®

John Parsons

Hach Company

Loveland, Co

jparsons@hach.com

970-461-3910

Lets Talk Iron and Manganese

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• Among the most abundant elements in the earth‟s crust

– Iron is the 1st most abundant metal

– Manganese is the 2nd most abundant metal

– Iron and manganese are found in nearly all natural waters.

– Aesthetic concerns are the primary reasons for monitoring

• Iron and manganese stain plumbing fixtures, appliances, surfaces, clothing, tools and kitchen utensils.

Significance in Drinking Water

• Iron and manganese also can

– Impart an unpleasant taste (often described as bitter or metallic)

– Cause color and turbidity in drinking water to foods and beverages

– Iron and manganese deposits can foul screens, filters, and water lines.

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Iron Manganese

Symbol Fe Mn

Atomic Number 26 25

Atomic Mass 56 55

Common Oxidation States +2, +3 +2, +4, +7

Abundance in the earth's crust5% ; 2nd most abundant

element

0.1% ; 12th most

abundant element

SMCL (Secondary - Aesthetic) 0.3 mg/l 0.05 mg/l

Staining Red to brown Brown to black

Metallic taste in water Yes Yes

Accumulation in and deterioration of plumbing fixtures and

appliances (hot water heaters)Yes Yes

Support growth of certain bacteria using iron and manganese

in their metabolic processes.Yes Yes

RDA for Adults

Men 19 - 8 mg/day 2.3 mg/day AI#*

Women 19-50 18 mg/day 1.8 mg/day AI#*

Women >50 8 mg/day 1.8 mg/day AI#*

*Linus Pauling Institute, Oregon State University # AI = Adequate Intake, no RDA has been established

Significance in Drinking Waater

Dietary Information*

Properties and Occurrence in Nature

Food Serving (mg) Food Serving (mg)

Pineapple, raw 1/2 cup, diced 0.91 Beef 3 oz, cooked 2.31

Pineapple juice 1/2 cup (4 oz.) 0.63 Chicken, dark meat 3 oz., cooked 1.13

Pecans 1 oz. 1.28 Oysters 6 medium 5.04

Almonds 1oz. 0.72 Shrimp 8 large, cooked 1.36

Peanuts 1 oz. 0.55 Tuna, light 3 oz., canned 1.3

Instant oatmeal (prepared

with water)1 packet 1.68 Black-strap molasses 1 tablespoon 3.5

Raisin bran cereal 1 cup 1.88 Raisin bran cereal 1 cup, dry 5

Brown rice, cooked 1/2 cup 0.88 Raisins, seedless 1 sm box (1.5 oz.) 0.89

Whole wheat bread 1 slice 0.6 Prune juice 6 fluid oz. 2.27

Pinto beans, cooked 1/2 cup 0.39 Prunes, dried ~ 5 prunes (1.5 oz.) 1.06

Lima beans, cooked 1/2 cup 0.49 Potato, with skin 1 med potato, baked 2.75

Navy beans, cooked 1/2 cup 0.48 Kidney beans 1/2 cup, cooked 2.6

Spinach, cooked 1/2 cup 0.84 Lentils 1/2 cup, cooked 3.3

Sweet potato, cooked 1/2 cup, mashed 0.5 Tofu, firm 1/4 block (~1/2 cup) 6.22

Tea (green) 1 cup (8 oz.) 0.41-1.58 Cashew nuts 1 oz. 1.7

Tea (black) 1 cup (8 oz.) 0.18-0.77

Manganese Iron

*Linus Pauling Institute, Oregon State University

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• Iron may be present without manganese but manganese in nearly all cases is accompanied by iron.

• No US EPA primary standard for drinking water maximum contaminant levels (MCL)

• US EPA Secondary drinking water standards - SMCLs – – Iron: 0.3 mg/l for iron – Manganese: 0.05 mg/l – Informal industry goals of 0.1 mg/l and 0.01 mg/l,

respectively.

Properties of Iron and Manganese

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• Over 80% of the known

world manganese

resources are found in

South Africa and

Ukraine.

• Other important

manganese deposits

are in China, Australia,

Brazil, Gabon, India,

and Mexico.

Natural Occurrence of Manganese

Psilomelane - a mineral containing significant amounts of manganese. This sample was collected from the Tower Mine region near Socorro, New Mexico, USA.

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• Concentration ranges from 1 to 200 µg/l (0.001 to 0.2 mg/l) in surface water.

– Rivers in the United States contain a range < 11 µg/l to > 50 µg/l. Median of 16 µg/l.

– 800 µg/l has been reported.

– Detected in about 97% of surface water sources.

• Ground water can range up to 9600 µg/l (9.6 mg/l) in acidic water sources

– Median in ground water in the United States is 5 µg/l.

– A study of 989 community water systems across the US found manganese in 68% of ground water systems with a median concentration of 10 µg/l.

Manganese in Water

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Manganese Staining

Photos courtesy of Herb Spencer, Shannon Chemical Corporation.

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• The principle ores of iron are Hematite, (70% iron) and

Magnetite, (72% iron).

• Taconite is a low-grade iron ore, containing up to 30%

Magnetite and Hematite.

• Iron is essential to plant and life

– The human body is 0.006% iron, the majority of which is in the

blood.

• Iron is present in nearly all natural water whether from a

surface or ground water source.

– Median concentration in water of 0.7 mg/l.

– Ground water can range from 0.5 to 10 mg/l but concentrations

of over 50 mg/l have been documented.

Natural Occurrence of Iron

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Iron Minerals

Jasperite –Taconite (silvery) banded in Jasper – red chert. Ispheming, MI, USA

Taconite over a core of quartzite, Marquette, MI, USA

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• Concentrations as low as

0.1 mg/l create a bitter or

metallic taste and

• Concentrations > 0.3

mg/l causing stains to

laundry.

• Reddish to reddish brown

stains on plumbing

fixtures.

Iron in Water

Photo courtesy of Herb Spencer Shannon Chemical Corporation.

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Iron build up in an instrument body

Iron and manganese stains in a clarifier

Iron staining and build up on instrument sample lines

Iron and manganese are

primarily aesthetic concerns but

may create increased

maintenance in treatment

facilities and analytical

instruments.

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• Low oxygen or anaerobic and low pH

environments.

• Peat bogs are common sources.

• Thermal stratification of lakes and reservoirs.

• Ground water with low dissolved oxygen and

high carbon dioxide.

• Iron and manganese bacteria and

microbiologically induced corrosion.

Sources of Iron and Manganese in Water

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• A consequence of water‟s maximum density at 4° C.

– > or < below 4° C the water is less dense.

• Typically stratification begins in early spring as the surface water warms– thus becoming less dense.

• The lower density, warm surface layer „floats‟ on the more dense, cooler water in lower regions. The upper layer is termed the epilimnion.

• The lower layer is termed the hypolimnion.

• With time a third, transitional layer forms, the thermocline.

– the temperature change is 1°C per meter of depth (about 0.55°F per foot).

Stratification, Destratification and Turn Over

Epilimnion

Thermocline

Hypolimnion

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• The epilimnion is well aerated.

• The hypolimnion approaches anaerobic conditions –

– organic matter decays,

– the pH can drop.

– iron and manganese may enter solution,

• During the fall season the

– epilimnion begins to cool and the

– thermocline decreases in thickness until finally it vanishes.

• The two layers mix (the reservoir „turns over‟) - the nutrient rich, oxygen starved water hypolimnion mixes with the oxygen rich epilimnion.

• Numerous problems can ensue –

– eutrophication (and resulting oxygen depletion),

– algal blooms,

– iron and manganese problems,

– turbidity,

– increase in TOC,

– potential increase in THM formation potential,

– undesirable taste and odor.

Destratification (Turn Over)

Epilimnion

Thermocline

Hypolimnion

Summer

Fall

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Tools for Reservoir Profiling

Portable meters such as the

HQ40d can be used for

simple reservoir profiling for

pH, temperature and DO.

Use the Hydrolab sondes for

reservoir profiling studies. Either

the DS5 or MS5 can be equipped

with a variety of sensors including

pH, conductivity, temperature,

pressure, chlorophyll A, Blue-

Green Algae, nitrate, dissolved

oxygen (DO), ORP, turbidity.

• Microbiological activity may also play a significant role in the presence of iron and manganese

• Iron and manganese related organisms include filamentous and single-celled organisms. – Iron bacteria commonly cited include Gallionella,

Crenothrix, Sphaerotilus, Leptothrix and Siderocapsa.

– Bacteria cited as manganese related include Planctomyces, Pedomicrobium and Metallogenium.

Iron and Manganese Bacteria

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Iron and Manganese Bacteria

Leptothrix in a stream near Hayward, WI. Photo courtesy of John Lindquist

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Problems Associated with Iron and Manganese

Organisms

•Staining •Slimes •Taste and Odor •Coats Filter Media •Microbiologically induced corrosion (MIC)

“The first time I ever witnessed an iron-bacteria problem I was called out by one of the ground water systems in my area… When I arrived at the site the operator explained that he had drained one of their pressure storage tanks. He then removed the bottom access cover and inside was a dark brown gelatinous material. I got some in my hand and it looked and felt like axle grease. But it was water soluble.” Danny Hutcherson, Hach Company

• Growths of microorganisms in water

distribution systems as some

filamentous organisms utilize iron (and

some also utilize manganese) as an

energy source. – cause discolored water

– slimes decrease the carrying capacity

(C-factor) of pipes

– harbor other organisms and shield them from

the disinfection process.

– The biological growths also can contribute to

corrosion of pipes

Microbiologically Induced corrosion

MIC. Photo courtesy Robert Spon

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• Manganese is a positive interference in chlorine measurement – For wastewater utilities, it may cause the appearance

the wastewater utility is out of compliance with their NPDES discharge permit, especially if their permit is for near zero

– For drinking water utilities, manganese can lead utilities to believe their chlorine residual is higher that it really is and may lead to an answer to questions such as – „gee, our chlorine residual is normal, how could we be getting positive bacterial tests?‟

• Every Hach chlorine residual procedure contains

instructions for overcoming the interference.

Manganese Interferes with Chlorine Measurement

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Monitoring Iron and Manganese Bacteria

• Biological Activity

Reaction Tests BARTS

Hach Cat. No. Application Description Model

24232-09 or

24323-27

DW, GW, SW, RW, WW, IW Iron Related Bacteria IRB

24234-09 or

24324-27

DW, GW, SW, RW, WW Sulfate Reducing Bacteria SRB

24904-09 or

24904-27

DW, GW, SW, RW, WW, IW Heterotrophic Aerobic Bacteria HAB

24235-09 or

24325-27

DW, GW, SW, RW, WW, IW Slime Forming Bacteria SLYM

26193-09 DW, GW, SW, RW, WW, IW Denitrifying Bacteria DN

26194-07 DW, GW, SW, RW, WW, IW Nitrifying Bacteria N

24326-09 DW, GW, SW, RW, Fluorescing Pseudomonades FLOR

24327-09 or

24327-27

DW, GW, SW, RW, WW Blue-Green Algae ALG

24904-09 or

24904-27

DW, GW, SW, RW, WW, IW Heterotrophic Aerobic Bacteria HAB

24784-09 RW Pool and Spa Bacteria POOL

DW – Drinking Water; GW – Ground Water; SW – Surface Water; RW – Recreational Water; WW –

Wastewater; IW – Industrial Water. -09: 9pkg; -27: 27/pkg.

Iron BART

• RoVer® Rust Remover

• Manganese stains only: – Mild: Equal thirds by volume

water, white vinegar and 3%

hydrogen peroxide

– Strong: By volume 70% white

vinegar, 30% 3% hydrogen

peroxide.

• Bleach may make the stains

worse

Removing Iron and Manganese Stains

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• Ferrous Iron: – 1,10-Phenanthroline Method. The Fe2+ procedure uses

Ferrous Iron Reagent Powder containing 1,10-Phenanthroline as an indicator.

• Total iron: – FerroVer® Iron Reagent. FerroVer Iron Reagent contains

1,10-Phenanthroline, combined with a reducing agent, to convert all but the most resistant forms of iron present in the sample to Fe2+.

– TPTZ Method for total iron has the advantages of simplicity, sensitivity, and freedom from common interferences. Iron in the sample, including precipitated or suspended iron such as rust, is converted to Fe2+ by a reducing agent.

– FerroZine® Iron Reagent Method for total iron is more than twice as sensitive as the 1,10-Phenanthroline Method. The FerroZine Method requires boiling to dissolve rust.

• High-range titration procedure utilizing sulfosalicylic acid as the indicator and EDTA as the titrant.

Methods for Determining Iron

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1,10 Phenanthroline Method

Ferrous Iron (Fe2+)

Soluble + Insoluble Soluble

Fe2+ and Fe3+

Digestion may be required*

Cooling water containing Molybdate-based

treatment?

Select one of the following total iron methods based on range

FerroMo Method

0.01 to 1.80 mg/l

FerroZine Method 0.009 to 1.4 mg/l

TPTZ Method*

0.012 to 1.800 mg/l FerroVer Method*

0.02 to 3.00 mg/l

(Digestion required for EPA approval)

TitraVer Titration

10-10,000 mg/l

Recommended for field use only.

Which iron test does my

application require?

Ferric Iron (Fe3+)

Total – Ferrous = Ferric

Total

(Ferrous + Ferric)

To obtain Ferric, run the total and ferrous procedures on the same size aliquots of

sample. Then subtract Ferrous from Total to get Ferric.

Low Range Mid Range

Higher Range

Very High Range

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–Select the right method for the

–Range

–Reporting requirement

–Application

Methods for Determining Manganese

• Periodate Oxidation Method gives a simple, rapid

test for high levels of manganese.

– High range 0.1- 20.0 mg/l

• 1-(2-Pyridylazo)-2-Napthol (PAN) Method is a

sensitive, rapid procedure for low levels of

manganese.

– Low range 0.006 - 0.700 mg/l (6 – 700 µg/l)

Discussion/Questions

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