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®
John Parsons
Hach Company
Loveland, Co
jparsons@hach.com
970-461-3910
Lets Talk Iron and Manganese
1
• 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.
2
3
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
4
• 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
5
• 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.
6
• 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
7
Manganese Staining
Photos courtesy of Herb Spencer, Shannon Chemical Corporation.
8
• 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
9
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.
11
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.
12
• 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
13
• 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
14
• 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
15
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
17
Iron and Manganese Bacteria
Leptothrix in a stream near Hayward, WI. Photo courtesy of John Lindquist
18
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
20
• 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
21
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
23
• 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
24
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
27
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