معالجة مياه الشرب(جرعات برمنجنات البوتاسيوم فى ازالة الطعم/الرائحة/اللون/الحديد/المنجنيز/الفيروسات/الطحالب من المياه)

POTASSIUM PERMANGANATE
Potassium permanganate (KMnO4) is used primarily to control taste and odors, remove color, control biological growth in treatment plants, and remove iron and manganese

In a secondary role potassium permanganate may be useful in controlling the formation of THMs and other DBPs by oxidizing precursors and reducing the demand for other disinfectants
potassium permanganate using to control taste and odors, color, algae, etc. instead of chlorine

Potassium Permanganate Chemistry
Oxidation Potential
Potassium permanganate is highly reactive under conditions found in the water industry

It will oxidize a wide variety of inorganic and organic substances

Potassium permanganate (Mn 7+) is reduced to manganese dioxide (MnO2) (Mn 4+) which precipitates out of solution
All reactions are exothermic

Under acidic conditions the oxidation half-reactions
MnO4 + 4H + 3e MnO2 + 2H2O E = 1.68V
MnO4 + 8H + 5e Mn + 4H2O E = 1.51V
Under alkaline conditions, the half-reaction is
MnO4 + 2H2O + 3e MnO2 + 4OH E = 0.60V
Reaction rates for the oxidation of constituents found in natural waters are relatively fast and depend on temperature, pH, and dosage

Ability To Form a Residual
It is not desirable to maintain a residual of KMnO4 because of its tendency to give water a pink color

Generation
Potassium permanganate is only supplied in dry form

A concentrated KMnO4 solution (typically 1 to 4 percent) is generated on-site for water treatment applications; the solution is pink or purple in color
KMnO4 has a bulk density of approximately 100 lb/ft and its solubility in water is 6.4 g/mL at 20oC

Primary Uses and Points of Application
Although potassium permanganate can inactivate various bacteria and viruses, it is not used as a primary or secondary disinfectant when applied at commonly used treatment levels

Potassium permanganate levels that may be required to obtain primary or secondary disinfection could be cost prohibitive

However, potassium permanganate is used in drinking water treatment to achieve a variety of other purposes including

Oxidation of iron and manganese
Oxidation of taste and odor compound
Control of nuisance organisms; and
Control of DBP formation

Primary Uses
Iron and Manganese Oxidation


Permanganate will oxidize iron and manganese to convert ferrous (2+) iron into the ferric (3+) state and 2+ manganese to the 4+ state The oxidized forms will precipitate as ferric hydroxide and manganese hydroxide
The precise chemical composition of the precipitate will depend on the nature of the water temperature, and pH

The classic reactions for the oxidation of iron and manganese are:
3Fe + KMnO4 + 7H2O 3Fe(OH)3(s) + MnO2(s) + K + 5H
3Mn + 2KMnO4 + 2H2O 5MnO2(s) + 2K + 4H

These reactions show that alkalinity is consumed through acid production at the rate of 1.49 mg/L as
CaCO3 per mg/L of Fe and 1.21 mg/L as CaCO3 per mg/L of Mn oxidized

This consumption of alkalinity should be considered when permanganate treatment is used along with alum coagulation which also requires alkalinity to form precipitates

The potassium permanganate dose required for oxidation is 0.94 mg/mg iron and 1.92 mg/mg manganes

In practice, the actual amount of potassium permanganate used has been found to be less than that indicated by stoichiometry

It is thought that this is because of the catalytic influence of MnO2 on the reactions

The oxidation time ranges from 5 to 10 minutes, provided that the pH is over 7.0

Oxidation of Taste and Odor Compounds

Potassium permanganate is used to remove taste and odor causing compounds

used permanganate to treat earthy-musty smelling compounds in drinking water

Doses of potassium permanganate used to treat taste and odor causing compounds range from 0.25 to 20 mg/L

Control of Nuisance Organisms

The adult Asiatic clam
the effectiveness of potassium permanganate to control the The adult Asiatic clam was found to be much more resistant to permanganate than the juvenile form

Potassium permanganate doses used to control the juvenile Asiatic clam range from 1.1 to 4.8 mg/L

Zebra Mussels

The effectiveness of permanganate against adult zebra mussels by Continuous potassium permanganate dosing of 0.5 to 2.5 mg/L proved to be the most effective

DBP Control

It is anticipated that potassium permanganate may play a role in disinfection and DBP control strategies in water treatment

Potassium permanganate could be used to oxidize organic precursors at the head of the treatment plant minimizing the formation of byproducts at the downstream disinfection stage of the plant

Test results from a study conducted at two water treatment plants showed that pretreatment with permanganate reduced chloroform formation; however, the reduction was small at doses typically used at water treatment plants

The study also indicated that pre-oxidation with permanganate had no net effect on the chlorine demand of the water

Points of Application


In conventional treatment plants, potassium permanganate solution is added to the raw water intake at the rapid mix tank in conjunction with coagulants, or at clarifiers upstream of filters

In direct filtration plants, this oxidant is typically added at the raw water intake to increase the contact time upstream of the filter units

In all cases, potassium permanganate is added prior to filtration

Potassium permanganate solution is typically pumped from the concentrated solution tank to the injection point

If the injection point is a pipeline, a standard injection nozzle protruding midway into the pipe section is used

Injection nozzles can also be used to supply the solution to mixing chambers and clarifiers

Permanganate is a reactive, fast-acting oxidizer and does not require special mixing equipment at the point of injection to be effective

Impact on Other Treatment Processes

The use of potassium permanganate has little impact on other treatment processes at the water treatment facility

Pathogen Inactivation and Disinfection Efficacy
Potassium permanganate is an oxidizing agent widely used throughout the water industry

While it is not considered a primary disinfectant, potassium permanganate has an effect on the development of a disinfection strategy by serving as an alternative to pre-chlorination or other oxidants at locations in a treatment plant where chemical oxidation is desired for control of color, taste and odor, and algae

Inactivation Mechanisms

The primary mode of pathogen inactivation by potassium permanganate is direct oxidation of cell material or specific enzyme destruction

In the same fashion, the permanganate ion (MnO4 ) attacks a wide range of microorganisms such as bacteria, fungi, viruses and algae

Application of potassium permanganate results in the precipitation of manganese dioxide

This mechanism represents an additional method for the removal of microorganisms from potable water
exposed OH groups

These groups are capable of adsorbing charged species and particles in addition
to neutral molecules In colloidal form, the manganese dioxide precipitant has an outer layer of

As the precipitant is formed, microorganisms can be adsorbed into the colloids and settled

Environmental Effects

Inactivation efficiency depends upon the permanganate concentration, contact time, temperature, pH and presence of other oxidizable material

pH

Alkaline conditions enhance the capability of potassium permanganate to oxidize organic matter however, the opposite is true for its disinfecting power

Typically, potassium permanganate is a better biocide under acidic conditions than under alkaline conditions

permanganate generally was a more effective biocide for E. coli at lower pHs, exhibiting more than a 2-log removal at a pH of 5.9 and a water temperature of both 0 and 20°C

pH ishe major factor affecting disinfection effectiveness with potassium permanganate

As such, natural waters with pH values of 5.9 or less would be conducive to potassium permanganate disinfection particularly as a substitute for prechlorination

potassium permanganate will inactivate Legionella pneumophila more rapidly at pH 6.0 than at pH 8.0
These results are consistent with earlier results concerning the effects of pH on commercial antiseptic performance

disinfection effectiveness of potassium permanganate increases with decreasing pH

Temperature

Higher temperatures slightly enhance bactericidal action of potassium permanganate

The results from a study conducted on polio virus showed that oxidation deactivation is enhanced by higher temperatures

Dissolved Organics and Inorganics

The presence of oxidizable organics or inorganics in the water reduces the disinfection effectiveness of this disinfectant because some of the applied potassium permanganate will be consumed in the oxidation of organics and inorganics

Permanganate oxidizes a wide variety of inorganic and organic substances in the pH range of 4 to 9

Under typical water conditions, iron and manganese are oxidized and precipitated and most contaminants that cause odors and tastes, such as phenols and algae, are readily degraded by permanganate


Use as a Disinfectant

A number of investigations have been performed to determine the relative capability of potassium permanganate as a disinfectant

The following sections contain a description of the disinfection efficiency of potassium permanganate in regards to bacteria, virus, and protozoa inactivation

Bacteria Inactivation

Early research showed that a dose of 2.5 mg/L was required for complete inactivation of coliform bacteria

was dosed with potassium permanganate at concentrations of 0 to 2.5 mg/L. Following mixing, the samples were placed in a darkened room for 2 hours at a constant temperature of 19.8 C

the disinfectant ability of potassium permanganate on several waterborne pathogenic microorganisms( Vibrio cholerae, Salm. typhi, and Bact. flexner

The results indicated that doses of 20 mg/L and contact times of 24 hours were necessary to deactivate these pathogens

complete removal of coliform bacteria were accomplished at doses of 1, 2, 3, 4, 5, and 6 mg/L)

Contact times of 30 minutes were provided with doses of 1 and 2 mg/L, and 10 minutes contact times were provided for higher dosages

Virus Inactivation

Potassium permanganate has been proven effective against certain viruses

A dose of 50 mg/L of potassium permanganate and a contact time of 2 hours was required for inactivation of poliovirus strain MVA)

contact time of 33 minutes was needed for 1-log inactivation of type 1 poliovirus a A “potassium” permanganate dose of 5.0 mg/L and

Potassium permanganate doses from 0.5 to 5 mg/L were capable of obtaining at least a 2 log inactivation of the surrogate virus, MS-2 bacteriophage with E. coli as the host bacterium

Results showed that at pH 6.0 and 8.0, a 2-log inactivation occurred after a contact time of at least 52 minutes and a residual of 0.5 mg/L

At a residual of 5.0 mg/L, approximately 7 and 13 minutes were required for 2-log inactivation at pHs of 8.0 and 6.0, respectively

These results due to potassium permanganate becomes more effective as the pH decreases

Advantages and Disadvantages of Potassium

Permanganate Use The following list highlights selected advantages and disadvantages of using potassium

permanganate as a disinfection method for drinking water

Because of the wide variation of system size, water quality, and dosages applied, some of these advantages and disadvantages may not apply to a particular system

Advantages

Potassium permanganate oxidizes iron and manganese.

Potassium permanganate oxidizes odor and taste-causing compounds.

Potassium permanganate is easy to transport, store, and apply.

Potassium permanganate is useful in controlling the formation of THMs and other DBPs.

Potassium permanganate controls nuisance organisms.

Treatment facility The use of potassium permanganate has little impact on other treatment processes at the water

Potassium permanganate has been proven effective against certain viruses.

Disadvantages

Long contact time is required.

Potassium permanganate has a tendency to give water a pink color.

Potassium permanganate is toxic and irritating to skin and mucous membranes.

No byproducts are generated when preparing the feed solution, however this
dark purple/black
crystalline solid can cause serious eye injury, is a skin and inhalation irritant, and can be fatal if swallowed

Over-dosing is dangerous and may cause health problems such as chemical jaundice and drop in blood pressure

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