# Potassium Permanganate

Potassium permanganate (KMnO~4~) 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
(Hazen and Sawyer, 1992). The mechanism of reduced DBPs may be as simple
as moving the point of chlorine application further downstream in the
treatment train using potassium permanganate to control taste and odors,
color, algae, etc. instead of chlorine. Although potassium permanganate
has many potential uses as an oxidant, it is a poor disinfectant.

## 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 (MnO~2~) (Mn 4+) which precipitates out of solution (Hazen and
Sawyer, 1992). All reactions are exothermic. Under acidic conditions the
oxidation half-reactions are (CRC, 1990):

*MnO~4~^-^* + 4*H*^+^ + 3*e^-^* *MnO~2~* + 2*H~2~O E^o^* = 1.68*V*

*MnO~4~^-^* + 8*H^+^* + 5*e*^-^ *Mn^2+^* + 4*H~2~O* *E^o^* = 1.51*V*

Under alkaline conditions, the half-reaction is (CRC, 1990):

*MnO~4~^-^* + 2*H~2~O* + 3*e*^-^ *MnO~2~* + 4*OH^-^* *E^o^* = 0.60*V*

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 KMnO~4~ because of its
tendency to give water a pink color.

## Generation

Potassium permanganate is only supplied in dry form. A concentrated
KMnO~4~ solution (typically 1 to 4 percent) is generated on-site for
water treatment applications; the solution is pink or purple in color.
KMnO~4~ has a bulk density of approximately 100 lb/ft^3^ and its
solubility in water is 6.4 g/mL at 20ºC.

Depending on the amount of permanganate required, these solutions can be
made up in batch modes, using dissolver/storage tanks with mixers and a
metering pump for small feed systems. Larger systems will include a dry
chemical feeder, storage hopper and dust collector configured to
automatically supply permanganate to the solution dissolver/storage
tank.

KMnO~4~ solution is made up of dry crystalline permanganate solids added
to make-up water and then stirred to obtain the desired permanganate
concentration. The cost of KMnO~4~ ranges from \$1.50 to \$2.00 per
pound (1997 costs), depending on the quantity ordered. Shipment
containers are typically buckets or drums. Potassium permanganate is
supplied in various grades. Pure KMnO~4~ is non-hygroscopic but
technical grades will absorb some moisture and will have a tendency to
cake together. For systems using dry chemical feeders, a free-flowing
grade is available that contains anti-caking additives (Hazen and
Sawyer, 1992).

Potassium permanganate is a strong oxidizer and should be carefully
handled when preparing the feed solution. No byproducts are generated
from making the 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. As such, special handling procedures
include the use of safety goggles and a face shield, an MSA/NIOSH
approved dust mask, and wearing impervious gloves, coveralls, and boots
to minimize skin contact.

## 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

A primary use of permanganate is iron and manganese removal.
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 (AWWA, 1991). 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:

3*Fe^2+^* + *KMnO~4~* + 7*H~2~O* 3*Fe(OH)~3(s)~* + *MnO~2(s)~* +
*K^+^* + 5*H^+^*

3*Mn^2+^* + 2*KMnO~4~* + 2*H~2~O* 5*MnO~2(s)~* + 2*K^+^* + 4*H^+^*

These reactions show that alkalinity is consumed through acid production
at the rate of 1.49 mg/L as CaCO~3~ per mg/L of Fe^+2^ and 1.21 mg/L as
CaCO~3~ per mg/L of Mn^+2^ 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 manganese (Culp/Wesner/Culp, 1986). 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 MnO~2~ on the reactions (O'Connell, 1978).
The oxidation time ranges from 5 to 10 minutes, provided that the pH is
over 7.0 (Kawamura, 1991).

#### Oxidation of Taste and Odor Compounds

Potassium permanganate is used to remove taste and odor causing
compounds. Lalezary et al. (1986) 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

##### Asiatic Clams {#asiatic-clams .unnumbered}

Cameron et al. (1989) investigated the effectiveness of potassium
permanganate to control the Asiatic clam in both the juvenile and adult
phases. 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 {#zebra-mussels .unnumbered}

Klerks and Fraleigh (1991) evaluated the effectiveness of permanganate
against adult zebra mussels. 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 (Hazen and Sawyer, 1992).
Test results from a study conducted at two water treatment plants in
North Carolina (Section 5.5.1) 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 (Singer et al., 1980).

### 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 (Montgomery,
1985). 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. See Section 5.7 for
permanganate operational considerations.

## 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 (Webber
and Posselt, 1972). In the same fashion, the permanganate ion
(MnO~4~^-^) 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 (Cleasby et al., 1964).
In colloidal form, the manganese dioxide precipitant has an outer layer
of exposed OH groups. These groups are capable of adsorbing charged
species and particles in addition to neutral molecules (Posselt et al.,
1967). 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. Several of the key parameters are discussed below.

#### 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 (Cleasby
et al., 1964 and Wagner, 1951). Results from a study conducted in 1964
indicated that 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 (Cleasby et al., 1964).
In fact, Cleasby found that pH is the 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. Moreover a study conducted at the University of Arizona
found that potassium permanganate will inactivate *Legionella
pneumophila* more rapidly at pH 6.0 than at pH 8.0 (Yahya et al.,
1990a).

These results are consistent with earlier results concerning the effects
of pH on commercial antiseptic performance (Hazen and Sawyer, 1992). In
general, based on the limited results from these studies, 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 (Lund,
1963). These results are consistent with results obtained for *E. coli.*
inactivation (Cleasby et al., 1964).

#### 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 (Hazen and
Sawyer, 1992).

### 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

High dosage rates were required to accomplish complete inactivation of
bacteria in three studies. Early research showed that a dose of 2.5 mg/L
was required for complete inactivation of coliform bacteria (Le Strat,
1944). In this study, water from the Marne River 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^o^C.

Banerjea (1950) investigated the disinfectant ability of potassium
permanganate on several waterborne pathogenic microorganisms. The
investigation studied *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; however, even
under these conditions the complete absence of *Salm. typhi* or *Bact.
flexner* was not assured, even at a potassium permanganate concentration
that turned the water an objectionable pink color.

Results from a study conducted in 1976 at the Las Vegas Valley Water
District/Southern Nevada System of Lake Mead water showed that complete
removal of coliform bacteria were accomplished at doses of 1, 2, 3, 4,
5, and 6 mg/L (Hazen and Sawyer, 1992). 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 in this study.

#### 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)
(Hazen and Sawyer, 1992). A "potassium" permanganate dose of 5.0 mg/L
and a contact time of 33 minutes was needed for 1-log inactivation of
type 1 poliovirus (Yahya et al., 1990b). Tests showed a significantly
higher inactivation rate at 23^o^C than at 7^o^C; however, there was no
significant difference in activation rates at pH 6.0 and pH 8.0.

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 (Yahya et al., 1989).
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 contradict the previously cited studies that potassium
permanganate becomes more effective as the pH decreases.

#### Protozoa Inactivation

No information pertaining to protozoa inactivation by potassium
permanganate is available in the literature. However, based on the other
disinfectants discussed in this report, protozoa are significantly more
resistant than viruses; therefore, it is likely that the dosages and
contact times required for protozoa inactivation would be impractical.

#### CT Curves

Table 5-1 shows CT values for the inactivation of bacteriophage MS-2.
These data have been provided as an indication of the potential of
potassium permanganate. These values are somewhat inconsistent and do
not include a safety factor and should not be used to establish CT
requirements.

[]{#__RefHeading___Toc450036426 .anchor}Table 5-1. Potassium
Permanganate CT Values for 2-log Inactivation of MS-2 Bacteriophage

+------------------------+----------------------+---------------------+
| **Residual**           | **pH 6.0^1^**        | **pH 8.0^1^**       |
|                        |                      |                     |
| **(mg/L)**             | **(mg min / L)**     | **(mg min / L)**    |
+------------------------+----------------------+---------------------+
| 0.5                    | 27.4 (a)             | 26.1 (a)            |
+------------------------+----------------------+---------------------+
| 1.5                    | 32.0 (a)             | 50.9 (b)            |
+------------------------+----------------------+---------------------+
| 2                      | \-                   | 53.5 (c)            |
+------------------------+----------------------+---------------------+
| 5                      | 63.8 (a)             | 35.5 (c)            |
+------------------------+----------------------+---------------------+

Source: USEPA, 1990.\
Note: ^1^ Letters indicate different experimental conditions.

A 1990 study investigated CT values for *Legionella pneumophila*
inactivation. CT values for 99 percent (2-log) inactivation of
*Legionella pneumophila* at pH 6.0 were determined to be 42.7 mg min/L
at a dose of 1.0 mg/L (contact time 42.7 minutes) and 41.0 mg min/L at a
dose of 5.0 mg/L (contact time 8.2 minutes) (Yahya et al., 1990a).

## Disinfection Byproduct Formation

No literature is available that specifically addressed DBPs when using
potassium permanganate. However, several studies have been conducted
with water treatment plants that have replaced the pre-chlorination
process with potassium permanganate and relocated the point of chlorine
addition for post-treatment disinfection. Pretreatment with permanganate
in combination with post-treatment chlorination will typically result in
lower DBP concentrations than would otherwise occur from traditional
pre-chlorination (Ficek and Boll, 1980; and Singer et al., 1980). Under
this approach, potassium permanganate serves as a substitute for
chlorine to achieve oxidation and may also reduce the concentration of
natural organic matter (NOM). However, systems should evaluate the
impact on CT values before moving the point of chlorination. The
following subsections summarize the outcomes of two studies.

### Chapel-Hill and Durham, North Carolina Water Treatment Plants

An investigation was conducted at the Chapel-Hill and Durham Water
Treatment Plants to evaluate the effects of potassium permanganate
pretreatment on trihalomethane formation (Singer et al., 1980). The
Chapel-Hill Water Treatment Plant uses pre-chlorination prior to the
rapid mix tank. At the Durham Water Treatment Plant, chlorine is not
added until after the sedimentation basin prior to the filtration. Both
are surface water treatment plants, treating water with low
concentrations of alkalinity. Both sources of water are known to have
high trihalomethane formation potentials (Young and Singer, 1979).

Raw water samples taken from Chapel-Hill were found to contain
relatively high turbidities, ranging from 46 to 110 NTU and total
organic carbon (TOC) concentrations ranging from 5.6 to 8.9 mg/L. The
Durham samples were coagulated then allowed to settle, which resulted in
better water quality than the Chapel-Hill samples. Following settling,
this sample had a turbidity of 6.4 NTU and a TOC of 2.9 mg/L. Sulfuric
acid and sodium hydroxide were used to adjust the sample pH to either
6.5 or 10.3. These pH values were selected because they encompass the pH
range typically found in surface water coagulation-filtration and
lime-softening treatment plants.

Potassium permanganate doses of 2 and 5 mg/L were found to be totally
consumed within 1 and 4 hours, respectively, by the Chapel-Hill samples.
At doses of 2 and 5 mg/L, the potassium permanganate demand of the
Durham samples after 4 hours were approximately 1.3 and 1.8 mg/L,
respectively.

This difference in permanganate demands between the Chapel-Hill and
Durham samples may be attributed to the water quality of the samples, in
particular the TOC concentrations. TOC measurements before and after the
application of permanganate were approximately equal; however, it is
likely that the TOC after disinfection was at a higher oxidation state.
Results of this study also showed that permanganate is more reactive as
an oxidant at higher pH values.

Despite the high degree of permanganate consumption, the reaction of
permanganate appears to have relatively little effect on chlorine
demands. For example, consumption of 6 mg/L of permanganate resulted in
a chlorine demand reduction of approximately 1 mg/L. This observation
suggests that permanganate reacts with water impurities in a different
manner, or at different sites, than chlorine. One other possible
explanation is that permanganate oxidizes certain organic substances,
thereby eliminating their chlorine demand and only partially oxidizing
other organic substances making them more reactive to chlorine.

Both the Chapel-Hill and Durham samples were tested for their chloroform
formation potential. This measurement is based on the amount of
chloroform produced after seven days. The potential of the Durham sample
was reduced by 30 and 40 percent at pH 6.5 and 10.3, respectively, as a
result of the application of 10 mg/L of potassium permanganate for a
period of 2 hours. Similar results were obtained for the Chapel-Hill
samples; however, the results at pH 6.5 did not show a reduction in
chloroform formation potential at low doses.

Two experiments were conducted on Chapel-Hill raw water to further
explore the effects of low doses of permanganate. The results indicated
that permanganate has no effect on chloroform production at doses up to
1 mg/L. At higher doses, chloroform formation potentials were reduced.

In summary, the key results obtained from the studies conducted at the
Chapel-Hill and Durham Water treatment plants were:

-   The reactivity of permanganate is a function of pH, permanganate
    dose, and raw water quality.

-   Permanganate reduces chloroform formation potentials. The reduction
    in the chloroform formation potential is proportional to the amount
    of permanganate available after the initial demand is overcome.
    Doses up to 1 mg/L were found to have no effect on chloroform
    formation potentials.

-   At pretreatment doses typically employed at water treatment plants,
    the effect of permanganate on the overall chloroform production is
    relatively small. If permanganate is to be used specifically to
    reduce trihalomethane formation, larger doses will be required.
    However, one advantage for using permanganate for pretreatment is
    that the point of application of chlorine can be shifted downstream
    of the sedimentation basins. This is likely to result in fewer
    trihalomethane compounds.

### American Water Works Association Research Foundation TTHM Study

Another investigation examined the impacts of potassium permanganate
addition on byproduct formation at four water treatment plants (Ficek
and Boll, 1980). All were conventional plants using pre-chlorination in
the treatment process. Plant design capacities ranged from 4.5 to 15
mgd. Process modifications were made at each plant to replace the
pre-chlorination facilities with oxidation facilities for potassium
permanganate addition. After the modifications were complete, an AWWARF
research team conducted a study to determine the impact of potassium
permanganate addition on total trihalomethane (TTHM) concentrations
(George et al., 1990).

Prior to switching from pre-chlorination to pre-oxidation with potassium
permanganate, average daily TTHM concentrations at all four plants were
between 79 and 99 g/L. The average TTHM concentration for all four
plants was 92 g/L. Following the conversion to potassium permanganate,
three of the four plants experienced greater than 30 percent reduction
in TTHM concentrations. In addition to TTHM reduction, potassium
permanganate was found to oxidize taste and odor causing compounds, iron
and manganese, organic and inorganic matter, and reduce algal growth.
Results from the study also showed that the simultaneous application of
potassium permanganate and chlorine can increase THM formation.

## Status of Analytical Methods

The atomic adsorption spectrophotometry method for the measurement of
manganese is the preferred method for measuring permanganate
concentrations. Two colorimetric methods, persulfate and periodate are
also available (Standard Methods, 1995).

## Operational Considerations

In utilizing potassium permanganate in water treatment, caution should
be taken to prevent overdosing, in which case, excess manganese will
pass through the treatment plant. Proper dosing should be maintained to
ensure that all of the permanganate is reduced (i.e., forming MnO~2~
solids) and removed from the plant upstream of, or within, the filters.
If residual manganese is reduced downstream of the filters, the
resulting solids can turn the finished water a brown/black color and
precipitate in the homes of consumers on heat exchange surfaces such as
hot water heaters and dishwashers.

Use of potassium permanganate can also be a source of manganese in the
finished water, which is regulated in drinking water with a secondary
maximum contaminant level of 0.05 mg/L. Under reducing conditions, the
MnO~2~ solids accumulated in filter backwash water and settling basins
can be reduced to soluble Mn^2+^ and pass through the filters thereby
remaining in the finished water.

Also, under these conditions, soluble Mn^2+^ in return water from
settling basin dewatering facilities and filter backwash water recycled
to the head of the plant are potential sources of manganese that will
have to be treated and/or controlled to minimize finished water
manganese levels (Singer, 1991).

Overdosing of permanganate in conventional plants is generally corrected
by settling the excess MnO~2~ solids in the settling basin. Removal of
the excess permanganate can be monitored qualitatively by observing the
disappearance of the pink color characteristic of permanganate. In
plants that do not utilize flocculation and sedimentation processes
permanganate dosing should be closely monitored (Montgomery, 1985).

In general, potassium permanganate does not interfere with other
treatment processes or plant conditions. Permanganate can be added
downstream of, or concurrently with, coagulant and filter polymer aids.
Powdered activated carbon (PAC) and permanganate should not be added
concurrently. PAC should be added downstream of permanganate because it
may consume permanganate, rendering it unavailable for the oxidation of
target organics. (Montgomery, 1985).

The space requirements for permanganate feed equipment vary depending on
the type and size of feed system. Dry feed systems require about half
the floor area of batch systems because batch systems typically have two
dissolving tanks for redundancy. However, the head space requirements
are greater for dry feed systems where the storage hopper and dust
collector are stacked on top of the dry feeder (Kawamura, 1991). On-site
storage of potassium permanganate also warrants some consideration. Per
OSHA requirements, oxidants such as permanganate should be stored
separate from organic chemicals such as polymers and activated carbon.

## Summary 

### 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.

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

-   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.

### Summary Table

More research is needed regarding the disinfection properties and
oxidation byproducts of permanganate in water treatment. Also, a CT
credit needs to be assigned to permanganate if it is to be utilized as a
disinfectant. However, given that alternative oxidants, such as ozone
and chlorine dioxide, demonstrate much greater efficacy in microbial
control, permanganate is not likely to be utilized as a primary oxidant
for precursor control. Table 5-2 summarizes the information presented in
this chapter regarding the use of potassium permanganate in the drinking
water treatment process.

[]{#__RefHeading___Toc450036427 .anchor}Table 5-2. Summary of Potassium
Permanganate Use

  -------------------------------------------------------------------------
  **Consideration**   **Description**
  ------------------- -----------------------------------------------------
  Generation          Product supplied in dry form in buckets, drums, and
                      bulk. On-site generation of solution is required
                      using chemical mixing and feed equipment.

  Primary uses        Control of odor and taste, remove color, control
                      biological growth, and remove iron and manganese.

  Inactivation        Not a good disinfectant. Can serve better as an
  efficiency          alternative to chlorine or other disinfectants where
                      chemical oxidation is desired.

  Byproduct formation No literature was found that specifically addressed
                      DBP formation from potassium permanganate oxidation.
                      Pretreatment with permanganate in combination with
                      post-treatment chlorination will typically result in
                      lower DBP concentrations than would otherwise occur
                      from traditional pre-chlorination.

  Limitations         Not a good disinfectant; primarily used for
                      pretreatment to minimize chlorine usage and byproduct
                      formation.

  Points of           Conventional Treatment: raw water addition, rapid mix
  application         tank in conjunction with coagulants, clarifiers
                      upstream of filters. Direct Filtration: raw water
                      intake. In all cases permanganate should be added
                      upstream of filters.

  Special             Caution should be taken to prevent overdosing. More
  considerations      research is needed to determine disinfection
                      properties and oxidation byproducts.
  -------------------------------------------------------------------------

## References

1.  AWWA (American Water Works Association). 1991. *Guidance Manual for
    Compliance with the Filtration and Disinfection Requirements for
    Public Water Systems Using Surface Water Sources*.

2.  Banerjea, R. 1950. "The Use of Potassium Permanganate in the
    Disinfection of Water." *Ind. Med. Gaz.* 85:214-219.

3.  Cameron, G.N., J.M. Symons, S.R. Spencer, and J.Y. Ma. 1989.
    "Minimizing THM Formation During Control of the Asiatic Clam: A
    Comparison of Biocides." *J. AWWA.* 81(10):53-62.

4.  Cleasby, J.L., E.R. Baumann, and C.D. Black. 1964. "Effectiveness of
    Potassium Permanganate for Disinfection." *J. AWWA.* 56:466-474.

5.  CRC. 1990. *Handbook of Chemistry and Physics*, seventy-first
    edition. D.L. Lide (editor). CRC Press, Boca Raton, FL.

6.  Culp/Wesner/Culp. 1986. *Handbook of Public Water Systems*. Van
    Nostrand Reinhold, New York, NY.

7.  Ficek, K.J., and J.E. Boll. 1980. "Potassium Permanganate: An
    Alternative to Prechlorination." *Aque*. 7:153-156.

8.  George, D.B., V.D. Adams, S.A. Huddleston, K.L. Roberts, and M.B.
    Borup. 1990. *Case Studies of Modified Disinfection Practices for
    Trihalomethane Control, Potassium Permanganate.* AWWAR and AWWA,
    Denver, CO.

9.  Hazen and Sawyer. 1992. *Disinfection Alternatives for Safe Drinking
    Water*. Van Nostrand Reinhold, New York, NY.

10. Kawamura, S. 1991. *Integrated Design of Water Treatment
    Facilities.* John Wiley & Sons, Inc., New York, NY.

11. Klerks, P.L. and P.C. Fraleigh. 1991. "Controlling Adult Zebra
    Mussels with Oxidants." *J.AWWA.* 83(12):92-100.

12. Lalezary, S., M. Pirbazari, and M.J. McGuire. 1986. "Oxidation of
    Five Earthy-Musty Taste and Odor Compounds." *J. AWWA.* 78(3):62.

13. Le Strat. 1944. "Comparison des pouvoirs sterilisants du
    permanganate de potasses et de l'eau de javel a l'egard d'eaux
    contaminees." *Ann. Hygiene*.

14. Lund, E. 1963. "Significance of Oxidation in Chemical Interaction of
    Polioviruses." *Arch. Ges. Virusdorsch.* 12(5):648-660.

15. Montgomery, J.M. 1985. *Water Treatment Principles and Design*. John
    Wiley & Sons, Inc., New York, NY.

16. O'Connell, R.T. 1978. "Suspended Solids Removal." *Water Treatment
    Plant Design*. R.L. Sanks (editor). Ann Arbor Science Publishers,
    Inc, Ann Arbor, MI.

17. Posselt, H.S., F. J. Anderson, and W.J. Webber. 1967. "The Surface
    Chemistry of Hydrous Manganese Dioxide." Presented at meeting of
    Water, Air, and Waste Chemistry Division, American Chemical Society,
    Bar Harbor, FL, April.

18. Singer, P.C. 1991. "Research Needs for Alternative Oxidants and
    Disinfectants." Presented at the Annual AWWA Conference,
    Philadelphia, June 23-27.

19. Singer, P.C., J.H. Borchardt, and J.M. Colthurst. 1980. "The Effects
    of Permanganate Pretreatment on Trihalomethane Formation in Drinking
    Water." *J. AWWA.* 72(10):573-578.

20. Standard Methods. 1995. *Standard Methods for the Examination of
    Water and Wastewater*, nineteenth edition. American Public Health
    Association, AWWA, and Water Pollution Control Fed., Washington,
    D.C.

21. USEPA. 1990. *Guidance Manual for Compliance with the Filtration and
    Disinfection Requirements for Public Works Systems Using Surface
    Water Sources*. Prepared by Malcolm Pirnie, Inc. and HDR Engineering
    for USEPA. Contract No. 68-01-6989.

22. Wagner, R.R. 1951. "Studies on the Inactivation of Influenza Virus."
    *Yale J. Biol. Med*. pp. 288-298.

23. Webber, W.J., Jr., and H.S. Posselt. 1972. "Disinfection."
    *Physicochemical Processes in Water Quality Control*. W. J. Webber
    (editor). John Wiley & Sons, New York, NY.

24. Yahya, M.T., T.M. Straub, and C.P. Gerba. 1990a. *Inactivation of
    poliovirus type 1 by Potassium Permanganate.* University of Arizona
    Preliminary Research Report, Tucson, AZ.

25. Yahya, M.T., Landeen, L.K., and Gerba, C.P. 1990b. Inactivation of
    *Legionella pneumophila* by Potassium Permanganate. *Environ.
    Technol.* 11:657-662.

26. Yahya, M.T., et al. 1989. "Evaluation of Potassium Permanganate for
    the Inactivation of MS-2 in Water Systems." *J. Environ. Sci.
    Health*. A34(8):979-989.

27. Young, J.S. and P.C. Singer. 1979. "Chloroform Formation in Public
    Water Supplies: A Case Study." *J. AWWA.* 71(2):87.

5\. Potassium Permanganate [5-1](#potassium-permanganate)

5.1 Potassium Permanganate Chemistry
[5-1](#potassium-permanganate-chemistry)

5.1.1 Oxidation Potential [5-1](#oxidation-potential)

5.1.2 Ability To Form a Residual [5-1](#ability-to-form-a-residual)

5.2 Generation [5-1](#generation)

5.3 Primary Uses and Points of Application
[5-2](#primary-uses-and-points-of-application)

5.3.1 Primary Uses [5-2](#primary-uses)

5.3.2 Points of Application [5-4](#points-of-application)

5.4 Pathogen Inactivation and Disinfection Efficacy
[5-4](#pathogen-inactivation-and-disinfection-efficacy)

5.4.1 Inactivation Mechanisms [5-4](#inactivation-mechanisms)

5.4.2 Environmental Effects [5-5](#environmental-effects)

5.4.3 Use as a Disinfectant [5-5](#use-as-a-disinfectant)

5.5 Disinfection Byproduct Formation
[5-7](#disinfection-byproduct-formation)

5.5.1 Chapel-Hill and Durham, North Carolina Water Treatment Plants
[5-7](#chapel-hill-and-durham-north-carolina-water-treatment-plants)

5.5.2 American Water Works Association Research Foundation TTHM Study
[5-9](#american-water-works-association-research-foundation-tthm-study)

5.6 Status of Analytical Methods [5-9](#status-of-analytical-methods)

5.7 Operational Considerations [5-9](#operational-considerations)

5.8 Summary [5-10](#summary)

5.8.1 Advantages and Disadvantages of Potassium Permanganate Use
[5-10](#advantages-and-disadvantages-of-potassium-permanganate-use)

5.8.2 Summary Table [5-11](#summary-table)

5.9 References [5-12](#references)

Table 5-1. Potassium Permanganate CT Values for 2-log Inactivation of
MS-2 Bacteriophage [5-7](#__RefHeading___Toc450036426)

Table 5-2. Summary of Potassium Permanganate Use
[5-12](#__RefHeading___Toc450036427)