- What is bacteria?
- What is hardwater?
- What is Iron?
- What is Sulfur?
- How does Reverse Osmosis Work?
- How does a Water Softener Work?
- How does a MG Filter Work?
Bacteria
The presence of bacteria and pathogenic (disease-causing) organisms is a
concern when considering the safety of drinking water. Pathogenic organisms
can cause intestinal infections, dysentery, hepatitis, typhoid fever,
cholera, and other illnesses.
Sources of Bacteria in Drinking Water
Bacterial contamination can result from a number of sources.
Human and animal wastes are a primary source of bacteria in water. These
sources of bacterial contamination include runoff from feedlots, pastures,
dog runs, and other land areas where animal wastes are deposited. Additional
sources include seepage or discharge from septic tanks and sewage treatment
facilities. Bacteria from these sources can enter wells that are either open
at the land surface, or do not have water-tight casings or caps, or do not
have a grout seal in the annular space (the space between the wall of the
drilled well and the outside of the well casing).
nsects, rodents or animals entering the well are other sources of
contamination. Old wells were dug by hand and lined (cased) with rocks or
bricks. These wells usually have large openings and casings that often are
not well-sealed. This makes it easy for insects, rodents, or animals to
enter the well.
Another way bacteria can enter a water supply is through inundation or
infiltration by flood waters or by surface runoff. Flood waters commonly
contain high levels of bacteria. Small depressions filled with flood water
provide an excellent breeding ground for bacteria.
Whenever a well is inundated by flood waters or surface runoff, bacterial
contamination is likely. Shallow wells and wells that do not have
water-tight casings can be contaminated by bacteria infiltrating with the
water through the soil near the well, especially in coarse-textured soils.
Older water systems, especially dug wells, spring-fed systems and
cistern-type systems are most vulnerable to bacterial contamination. Any
system with casings or caps that are not water-tight, or lacking a grout
seal in the annular space, are vulnerable. This is particularly true if the
well is located so surface runoff might be able to enter the well. During
the last five to 10 years, well and water distribution system construction
has improved to the point where bacterial contamination is rare in newer
wells.
Indications of Bacteria
Bacterial contamination cannot be detected by sight, smell or taste. The
only way to know if a water supply contains bacteria is to have it tested.
The Environmental Protection Agency (EPA) requires that all public water
suppliers regularly test for coliform bacteria and deliver water that meets
the EPA standards. Frequency of testing depends on the size of the
population served. Bacteria test results are available from the supplier and
there must be a public notification if the water supply does not meet the
standard.
Owners of private water supplies are responsible to themselves for having
their water supply tested to ensure it is safe from bacterial contamination.
Generally, private water supplies should be tested for bacterial safety as
follows:
- at least once a year;
- when a new well is constructed;
- when an existing well is returned to service;
- any time a component of the water system is opened
for repair – the water system includes the well, pump, pressure tank,
piping, and any other components the water will contact;
- whenever the well is inundated by flood waters or
surface runoff;
- whenever bacterial contamination is suspected, as
might be indicated by continuing illness;
- when a laboratory test indicates high nitrate and
human or livestock waste is suspected.
-
Often, lending agencies require private water supplies be tested before
home loans will be approved, including refinancing a loan.
Potential Health Effects
Coliform bacteria may not cause disease, but can be indicators of
pathogenic organisms that cause diseases. The latter could cause intestinal
infections, dysentery, hepatitis, typhoid fever, cholera and other
illnesses. However, these illnesses are not limited to disease-causing
organisms in drinking water. Other factors not associated with drinking
water may be the cause.
Intestinal infections and dysentery are generally considered minor health
problems. They can, however, prove fatal to infants, the elderly, and those
who are ill. Today typhoid, hepatitis and cholera are rarely encountered in
the United States.
Other bacteria also may be present in water. No specific sanitary
significance or health standards have been indicated for non-pathogenic non-coliform
bacteria.
Testing
Testing for all individual pathogens is impractical and expensive.
Instead, the EPA has designated total coliform bacteria as a standard to
determine bacterial safety of water.
Coliform bacteria originate in the intestinal tract of warm-blooded
animals and can be found in their wastes. Coliforms also occur in soil and
vegetation.
Coliform bacteria are relatively simple to identify and are present in
much larger numbers than more dangerous pathogens. Coliform bacteria react
to the natural environment and treatment processes in a manner and degree
similar to pathogens. By monitoring coliform bacteria, the increase or
decrease of many pathogenic bacteria can be estimated.
Due to this association, bacterial safety of drinking water is monitored
by testing for coliform bacteria. Bacterial testing is provided, for a fee,
by the Nebraska Health and
After selecting a laboratory, contact them to obtain a drinking water
bacterial purity test kit. The kit will contain a sterilized sampling
bottle, an information form, sampling instructions, and a return mailing
box. Use of the bacterial test kit is necessary to help ensure the test is
accurate. The bottle in the kit is completely sterilized. This assures the
sample is not contaminated by bacteria in the bottle. The use of any other
container is discouraged.
To avoid unnecessary delays and possibly a need for resampling, mail or
carry the sample to the laboratory immediately. The sample must be received
at the laboratory within 48 hours after collection or it will not be tested.
Avoid mailing samples when they may be delayed over a weekend or a holiday.
In most cases, samples need to arrive at the laboratory on Monday, Tuesday,
Wednesday or Thursday.
Be sure the form accompanying the sample is accurate and complete. If
there is no date or time of collection on the form, it will be assumed the
sample is over 48 hours old. If there is no return address, test results
cannot be sent to you.
When a laboratory receives a water sample, it gives the sample a number
and the time of arrival is stamped on the accompanying form. One hundred
milliliters (ml) (about 3.4 fl. oz.) of the sample is then drawn through a
membrane filter. This filter is placed on a nutrient broth culture plate and
placed in an incubator for 24 hours at 35° C (95° F) for culturing. The
plates then are removed from the incubator and the number of coliform
bacteria colonies are counted.
The kit contains detailed instructions on how to collect the water
sample. Follow the instructions carefully to avoid outside contamination and
to obtain a good representative sample.
Interpreting Test Results
The EPA establishes standards for drinking water which fall into two
categories – Primary Standards and Secondary Standards.
Primary Standards are based on health considerations, and are designed to
protect people from three classes of toxic pollutants; pathogens,
radioactive elements and toxic chemicals.
Bacterial contamination falls under the category of pathogens. The EPA
Maximum Contaminant Level (MCL) for coliform bacteria in drinking water is
zero (or no) total coliform per 100 ml of water.
The number of coliform colonies found in the incubated water sample, if
any, is reported and the form is checked to indicate whether or not the
water meets the EPA bacteriological standard of zero. At times, excessive
numbers of other bacteria in a sample can interfere with the counting of
coliform types. These samples may be classified as "too numerous to count"
or "confluent growth."
If the laboratory report indicates the presence of coliforms, or states
"too numerous to count," or "confluent growth," the Nebraska Health and
Human Services System Department of Regulation and Licensure recommends
another sample be analyzed to help evaluate the contamination.
If you suspect bacterial contamination in your water supply, use an
alternative water supply or disinfect your water supply while waiting for
test results.
Summary
Bacterial contamination of drinking water can be a problem. A water test
is the only way to evaluate whether bacteria is present in a water supply.
Proper well location and construction are keys to avoiding bacterial
contamination of drinking water. If contamination is present, attempt to
identify and eliminate the source of the contamination. A contaminated water
supply can be disinfected.
What is Hard Water?
Water
described as "hard" is high in dissolved minerals, specifically calcium and
magnesium. Hard water is not a health risk, but a nuisance because of
mineral buildup on fixtures and poor soap and/or detergent performance.
Sources of Hardness Minerals in Drinking Water
Water is a good solvent and
picks up impurities easily. Pure water -- tasteless, colorless, and odorless
-- is often called the universal solvent. When water is combined with carbon
dioxide to form very weak carbonic acid, an even better solvent results.
As water moves through soil and rock, it dissolves
very small amounts of minerals and holds them in solution. Calcium and
magnesium dissolved in water are the two most common minerals that make
water "hard." The degree of hardness becomes greater as the calcium and
magnesium content increases.
Indications of Hard Water
Hard water interferes with
almost every cleaning task, from laundering and dishwashing to bathing and
personal grooming. Clothes laundered in hard water may look dingy and feel
harsh and scratchy. Dishes and glasses may be spotted when dry. Hard water
may cause a film on glass shower doors, shower walls, bathtubs, sinks,
faucets, etc. Hair washed in hard water may feel sticky and look dull. Water
flow may be reduced by hard water deposits in pipes.
Dealing with hard water problems in the home can
be a nuisance. The amount of hardness minerals in water affects the amount
of soap and detergent necessary for cleaning. Soap used in hard water
combines with the minerals to form a sticky soap curd. Some synthetic deter-
gents are less effective in hard water because the active ingredient is
partially inactivated by hardness, even though it stays dissolved.
Bathing with soap in hard water leaves a film of
sticky soap curd on the skin. The film may prevent removal of soil and
bacteria. Soap curd interferes with the return of skin to its normal,
slightly acid condition, and may lead to irritation. Soap curd on hair may
make it dull, lifeless and difficult to manage.
When doing laundry in hard water, soap curds lodge
in fabric during washing to make fabric stiff and rough. Incomplete soil
removal from laundry causes graying of white fabric and the loss of
brightness in colors. A sour odor can develop in clothes. Continuous
laundering in hard water can shorten the life of clothes.
In addition, soap curds can deposit on dishes,
bathtubs and showers, and all water fixtures.
Hard water also contributes to inefficient and
costly operation of water-using appliances. Heated hard water forms a scale
of calcium and magnesium minerals that can contribute to the inefficient
operation or failure of water-using appliances. Pipes can become clogged
with scale that reduces water flow and ultimately requires pipe replacement.
Options
There are two ways to help
control water hardness: use a packaged water softener, or use a mechanical
water softening unit.
Packaged water softeners are chemicals that help
control water hardness. They fall into two categories: precip-itating and
non-precipitating.
Precipitating water softeners include washing soda
and borax. These products form an insoluble precipitate with calcium and
magnesium ions. The mineral ions then cannot interfere with cleaning
efficiency, but the precipitate makes water cloudy and can build up on
surfaces.
Precipitating water softeners increase alkalinity
of the cleaning solution and this may damage skin and other materials being
cleaned.
Non-precipitating water softeners use complex
phosphates to sequester calcium and magnesium ions. There is no precipitate
to form deposits and alkalinity is not increased.
If used in enough quantity, non-precipitating
water softeners will help dissolve soap curd for a period of time.
Mechanical water softening units can be
permanently installed into the plumbing system to continuously remove
calcium and magnesium.
Water softeners operate on the ion exchange
process. In this process, water passes through a media bed, usually
sulfonated polystyrene beads. The beads are supersaturated with sodium. The
ion exchange process takes place as hard water passes through the softening
material. The hardness minerals attach themselves to the resin beads while
sodium on the resin beads is released simultaneously into the water
When the resin becomes saturated with calcium and
magnesium, it must be recharged. The recharging is done by passing a salt
(brine) solution through the resin. The sodium replaces the calcium and
magnesium which are discharged in the waste water.
Hard water treated with an ion exchange water
softener has sodium added. According to the Water Quality Association (WQA),
the ion exchange softening process adds sodium at the rate of about 8
mg/liter for each grain of hardness removed per gallon of water.
For example, if the water has a hardness of 10
grains per gallon, it will contain about 80 mg/liter of sodium after being
softened in an ion exchange water softener if all hardness minerals are
removed.
Because of the sodium content of softened water,
some individuals may be advised by their physician, not to install water
softeners, to soften only hot water or to bypass the water softener with a
cold water line to provide unsoftened water for drinking and cooking;
usually to a separate faucet at the kitchen sink.
Softened water is not recommended for watering
plants, lawns, and gardens due to its sodium content.
Although not commonly used, potassium chloride can
be used to create the salt brine. In that case potassium rather than sodium
is exchanged with calcium and magnesium.
Before selecting a mechanical water softener, test
water for hardness and iron content. When selecting a water softener, the
regeneration control system, the hardness removal capacity, and the iron
limitations are three important elements to consider.
There are three common regeneration control
systems. These include a time-clock control (you program the clock to
regenerate on a fixed schedule); water meter control (regenerates after a
fixed amount of water has passed through the softener); and hardness sensor
control (sensor detects hardness of the water leaving the unit, and signals
softener when regeneration is needed).
Hardness removal capacity, between regenerations,
will vary with units. Softeners with small capacities must regenerate more
often.
Your daily softening need depends on the amount of
water used daily in your household and the hardness of your water. To
determine your daily hardness removal need, multiply daily household water
use (measured in gallons) by the hardness of the water (measured in grains
per gallon).
Iron removal limitations will vary with water
softener units. If the iron level in your water exceeds the maxi- mum iron
removal capacity recommended by the manufacturer of the unit you are
considering, iron may foul the softener, eventually causing it to become
plugged.
For additional information on water softeners,
including information on how a water softener works, maintenance
requirements of water softeners, difference in softener salt, etc.
Summary
Hard water is not a health
hazard, but dealing with hard water in the home can be a nuisance. The
hardness (calcium and magnesium concentration) of water can be approximated
with a home-use water testing kit, or can be measured more accurately with a
laboratory water test. Water hardness can be managed with packaged water
softeners or with a mechanical ion exchange softening unit. |
What is Iron?
Iron and manganese are
non-hazardous elements that can be a nuisance in a water supply. Iron and
manganese are chemically similar and cause similar problems. Iron is the
most frequent of the two contaminants in water supplies; manganese is
typically found in iron-bearing water.
Sources of Iron and Manganese in Drinking Water
Iron and manganese are common metallic elements found in the earth's
crust. Water percolating through soil and rock can dissolve minerals
containing iron and manganese and hold them in solution. Occasionally, iron
pipes also may be a source of iron in water.
Indications of Iron and Manganese
In deep wells, where oxygen content is low, the iron/manganese-bearing
water is clear and colorless (the iron and manganese are dissolved). Water
from the tap may be clear, but when exposed to air, iron and manganese are
oxidized and change from colorless, dissolved forms to colored, solid forms.
Oxidation of dissolved iron particles in water changes the iron to white,
then yellow and finally to red-brown solid particles that settle out of the
water. Iron that does not form particles large enough to settle out and that
remains suspended (colloidal iron) leaves the water with a red tint.
Manganese usually is dissolved in water, although some shallow wells contain
colloidal manganese (black tint). These sediments are responsible for the
staining properties of water containing high concentrations of iron and
manganese. These precipitates or sediments may be severe enough to plug
water pipes.
Iron and manganese can affect the flavor and color of food and water.
They may react with tannins in coffee, tea and some alcoholic beverages to
produce a black sludge, which affects both taste and appearance. Manganese
is objectionable in water even when present in smaller concentrations than
iron.
Iron will cause reddish-brown staining of laundry, porcelain, dishes,
utensils and even glassware. Manganese acts in a similar way but causes a
brownish-black stain. Soaps and detergents do not remove these stains, and
use of chlorine bleach and alkaline builders (such as sodium and carbonate)
may intensify the stains.
Iron and manganese deposits will build up in pipelines, pressure tanks,
water heaters and water softeners. This reduces the available quantity and
pressure of the water supply. Iron and manganese accumulations become an
economic problem when water supply or water softening equipment must be
replaced. There also are associated increases in energy costs from pumping
water through constricted pipes or heating water with heating rods coated
with iron or manganese mineral deposits.
A problem that frequently results from iron or manganese in water is
iron or manganese bacteria. These nonpathogenic (not health threatening)
bacteria occur in soil, shallow aquifers and some surface waters. The
bacteria feed on iron and manganese in water. These bacteria form red-brown
(iron) or black-brown (manganese) slime in toilet tanks and can clog water
systems.
Potential Health Effects
Iron and manganese in drinking water are not considered health hazards.
Testing
The method used to test water for iron and manganese depends on the form
of the element. If water is clear when first drawn but red or black
particles appear after the water sits in a glass, dissolved (ferrous)
iron/manganese is present. If the water has a red tint with particles so
small they cannot be detected nor do they settle out after a time, colloidal
(ferric) iron is the problem.
Typically, laboratory tests are needed only to quantify the extent of
iron and manganese contamination, but testing of additional water parameters
such as pH, silica content, oxygen content, hardness and sulfur may be
necessary to determine the most appropriate water treatment system.
Iron and manganese testing is provided for a fee by the Nebraska
Department of Health Laboratory and some commercial water testing
laboratories.
Select a laboratory and contact them to obtain a drinking water iron
and/or manganese test kit. The kit will contain a sample bottle, an
information form, sampling instructions and a return mailing box.
The sampling instructions provide information on how to collect the
sample. Follow these instructions to avoid contamination and to obtain a
representative sample. Promptly mail the sample with the completed
information form to the laboratory. Take the sample on a day when it can be
mailed to arrive at the laboratory Monday through Thursday. Avoid weekends
and holidays which may delay the mail or lab analysis.
Samples may be taken from the inside surfaces of the plumbing system to
confirm iron or manganese bacteria presence. The interior of the toilet tank
is a good location for obtaining a bacteria sample. Check with the
laboratory for further information on bacterial colony sampling.
Interpreting Test Results
The Environmental Protection Agency (EPA) standards for drinking water
fall into two categories --- Primary Standards and Secondary Standards.
Primary Standards are based on health considerations and are designed to
protect people from three classes of pollutants: pathogens, radioactive
elements and toxic chemicals.
Secondary Standards are based on taste, odor, color, corrosivity, foaming
and staining properties of water. Iron and manganese are both classified
under the Secondary Maximum Contaminant Level (SMCL) standards.
The SMCL for iron in drinking water is 0.3 milligrams per liter (mg/l),
sometimes expressed as 0.3 parts per million (ppm), and 0.05 mg/l (ppm) for
manganese. Water with less than these concentrations should not have an
unpleasant taste, odor, appearance or side effect caused by a secondary
contaminant.
Options
If excessive iron or manganese is present in your water supply, you have
two basic options -- obtain an alternate water supply or use some type of
treatment to remove the impurity.
The need for an alternate water supply or impurity removal should be
established before making an investment in treatment equipment or an
alternate supply. Base the decision on a water analysis by a reputable
laboratory.
It may be possible to obtain a satisfactory alternate water supply by
drilling a new well in a different location or a deeper well in a different
aquifer.
Several methods of removing iron and manganese from water are available.
The most appropriate method depends on many factors, including the
concentration and form of iron/manganese in the water, if iron or manganese
bacteria are present, and how much water you need to treat.
Generally speaking, there are five basic methods for treating water
containing these contaminants. They are: (1) phosphate compounds;
(2) ion exchange water softeners; (3) oxidizing filters;
(4) aeration (pressure type) followed by filtration; and (5)
chemical oxidation followed by filtration. Table I
summarizes iron and manganese treatment options.
These treatment techniques are effective in water that has an almost
neutral pH (approximately 7.0). The phosphate compound treatment is an
exception and is effective in the pH range of 5.0 to 8.0. Exceptions are
noted for manganese removal.
Phosphate treatment
Low levels of dissolved iron and manganese
at combined concentrations up to 3 mg/l can be remedied using phosphate
compound treatment. Phosphate compounds are a family of chemicals that can
surround minerals and keep them in solution. Phosphate compounds injected
into the water system can stabilize and disperse dissolved iron at this
level. As a result, the iron and manganese are not available to react with
oxygen and separate from solution.
The phosphate compounds must be introduced
into the water at a point where the iron is still dissolved in order to
maintain water clarity and prevent possible iron staining. This should be
before the pressure tank and as close to the well discharge point as
possible.
Phosphate compound treatment is a relatively
inexpensive way to treat water for low levels of iron and manganese. Since
phosphate compounds do not actually remove iron, water treated with these
chemicals will retain a metallic taste. In addition, too great a
concentration of phosphate compounds will make water feel slippery.
Phosphate compounds are not stable at high
temperatures. If phosphate compound-treated water is heated (for example, in
a water heater or boiled water), the phosphates will break down and release
iron and manganese. The released iron and manganese will then react with
oxygen and precipitate.
Adding phosphate compounds is not recommended
where the use of phosphate in most cleaning products is banned. Phosphate,
from any source, contributes to excess nutrient content in surface water.
Ion exchange water
softener
Low to moderate levels of dissolved iron,
at less than 5 mg/l concentrations, usually can be removed using an ion
exchange water softener. Be sure to check the manufacturer's maximum iron
removal level recommendations before you purchase a unit. Capacities for
treating dissolved iron typically can range from 1 to 5 mg/l. Oxidized iron
or levels of dissolved iron exceeding the manufacturer's recommendations
will cause a softener to become plugged.
The principle is the same as that used to
remove the hardness minerals, calcium and magnesium; i.e., iron in the
untreated water is exchanged with sodium on the ion exchange medium. Iron is
flushed from the softener medium by backwashing (forcing sodium-rich water
back through the device). This process adds sodium to the resin medium, and
the iron is carried away in the waste water.
Since iron removal reduces the softening
capacity of the unit, the softener will have to be recharged more often. The
manufacturer of the softener medium is able to make recommendations
concerning the appropriate material to use for a particular concentration of
iron. Some manufacturers recommend adding a "bed cleaning" chemical with
each backwashing to prevent clogging.
Not all water softeners are able to remove
iron from water. The manufacturer's specifications should indicate whether
or not the equipment is appropriate for iron removal.
Water softeners add sodium to the water, a
health concern for people on sodium-restricted diets. Consider installing a
separate faucet to provide unsoftened water for cooking and drinking.
Oxidizing filter
An oxidizing filter treatment system is an
option for moderate levels of dissolved iron and manganese at combined
concentrations up to 15 mg/l. The filter material is usually natural
manganese greensand or manufactured zeolite coated with manganese oxide,
which adsorbs dissolved iron and manganese. Synthetic zeolite requires less
backwash water and softens the water as it removes iron and manganese. The
system must be selected and operated based on the amount of dissolved
oxygen. Dissolved oxygen content can be determined by field test kits, some
water treatment companies or in a laboratory.
Aeration followed by filtration
High levels of dissolved iron and manganese
at combined concentrations up to 25 mg/l can be oxidized to a solid form
by aeration (mixing with air). For domestic water processing, the
"pressure-type aerator" often is used.
In this system, air is sucked in and mixed
with the passing stream of water. This air-saturated water then enters the
precipitator/aerator vessel where air separates from the water. From this
point, the water flows through a filter where various filter media are used
to screen out oxidized particles of iron, manganese and some carbonate or
sulfate.
The most important maintenance step involved
in operation is periodic backwashing of the filter. Manganese oxidation is
slower than for iron and requires greater quantities of oxygen. Aeration is
not recommended for water containing organic complexes of iron/manganese or
iron/manganese bacteria that will clog the aspirator and filter.
Chemical oxidation followed by filtration
High levels of dissolved or oxidized iron
and manganese greater than 10 mg/l can be treated by chemical oxidation,
using an oxidizing chemical such as chlorine, followed by a sand trap filter
to remove the precipitated material. Iron or manganese also can be oxidized
from the dissolved to solid form by adding potassium permanganate or
hydrogen peroxide to untreated water. This treatment is particularly
valuable when iron is combined with organic matter or when iron bacteria is
present.
The oxidizing chemical is put into the water
by a small feed pump that operates when the well pump operates. This may be
done in the well, but typically is done just before the water enters a
storage tank. A retention time of at least 20 minutes is required to allow
oxidation to take place. The resulting solid particles then must be
filtered. When large concentrations of iron are present, a flushing sand
filter may be needed for the filtering process.
If organic-complexed or colloidal
iron/manganese is present in untreated water, a longer contact time and
higher concentrations of chemicals are necessary for oxidation to take
place. Adding aluminum sulfate (alum) improves filtration by causing larger
iron/manganese particles to form.
When chlorine is used as the oxidizing agent,
excess chlorine remains in treated water. If the particle filter is made of
calcite, sand, anthracite or aluminum silicate, a minimum quantity of
chlorine should be used to avoid the unpleasant taste that results from
excess chlorine. An activated carbon filter can be used to remove excess
chlorine and small quantities of solid iron/manganese particles.
Any filtration material requires frequent and
regular backwashing or replacement to eliminate the solid iron/manganese
particles. Some units have an automatic backwash cycle to handle this task.
The ideal pH range for chlorine bleach to
oxidize iron is 6.5 to 7.5. Chlorination is not the method of choice for
high manganese levels since a pH greater than 9.5 is required for complete
oxidation. Potassium permanganate will effectively oxidize manganese at pH
values above 7.5 and is more effective than chlorine oxidation of organic
iron if that is a problem.
Potassium permanganate is poisonous and a skin
irritant. There must be no excess potassium permanganate in treated water
and the concentrated chemical must be stored in its original container away
from children and animals. Careful calibration, maintenance and monitoring
are required when potassium permanganate is used as an oxidizing agent.
|
Table I. Treatment of iron and manganese in drinking water |
|
Indication |
Cause |
Treatment |
|
Water clear when drawn but red-brown or black particles appear as water
stands; red-brown or black stains on fixtures or laundry |
Dissolved iron or manganese |
- Phosphate compounds (< 3 mg/l iron)
- Water softener (<5 mg/l combined
concentrations of iron and manganese)
- Oxidizing filter (manganese greensand or
zeolite) (<15 mg/l combined concentrations of iron and manganese)
- Aeration (pressure) (<25mg/l combined
concentrations of iron and manganese)
- Chemical oxidation with potassium permanganate
or chlorine; followed with filtration (>10 mg/l combined
concentrations of iron and manganese)
|
|
Water contains red-brown particles when drawn; particles settle out as
water stands |
Iron particles from corrosion of pipes and equipment |
Raise pH with neutralizing filter |
|
Water contains red-brown or black particles when drawn; particles settle
out as water stands |
Oxidized iron/manganese due to exposure of water to air prior to tap |
Particle filter (if quantity of oxidized material is high, use larger
filter than inline; e.g., sand filter) |
|
Red-brown or black slime appears in toilet tanks or from clogs in
faucets |
Iron or manganese bacteria |
Kill bacteria masses by shock treatment with chlorine or potassium
permanganate, then filter; bacteria may originate in well, so it may
require continuous feed of chlorine or potassium permanganate, then
filter |
|
Reddish or black color that remains longer than 24 hours |
Colloidal iron/manganese; organically complexed iron/manganese |
Chemical oxidation with chlorine or potassium permanganate; followed
with filtration |
Adapted from "Iron and Manganese in Household Water," Water Treatment
Notes. Fact Sheet 6, Cornell Cooperative Extension. (1989).
Plumbing corrosion
Corroded pipes and equipment may cause reddish-brown particles in the
water that, when drawn from the tap, will settle out as the water stands.
This can indicate oxidized iron or, in some cases, it may only be iron
corrosion particles. Raising the water's pH and using a sediment filter is
the simplest solution to this problem.
Iron and manganese bacteria
The most common approach to control of iron and manganese bacteria is
shock chlorination. It is almost impossible to kill all the iron and
manganese bacteria in your system. They will grow back eventually so be
prepared to repeat the treatment from time to time.
If bacteria regrowth is rapid, repeated shock chlorination becomes time
consuming. Continuous application of low levels of chlorine may be less work
and more effective. An automatic liquid chlorine injector pump or a
dispenser that drops chlorine pellets into the well are common choices.
Chlorine rapidly changes dissolved iron into oxidized (colored) iron that
will precipitate. A filter may be needed to remove oxidized iron if
continuous chlorination is used to control iron bacteria.
Multistage treatment
If the water has high levels of iron and manganese and they are both the
dissolved and solid forms, a multistage treatment operation is necessary.
For example, a troublesome supply could be chlorinated to oxidize dissolved
iron and kill iron bacteria, and filtered through a mechanical device to
remove particles. This can be followed by activated carbon filtration to
remove excess chlorine and a water softener for hardness control as well as
removal of any residual, dissolved iron or manganese.
Often hydrogen sulfide, iron and manganese contaminants can be removed
using the same treatment.
Summary
Iron and manganese are common water contaminants that are not considered
health hazards. Their presence in water results in staining as well as
offensive tastes and appearances. Treatment of these elements depends on the
form in which they occur in the untreated water. Therefore, accurate testing
is important before considering options and/or selecting treatment
equipment. A summary of treatment options is shown in Table I. Often
the treatment for iron and manganese is the same for hydrogen sulfide,
allowing removal of all three contaminants in one process. |
What's Sulfur?
Two forms of sulfur are commonly
found in drinking water supplies: sulfate and hydrogen sulfide. Both forms
are nuisances that usually do not pose a health risk at the concentrations
found in domestic water supplies
Sources of Sulfate and Hydrogen Sulfide in Drinking Water
Sulfate
Sulfates are a combination of sulfur and oxygen and are
a part of naturally occurring minerals in some soil and rock formations that
contain groundwater. The mineral dissolves over time and is released into
groundwater.
Hydrogen sulfide
Sulfur-reducing bacteria, which use sulfur as an energy
source, are the primary producers of large quantities of hydrogen sulfide.
These bacteria chemically change natural sulfates in water to hydrogen
sulfide. Sulfur-reducing bacteria live in oxygen-deficient environments such
as deep wells, plumbing systems, water softeners and water heaters. These
bacteria usually flourish on the hot water side of a water distribution
system.
Hydrogen sulfide gas also occurs naturally in some groundwater. It is
formed from decomposing underground deposits of organic matter such as
decaying plant material. It is found in deep or shallow wells and also can
enter surface water through springs, although it quickly escapes to the
atmosphere. Hydrogen sulfide often is present in wells drilled in shale or
sandstone, or near coal or peat deposits or oil fields.
Occasionally, a hot water heater is a source of hydrogen sulfide odor.
The magnesium corrosion control rod present in many hot water heaters can
chemically reduce naturally occurring sulfates to hydrogen sulfide.
Indications of Sulfate and Hydrogen Sulfide
Sulfate
Sulfate minerals can cause scale buildup in water pipes
similar to other minerals and may be associated with a bitter taste in water
that can have a laxative effect on humans and young livestock.
Sulfate can make cleaning clothes difficult. Using chlorine bleach in
sulfur water may reduce the cleaning power of detergents.
Sulfur-oxidizing bacteria produce effects similar to those of iron
bacteria. They convert sulfide into sulfate, producing a dark slime that can
clog plumbing and/or stain clothing. Blackening of water or dark slime
coating the inside of toilet tanks may indicate a sulfur-oxidizing bacteria
problem. Sulfur-oxidizing bacteria are less common than sulfur-reducing
bacteria.
Hydrogen Sulfide
Hydrogen sulfide gas produces an offensive "rotten egg"
or "sulfur water" odor and taste in the water. In some cases, the odor may
be noticeable only when the water is initially turned on or when hot water
is run. Heat forces the gas into the air which may cause the odor to be
especially offensive in a shower.
A nuisance associated with hydrogen sulfide includes its corrosiveness to
metals such as iron, steel, copper and brass. It can tarnish silverware and
discolor copper and brass utensils. Hydrogen sulfide also can cause yellow
or black stains on kitchen and bathroom fixtures. Coffee, tea and other
beverages made with water containing hydrogen sulfide may be discolored and
the appearance and taste of cooked foods can be affected.
High concentrations of dissolved hydrogen sulfide also can foul the resin
bed of an ion exchange water softener. When a hydrogen sulfide odor occurs
in treated water (softened or filtered) and no hydrogen sulfide is detected
in the non-treated water, it usually indicates the presence of some form of
sulfate-reducing bacteria in the system. Water softeners provide a
convenient environment for these bacteria to grow. A "salt-loving" bacteria,
that uses sulfates as an energy source, may produce a black slime inside
water softeners.
Potential Health Effects
Sulfate
Sulfate may have a laxative effect that can lead to
dehydration and is of special concern for infants. With time, people and
young livestock will become acclimated to the sulfate and the symptoms
disappear. Sulfur-oxidizing bacteria pose no known human health risk.
Hydrogen Sulfide
Hydrogen sulfide is flammable and poisonous. Usually it
is not a health risk at concentrations present in household water, except in
very high concentrations. While such concentrations are rare, hydrogen
sulfide's presence in drinking water when released in confined areas has
been known to cause nausea, illness and, in extreme cases, death.
Water with hydrogen sulfide alone does not cause disease. In rare
cases, however, hydrogen sulfide odor may be from sewage pollution which can
contain disease-producing contaminants.
.
Testing
Sulfate
Select a laboratory and contact them to obtain a drinking water sulfate
test kit. This kit will contain a sample bottle, an information form,
sampling instructions and a return mailing box.
The sampling instructions provide information on how to collect the
sample. Follow these instructions carefully to avoid contamination and to
obtain a representative sample. Promptly mail the sample with the completed
information form to the laboratory. Take the sample on a day when it can be
mailed to arrive at the laboratory Monday through Thursday. Avoid weekends
or holidays which may delay the mail or lab analysis.
Hydrogen Sulfide
The offensive odor of hydrogen sulfide gas generally
makes testing unnecessary. Most people recognize the "rotten egg" or
"sulfur" odor and proceed to correct the problem. Hydrogen sulfide is one of
a few water contaminants that can be detected at low concentrations by the
human senses. The gas readily dissipates when water is exposed to the
atmosphere.
Since hydrogen sulfide is a gas that is dissolved in water and can
vaporize (escape) from it, laboratory analysis of hydrogen sulfide in water
requires the sample be stabilized or the test be conducted at the water
source site. Contact the water testing laboratory for specific instructions
if there is a need to test for hydrogen sulfide.
Interpreting Sulfate and Hydrogen Sulfide Test Results
Sulfate
The Environmental Protection Agency (EPA) standards for
drinking water fall into two categories -- Primary Standards and Secondary
Standards. Primary Standards are based on health considerations and are
designed to protect people from three classes of toxic pollutants --
pathogens, radioactive elements and toxic chemicals.
Secondary Standards are based on taste, odor, color, corrosivity, foaming
and staining properties of water. Sulfate is classified under the secondary
maximum contaminant level (SMCL) standards. The SMCL for sulfate in drinking
water is 250 milligrams per liter (mg/l), sometimes expressed as 250 parts
per million (ppm).
Hydrogen Sulfide
Although many impurities are regulated by Primary or
Secondary Drinking Water Standards set by the EPA, hydrogen sulfide is not
regulated because a concentration high enough to be a drinking water health
hazard also makes the water unpalatable.
The odor of water with as little as 0.5 ppm of hydrogen sulfide
concentration is detectable by most people. Concentrations less than 1 ppm
give the water a "musty" or "swampy" odor. A 1-2 ppm hydrogen sulfide
concentration gives water a "rotten egg" odor and makes the water very
corrosive to plumbing.
Generally, hydrogen sulfide levels are less than 10 ppm but,
occasionally, amounts of 50 to 75 ppm are found.
Options
If excessive sulfate or hydrogen sulfide is present in
your water supply, you have two basic options -- obtain an alternate water
supply or use some type of treatment to remove the impurity.
The need for an alternate water supply or impurity removal should be
established before making an investment in treatment equipment or an
alternate supply. Base the decision on a water analysis by a reputable
laboratory and after consulting with your physician to help you evaluate the
level of risk.
It may be possible to obtain a satisfactory alternate water supply by
drilling a new well in a different location or a deeper well in a different
aquifer.
The Conservation and Survey Division of the University of
Nebraska-Lincoln can provide general information on the possible location of
a water supply with satisfactory quality.
Another alternate source of water is bottled water that can be purchased
in stores or direct from bottling companies. This alternative might be
considered especially when the primary concern is water for food preparation
and drinking.
Sulfate
Several methods of removing sulfate from water are
available. The treatment method selected depends on many factors including
the level of sulfate in the water, the amount of iron and manganese in the
water, and if bacterial contamination also must be treated. The option you
choose also depends on how much water you need to treat.
Two methods for treating small quantities of water (drinking and cooking
only) include distillation and reverse osmosis.
Distillation boils water to form steam that is then cooled and
condensed to form pure water. Minerals, such as sulfate, do not vaporize
with the steam and are left behind in the boiling chamber.
Reverse osmosis membranes have tiny pores that permit water
molecules to pass through, leaving minerals such as sulfate behind.
The most common method of treating large quantities of water is ion
exchange. This process works similar to a water softener. Ion-exchange
resin, contained inside the unit, adsorbs sulfate. When the resin is loaded
to full capacity with sulfate, treatment ceases. The resin then must be
"regenerated" with a salt (sodium chloride) brine solution before further
treatment can occur.
Hydrogen Sulfide
If hydrogen sulfide odor is associated primarily with the hot water
system, a hot water heater modification may reduce the odor. Replacing the
water heater's magnesium corrosion control rod with one made of aluminum or
another metal may improve the situation.
To remove low levels of hydrogen sulfide, install an activated carbon
filter. The filter must be replaced periodically to maintain performance.
Frequency of replacement will depend on daily water use and concentration of
hydrogen sulfide in the water.
Hydrogen sulfide concentrations up to about 6 ppm can be removed using an
oxidizing filter (same as an iron filter). This filter contains sand with a
manganese dioxide coating that changes hydrogen sulfide gas to tiny
particles of sulfur that are trapped inside the filter. The sand filter must
be backflushed regularly and treated with potassium permanganate to maintain
the coating.
Hydrogen sulfide concentrations exceeding 6 ppm can be removed by
injecting an oxidizing chemical such as household bleach or potassium
permanganate and using a filter. The oxidizing chemical should enter the
water upstream from the storage or mixing tank to provide at least 20
minutes of contact time between the chemical and water. Sulfur particles can
then be removed using a sediment filter. Excess chlorine can be removed by
activated carbon filtration. When potassium permanganate is used a manganese
greensand filter is recommended.
Often the treatment for hydrogen sulfide is the same as for iron and
manganese, allowing removal of all three contaminants in one process.
Summary
Sulfates and hydrogen sulfide are both common nuisance
contaminants. Although neither is usually a significant health hazard,
sulfates can have a temporary laxative effect on humans and young livestock.
Sulfates also may clog plumbing and stain clothing.
Hydrogen sulfide produces an offensive "rotten egg" odor and taste in the
water, especially when the water is heated.
Treatment options depend on the form and quantities in which sulfates
and/or hydrogen sulfide occur in untreated water. Small quantities of
sulfate may be removed from water using distillation or reverse osmosis,
while large quantities may be removed using ion exchange treatment.
Hydrogen sulfide may be reduced or removed by shock chlorination, water
heater modification, activated carbon filtration, oxidizing filtration or
oxidizing chemical injection. Often treatment for hydrogen sulfide is the
same as for iron and manganese, allowing the removal of all three
contaminants in one process. |
How Does Reverse Osmosis Work?
Osmosis is the passage of molecules through the microscopic
pores of a living or synthetic membrane. In normal osmosis, if there is a
difference in concentration of molecules between on side of the membrane and the
other, the more concentrated molecules will pass through the membrane to
equalize the concentration on both sides.
In reverse osmosis water treatment, a thin
synthetic membrane is used. Its pores are large enough to pass water molecules
but too small to pass larger molecules. Water pressure forces water molecules
through the membrane but leaves larger molecules of pollutants behind. The
process is called Reverse Osmosis because instead of equalizing the
concentration of substances on either side of the membrane (as in osmosis), the
water pressure creates pure water on one side and a concentrate of pollutants on
the other. The pure water is channeled to the RO output, and the water
containing pollutants (as well as minerals) is channeled to the drain.
RO is a very slow process because water molecules
must individually pass through very small pores in the membrane. An RO membrane
is tightly coiled within a cylinder to provide a large surface area, but it
still takes several hours to produce one gallon of RO water. Because the RO
process is so slow, small storage tanks, holding one to five gallons for
drinking water systems, and large holding tanks for Aquarium systems are used
Most RO purifiers waste water. Between three to
five gallons of tap water are used to produce one gallon of purified water; the
remainder is drained away. ( The amount of purified water produced in comparison
with the total amount of water used is called the Recovery Rate ) However, a few
RO designs are more effective. In a recalculating RO, drain water is reused
several times, reducing water wastage. And high pressure units produce large
amount of water in a short period of time thus reducing wastage.
An advantage of RO units over filters is that
they remove a wider variety of pollutants. A good quality RO unit will remove
80-98 percent of most toxic minerals and organic chemicals form water. RO's
cannot, however, remove Radon or Chlorine. In theory, microorganisms which are
much larger then the pores in of an RO membrane, should all be rejected by the
membrane. But in practice the pores of the membrane are not uniform enough to
insure the removal of all microorganisms. Because of this, RO units, by
themselves, cannot be used for disinfecting water
There are several installation restrictions on RO
units. They cannot be installed on private systems unless the water has been
disinfected. High levels of dissolved minerals in water ( TDS or total dissolved
solids ) adversely affect the membranes. Water with a TDS of over 500 ppm (
parts per million) should use a resin water softener before the RO unit. The
performance of RO units is also proportionate to water pressure: the higher the
pressure, the better the performance. RO units installed in low-pressure systems
( pressure below 40 psi ) requires a special booster pump to increase the
pressure. Where tap water comes from a public water system, and the water
quality is known, there is usually no difficulty in operating an RO unit.
Unlike filters, RO membranes do not accumulate
any pollutants- the pollutants are constantly being washed away. And since there
is no accumulation of pollutants there is no chance of pollutant breakaway as
there is with filters. RO membranes degrade with use. With clean city water and
regular prefilter changes a membrane can last up to three years.Membranes for RO
units are made of two types: Cellulose Acetate (CA) or of Thin Film Composite (TFC).
TFC membranes outperform CA membranes and last longer. They are slightly more
expensive. There disadvantage is that they cannot tolerate chlorinated water.
How Does a Water Softener Work?
Service
Service is when the softener is providing soft water. Hard water comes
from the main water pipe into the softener. Inside the softener resin tank
there are thousands of tiny, plastic resin beads. As hard water passes
through these beads, each bead attracts hardness minerals. This process is
referred to as ion-exchanging. Water without the hardness minerals flows out
of the softener and into the house as soft water.
After a period of time, the resin beads need to be cleaned because
they have been coated with hardness materials. This cleaning is called
regeneration or recharge. The timer on a water softener is usually set so
that it starts regeneration early in the morning. There are five cycles that
regeneration consists of: Fill, Brining, Brine Rinse, Backwash, and Fast
Rinse.
Fill
Salt that is dissolved into water is called brine.
Brine is needed to clean the resin beads free from hardness. To make brine,
water flows into the salt storage tank during the fill stage. The fill cycle
length will depend on how much soft water you have used since the last
regeneration. A larger amount of brine is needed to clean more hardness
materials from the resin beads.
Brining and Brine Rinse
In the brining cycle, the brine is moved from the salt storage tank,
and into the resin tank. In the resin tank, brine removes the hardness
minerals from the beads and they are released into the drain. Suction is
needed to pull brine from the salt tank into the resin tank, the nozzle and
venturi produce this suction. The flow of the brine is fed at a slow rate to
get the best resin cleaning with the smallest amount of salt.
During brine rinse, all the brine goes into the resin tank and the
brine valve closes. Water flows in the same way it did during the brine
cycle except that the brine flow has stopped. Hardness released from the
resin beads and brine flush from the resin tank and into the drain. The
length of the brine cycle and the brine rinse cycle vary relatively to the
fill cycle length.
Backwash
During the backwash cycle, water flows up at a fast
rate to flush iron minerals, dirt and sediments from the resin bed and to
the drain. The resin bed expands and lifts for cleaning.
Fast Rinse
After backwash, a fast flow of water goes through the resin tank. This
fast flow packs the resin beads and gets the softener ready to return to
service.
How does a MG Filter Work?
Manganese Greensand Filtration
The automatic manganese
greensand filter consists of a bed of filter media contained in a fiberglass
tank, a container with potassium permanganate for the regeneration of the filter
and an automatic control valve.
Raw
water enters your home through the main supply line, enters your iron filter and
passes down through the filter media. Any iron, manganese or hydrogen sulfide
present in your water supply is exposed to oxygen stored in the filter media.
The oxygen causes precipitation of the minerals and they are trapped in the
filter media. Only clean, filtered water flows to your household water line. The
filter media is periodically regenerated automatically, backwashing the trapped
minerals to the drain and regenerated by replacing the oxygen. This is done by
introducing potassium permanganate to the media.
1.
In the service position, filtered water is supplied for household use.
2.
The automatic control reverses the flow of the water through the filter,
backwashing minerals trapped in the filter to the drain. Untreated water is
automatically bypassed for household use.
3.
The control pulls a vacuum on the potassium permanganate container,
drawing an exact volume of saturated potassium permanganate solution into the
filter tank.
4.
The control slowly rinses the chemical through the media tank. The
potassium permanganate supplies oxygen to the filter media.
5.
The control fast rinses the media bed to settle it and to ensure that all
the chemical and mineral precipitate is removed.
6.
The control adds the correct amount of water to the previously evacuated
container in preparation for the next regeneration.
7.
The control puts the system into service, supplying iron-free water to
the household.
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