we cannot prevent
its formation.
๏ƒ˜ Ca requirement for P removal is a function of
carbonate alkalinity. Avoid if alkalinity is too high.
(CaCO3 sludge) See Fig. 6-11 from Met-Calf&Eddy
๏ƒ˜ High pH is required (pH : 10 โ€“ 11) See Fig. 2-2

๏ƒ˜ Neutralize or recarbonate (CO2) to bring the pH
down after precipitation.
Phosphorus Removal in Various Stages
โ€ข Addition of metal coagulants to wastewater can
have a significant impact on the amount of
sludge produced.
โ€ข There are a variety of chemical application points
in the treatment scheme.
โ€ข The common addition points for metals in
biological treatment plants are before the
primary clarifier or before the secondary clarifier
or during tertiary treatment.
โ€ข Some alternative treatment schemes are shown
in the following slide.
During Primary Treatment
๏ƒ˜ Increases BOD and SS removal
๏ƒ˜ Least efficient use of salts. Therefore you have to add
too much chemical.

๏ƒ˜ Fe and Al sludges are difficult to dewater.
๏ƒ˜ Results in sludge mass increases from 50 to 100%
from the primary clarifier and an overall increase of 60 โ€“
70% in the sludge mass produced by the plant.
During Secondary Treatment

๏ƒ˜ Lime cannot be used because of high pH.
๏ƒ˜ Overdose of Al or Fe salts may cause low pH
and toxicity.
๏ƒ˜ Increases in sludge mass are 35 โ€“ 45% from
the clarifier and 10 โ€“ 25% for the whole plant.
๏ƒ˜ These salts will also have an impact on sludge
dewaterability.
Tertiary Treatment
๏ƒ˜ Highest capital cost because you need to have another
sedimentation tank.
๏ƒ˜ Most efficient metal use. You use the least amount of chemical
and produce the least amount of sludge.
๏ƒ˜ Lowest P in the effluent.
๏ƒ˜ Lime recovery is possible.
sludge

Heat

CaO + CO2
Recalcination

๏ƒ˜ Separate disposal of chemical precipitation.

More Related Content

What's hot

Biological phosphorus removal for waste water treatment
Biological phosphorus removal for waste water treatmentBiological phosphorus removal for waste water treatment
Biological phosphorus removal for waste water treatmentAnjaliBabu12
ย 
WATER QUALITY PARAMETERS
WATER QUALITY PARAMETERSWATER QUALITY PARAMETERS
WATER QUALITY PARAMETERSJenson Samraj
ย 
Biochemical oxygen demand
Biochemical oxygen demandBiochemical oxygen demand
Biochemical oxygen demandutpal sharma
ย 
Wastewater treatment technologies for removal of nitrogen and phosphorus
Wastewater treatment technologies for removal of nitrogen and phosphorusWastewater treatment technologies for removal of nitrogen and phosphorus
Wastewater treatment technologies for removal of nitrogen and phosphorusRabia Aziz
ย 
advanced oxidation process
advanced oxidation processadvanced oxidation process
advanced oxidation processMahendheran Mech
ย 
Wastewater treatment technologies
Wastewater treatment technologiesWastewater treatment technologies
Wastewater treatment technologiesAkshay More
ย 
An introduction to electrocoagulation
An introduction to electrocoagulationAn introduction to electrocoagulation
An introduction to electrocoagulationChristos Charisiadis
ย 
Acidity in Water
Acidity in WaterAcidity in Water
Acidity in WaterPurva Saxena
ย 
harness of water ppt
harness of water pptharness of water ppt
harness of water pptvicky264patel
ย 
Njp 1919021014 adsorption for wastewater treatment
Njp 1919021014 adsorption for wastewater treatmentNjp 1919021014 adsorption for wastewater treatment
Njp 1919021014 adsorption for wastewater treatmentJean Paul Nkundabose
ย 
Biological Nutrient Removal (BNR)
Biological Nutrient Removal (BNR)Biological Nutrient Removal (BNR)
Biological Nutrient Removal (BNR)Seminar Links
ย 
Chemical oxygen demand
Chemical oxygen demandChemical oxygen demand
Chemical oxygen demandUsman Khawaja
ย 
Chapter 5 water quality
Chapter 5 water qualityChapter 5 water quality
Chapter 5 water qualityMohammed Salahat
ย 
WATER ANALYSIS /Water quality testing p.k.k
WATER ANALYSIS /Water quality testing p.k.kWATER ANALYSIS /Water quality testing p.k.k
WATER ANALYSIS /Water quality testing p.k.kPUSHPA KHOLA
ย 
Removal of iron &; Manganese
Removal of iron &; ManganeseRemoval of iron &; Manganese
Removal of iron &; ManganeseGAURAV. H .TANDON
ย 

What's hot (20)

Bod types
Bod typesBod types
Bod types
ย 
Biological phosphorus removal for waste water treatment
Biological phosphorus removal for waste water treatmentBiological phosphorus removal for waste water treatment
Biological phosphorus removal for waste water treatment
ย 
WATER QUALITY PARAMETERS
WATER QUALITY PARAMETERSWATER QUALITY PARAMETERS
WATER QUALITY PARAMETERS
ย 
Biochemical oxygen demand
Biochemical oxygen demandBiochemical oxygen demand
Biochemical oxygen demand
ย 
Wastewater treatment technologies for removal of nitrogen and phosphorus
Wastewater treatment technologies for removal of nitrogen and phosphorusWastewater treatment technologies for removal of nitrogen and phosphorus
Wastewater treatment technologies for removal of nitrogen and phosphorus
ย 
advanced oxidation process
advanced oxidation processadvanced oxidation process
advanced oxidation process
ย 
Wastewater treatment technologies
Wastewater treatment technologiesWastewater treatment technologies
Wastewater treatment technologies
ย 
An introduction to electrocoagulation
An introduction to electrocoagulationAn introduction to electrocoagulation
An introduction to electrocoagulation
ย 
Acidity in Water
Acidity in WaterAcidity in Water
Acidity in Water
ย 
BOD & COD
BOD & CODBOD & COD
BOD & COD
ย 
DO, BOD and COD
DO, BOD and CODDO, BOD and COD
DO, BOD and COD
ย 
harness of water ppt
harness of water pptharness of water ppt
harness of water ppt
ย 
Njp 1919021014 adsorption for wastewater treatment
Njp 1919021014 adsorption for wastewater treatmentNjp 1919021014 adsorption for wastewater treatment
Njp 1919021014 adsorption for wastewater treatment
ย 
Biological Nutrient Removal (BNR)
Biological Nutrient Removal (BNR)Biological Nutrient Removal (BNR)
Biological Nutrient Removal (BNR)
ย 
Chemical oxygen demand
Chemical oxygen demandChemical oxygen demand
Chemical oxygen demand
ย 
01 water quality
01 water quality01 water quality
01 water quality
ย 
Chapter 5 water quality
Chapter 5 water qualityChapter 5 water quality
Chapter 5 water quality
ย 
WATER ANALYSIS /Water quality testing p.k.k
WATER ANALYSIS /Water quality testing p.k.kWATER ANALYSIS /Water quality testing p.k.k
WATER ANALYSIS /Water quality testing p.k.k
ย 
Removal of iron &; Manganese
Removal of iron &; ManganeseRemoval of iron &; Manganese
Removal of iron &; Manganese
ย 
Do,cod,bod
Do,cod,bodDo,cod,bod
Do,cod,bod
ย 

Viewers also liked

Cultural and Mechanical Control of Weeds
Cultural and Mechanical Control of WeedsCultural and Mechanical Control of Weeds
Cultural and Mechanical Control of WeedsKarl Obispo
ย 
DETERMINATION OF PHOSPHOROUS IN SOIL
DETERMINATION OF PHOSPHOROUS IN SOILDETERMINATION OF PHOSPHOROUS IN SOIL
DETERMINATION OF PHOSPHOROUS IN SOILNarendrareddy123
ย 
Problem soil management
Problem soil managementProblem soil management
Problem soil managementIIM Ahmedabad
ย 
Problematic soil
Problematic soilProblematic soil
Problematic soilAAMIR CHAUDHARY
ย 

Viewers also liked (8)

Som lecture 1
Som lecture 1Som lecture 1
Som lecture 1
ย 
Soil ex
Soil exSoil ex
Soil ex
ย 
Cultural and Mechanical Control of Weeds
Cultural and Mechanical Control of WeedsCultural and Mechanical Control of Weeds
Cultural and Mechanical Control of Weeds
ย 
DETERMINATION OF PHOSPHOROUS IN SOIL
DETERMINATION OF PHOSPHOROUS IN SOILDETERMINATION OF PHOSPHOROUS IN SOIL
DETERMINATION OF PHOSPHOROUS IN SOIL
ย 
Problem soil management
Problem soil managementProblem soil management
Problem soil management
ย 
Managing Organic Matter for Soil Health and Fertility
Managing Organic Matter for Soil Health and FertilityManaging Organic Matter for Soil Health and Fertility
Managing Organic Matter for Soil Health and Fertility
ย 
Problematic soil
Problematic soilProblematic soil
Problematic soil
ย 
Soil organic matter pp
Soil organic matter ppSoil organic matter pp
Soil organic matter pp
ย 

Similar to 13.phosphorus removal by chem ppt

Advanced wastewater treatment
Advanced wastewater treatmentAdvanced wastewater treatment
Advanced wastewater treatmentNikka Lopez
ย 
acidityalkalinity of water sample
acidityalkalinity of water sampleacidityalkalinity of water sample
acidityalkalinity of water sampleJenithM
ย 
acidity and alkalinity of water
acidity and alkalinity of wateracidity and alkalinity of water
acidity and alkalinity of waterJenithM
ย 
22CYL11 & Chemistry Laboratory for Electrical Systems (EIE-Alkalinity).ppt
22CYL11 & Chemistry Laboratory for Electrical Systems (EIE-Alkalinity).ppt22CYL11 & Chemistry Laboratory for Electrical Systems (EIE-Alkalinity).ppt
22CYL11 & Chemistry Laboratory for Electrical Systems (EIE-Alkalinity).pptkowshalya21
ย 
Discuss the carbonate conditioning and phosphate conditioning with respect to...
Discuss the carbonate conditioning and phosphate conditioning with respect to...Discuss the carbonate conditioning and phosphate conditioning with respect to...
Discuss the carbonate conditioning and phosphate conditioning with respect to...SamiaSalman1
ย 
Soils 502 lecture no 18 22 phosphorus
Soils 502 lecture no 18 22 phosphorusSoils 502 lecture no 18 22 phosphorus
Soils 502 lecture no 18 22 phosphorusDrAnandJadhav
ย 
Alkalinity and Hardness teri maaka bhosda
Alkalinity and Hardness teri maaka bhosdaAlkalinity and Hardness teri maaka bhosda
Alkalinity and Hardness teri maaka bhosdaBITTUGAMING1
ย 
AcidBase_Balance.biochemistry assigments
AcidBase_Balance.biochemistry assigmentsAcidBase_Balance.biochemistry assigments
AcidBase_Balance.biochemistry assigmentsbasmaqazi89
ย 
Lab 4 alkalinity โ€“acidity and determination of alkalinity in water
Lab 4 alkalinity โ€“acidity and determination of alkalinity in waterLab 4 alkalinity โ€“acidity and determination of alkalinity in water
Lab 4 alkalinity โ€“acidity and determination of alkalinity in waterAnas Maghayreh
ย 
Apchemunit14presentationpart2 120227191453-phpapp02
Apchemunit14presentationpart2 120227191453-phpapp02Apchemunit14presentationpart2 120227191453-phpapp02
Apchemunit14presentationpart2 120227191453-phpapp02Cleophas Rwemera
ย 
Characteristics of the Major Elements as Fertilizer
Characteristics of the Major Elements as Fertilizer Characteristics of the Major Elements as Fertilizer
Characteristics of the Major Elements as Fertilizer Japhet Paypa
ย 
A new perspective on metabolic acidosis
A new perspective on metabolic acidosisA new perspective on metabolic acidosis
A new perspective on metabolic acidosisstevechendoc
ย 
THE PREPARATION , ANALYSIS AND REACTION OF AN ETHANEDIOATE (OXALATE) COMPLEX ...
THE PREPARATION , ANALYSIS AND REACTION OF AN ETHANEDIOATE (OXALATE) COMPLEX ...THE PREPARATION , ANALYSIS AND REACTION OF AN ETHANEDIOATE (OXALATE) COMPLEX ...
THE PREPARATION , ANALYSIS AND REACTION OF AN ETHANEDIOATE (OXALATE) COMPLEX ...Augustine Adu
ย 
Structures, Names and Physical Properties of Alcohol
Structures, Names and Physical Properties of AlcoholStructures, Names and Physical Properties of Alcohol
Structures, Names and Physical Properties of Alcoholbuk 369
ย 
22CYL23 & Chemistry Laboratory for Chemical Engineering (Chemical-B-Alkalinit...
22CYL23 & Chemistry Laboratory for Chemical Engineering (Chemical-B-Alkalinit...22CYL23 & Chemistry Laboratory for Chemical Engineering (Chemical-B-Alkalinit...
22CYL23 & Chemistry Laboratory for Chemical Engineering (Chemical-B-Alkalinit...KrishnaveniKrishnara1
ย 
Organic Chemistry: Carbonyl Compounds and Nitrogen Compounds
Organic Chemistry: Carbonyl Compounds and Nitrogen CompoundsOrganic Chemistry: Carbonyl Compounds and Nitrogen Compounds
Organic Chemistry: Carbonyl Compounds and Nitrogen CompoundsIndra Yudhipratama
ย 
05 acids + bases
05 acids + bases05 acids + bases
05 acids + basesmrtangextrahelp
ย 

Similar to 13.phosphorus removal by chem ppt (20)

Sdi
SdiSdi
Sdi
ย 
Advanced wastewater treatment
Advanced wastewater treatmentAdvanced wastewater treatment
Advanced wastewater treatment
ย 
acidityalkalinity of water sample
acidityalkalinity of water sampleacidityalkalinity of water sample
acidityalkalinity of water sample
ย 
acidity and alkalinity of water
acidity and alkalinity of wateracidity and alkalinity of water
acidity and alkalinity of water
ย 
22CYL11 & Chemistry Laboratory for Electrical Systems (EIE-Alkalinity).ppt
22CYL11 & Chemistry Laboratory for Electrical Systems (EIE-Alkalinity).ppt22CYL11 & Chemistry Laboratory for Electrical Systems (EIE-Alkalinity).ppt
22CYL11 & Chemistry Laboratory for Electrical Systems (EIE-Alkalinity).ppt
ย 
Discuss the carbonate conditioning and phosphate conditioning with respect to...
Discuss the carbonate conditioning and phosphate conditioning with respect to...Discuss the carbonate conditioning and phosphate conditioning with respect to...
Discuss the carbonate conditioning and phosphate conditioning with respect to...
ย 
Soils 502 lecture no 18 22 phosphorus
Soils 502 lecture no 18 22 phosphorusSoils 502 lecture no 18 22 phosphorus
Soils 502 lecture no 18 22 phosphorus
ย 
Alkalinity and Hardness teri maaka bhosda
Alkalinity and Hardness teri maaka bhosdaAlkalinity and Hardness teri maaka bhosda
Alkalinity and Hardness teri maaka bhosda
ย 
AcidBase_Balance.biochemistry assigments
AcidBase_Balance.biochemistry assigmentsAcidBase_Balance.biochemistry assigments
AcidBase_Balance.biochemistry assigments
ย 
Lab 4 alkalinity โ€“acidity and determination of alkalinity in water
Lab 4 alkalinity โ€“acidity and determination of alkalinity in waterLab 4 alkalinity โ€“acidity and determination of alkalinity in water
Lab 4 alkalinity โ€“acidity and determination of alkalinity in water
ย 
Apchemunit14presentationpart2 120227191453-phpapp02
Apchemunit14presentationpart2 120227191453-phpapp02Apchemunit14presentationpart2 120227191453-phpapp02
Apchemunit14presentationpart2 120227191453-phpapp02
ย 
Dark reactions
Dark reactionsDark reactions
Dark reactions
ย 
Characteristics of the Major Elements as Fertilizer
Characteristics of the Major Elements as Fertilizer Characteristics of the Major Elements as Fertilizer
Characteristics of the Major Elements as Fertilizer
ย 
A new perspective on metabolic acidosis
A new perspective on metabolic acidosisA new perspective on metabolic acidosis
A new perspective on metabolic acidosis
ย 
THE PREPARATION , ANALYSIS AND REACTION OF AN ETHANEDIOATE (OXALATE) COMPLEX ...
THE PREPARATION , ANALYSIS AND REACTION OF AN ETHANEDIOATE (OXALATE) COMPLEX ...THE PREPARATION , ANALYSIS AND REACTION OF AN ETHANEDIOATE (OXALATE) COMPLEX ...
THE PREPARATION , ANALYSIS AND REACTION OF AN ETHANEDIOATE (OXALATE) COMPLEX ...
ย 
Structures, Names and Physical Properties of Alcohol
Structures, Names and Physical Properties of AlcoholStructures, Names and Physical Properties of Alcohol
Structures, Names and Physical Properties of Alcohol
ย 
22CYL23 & Chemistry Laboratory for Chemical Engineering (Chemical-B-Alkalinit...
22CYL23 & Chemistry Laboratory for Chemical Engineering (Chemical-B-Alkalinit...22CYL23 & Chemistry Laboratory for Chemical Engineering (Chemical-B-Alkalinit...
22CYL23 & Chemistry Laboratory for Chemical Engineering (Chemical-B-Alkalinit...
ย 
Phenols
PhenolsPhenols
Phenols
ย 
Organic Chemistry: Carbonyl Compounds and Nitrogen Compounds
Organic Chemistry: Carbonyl Compounds and Nitrogen CompoundsOrganic Chemistry: Carbonyl Compounds and Nitrogen Compounds
Organic Chemistry: Carbonyl Compounds and Nitrogen Compounds
ย 
05 acids + bases
05 acids + bases05 acids + bases
05 acids + bases
ย 

Recently uploaded

VIP Call Girl in Mumbai ๐Ÿ’ง 9920725232 ( Call Me ) Get A New Crush Everyday Wit...
VIP Call Girl in Mumbai ๐Ÿ’ง 9920725232 ( Call Me ) Get A New Crush Everyday Wit...VIP Call Girl in Mumbai ๐Ÿ’ง 9920725232 ( Call Me ) Get A New Crush Everyday Wit...
VIP Call Girl in Mumbai ๐Ÿ’ง 9920725232 ( Call Me ) Get A New Crush Everyday Wit...dipikadinghjn ( Why You Choose Us? ) Escorts
ย 
VIP Independent Call Girls in Bandra West ๐ŸŒน 9920725232 ( Call Me ) Mumbai Esc...
VIP Independent Call Girls in Bandra West ๐ŸŒน 9920725232 ( Call Me ) Mumbai Esc...VIP Independent Call Girls in Bandra West ๐ŸŒน 9920725232 ( Call Me ) Mumbai Esc...
VIP Independent Call Girls in Bandra West ๐ŸŒน 9920725232 ( Call Me ) Mumbai Esc...dipikadinghjn ( Why You Choose Us? ) Escorts
ย 
Indore Real Estate Market Trends Report.pdf
Indore Real Estate Market Trends Report.pdfIndore Real Estate Market Trends Report.pdf
Indore Real Estate Market Trends Report.pdfSaviRakhecha1
ย 
05_Annelore Lenoir_Docbyte_MeetupDora&Cybersecurity.pptx
05_Annelore Lenoir_Docbyte_MeetupDora&Cybersecurity.pptx05_Annelore Lenoir_Docbyte_MeetupDora&Cybersecurity.pptx
05_Annelore Lenoir_Docbyte_MeetupDora&Cybersecurity.pptxFinTech Belgium
ย 
WhatsApp ๐Ÿ“ž Call : 9892124323 โœ…Call Girls In Chembur ( Mumbai ) secure service
WhatsApp ๐Ÿ“ž Call : 9892124323  โœ…Call Girls In Chembur ( Mumbai ) secure serviceWhatsApp ๐Ÿ“ž Call : 9892124323  โœ…Call Girls In Chembur ( Mumbai ) secure service
WhatsApp ๐Ÿ“ž Call : 9892124323 โœ…Call Girls In Chembur ( Mumbai ) secure servicePooja Nehwal
ย 
Booking open Available Pune Call Girls Talegaon Dabhade 6297143586 Call Hot ...
Booking open Available Pune Call Girls Talegaon Dabhade  6297143586 Call Hot ...Booking open Available Pune Call Girls Talegaon Dabhade  6297143586 Call Hot ...
Booking open Available Pune Call Girls Talegaon Dabhade 6297143586 Call Hot ...Call Girls in Nagpur High Profile
ย 
Solution Manual for Financial Accounting, 11th Edition by Robert Libby, Patri...
Solution Manual for Financial Accounting, 11th Edition by Robert Libby, Patri...Solution Manual for Financial Accounting, 11th Edition by Robert Libby, Patri...
Solution Manual for Financial Accounting, 11th Edition by Robert Libby, Patri...ssifa0344
ย 
Top Rated Pune Call Girls Viman Nagar โŸŸ 6297143586 โŸŸ Call Me For Genuine Sex...
Top Rated  Pune Call Girls Viman Nagar โŸŸ 6297143586 โŸŸ Call Me For Genuine Sex...Top Rated  Pune Call Girls Viman Nagar โŸŸ 6297143586 โŸŸ Call Me For Genuine Sex...
Top Rated Pune Call Girls Viman Nagar โŸŸ 6297143586 โŸŸ Call Me For Genuine Sex...Call Girls in Nagpur High Profile
ย 
The Economic History of the U.S. Lecture 25.pdf
The Economic History of the U.S. Lecture 25.pdfThe Economic History of the U.S. Lecture 25.pdf
The Economic History of the U.S. Lecture 25.pdfGale Pooley
ย 
The Economic History of the U.S. Lecture 21.pdf
The Economic History of the U.S. Lecture 21.pdfThe Economic History of the U.S. Lecture 21.pdf
The Economic History of the U.S. Lecture 21.pdfGale Pooley
ย 
Call Girls Koregaon Park Call Me 7737669865 Budget Friendly No Advance Booking
Call Girls Koregaon Park Call Me 7737669865 Budget Friendly No Advance BookingCall Girls Koregaon Park Call Me 7737669865 Budget Friendly No Advance Booking
Call Girls Koregaon Park Call Me 7737669865 Budget Friendly No Advance Bookingroncy bisnoi
ย 
Gurley shaw Theory of Monetary Economics.
Gurley shaw Theory of Monetary Economics.Gurley shaw Theory of Monetary Economics.
Gurley shaw Theory of Monetary Economics.Vinodha Devi
ย 
The Economic History of the U.S. Lecture 20.pdf
The Economic History of the U.S. Lecture 20.pdfThe Economic History of the U.S. Lecture 20.pdf
The Economic History of the U.S. Lecture 20.pdfGale Pooley
ย 
Top Rated Pune Call Girls Sinhagad Road โŸŸ 6297143586 โŸŸ Call Me For Genuine S...
Top Rated  Pune Call Girls Sinhagad Road โŸŸ 6297143586 โŸŸ Call Me For Genuine S...Top Rated  Pune Call Girls Sinhagad Road โŸŸ 6297143586 โŸŸ Call Me For Genuine S...
Top Rated Pune Call Girls Sinhagad Road โŸŸ 6297143586 โŸŸ Call Me For Genuine S...Call Girls in Nagpur High Profile
ย 
The Economic History of the U.S. Lecture 19.pdf
The Economic History of the U.S. Lecture 19.pdfThe Economic History of the U.S. Lecture 19.pdf
The Economic History of the U.S. Lecture 19.pdfGale Pooley
ย 
Kharghar Blowjob Housewife Call Girls NUmber-9833754194-CBD Belapur Internati...
Kharghar Blowjob Housewife Call Girls NUmber-9833754194-CBD Belapur Internati...Kharghar Blowjob Housewife Call Girls NUmber-9833754194-CBD Belapur Internati...
Kharghar Blowjob Housewife Call Girls NUmber-9833754194-CBD Belapur Internati...priyasharma62062
ย 
The Economic History of the U.S. Lecture 18.pdf
The Economic History of the U.S. Lecture 18.pdfThe Economic History of the U.S. Lecture 18.pdf
The Economic History of the U.S. Lecture 18.pdfGale Pooley
ย 
Mira Road Memorable Call Grls Number-9833754194-Bhayandar Speciallty Call Gir...
Mira Road Memorable Call Grls Number-9833754194-Bhayandar Speciallty Call Gir...Mira Road Memorable Call Grls Number-9833754194-Bhayandar Speciallty Call Gir...
Mira Road Memorable Call Grls Number-9833754194-Bhayandar Speciallty Call Gir...priyasharma62062
ย 
VIP Independent Call Girls in Mira Bhayandar ๐ŸŒน 9920725232 ( Call Me ) Mumbai ...
VIP Independent Call Girls in Mira Bhayandar ๐ŸŒน 9920725232 ( Call Me ) Mumbai ...VIP Independent Call Girls in Mira Bhayandar ๐ŸŒน 9920725232 ( Call Me ) Mumbai ...
VIP Independent Call Girls in Mira Bhayandar ๐ŸŒน 9920725232 ( Call Me ) Mumbai ...dipikadinghjn ( Why You Choose Us? ) Escorts
ย 
VIP Independent Call Girls in Andheri ๐ŸŒน 9920725232 ( Call Me ) Mumbai Escorts...
VIP Independent Call Girls in Andheri ๐ŸŒน 9920725232 ( Call Me ) Mumbai Escorts...VIP Independent Call Girls in Andheri ๐ŸŒน 9920725232 ( Call Me ) Mumbai Escorts...
VIP Independent Call Girls in Andheri ๐ŸŒน 9920725232 ( Call Me ) Mumbai Escorts...dipikadinghjn ( Why You Choose Us? ) Escorts
ย 

Recently uploaded (20)

VIP Call Girl in Mumbai ๐Ÿ’ง 9920725232 ( Call Me ) Get A New Crush Everyday Wit...
VIP Call Girl in Mumbai ๐Ÿ’ง 9920725232 ( Call Me ) Get A New Crush Everyday Wit...VIP Call Girl in Mumbai ๐Ÿ’ง 9920725232 ( Call Me ) Get A New Crush Everyday Wit...
VIP Call Girl in Mumbai ๐Ÿ’ง 9920725232 ( Call Me ) Get A New Crush Everyday Wit...
ย 
VIP Independent Call Girls in Bandra West ๐ŸŒน 9920725232 ( Call Me ) Mumbai Esc...
VIP Independent Call Girls in Bandra West ๐ŸŒน 9920725232 ( Call Me ) Mumbai Esc...VIP Independent Call Girls in Bandra West ๐ŸŒน 9920725232 ( Call Me ) Mumbai Esc...
VIP Independent Call Girls in Bandra West ๐ŸŒน 9920725232 ( Call Me ) Mumbai Esc...
ย 
Indore Real Estate Market Trends Report.pdf
Indore Real Estate Market Trends Report.pdfIndore Real Estate Market Trends Report.pdf
Indore Real Estate Market Trends Report.pdf
ย 
05_Annelore Lenoir_Docbyte_MeetupDora&Cybersecurity.pptx
05_Annelore Lenoir_Docbyte_MeetupDora&Cybersecurity.pptx05_Annelore Lenoir_Docbyte_MeetupDora&Cybersecurity.pptx
05_Annelore Lenoir_Docbyte_MeetupDora&Cybersecurity.pptx
ย 
WhatsApp ๐Ÿ“ž Call : 9892124323 โœ…Call Girls In Chembur ( Mumbai ) secure service
WhatsApp ๐Ÿ“ž Call : 9892124323  โœ…Call Girls In Chembur ( Mumbai ) secure serviceWhatsApp ๐Ÿ“ž Call : 9892124323  โœ…Call Girls In Chembur ( Mumbai ) secure service
WhatsApp ๐Ÿ“ž Call : 9892124323 โœ…Call Girls In Chembur ( Mumbai ) secure service
ย 
Booking open Available Pune Call Girls Talegaon Dabhade 6297143586 Call Hot ...
Booking open Available Pune Call Girls Talegaon Dabhade  6297143586 Call Hot ...Booking open Available Pune Call Girls Talegaon Dabhade  6297143586 Call Hot ...
Booking open Available Pune Call Girls Talegaon Dabhade 6297143586 Call Hot ...
ย 
Solution Manual for Financial Accounting, 11th Edition by Robert Libby, Patri...
Solution Manual for Financial Accounting, 11th Edition by Robert Libby, Patri...Solution Manual for Financial Accounting, 11th Edition by Robert Libby, Patri...
Solution Manual for Financial Accounting, 11th Edition by Robert Libby, Patri...
ย 
Top Rated Pune Call Girls Viman Nagar โŸŸ 6297143586 โŸŸ Call Me For Genuine Sex...
Top Rated  Pune Call Girls Viman Nagar โŸŸ 6297143586 โŸŸ Call Me For Genuine Sex...Top Rated  Pune Call Girls Viman Nagar โŸŸ 6297143586 โŸŸ Call Me For Genuine Sex...
Top Rated Pune Call Girls Viman Nagar โŸŸ 6297143586 โŸŸ Call Me For Genuine Sex...
ย 
The Economic History of the U.S. Lecture 25.pdf
The Economic History of the U.S. Lecture 25.pdfThe Economic History of the U.S. Lecture 25.pdf
The Economic History of the U.S. Lecture 25.pdf
ย 
The Economic History of the U.S. Lecture 21.pdf
The Economic History of the U.S. Lecture 21.pdfThe Economic History of the U.S. Lecture 21.pdf
The Economic History of the U.S. Lecture 21.pdf
ย 
Call Girls Koregaon Park Call Me 7737669865 Budget Friendly No Advance Booking
Call Girls Koregaon Park Call Me 7737669865 Budget Friendly No Advance BookingCall Girls Koregaon Park Call Me 7737669865 Budget Friendly No Advance Booking
Call Girls Koregaon Park Call Me 7737669865 Budget Friendly No Advance Booking
ย 
Gurley shaw Theory of Monetary Economics.
Gurley shaw Theory of Monetary Economics.Gurley shaw Theory of Monetary Economics.
Gurley shaw Theory of Monetary Economics.
ย 
The Economic History of the U.S. Lecture 20.pdf
The Economic History of the U.S. Lecture 20.pdfThe Economic History of the U.S. Lecture 20.pdf
The Economic History of the U.S. Lecture 20.pdf
ย 
Top Rated Pune Call Girls Sinhagad Road โŸŸ 6297143586 โŸŸ Call Me For Genuine S...
Top Rated  Pune Call Girls Sinhagad Road โŸŸ 6297143586 โŸŸ Call Me For Genuine S...Top Rated  Pune Call Girls Sinhagad Road โŸŸ 6297143586 โŸŸ Call Me For Genuine S...
Top Rated Pune Call Girls Sinhagad Road โŸŸ 6297143586 โŸŸ Call Me For Genuine S...
ย 
The Economic History of the U.S. Lecture 19.pdf
The Economic History of the U.S. Lecture 19.pdfThe Economic History of the U.S. Lecture 19.pdf
The Economic History of the U.S. Lecture 19.pdf
ย 
Kharghar Blowjob Housewife Call Girls NUmber-9833754194-CBD Belapur Internati...
Kharghar Blowjob Housewife Call Girls NUmber-9833754194-CBD Belapur Internati...Kharghar Blowjob Housewife Call Girls NUmber-9833754194-CBD Belapur Internati...
Kharghar Blowjob Housewife Call Girls NUmber-9833754194-CBD Belapur Internati...
ย 
The Economic History of the U.S. Lecture 18.pdf
The Economic History of the U.S. Lecture 18.pdfThe Economic History of the U.S. Lecture 18.pdf
The Economic History of the U.S. Lecture 18.pdf
ย 
Mira Road Memorable Call Grls Number-9833754194-Bhayandar Speciallty Call Gir...
Mira Road Memorable Call Grls Number-9833754194-Bhayandar Speciallty Call Gir...Mira Road Memorable Call Grls Number-9833754194-Bhayandar Speciallty Call Gir...
Mira Road Memorable Call Grls Number-9833754194-Bhayandar Speciallty Call Gir...
ย 
VIP Independent Call Girls in Mira Bhayandar ๐ŸŒน 9920725232 ( Call Me ) Mumbai ...
VIP Independent Call Girls in Mira Bhayandar ๐ŸŒน 9920725232 ( Call Me ) Mumbai ...VIP Independent Call Girls in Mira Bhayandar ๐ŸŒน 9920725232 ( Call Me ) Mumbai ...
VIP Independent Call Girls in Mira Bhayandar ๐ŸŒน 9920725232 ( Call Me ) Mumbai ...
ย 
VIP Independent Call Girls in Andheri ๐ŸŒน 9920725232 ( Call Me ) Mumbai Escorts...
VIP Independent Call Girls in Andheri ๐ŸŒน 9920725232 ( Call Me ) Mumbai Escorts...VIP Independent Call Girls in Andheri ๐ŸŒน 9920725232 ( Call Me ) Mumbai Escorts...
VIP Independent Call Girls in Andheri ๐ŸŒน 9920725232 ( Call Me ) Mumbai Escorts...
ย 

13.phosphorus removal by chem ppt

  • 1. CHEMICAL PRECIPITATION Practiced in water and wastewater treatment for ๏ƒ˜ Phosphorus removal (ww. treatment) AlPO4 (s) , FePO4 (s) , Ca5(OH)(PO4)3 ๏ƒ˜ Hardness removal, water softening CaCO3 (s) , Mg(OH)2 (s)
  • 2. ๏ƒ˜ Iron and Manganese removal Fe(OH)3 (s) ; MnO2 (s) ๏ƒ˜ Removal of heavy metals, radionuclei As (V) or As (III), Ba, Cd, Hg, Zn, Ni, Cr (III) precipitates in the form of As(V) Mn+ + n OH- M(OH)n (s)
  • 3. If discharge limitations are lower S= ppt. is preferred because solubility of sulfide salts is lower. Mn+ + S2- MS (s) mostly in the form of H2S (g)
  • 4. ๏ƒ˜ Water conditioning (To control scale formation or corrosion) ๏ƒ˜ Sulfate removal from wastewaters CaSO4 (s) ; BaSO4 (s)
  • 5. PHOSPHORUS REMOVAL The Types of P 1. Orthophosphate H3PO4 , H2PO4- , HPO4= , PO43- As a fertilizer, phosphorus must be in the form of orthophosphate. pKa1 = 2.1 pH 2.1 7.2 12.3 H3PO4 H2PO4- HPO4= PO43- pKa2 = 7.2 pKa3 = 12.3
  • 6.
  • 7. In the pH range of wastewaters (around 7), the dominant forms of orthophosphate are H2PO4- and HPO4=. As the pH increases, the equation moves toward the formation of PO43-.
  • 8. 2. Condensed (polyphosphates) When H3PO4 is heated, it decomposes, losing molecules of water forming the P - O - P bonds. The process of losing water is called condensation. O O Hโ€“Oโ€“Pโ€“Oโ€“H + Hโ€“Oโ€“Pโ€“Oโ€“H O O Hโ€“Oโ€“P โ€“Oโ€“Pโ€“Oโ€“H O O O O H H H H Orthophosphoric acid Dipolyphosphoric acid or Pyrophosphoric acid All of the hydrogen atoms are ionizable.
  • 9. Properties of condensed phosphates โ€ข Condensed phosphates are inorganic and contain more than one P per molecule. โ€ข They are used in corrosion control and in detergents as complexation agents. Ex. Pyrophosphate H4P2O7 and its ionization products. โ€ข They do not form precipitates. But they undergo hydrolysis in aqueous solutions and transform into the orthophosphates. โ€ข Microorganisms convert polyphosphates into orthophosphates.
  • 10. 3. Organic P : ATO, ADP, etc. When organic compounds containing P are attacked by microorganisms, they also undergo hydrolysis into the orthophosphate forms. ๏ƒ˜ Typical municipal waste : 10 โ€“ 15 mg/L as P 30 % from human waste + 70 % from detergents (mostly in the form of polyphosphates) ๏ƒ˜ P being a nutrient, causes algal blooms (eutrophication) 106 CO2 + 16 NO3- + HPO4= + 18 H+ + 122 H2O C106H263O110N16P + 154 O2
  • 11. ๏ƒ˜ In most lakes P is the growth limiting nutrient for algae. P > 0.01 mg/L stimulates algal growth. ๏ƒ˜ 80 % removal of P or a residual of 1 mg/L as P is required in effluents discharged to streams which are tributaries to lakes. ๏ƒ˜ Effluent concentrations are commonly specified to be 1 mg/L or less to minimize environmental effects. Primary clarification removes 5 โ€“ 10 % of P. Primary + secondary treatment removes 10 โ€“ 20 % of P.
  • 12. Phosphorus Removal The most common method to remove phosphorus from a waste stream is chemical precipitation. The common precipitating cations used are Ca, Al and Fe.
  • 13. Removal of P by Chemical Precipitation Salts of Al (III), Fe (III) and Ca(II) Solubility Product Constants for Phosphate Precipitation Precipitation Product Ca5(PO3)3(OH) Ca3(PO4)2 AlPO4 FePO4 Solubility Product , Ksp at 25 ยบC 10-55.9 10-25 10-21 10-21.9
  • 14. Precipitation by Calcium Calcium is usually added as lime (Ca(OH)2). The reaction is represented as: 2๏€ซ 3๏€ญ 4 10Ca ๏€ซ 6PO ๏€ซ 2OH ๏€ญ Ca10 (PO 4 ) 6 (OH) 2 (s)
  • 15. Calcium โ€ข Lime dosage is primarily a function of system alkalinity. โ€ข The key parameter here is pH. โ€ข pH has to be elevated to somewhere between 10.5 and 11 to get effective P removal. โ€ข As a rule of thumb, lime dose to attain this pH is about 1.5 times the alkalinity represented in mg/L as CaCO3
  • 16. Disadvantages of lime addition Lime addition is seldom practiced because โ€ข it produces large amount of sludge, and โ€ข the elevated pH has to be readjusted typically by recarbonation.
  • 17. Precipitation by Al and Fe Phosphate precipitation of by Al 3๏€ซ Al ๏€ซ H n PO (3๏€ญ n ) ๏€ญ 4 ๏‚ฎ AlPO 4 (s) ๏€ซ nH ๏€ซ Phosphate precipitation of by Fe 3๏€ซ Fe ๏€ซ H n PO (3๏€ญ n ) ๏€ญ 4 ๏‚ฎ FePO 4 (s) ๏€ซ nH ๏€ซ 1 mol of Al or Fe precipitates 1 mol of phosphate. However, these reactions are simple and must be considered in the light of many competing reactions.
  • 18. In general, with Ca, Al or Fe addition to precipitate PO43- higher pH is favorable (more PO43- as opposed to HPO42- or H2PO4- ). However, soluble Al-PO4-OH complexes begin to form as pH increases. For example, the following soluble species can form: 0 Al2 PO4 (OH)3 , Al2 PO4 (OH)๏€ซ , AlPO4 (OH)๏€ญ 2
  • 19. Al2(SO4)3.XH2O Al3+ , Al(OH)2+ , Al(OH)2+ , Al(OH)4- etc. forms below pH 2 Al(OH)3 (s) according to pH. tremendous waste of chemical.
  • 20. ๏‚ง The chemistry of phosphate precipitate formation is complex because of complexes formed between phosphate and metals, and between metals and other ligands in the wastewater. ๏‚ง Side reactions of the metals with alkalinity to form hydroxide precipitates are another factor to be considered. ๏‚ง The amount of metal needed to remove phosphorus exceeds the stoichiometric amount at the low levels at which phosphorus is present in a wastewater. ๏‚ง The common precipitates formed by the metals are given in the following table.
  • 21. Table 15.5 Phosphate Precipitates Metal Ca+2 Precipitates Various calcium phosphates , e.g. , Ca3(PO4)2 , Ca5(OH)(PO4)3 , CaHPO4, CaCO3 pH range โ‰ฅ10 โ‰ค9.5 Fe2+ Fe3(PO4)2 , Fex(OH)y(PO4)3 Fe(OH)2 , Fe(OH)3 6 โ€“ 8.5 Fe3+ Fex(OH)y(PO4)z , Fe(OH)3 6 โ€“ 8.5 Al3+ Alx(OH)y(PO4)3 , Al(OH)3 6 โ€“ 8.5 Comment Produces lowest residual P concentrations. The alkalinity of the water determines the dose because of the formation of CaCO3. Residual P in the range of 1 โ€“ 2 mg/L. There will be some oxidation of Fe2+ to Fe3+.
  • 22. Purpose Al3+ + PO4- Al(PO4) (s) So Al3+ required is more than 1:1 ratio. Same for Fe (III) Fe3+ + PO4- Fe(PO4) (s)
  • 23. โ€ข In order to determine the chemical requirement, site specific experiments, which involve testing the amount of phosphorus removal at different dosages, are needed. โ€ข Chemical requirement depends upon ๏ƒผ pH, ๏ƒผ Alkalinity, ๏ƒผ initial PT, and ๏ƒผ desired % P removal
  • 24. โ€ข On-site tests under actual plant conditions are preferred. โ€ข A reasonably good correlation can be obtained by plotting the log of the fraction of soluble phosphorus remaining as a function of the weight ratio of metal to soluble phosphorus. โ€ข The required ratio of metal ion to influent soluble phosphorus for a specified phosphorus removal can be obtained from such a plot. โ€ข This ratio is multiplied by the soluble influent phosphorus concentration in mg/L to determine the required chemical dose in mg/L.
  • 25. Data are from several ferric chloride phosphorus removal studies conducted in the Great Lakes region. Ref: National Service Center for Environmental Publications (NSCEP) Process Design Manual for Phosphorus Removal, April 1976
  • 26. For iron and aluminum salts, without jar tests, the general guideline for the metal dose to achieve total soluble residual P concentrations of 1 to 2 mg P/L is Typical Al or Fe requirement per mole P % P removal 1.5 75 1.7 2.3 85 95
  • 27. Al3+ + PO43- AlPO4 Ksp = [Al3+][PO43-] Ksp = [Al3+](ฮฑ3.Ptotal) [PO43- ] ฮฑ3 = [H3PO4 ] + [H 2 PO4- ] + [HPO4 = ] + [PO 43- ] ฮฑ3 = fraction of PO43- in total P species. PT = K sp ฮฑ3 . [Al3+ ] [Al3+] as pH and ฮฑ3 as pH
  • 28. P solubility as a function of pH: Pure metal phosphates are precipitated within the shaded area. Mixed complex polynuclear species are formed outside toward higher and lower pH values. Figures : 6 โ€“ 12 a- b from Metcalf (pg:502)
  • 29. Hydro-Complexes of Aluminum Al Al Al 3๏€ซ 3๏€ซ ๏€ซ H 2O ๏€ซ 2 H 2O Al (OH ) 2๏€ซ ๏€ซH ๏€ซ ๏€ซ Al (OH ) 2 ๏€ซ 2 H ๏€ซ 3๏€ซ ๏€ซ 3H 2O Al (OH ) 3 ( s ) ๏€ซ 3H 3๏€ซ ๏€ซ 4 H 2O Al (OH ) 4 ๏€ซ 4 H Al ๏€ญ ๏€ซ ๏€ซ โ€ข pH drops and alkalinity of water is reduced due to acid formation. โ€ข If Al(OH)3 precipitate is formed, 3 equivalents of alkalinity is reduced per mole of Al3+ added. A similar set of reactions can be written for Fe3+ .
  • 30. โ€ข So there is a minimum point for Ptotal at about pH = 6โ€“7. For FePO4, minimum Ptotal is at about pH = 5โ€“6. โ€ข Use Fe salts if alkalinity is low. โ€ข When salts are added, pH drops (hydrolysis reactions and alkalinity consumption). โ€ข This helps the precipitation, if the pH is above the minimum solubility point. โ€ข Otherwise, pH drop is detrimental.
  • 31.
  • 32. Sodium Aluminate NaAlO2 AlO2- + H2O Na+ + AlO2- Al3+ + Al(OH)2+ + Al(OH)2+ etc. + OH- โ€ข NaAlO2 is more expensive than Alum but you generate OH- instead of H+. โ€ข OH- is released in the reaction. So, aluminate behaves as a base and pH increases. โ€ข If water is acidic, use NaAlO2 not Al2(SO4)3 or use a mixture to adjust to the optimum pH. โ€ข Higher Al (III) requirement with aluminate than alum.
  • 33. Ref: National Service Center for Environmental Publications (NSCEP) Process Design Manual for Phosphorus Removal, April 1976
  • 34. Addition of Ca โ€ข Lime is cheaper than alum, FeCl3 or Fe2(SO4)3. โ€ข It can achieve the lowest residual phosphate concentration because of the formation of apatites, Ca5(OH)(PO4)3. โ€ข Apatites are highly insoluble Ksp = 10-55.0, however a high pH must be attained to realize their formation. โ€ข Because calcium forms CaCO3 near pH 9.5 and pHs higher than 9.5 are required for significant apatite formation, the alkalinity of water is the governing factor for the required dose of lime.
  • 35. Very high doses of lime are required, which makes this choice costly compared to other metal agents, although the lowest residual P concentrations can be achieved. Ca(OH)2, CaO : Both Ca++ and OH- source. 5 Ca2+ + OH- + 3 PO43Ca2+ + CO3= Ca5(OH)(PO4)3 (s) CaCO3 (s) This reaction is not our purpose but we cannot prevent its formation.
  • 36. ๏ƒ˜ Ca requirement for P removal is a function of carbonate alkalinity. Avoid if alkalinity is too high. (CaCO3 sludge) See Fig. 6-11 from Met-Calf&Eddy ๏ƒ˜ High pH is required (pH : 10 โ€“ 11) See Fig. 2-2 ๏ƒ˜ Neutralize or recarbonate (CO2) to bring the pH down after precipitation.
  • 37.
  • 38.
  • 39. Phosphorus Removal in Various Stages โ€ข Addition of metal coagulants to wastewater can have a significant impact on the amount of sludge produced. โ€ข There are a variety of chemical application points in the treatment scheme. โ€ข The common addition points for metals in biological treatment plants are before the primary clarifier or before the secondary clarifier or during tertiary treatment. โ€ข Some alternative treatment schemes are shown in the following slide.
  • 40.
  • 41. During Primary Treatment ๏ƒ˜ Increases BOD and SS removal ๏ƒ˜ Least efficient use of salts. Therefore you have to add too much chemical. ๏ƒ˜ Fe and Al sludges are difficult to dewater. ๏ƒ˜ Results in sludge mass increases from 50 to 100% from the primary clarifier and an overall increase of 60 โ€“ 70% in the sludge mass produced by the plant.
  • 42. During Secondary Treatment ๏ƒ˜ Lime cannot be used because of high pH. ๏ƒ˜ Overdose of Al or Fe salts may cause low pH and toxicity. ๏ƒ˜ Increases in sludge mass are 35 โ€“ 45% from the clarifier and 10 โ€“ 25% for the whole plant. ๏ƒ˜ These salts will also have an impact on sludge dewaterability.
  • 43. Tertiary Treatment ๏ƒ˜ Highest capital cost because you need to have another sedimentation tank. ๏ƒ˜ Most efficient metal use. You use the least amount of chemical and produce the least amount of sludge. ๏ƒ˜ Lowest P in the effluent. ๏ƒ˜ Lime recovery is possible. sludge Heat CaO + CO2 Recalcination ๏ƒ˜ Separate disposal of chemical precipitation.