This document discusses various methods for removing iron and manganese from water. It describes how ferrous iron and manganous manganese are soluble but oxidize to insoluble ferric iron and manganic manganese when exposed to air. Common removal methods include aeration, sedimentation, filtration, chemical oxidation using chlorine or potassium permanganate, and manganese zeolite processes. Other options mentioned are water softening, biological treatment using iron- and manganese-oxidizing bacteria, and sequestering with chemicals like silicates and phosphates.

1. Iron andIron and
ManganeseManganese
RemovalRemoval
ByBy
Er. Prateek GuptaEr. Prateek Gupta
Waterland Environmental TechnologiesWaterland Environmental Technologies
Kolkata – 70, M: +91 85840 49973Kolkata – 70, M: +91 85840 49973
E: waterland.kolkata@gmail.comE: waterland.kolkata@gmail.com

2. Fe++ and Mn++Fe++ and Mn++
 Ferrous iron Fe++ and manganous manganeseFerrous iron Fe++ and manganous manganese
Mn++ areMn++ are
solublesoluble
invisibleinvisible
 When exposed to air, they are oxidized toWhen exposed to air, they are oxidized to
ferric iron Fe+++ and manganic manganeseferric iron Fe+++ and manganic manganese
Mn++++, which are:Mn++++, which are:
insolubleinsoluble
visiblevisible

3. OxidationOxidation
 The oxidation rate depends on:The oxidation rate depends on:
pHpH
alkalinityalkalinity
organic contentorganic content
presence of oxidizing agentspresence of oxidizing agents
 If not removed from water, iron andIf not removed from water, iron and
manganese oxides create problem of brownmanganese oxides create problem of brown
color formation.color formation.

4. OxidationOxidation
 Reduced iron in water promotes the growth ofReduced iron in water promotes the growth of
autotrophic bacteria in distribution mains.autotrophic bacteria in distribution mains.
 Elimination of iron bacteria is difficult andElimination of iron bacteria is difficult and
expensive.expensive.
 When decays, iron bacteria release foul tasteWhen decays, iron bacteria release foul taste
and odor.and odor.
 Heavy chlorination followed by flushingHeavy chlorination followed by flushing
proved to be successful in some case.proved to be successful in some case.
 Removal of iron and manganese from water isRemoval of iron and manganese from water is
the best solution to that problem.the best solution to that problem.

5. +−+
−++
++
+−+
−++
++
++→++
++→++
+→++
++→++
++→++
+→++
HClOMnOOHClOMn
ClHMnOOHClMn
HMnOOHOMn
HClOOHFeOHClOFe
ClHOHFeOHClFe
HOHFeOHOFe
4222
242
4222
3)(3
26)(262
8)(4104
2222
2
222
2
222
2
2322
2
322
2
322
2
Oxidation of Iron and Manganese withOxidation of Iron and Manganese with
Oxygen, Chlorine, and ChlorineOxygen, Chlorine, and Chlorine
DioxideDioxide

6. Treatment AlternativesTreatment Alternatives

7. Aeration, Sedimentation, andAeration, Sedimentation, and
FiltrationFiltration
 Aeration (air oxidation) is the simplest treatment inAeration (air oxidation) is the simplest treatment in
removing iron. The reaction that takes place is in theremoving iron. The reaction that takes place is in the
form of:form of:
 Fe++(ferrous) + oxygenFe++(ferrous) + oxygen ⇒⇒ FeOx (ferric oxide)FeOx (ferric oxide)
Soluble ironSoluble iron Insoluble ironInsoluble iron
 Air oxidation can not remove manganese effectively.Air oxidation can not remove manganese effectively.
Increasing the pH to 8.5 can enhance the oxidationIncreasing the pH to 8.5 can enhance the oxidation
process. If manganese was not effectively removedprocess. If manganese was not effectively removed
from the water, it can cause problems with post-from the water, it can cause problems with post-
chlorination. When oxidized:chlorination. When oxidized:
 it can clog the solution-feed chlorinatorit can clog the solution-feed chlorinator
 it cause a staining waterit cause a staining water

8. Aeration, Chemical Oxidation,Aeration, Chemical Oxidation,
Sedimentation, and FiltrationSedimentation, and Filtration
 This is a common method for removing iron and manganese fromThis is a common method for removing iron and manganese from
well water without softening treatment.well water without softening treatment.
 Preliminary aeration strips out dissolved gases and adds oxygen.Preliminary aeration strips out dissolved gases and adds oxygen.
 Iron and manganese are oxidized by free chlorine residual:Iron and manganese are oxidized by free chlorine residual:
 FeFe++++
+ Mn+ Mn++++
+ Oxygen+ Oxygen ⇒⇒ FeOFeOxx + MnO+ MnO22
Soluble ionsSoluble ions Insoluble metal oxidesInsoluble metal oxides
 or by potassium permanganateor by potassium permanganate
 Fe(HCOFe(HCO33))22 + KMnO+ KMnO44 ⇒⇒ Fe(OH)Fe(OH)33 + MnO+ MnO22
Ferrous bic. Potas. Perm. Ferric Hydrx. Mang. Diox.Ferrous bic. Potas. Perm. Ferric Hydrx. Mang. Diox.
 Mn(HCOMn(HCO33))22 + KMnO+ KMnO44 ⇒⇒ MnOMnO22
Manganous bic Potas Perm Mang. Diox.Manganous bic Potas Perm Mang. Diox.
 Potassium permanganate oxidizes iron and manganese at rates fasterPotassium permanganate oxidizes iron and manganese at rates faster
than dissolved oxygen and its reaction is relatively pH independent.than dissolved oxygen and its reaction is relatively pH independent.
 Since iron and manganese can not be completely removed bySince iron and manganese can not be completely removed by
sedimentation, effective filtration is required.sedimentation, effective filtration is required.

9. Manganese Zeolite ProcessManganese Zeolite Process
Manganese zeolite is a natural greensand coatedManganese zeolite is a natural greensand coated
with manganese dioxide. It has the capability towith manganese dioxide. It has the capability to
remove iron and manganese from solution.remove iron and manganese from solution.
When manganese zeolite becomes saturated withWhen manganese zeolite becomes saturated with
metal ions, it can be generated using potassiummetal ions, it can be generated using potassium
permanganate. A continuos flow diagram ispermanganate. A continuos flow diagram is
shown in the following Figure.shown in the following Figure.

11. 2432
3
32
2
2
3
32
2
2
Re
MnOZKMnOOMnZ
generation
MnOMnZMnMnOZ
FeOMnZFeMnOZ
Oxidation
−→+−
+−→+−
+−→+−
++
++
Reaction EquationsReaction Equations

12. Manganese Zeolite ProcessManganese Zeolite Process
 KMnOKMnO44 is applied prior to filtration.is applied prior to filtration.
 The filter is a dual-media filter with anthracite isThe filter is a dual-media filter with anthracite is
placed on top of the manganese zeolite.placed on top of the manganese zeolite.
 Iron and manganese are oxidized by KMnOIron and manganese are oxidized by KMnO44..
 The upper layer will remove the insoluble metal ions.The upper layer will remove the insoluble metal ions.
 Any iron and manganese ions not oxidized, it will beAny iron and manganese ions not oxidized, it will be
captured by the lower layer of manganese zeolite.captured by the lower layer of manganese zeolite.
 Any surplus KMnOAny surplus KMnO44 will regenerate the greensand.will regenerate the greensand.
 When the bed becomes saturated, it is backwashed byWhen the bed becomes saturated, it is backwashed by
KMnOKMnO44 to remove particles from the upper layer andto remove particles from the upper layer and
regenerate the greensand.regenerate the greensand.

13. Water SofteningWater Softening
Lime and soda ash, which are used in waterLime and soda ash, which are used in water
softening, can remove iron and manganese fromsoftening, can remove iron and manganese from
water.water.

14. Biological TreatmentBiological Treatment
 New processNew process
 In the form of filters that support:In the form of filters that support:
 Iron-oxidizing bacteriaIron-oxidizing bacteria
 Manganese-oxidizing bacteriaManganese-oxidizing bacteria
 Two separate filters are usedTwo separate filters are used
 pH and dissolved oxygen of the feed are criticalpH and dissolved oxygen of the feed are critical
 Filtration rates are:Filtration rates are:
 25 to 40 m/h for iron25 to 40 m/h for iron
 10 to 40 m/h for manganese10 to 40 m/h for manganese
 Coarse sand is usedCoarse sand is used

15. SequesteringSequestering
 Sequestering agents are usedSequestering agents are used
 Sodium silicatesSodium silicates
 PhosphatesPhosphates
 polyphosphatespolyphosphates
 Agents are added:Agents are added:
 In the form of colloidal complexesIn the form of colloidal complexes
 to bind iron and manganese and prevent them from forming color andto bind iron and manganese and prevent them from forming color and
turbidityturbidity
 In distribution systemIn distribution system
 Chlorine is added simultaneously to oxidize iron andChlorine is added simultaneously to oxidize iron and
manganesemanganese
 Normal doses of silicates are 5 to 25 mg/l as SiONormal doses of silicates are 5 to 25 mg/l as SiO22
 Iron is sequestered more with silicates than manganeseIron is sequestered more with silicates than manganese

16. Thanks for the concernThanks for the concern
We’ll get back To You soonWe’ll get back To You soon