Common Water Problems
ACIDIC WATER - EPA Maximum
Contaminant Level: 6.5 pH
Source - Acidic waters
usually attain their acidity from the seepage of acid mine waters, or acidic
industrial wastes. Acid mine waters are frequently too low in pH
to provide suitable drinking water even after neutralization and treatment.
Treatment - Acidic water
can be corrected by injecting soda ash or caustic soda (sodium hydroxide) into
the water supply to raise the pH. Utilization of these two chemicals slightly
increases the alkalinity in direct proportion to the amount used. Acidic water
can also be neutralized up to a point by running it through calcite, corosex or a combination of the two. The calcite and the corosex both neutralize by dissolving and they add hardness
to the water as the neutralization takes place; therefore, they both need to be
replenished on a periodic basis.
ALUMINUM
Source - Aluminum (Al+3)
is an abundant metal in the Earth's surface, but its solubility in water is so
low that it is seldom a concern in municipal or industrial water systems. The
majority of natural water contains from 0.1 ppm up to 9.0 ppm of Aluminum,
however the primary Source of Aluminum in drinking water comes from the use of
aluminum sulfate (alum) as a coagulant in water treatment plants.
The total dietary exposure to aluminum salts averages around 20 mg/day.
Aluminum is on the US EPA's Secondary Drinking Water Standards list with
suggested levels of 0.05 - 0.2 mg/l; dependent on case-by-case circumstances.
Treatment - Aluminum can
be removed from water by a cation exchanger but hydrochloric acid or sulfuric
acid must be used for regeneration to remove the aluminum from the resin. While
this is suitable for an industrial application it is not recommended for
domestic use unless it is in the form of a cation exchange tank. Reverse Osmosis
will reduce the aluminum content of drinking water by 98 + %. Distillation will
reduce the aluminum content of water by 99 + %. Electro dialysis is also very
effective in the reduction of aluminum.
AMMONIA
Source - Ammonia (NH3)
gas, usually expressed as Nitrogen, is extremely soluble in water. It is the
natural product of decay of organic nitrogen compounds. Ammonia finds its way
into surface supplies from the runoff in agricultural areas where it is applied
as fertilizer. It can also find its way to underground aquifers from animal
feed lots. Ammonia is oxidized to nitrate by bacterial action. A concentration
of 0.1 to 1.0 ppm is typically found in most surface water supplies, and is expressed
as N. Ammonia is not usually found in well water supplies because the bacteria
in the soil converts it nitrates. The concentration of Ammonia is not
restricted by drinking water standards. Since Ammonia is corrosive to copper
alloys it is a concern in cooling systems and in boiler feed.
Treatment - Ammonia can
be destroyed chemically by chlorination. The initial reaction forms chloramine,
and must be completely broken down before there is a chlorine residual. Organic
contaminants in the waste stream will be destroyed by the chlorine before it
will react with the ammonia. Ammonia can also be removed by cation exchange
resin in the hydrogen form, which is the utilization of acid as a regenerant.
Degasification will also remove Ammonia.
ARSENIC
Source - Arsenic (As) is
not easily dissolved in water, therefore, if it is found in a water supply, it
usually comes from mining or metallurgical operations or from runoff from
agricultural areas where materials containing arsenic were used as industrial
poisons. Arsenic and phosphate easily substitute for one another chemically, therefore commercial grade phosphate can have
some arsenic in it. Arsenic is highly toxic and has been classified by the US
EPA as a carcinogen. The current MCL for arsenic is 0.05 mg/l, which was
derived from toxicity considerations rather than carcinogenicity.
Treatment - If in an
inorganic form, arsenic can be removed or reduced by conventional water
treatment processes. There are five ways to remove inorganic contaminants; reverse
osmosis, activated alumina, ion exchange, activated carbon, and distillation.
Filtration through activated carbon will reduce the amount of arsenic in
drinking water from 40 - 70%. Anion exchange can reduce it by 90 - 100%.
Reverse Osmosis has a 90% removal rate, and Distillation will remove 98%. If
the arsenic is present in organic form, it can be removed by oxidation of the
organic material and subsequent coagulation.
BACTERIA
Source - Bacteria are
tiny organisms occurring naturally in water. Not all types of bacteria are
harmful. Many organisms found in water are of no health concern since they do
not cause disease. Biological contamination may be separated into two groups:
(1) pathogenic (disease causing) and
(2)
non-pathogenic (not disease causing). Pathogenic
bacteria cause illnesses such as typhoid fever, dysentery, gastroenteritis,
infectious hepatitis, and cholera. All water supplies should be tested for
biological content prior to use and consumption. E.Coli
(Escherichia Coli) is the coliform bacterial organism which is looked for when
testing the water. This organism is found in the intestines and fecal matter of
humans and animals. If E.Coli is found in a water
supply along with high nitrate and chloride levels, it usually indicates that
waste has contaminated the supply from a septic system or sewage dumping, and
has entered by way of runoff, a fractured well casing, or broken lines. If coliform bacteria is present, it is an indication that
disease causing bacteria may also be present. Four or fewer colonies / 100 ml
of coliforms, in the absence of high nitrates and
chlorides, implies that surface water is entering the
water system. If pathogenic bacteria is suspected, a
sample of water should be submitted to the Board of Health or US EPA for
bacteriological testing and recommendations. The most common non-pathogenic
bacteria found in water, is iron bacteria. Iron bacteria can be readily
identified by the red, feathery floc which forms
overnight at the bottom of a sample bottle containing iron and iron bacteria.
Treatment - Bacteria can
be treated by microfiltration, reverse osmosis, ultra
filtration, or chemical oxidation and disinfection. Ultraviolet sterilization
will also kill bacteria; but turbidity, color, and organic impurities interfere
with the transmission of ultraviolet energy and may decrease the disinfection
efficiency below levels to insure destruction. Ultraviolet treatment also does
not provide residual bactericidal action, therefore
periodic flushing and disinfection must be done. Ultraviolet sterilization is
usually followed by 0.2 micron filtration when dealing with high purity water
systems. The most common and undisputed method of bacteria destruction is
chemical oxidation and disinfection. Ozone injection into a water supply is one
form of chemical oxidation and disinfection. A residual of 0.4 mg/l must be
established and a retention time of four minutes is required. Chlorine
injection is the most widely recognized method of chemical oxidation and
disinfection. Chlorine must be fed at 3 to 5 ppm to treat for bacteria and a
residual of 0.4 ppm of free chlorine must be maintained for 30 minutes in order
to meet US EPA standards. Reverse Osmosis will remove 99+ % of the bacteria in
a drinking water system.
BARIUM
Source - Barium (Ba+2)is a naturally occurring alkaline earth metal found
primarily in the midwest. Traces of the element are
found in surface and ground waters. It can also be found in oil and gas
drilling muds, waste from coal fired power plants,
jet fuels, and automotive paints. Barium is highly toxic when its soluble salts
are ingested. The current MCL for Barium is 2.0 mg/l.
Treatment - Sodium form cation
exchange units (softeners) are very effective at removing Barium. Reverse Osmosis
is also extremely effective in its removal, as well as Electrodialysis.
BENZENE
Source - Benzene, a byproduct
of petroleum refining, is used as an intermediate in the production of
synthesized plastics, and is also an additive in gasoline. Gasoline contains
approximately 0.8 percent benzene by volume. Benzene is classified as a
volatile organic chemical (VOC) and is considered a carcinogen by the US EPA.
Benzene makes its way into water supplies from leaking fuel tanks, industrial
chemical waste, pharmaceutical industry waste, or from run off of pesticides.
The current US EPA MCL for Benzene is 0.005 mg/l.
Treatment - Benzene can
be removed with activated carbon. Approximately 1000 gallons of water
containing 570 ppb of benzene can be treated with 0.35 lbs of activated carbon,
in other words; 94,300 gallons of water can be treated for every cubic foot of
carbon. The benzene must be in contact with the carbon for a minimum of 10
minutes. If the required flow rate is 5 gpm, then 50 gallon of carbon is
required; which converts to approx. 7 cu. ft. The activated carbon must be
replaced when exhausted.
BICARBONATE
ALKALINITY
Source - The Bicarbonate
(HCO3) ion is the principal alkaline constituent in almost all water supplies.
Alkalinity in drinking water supplies seldom exceeds 300 mg/l. Bicarbonate
alkalinity is introduced into the water by CO2 dissolving carbonate-containing
minerals. Alkalinity control is important in boiler feed water, cooling tower
water, and in the beverage industry. Alkalinity neutralizes the acidity in fruit
flavors; and in the textile industry, it interferes with acid dying. Alkalinity
is known as a "buffer".
Treatment - In the pH
range of 5.0 to 8.0 there is a balance between excess CO2 and bicarbonate ions.
The bicarbonate alkalinity can be reduced by removing the free CO2 through
aeration. The alkalinity can also be reduced by feeding acid to lower the pH.
At pH 5.0 there is only CO2
and 0
alkalinity. A strong base Anion Exchanger will also remove alkalinity.
BORATE (BORON)
Source - Borate B(OH)4- is a compound of Boron. Most of the world's boron is
contained in sea water. Sodium borate occurs in arid regions where inland seas
once existed but have long since evaporated. Boron is frequently present in
fresh water supplies in these same areas in the form of non-ionized boric acid.
The amount of boric acid is not limited by drinking water standards, but it can
be damaging to citrus crops if it is present in irrigation water and becomes
concentrated in the soil.
Treatment - Boron
behaves like silica when it is in an aqueous solution. It can be removed with
an Anion Exchanger or adsorbed utilizing an Activated Carbon Filter.
BROMINE (BROMIDE)
Source - Bromine is
found in sea water and exists as the bromide ion at a level of about 65 mg/l.
Bromine has been used in swimming pools and cooling towers for disinfection,
however use in drinking water is not recommended. Ethylene bromide is used as
an anti-knock additive in gasoline, and methyl bromide is a soil fumigant.
Bromine is extremely reactive and corrosive, and will produce irritation and
burning to exposed tissues. Over 0.05 mg/l in fresh water may indicate the
presence of industrial wastes, possibly from the use of pesticides of biocides
containing bromine. Bromide is extensively used in the pharmaceutical industry,
and occurs normally in blood in the range of 1.5 to 50 mg/l.
Treatment - Reverse
Osmosis will remove 93 -96 % of the bromide from drinking water. Since bromine
is a disinfectant, it along with the disinfection by-products can also be
removed with Activated Carbon, Ultra filtration, or Electrodialysis.
CADMIUM
Source - Cadmium enters
the environment through a variety of industrial operations, it is an impurity
found in zinc. By-products from mining, smelting, electroplating, pigment, and
plasticizer production can contain cadmium. Cadmium emissions come from fossil
fuel use. Cadmium makes its way into the water supplies as a result of
deterioration of galvanized plumbing, industrial waste or fertilizer
contamination.. The US EPA Primary Drinking Water
Standards lists Cadmium with a 0.005 mg/l MCL.
Treatment - Cadmium can
be removed from drinking water with a sodium form cation exchanger (softener).
Reverse Osmosis will remove 95 - 98 % of the cadmium in the water. Electro
dialysis will also remove the majority of the cadmium.
CALCIUM
Source - Calcium is the
major component of hardness in water and is usually in the range of 5 - 500
mg/l, as CaCO3 . Calcium is derived from nearly all
rock, but the greatest concentrations come from limestone and gypsum. Calcium
ions are the principal cations in most natural
waters. Calcium reduction is required in treating cooling tower makeup.
Complete removal is required in metal finishing, textile operations, and boiler
feed applications.
Treatment - Calcium, as
with all hardness, can be removed with a simple sodium form cation exchanger
(softener). Reverse Osmosis will remove
95 -
98 % of the calcium in the water. Electro dialysis and Ultra filtration also
will remove calcium. Calcium can also be removed with the hydrogen form cation
exchanger portion of a deionizer system.
Source - Free carbon
dioxide (CO2) exists in varying amounts in most natural water supplies. Most
well waters will contain less than 50 ppm. Carbon Dioxide in water yields an
acidic condition. Water (H2O) plus carbon dioxide (CO2) yields carbonic acid
(H2CO3). The dissociation of carbonic acid yields hydrogen (H+) and bicarbonate
alkalinity (HCO3). The pH value will drop as the concentration of carbon
dioxide increases, and conversely will increase as the bicarbonate alkalinity
content increases.
H2O
+ CO2 <====> H2CO3 <====> H+ + HCO3-
Water
with a pH of 3.5 or below generally, contains mineral acids such as sulfuric or
hydrochloric acid. Carbon Dioxide can exist in waters with pH values from 3.6
to 8.4, but will never be present in waters having a pH of 8.5 or above. The pH
value is not a measurement of the amount of carbon dioxide in the water, but
rather the relationship of carbon dioxide and bicarbonate alkalinity.
Treatment - Free CO2 can
be easily dissipated by aeration. A two column deionizer (consisting of a
hydrogen form strong acid cation and a hydroxide form strong base anion) will
also remove the carbon dioxide. The cation exchanger adds the hydrogen ion (H+)
which shifts the above equation to the left in favor of water and carbon
dioxide release. The anion resin removes the carbon dioxide by actually
removing the bicarbonate ion. A forced draft degasifier
placed between the cation and anion will serve to blow off the CO2 before it
reaches the anion bed, thus reducing the capacity requirements for the anion
resin. The CO2 can be eliminated by raising the pH
to 8.5 or above with a soda ash or caustic soda chemical feed system.
CARBON TETRACHLORIDE
Source - Carbon
tetrachloride (CCl4) is a volatile organic chemical (VOC), and is primarily
used in the manufacture of chlorofluoromethane but
also in grain fumigants, fire extinguishers, solvents, and cleaning agents.
Many water supplies across the country have been found to contain measurable
amounts of VOC's. VOC's pose a possible health risk because a number of them
are probable or known carcinogens. The detection of VOC's in a water supply
indicates that a pollution incident has occurred, because these chemicals are
man-made. See Volatile Organic Chemicals for a complete listing. The US EPA has
classified carbon tetrachloride as a probable human carcinogen and established
an MCL of 0.005 mg/l.
Treatment - Reverse
Osmosis will remove 70 to 80% of the VOC's in drinking water as will ultrafiltration and electrodialysis.
Carbon tetrachloride as well as the other volatile organic chemicals (VOC's)
can also be removed from drinking water with activated carbon filtration. The
adsorption capacity of the carbon will vary with each type of VOC. The carbon
manufacturers can run computer projections on many of these chemicals and give
an estimate as to the amount of VOC which can be removed before the carbon will
need replacement.
CHLORIDE
Source- Chloride (Cl-1)
is one of the major anions found in water and are generally combined with
calcium, magnesium, or sodium. Since almost all chloride salts are highly
soluble in water, the chloride content ranges from 10 to 100 mg/l. Sea water
contains over 30,000 mg/l as NaCl. Chloride is associated with the corrosion of
piping because of the compounds formed with it; for example, magnesium chloride
can generate hydrochloric acid when heated. Corrosion rates and the iron
dissolved into the water from piping increases as the sodium chloride content
of the water is increased. The chloride ion is instrumental in breaking down passivating films which protect ferrous metals and alloys
from corrosion, and is one of the main causes for the pitting corrosion of
stainless steel. The SMCL (suggested maximum contaminant level) for chloride is
250 mg/l which is due strictly to the objectionable salty taste produced in
drinking water.
Treatment - Reverse
Osmosis will remove 90 - 95% of the chlorides because of it's
salt rejection capabilities. Electrodialysis and
distillation are two more processes which can be used to reduce the chloride
content of water. Strong base Anion Exchanger which is the later portion of a
two column deionizer does an excellent job at removing chlorides for industrial
applications.
CHLORINE
Source- Chlorine is the
most commonly used agent for the disinfection of water supplies. Chlorine is a
strong oxidizing agent capable of reacting with many impurities in water
including ammonia, proteins, amino acids, iron, and manganese. The amount of
chlorine required to react with these substances is called the chlorine demand.
Liquid chlorine is sodium hypochlorite. Household liquid bleach is 5-1/4%
sodium hypochlorite. Chlorine in the form of a solid is calcium hypochlorite.
When chlorine is added to water, a variety of chloro-compounds
are formed. An example of this would be when ammonia is present, inorganic
compounds known as chloramines are produced. Chlorine also reacts with residual
organic material to produce potentially carcinogenic compounds, the
Trihalomethanes (THM's): chloroform, bromodichloromethane,
bromoform, and chlorodibromomethane.
THM regulations has required that other oxidants and
disinfectants be considered in order to minimize THM formation. The other
chemical oxidants being examined are: potassium permanganate, hydrogen
peroxide, chloramines, chlorine dioxide, and ozone. No matter what form of
chlorine is added to water, hypochlorite, hypochlorous
acid, and molecular chlorine will be formed. The reaction lowers the pH, thus
making the water more corrosive and aggressive to steel and copper pipe.
Treatment - Chlorinated
water can be dosed with sulfite-bisulfite-sulfur
dioxide or passed through a activated carbon filter.
Activated carbon will remove 880,000 ppm of free chlorine per cubic foot of
media.
CHROMIUM
Source - Chromium is
found in drinking water as a result of industrial waste contamination. The
occurrence of excess chromium is relatively infrequent. Proper tests must be run
on the water supply to determine the form of the chromium present. Trivalent
chromium (Cr=3 ) is slightly soluble in water, and is
considered essential in man and animals for efficient lipid, glucose, and
protein metabolism. Hexavalent chromium
(Cr=6 ) on the other hand is considered toxic. The US EPA
classifies chromium as a human carcinogen. The current Drinking Water Standards
MCL is .005 mg/l.
Treatment - Trivalent
chromium (Cr+3)can be removed with strong acid cation
resin regenerated with hydrochloric acid. Hexavalent
chromium (Cr+6)on the other hand requires the
utilization of a strong base anion exchanger which must be regenerated with
caustic soda (sodium hydroxide) NaOH. Reverse Osmosis
can effectively reduce both forms of chromium by 90 to 97%. Distillation will
also reduce chromium.
COLOR
Source - Color in water
is almost always due to organic material which is usually extracted from
decaying vegetation. Color is common in surface water supplies, while it is
virtually non-existent in spring water and deep wells. Color in water may also
be the result of natural metallic ions (iron and manganese). A yellow tint to
the water indicates that humic acids are present,
referred to as "tannins". A reddish color would indicate the presence
of precipitated iron. Stains on bathroom fixtures and on laundry are often
associated with color also. Reddish-brown is ferric hydroxide (iron) will
precipitate when the water is exposed to air. Dark brown to black stains are
created by manganese. Excess copper can create blue stains.
Treatment - Color is
removed by chemical feed, retention and filtration. Activated carbon filtration
will work most effectively to remove color in general. Anion scavenger resin
will remove tannins, but must be preceded by a softener or mixed with fine mesh
softener resin. See the headings Iron, Manganese, and Copper for information
their removal or reduction.
COPPER - EPA Maximum Contaminant Level: 1.3 mg/L
Source - Copper (Cu+3)
in drinking water can be derived from rock weathering, however the principal
Sources are the corrosion of brass and copper piping and the addition of copper
salts when treating water supplies for algae control. Copper is required by the
body for proper nutrition. Insufficient amounts of copper leads to iron
deficiency. However, high doses of copper can cause liver damage or anemia. The
taste threshold for copper in drinking water is 2 - 5 mg/l. The US EPA has
proposed a maximum contaminant level (MCL) of 1.3 mg/l for copper.
Treatment - Copper can
be reduced or removed with sodium form strong acid cation resin (softener)
dependent on the concentration. If the cation resin is regenerated with acid
performance will be enhanced. Reverse osmosis or electrodialysis
will remove 97 - 98 % of the copper in the water supply. Activated carbon
filtration will also remove copper by adsorption.
CRYPTOSPORIDIUM
Source - Cryptosporidium
is a protozoan parasite which exists as a round oocyst
about 4 to 6 microns in diameter. Oocysts pass
through the stomach into the small intestine where it's
sporozoites invade the cell lining of the
gastrointestinal tract. Symptoms of infection include diarrhea, cramps, nausea,
and low grade fever.
Treatment - Filtration
is the most effective treatment for protozoan cysts. Cartridge POU filters
rated at 0.5 micron are designed for this purpose.
CYANIDE
Source - Cyanide (CN-)
is extremely toxic and is not commonly found at significant levels in drinking
water. Cyanide is normally found in waste water from metal finishing
operations. The US EPA has not classified cyanide as a carcinogen because of
inadequate data. No MCL level established or even proposed.
Treatment - Chlorine
feed, retention, and filtration will break down the cyanide. Reverse Osmosis or
Electrodialysis will remove 90 - 95 % of it.
FLUORIDE
Source - Fluoride (F+)
is a common constituent of many minerals. Municipal water treatment plants
commonly add fluoride to the water for prevention of tooth decay, and maintain
a level of 1.5 - 2.5 mg/l. Concentrations above 5 mg/l are detrimental to tooth
structure. High concentrations are contained in waste water from the
manufacture of glass and steel, as well as from foundry operations. Organic
fluorine is present in vegetables, fruits, and nuts. Inorganic fluorine, under
the name of sodium fluoride, is a waste product of aluminum and is used in some
rat poisons. The MCL established for drinking water by the US EPA is 4 mg/l.
Treatment - Fluoride can
be reduced by anion exchange. Adsorption by calcium phosphate, magnesium
hydroxide or activated carbon will also reduce the fluoride content of drinking
water. Reverse osmosis will remove 93 - 95 % of the fluoride.
GIARDIA LAMBLIA
Source- Giardia is a
protozoan which can exist as a trophozoite, usually 9
to 21 mm long, or as an ovoid cyst, approximately 10 mm long and 6 mm wide.
Protozoans are unicellular and colorless organisms that lack a cell wall. When
Giardia are ingested by humans, symptoms include
diarrhea, fatigue, and cramps. The US EPA has a treatment technique in effect
for Giardia.
Treatment - Slow sand
filtration or a diatomaceous earth filter can remove up to 99 % of the cysts
when proper pretreatment is utilized. Chemical oxidation - disinfection, Ultrafiltration, and reverse osmosis all effectively remove
Giardia cysts. Ozone appears to be very effective against the cysts when
utilized in the chemical oxidation - disinfection process instead of chlorine.
The most economical and widely used method of removing Giardia is mechanical
filtration. Because of the size of the parasite, it can easily be removed with precoat, solid block carbon, ceramic, pleated membrane, and
spun wrapped filter cartridges.
HARDNESS – EPA
Maximum Contaminant Level: N/A
Source - Hard water is
found over 80% of the United States. The hardness of a water supply is
determined by the content of calcium and magnesium salts. Calcium and magnesium
combine with bicarbonates, sulfates, chlorides, and nitrates to form these
salts. The standard domestic measurement for hardness is grains per gallon
(gpg) as CaCO3 . Water having a hardness content less
than 0.6 gpg is considered commercially soft. The calcium and magnesium salts
which form hardness are divided into two categories: 1) Temporary Hardness
(containing carbonates), and 2) Permanent Hardness (containing non-carbonates).
Below find listings of the various combinations of permanent and temporary
hardness along with their chemical formula and some information on each.
***
Temporary Hardness Salts ***
***
Permanent Hardness Salts ***
Sodium
salts are also found in household water supplies, but they are considered
harmless as long as they do not exist in large quantities. The US EPA currently
has no national policy with respect to the hardness or softness of public water
supplies.
Treatment - Softeners
can remove compensated hardness up to a practical limit of 100 gpg. If the
hardness is above 30 gpg or the sodium to hardness ratio is greater than 33%,
then economy salt settings can not be used. If the hardness is high, then the
sodium will be high after softening, and may require that reverse osmosis be
used for producing drinking water.
HYDROGEN SULFIDE
Source - Hydrogen
Sulfide (H2S) is a gas which imparts its "rotten egg" SULFIDE odor to
water supplies. Such waters are distasteful for drinking purposes and processes
in practically all industries. Most sulfur waters contain from 1 to 5 ppm of
hydrogen sulfide. Hydrogen sulfide can interfere with readings obtained from
water samples. It turns hardness and pH tests gray, and makes iron tests
inaccurate. Chlorine bleach should be added to eliminate the H2S odor; then the
hardness, pH and iron tests can be done. Hydrogen sulfide can not be tested in
a lab, it must be done in the field. Hydrogen sulfide
is corrosive to plumbing fixtures even at low concentrations. H2S fumes will
blacken or darken painted surfaces, giving them a "smoked"
appearance.
Treatment - H2S requires
chlorine to be fed in sufficient quantities to eliminate it, while leaving a residual
in the water (3 ppm of chlorine is required for each ppm of hydrogen sulfide).
Activated carbon filtration may then be installed to remove the excess
chlorine.
IRON – EPA Maximum
Allowed Level: 0.3ppm
Source - Iron occurs
naturally in ground waters in three forms, Ferrous Iron (clear water iron),
Ferric Iron (red water iron), and Heme Iron (organic iron). Each can exist
alone or in combination with the others. Ferrous iron, or clear water iron as
it is sometimes called, is ferrous bicarbonate. The water is clear when drawn
but when turns cloudy when it comes in contact with air. The air oxidizes the
ferrous iron and converts it to ferric iron. Ferric iron, or ferric hydroxide,
is visible in the water when drawn; hence the name "red water iron". Heme
iron is organically bound iron complexed with
decomposed vegetation. The organic materials complexed
with the iron are called tannins or lignins. These
organics cause the water to have a weak tea or coffee color. Certain types of
bacteria use iron as an energy Source. They oxidize the iron from its ferrous
state to its ferric state and deposit it in the slimy gelatinous material which surround them. These bacteria grow in stringy
clumps and are found in most iron bearing waters.
Treatment - Ferrous iron
(clear water iron) can be removed with a softener provided it is less than 0.5
ppm for each grain of hardness and the pH of the water is greater than 6.8. If
the ferrous iron is more than 5.0 ppm, it must be converted to ferric iron by
contact with a oxidizing agent such as chlorine,
before it can be removed by mechanical filtration. Ferric iron (red water iron)
can simply be removed by mechanical filtration. Heme iron can be removed by an
organic scavenger anion resin, or by oxidation with
chlorine followed by mechanical filtration. Oxidizing agents such as chlorine
will also kill iron bacteria if it is present.
LEAD
Source - Lead (Pb+2)
found in fresh water usually indicates contamination from metallurgical wastes
or from lead-containing industrial poisons. Lead in drinking water is primarily
from the corrosion of the lead solder used to put together the copper piping.
Lead in the body can cause serious damage to the brain, kidneys, nervous
system, and red blood cells. The US EPA considers lead to be a highly toxic
metal and a major health threat. The current level of lead allowable in
drinking water is 0.05 mg/l.
Treatment - Lead can be
reduced considerably with a water softener. Activated carbon filtration can
also reduce lead to a certain extent. Reverse Osmosis can remove 94 to 98 % of
the lead in drinking water at the point-of-use. Distillation will also remove
the lead from drinking water.
LEGIONELLA
Source - In July 1976,
there was an outbreak of pneumonia effecting 221 people attending the annual
Pennsylvania American Legion convention at the Bellvue-Stratford
Hotel in Philadelphia. Out of the 221 people infected, 34 died. It wasn't until
December 1977 that microbiologists were able to isolate a bacterium from the
autopsy of the lung tissue of one of the legionnaires. The bacterium was named
"Legionella pneumophila"
(Legionella in honor of the American Legion, and pneumophila which is Greek for "lung-loving") and
was found to be completely different from other bacteria. Unlike patients with
other pneumonias, patients with legionnaire's disease often have severe
gastrointestinal symptoms, including diarrhea, nausea, and vomiting. The US EPA
has not set a MCL (maximum contamination level) for Legionella,
instead it has outlined the treatment method which must be followed and the
MCLG is 0 mg/l.
Treatment - Chemical
oxidation-disinfection followed by retention, then filtration could be used.
Since Legionella is a bacteria, Reverse osmosis or Ultrafiltration are the preferred removal techniques.
MAGNESIUM
Source - Magnesium
(Mg+2) hardness is usually approximately 33% of the total hardness of a
particular water supply. Magnesium is found in many minerals, including
dolomite, magnesite, and many types of clay. It is in
abundance in sea water where its' concentration is five (5) times the amount of
calcium. Magnesium carbonate is seldom a major component of in scale. However,
it must be removed along with calcium where soft water is required for boiler
make-up, or for process applications.
Treatment - Magnesium
may be reduced to less than 1 mg/l with the use of a softener or cation
exchanger in hydrogen form. Also see "Hardness".
MANGANESE
Source - Manganese
(Mn+4, Mn+2) is present in many soils and sediments as well as in rocks whose
structures have been changed by heat and pressure. It is used in the
manufacture of steel to improve corrosion resistance and hardness. Manganese is
considered essential to plant and animal life and can be derived from such
foods as corn, spinach, and whole wheat products. It is known to be important
in building strong bones and may be beneficial to the cardiovascular system.
Manganese may be found in deep well waters at concentrations as high as 2 - 3
mg/l. It is hard to treat because of the complexes it can form which are
dependent on the oxidation state, pH, bicarbonate-carbonate-OH ratios, and the
presence of other minerals, particularly iron. Concentrations
higher than 0.05 mg/l cause manganese deposits and staining of clothing and
plumbing fixtures. The stains are dark brown to black in nature. The use
of chlorine bleach in the laundry will cause the stains to set. The chemistry
of manganese in water is similar to that of iron. High levels
of manganese in the water produces an unpleasant odor and taste. Organic
materials can tie up manganese in the same manner as they do iron,
therefore destruction of the organic matter is a necessary part of manganese
removal.
Treatment - Removal of
manganese can be done by ion exchange (sodium form cation - softener) or
chemical oxidation - retention - filtration. Removal with a water softener
dictates that the pH be 6.8 or higher and is beneficial to use countercurrent
regeneration with brine make-up and backwash utilizing soft water. It takes 1
ppm of oxygen to treat 1.5 ppm of manganese. Greensand filter with potassium
will remove up to 10 ppm if pH is above 8.0. Birm
filter with air injection will reduce manganese if pH is 8.0 to 8.5. Chemical
feed (chlorine, potassium permanganate, or hydrogen peroxide) followed by 20
minutes retention and then filtered with birm,
greensand, carbon, or Filter Ag will also remove the manganese.
MERCURY
Source - Mercury (Hg) is
one of the least abundant elements in the earth's crust. It exists in two forms,
an inorganic salt or an organic compound (methyl mercury). Mercury detected in
drinking water is of the inorganic type. Organic mercury inters the food chain
through fish and comes primarily from industrial chemical manufacturing waste
or from the leaching of coal ash. If inorganic mercury inters the body, it
usually settles in the kidneys. Whereas organic mercury
attacks the central nervous system. The MCL (maximum contamination
level) for mercury set by the US EPA is 0.002 mg/l.
Treatment - Activated
carbon filtration is very effective for the removal of mercury. Reverse osmosis
will remove 95 - 97 % of it.
METHANE
Source - Methane (CH4),
often called marsh gas, is the primary component of natural gas. It is commonly
found where land fills once existed and is generated from decaying of plants or
other carbon based matter. It can also be found in and around oil fields.
Methane is colorless, odorless, nearly invisible, highly flammable, and often
found in conjunction with other gases such as hydrogen sulfide. Even though
methane gas gives water a milky appearance which makes it aesthetically
unpleasant, there are no known health effects.
Treatment - Aeration or
degasification is the only way to eliminate the problem of methane gas. Venting
the casing and/or the cap of the well will reduce the problem of methane in the
water, but may not completely eliminate it. Another method is to provide an
atmospheric holding tank where the methane laden water can be vented to allow
the gas to dissipate. This method may not be 100% effective either. An aerator
or degasifier is the proper piece of equipment to
utilize for the removal of methane. Water is introduced through the top,
sometimes through spray nozzles, and allowed to percolate through a packing material.
Air is forced in the opposite direction to the water flow. The water is then
collected in the bottom of the unit and repressurized.
Source - Nickel (Ni+2)
is common, and exists in approximately 85% of the water supplies, and is usually
around 1 ppb (part per billion). The US EPA has classified nickel as a possible
human carcinogen based on inhalation exposure. Nickel has not been shown to be
carcinogenic via oral exposure. No MCLG (maximum contamination level goal) has
been proposed.
Treatment - Nickel
behaves the same as iron, and can be removed by a strong acid cation exchanger.
Activated carbon filtration can be used to reduce the amount of nickel in
drinking water, but may not remove it all. Reverse osmosis will remove 97 - 98
% of the nickel from drinking water.
NITRATE
Source - Nitrate (NO3)
comes into water supplies through the nitrogen cycle rather than via dissolved
minerals. It is one of the major ions in natural waters. Most nitrate that occurs in drinking water is the result of
contamination of ground water supplies by septic systems, feed lots, and
agricultural fertilizers. Nitrate is reduced to nitrite in the body. The US
EPA's MCL for nitrate is 10 mg/l.
Treatment - Reverse
Osmosis will remove 92 - 95% of the nitrates and/or nitrites. Anion exchange
resin will also remove both as will distillation.
NITRITE
Source - Nitrites are
not usually found in drinking water supplies at concentrations above 1 or 2
mg/l (ppm). Nitrates are reduced to nitrites in the saliva of the mouth and
upper GI tract. This occurs to a much greater degree in infants than in adults,
because of the higher alkaline conditions in their GI tract. The nitrite then
oxidizes hemoglobin in the blood stream to methemoglobin,
thus limiting the ability of the blood to carry oxygen throughout the body.
Anoxia (an insufficiency of oxygen) and death can occur. The US EPA has
established the MCL (maximum contaminant level) for nitrite at 1 mg/l.
Treatment - Nitrites are
removed in the same manner as nitrates; reverse osmosis, anion exchange, or
distillation. See Nitrate - Treatment.
ODOR
Source - Taste and odor
problems of many different types can be encountered in drinking water.
Troublesome compounds may result from biological growth or industrial
activities. The tastes and odors may be produced in the water supply, in the
water treatment plant from reactions with treatment chemicals, in the
distribution system, and/or in the plumbing of consumers. Tastes and odors can
be caused by mineral contaminants in the water, such as the "salty"
taste of water when chlorides are 500 mg/l or above, or the "rotten
egg" odor caused by hydrogen sulfide. Odor in the drinking water is
usually caused by blue-green algae. Moderate concentrations of algae in the water
can cause it to have a "grassy", "musty" or
"spicy" odor. Large quantities can cause the water to have a"rotten", "septic", "fishy"
or "medicinal" odor. Decaying vegetation is probably the most common
cause for taste and odor in surface water supplies. In treated water supplies
chlorine can react with organics and cause odor problems. Odor is listed in the
Secondary Drinking Water Standards by the US EPA. The contaminant effects are
strictly aesthetic and a suggested Threshold Odor Number (TON) of 3 is
recommended.
Treatment - Odor can be
removed by oxidation-reduction or by activated carbon adsorption. Aeration can
be utilized if the contaminant is in the form of a gas, such as H2S (hydrogen sulfide).
Chlorine is the most common oxidant used in water treatment, but is only
partially effective on taste and odor. Potassium permanganate and oxygen are
also only partially effective. Chloramines are not at all effective for the
treatment of taste and odor. The most effective oxidizers for treating taste
and odor, are chlorine dioxide and ozone. Activated
carbon has an excellent history of success in treating taste and odor problems.
The life of the carbon depends on the presence of organics competing for sites
and the concentration of the odor causing compound.
ORGANICS
Source - Organic matter
makes up a significant part of the soil, therefore
water soluble organic compounds are present in all water supplies. Organic
matter is reported on a water analysis as carbon, as it is in the TOC (total
organic carbon) determination.
Organics
come from three major Sources:
The
first Source is
comprised of humic materials, microorganisms, and
petroleum-based aliphatic and aromatic hydrocarbons. The second source, derived from domestic
and commercial chemical wastes include wastewater discharges, agricultural
runoff, urban runoff, and leaching from contaminated soils. Organic
contaminants comprising the third
source which are formed during water treatment include
disinfection by-products such as THM's (Trihalomethanes), or undesirable
components of piping assembly such as joint adhesives.
Treatment - Activated
carbon is generally used to remove organics, color, and taste-and-odor causing
compounds. The contact time and service flow rate dictate the size of the
carbon filter. When removing organics, restrict flow rates to 2 gpm per square
foot of the filter bed. Reverse Osmosis will remove 98 to 99% of the organics
in the water. Ultrafiltration (UF) and nanofiltration (NF) have both been proven to remove
organics. Anion exchange resin also retains organics, but periodically needs
cleaning.
PESTICIDES
Source - Pesticides are
common synthetic organic chemicals (SOCs). Pesticides
reach surface and well water supplies from the runoff in agricultural areas
where they are used. Certain pesticides are banned by the government because of
their toxicity to humans or their adverse effect on the environment. Pesticides
usually decompose and break down as they perform their intended function. Low
levels of pesticides are found where complete break down does not occur. There
is no US EPA maximum contamination level (MCL) for pesticides as a total, each
substance is considered separately.
Treatment - Activated
carbon filtration is the most effective way to remove organics whether
synthetic (like pesticides) or natural. Ultrafiltration
will also remove organic compounds. Reverse Osmosis will remove 97 - 99% of the
pesticides.
pH
Source - The term "pH"
is used to indicate acidity or alkalinity of a given solution. It is not a
measure of the quantity of acid or alkali, but rather a measure of the
relationship of the acid to the alkali. The pH value of a solution describes
its hydrogen-ion activity. The pH scale ranges between
0 and 14.
Acidic
[ 0 ]=========[ 7 ]==========[ 14 ] Alkaline
Typically
all natural waters fall within the range of 6.0 to 8.0 pH. A value of 7.0 is
considered to be a neutral pH. Values below 7.0 are acidic and values above 7.0
are alkaline. The pH value of water will decrease as the content of CO2
increases, and will increase as the content of bicarbonate alkalinity
increases. The ratio of carbon dioxide and bicarbonate alkalinity (within the
range of 3.6 to 8.4) is an indication of the pH value of the water. Water with
a pH value of 3.5 or below, generally contains mineral acids such as sulfuric
or hydrochloric acid.
Treatment - The pH can
be raised by feeding sodium hydroxide (caustic soda), sodium carbonate (soda
ash), sodium bicarbonate, potassium hydroxide, etc. into the water stream. A
neutralizing filter containing Calcite (calcium carbonate - CaCO3
) and/or Corosex (magnesium oxide - MgO) will combat low pH problems, if within the range of 5
to 6. the peak flow rate of a neutralizing filter is 6
gpm / sq. ft. Downflow filters require frequent
backwashing is required to prevent "cementing of the bed". A 50 - 50 mix of the two seems to provide the best all around results.
Upflow neutralizers don't experience the problem of
"cementing" of the bed.
POTASSIUM
Source - Potassium (K+)
is an alkaline metal closely related to sodium. It is seldom that one sees it
analyzed separately on a water analysis. Potassium is not a major component in
public or industrial water supplies. Potassium is, however, essential in a well
balanced diet and can be found in fruits such as bananas.
Treatment - Potassium
can be removed by a cation exchange resin, usually in the form of a softener.
It can also be reduced by 94 - 97% utilizing Electrodialysis
or reverse osmosis.
RADIUM
Source - Radium (Ra) is
a radioactive chemical element which can be found in very small amounts in
pitchblende and other uranium minerals. It is used in the treatment of cancer and
some skin diseases. Radium 226 and radium 228 are of most concern when found in
drinking water because of the effects on the health of individuals. Radium 228
causes bone sarcomas. Radium 226 induces carcinomas in the head. Radioactivity
in water can be naturally occurring or can be from man-made contamination.
Radiation is generally measured in curies (Ci). One
curie equals 3.7 x 1010 nuclear transformations per second. A picocurie (pCi) equals 10-12
curies. The US EPA has set the MCL (maximum contamination level) for radium 226
and 228 at 5 pCi/L under the NIPDWR
(national interim primary drinking water regulations).
Treatment - Radium can
be removed by sodium for cation exchange resin in the form of a water softener.
Reverse Osmosis will remove 95 - 98% of any radioactivity in the drinking
water.
RADON
Source - Radon (Rn) is a radioactive gaseous chemical element formed in the
atomic disintegration of radium. Radon 222 is one of the radionuclides
of most concern when found in drinking water. It is a naturally occurring
isotope, but can also come from man-made Sources. All radionuclides
are considered carcinogens, but the organs they target vary. Since radon 222 is
a gas, it can be inhaled during showers or while washing dishes. There is a
direct relationship between radon 222 and lung cancer.Under
the NIPDWR (national interim primary drinking water regulations), the MCL (maximum contamination level) for radon 222 is set
at 15 pCi/L (see radium for explanation of how
radiation is measured).
Treatment - Radon is
easily removed by aeration, since it is a gas. Carbon filtration is also very
effective in removing radon.
ROTTON EGG ODOR IN COLD WATER- EPA Maximum Contaminant
level: N/A
Caused
by hydrogen sulfide gas . This gas is very corrosive
and will react with iron to form a black sludge of iron sulfide. Most sulfur
waters contain from 1 to 5 ppm of hydrogen sulfide. Use a chemical feed pump to feed chlorine
(bleach) in to the line ahead of the pressure tank (3 ppm of chlorine is
required for each ppm of hydrogen sulfide). Chlorine causes the formation of
sulfur particles that can be filtered. Install an activated carbon filter
following the pressure tank to remove the sulfur particles as well as any
excess chlorine. If it is your desire to have a non-maintenance,
non-chemical solution, an aerator
(up to 5 ppm of hydrogen sulfide) will solve your problem.
SALTY OR BRACKISH TASTE - EPA Maximum Contaminant level: 250
mg/L
Caused by high chloride or sulfate content. When the total of chlorides and
sulfates exceeds 65 grains per gallon, the disagreeable taste will be noticed
by almost all people. Filtering by
Reverse Osmosis is the best way to solve this problem.
SELENIUM
Source - Selenium (Se)
is essential for human nutrition, with the majority coming from food. The
concentration found in drinking water is usually low, and comes from natural
minerals. Selenium is also a by-product of copper mining / smelting. It is used
in photoelectric devises because it's electrical
conductivity varies with light. Naturally occurring selenium compounds have not
been shown to be carcinogenic in animals. However, acute toxicity caused by high
selenium intake has been observed in laboratory animals and in animals grazing
in areas where high selenium levels exist in the soil. The US EPA has
established the MCL for selenium at 0.05 mg/l.
Treatment - Anion
exchange can reduce the amount of selenium in drinking water by 60 - 95%.
Reverse Osmosis is excellent at reduction of selenium.
SEWAGE - EPA Maximum Contaminant level: Varies on compound
The
first thing to do if you suspect that your water is contaminated by sewage is
to send a water sample to your local, provincial, or national governing body to
determine if sewage pollution is present in your water supply. Eliminate the source of contamination if
possible (Surface runoff, cracked well casing, proximity to septic tank, faulty
well seal, etc..). Next, install a chemical feed pump
to feed chlorine (household bleach) into the system to a slight excess (i.e.
more than is required to react with the amount of contamination present). This
assures sufficient chlorine in the system to protect against small fluctuations
in the amount of contamination present. Install a drip valve after the
chlorinator and get a test kit to test chlorine content. Install a backwashable carbon filter to remove excess chlorine and
test for chlorine both before the block carbon filter and after. The reduction
of chlorine should be considerable.
Finally, a reverse osmosis unit at the end of the process is recommended
(CTA membrane).
SILICA
Source - Silica (SiO2) is
an oxide of silicon, and is present in almost all minerals. It is found in
surface and well water in the range of 1 - 100 mg/l. Silica is considered to be
colloidal in nature because of the way it reacts with adsorbents. A colloid is
a gelatinous substance made up of non-diffusible particles that remain
suspended in a fluid medium. Silica is objectionable in cooling tower makeup
and boiler feedwater. Silica evaporates in a boiler
at high temperatures and then redeposits on the
turbine blades. These deposits must be periodically removed or damage to the
turbine will occur. Silica is not listed in the Primary or the Secondary
Drinking Water Standards issued by the US EPA.
Treatment - Silica can
be removed by the anion exchange portion of the demineralization process.
Reverse Osmosis will reject 85 - 90% of the silica content in the water.
SILVER
Source - Silver (Ag) is
a white, precious, metallic chemical element found in natural and finished
water supplies. Silver oxide can be used as a disinfectant, but usually is not.
Chronic exposure to silver results in a blue-gray color of the skin and organs.
This is a permanent aesthetic effect. Silver shows no evidence of
carcinogenicity. Silver has a suggested level of 0.1 mg/l under the US EPA
Secondary Drinking Water Standards.
Treatment - Silver can
be reduced by 98% with distillation, up to 60% with activated carbon
filtration, up to 90% with cation exchange or anion exchange (dependent on the
pH), or up to 90% by Reverse Osmosis.
SOCs (Synthetic Organic Chemicals)
Source - Over 1000 SOCs (Synthetic Organic Chemicals) have been detected in
drinking water at one time or another. Most are of no concern,but some are potentially a health risk to consumers.
Treatment - Activated carbon
is generally used to remove organics. Flow rates should be restricted to 2 gpm
per square foot of the filter bed. Reverse Osmosis will remove 98 to 99% of the
organics in the water. Ultrafiltration (UF) and nanofiltration (NF) both will remove organics. Anion
exchange resin also retains organics, but periodically needs cleaning.
SODIUM
Source - Sodium (Na) is
a major component in drinking water. All water supplies contain some sodium.
The amount is dependent on local soil conditions. The higher the sodium content
of water, the more corrosive the water becomes. A major Source of sodium in
natural waters is from the weathering of feldspars, evaporates and clay. The
American Heart Association has recommended a maximum sodium level of 20 mg/l in
drinking water for patients with hypertension or cardiovascular disease. Intake
from food is generally the major Source of sodium, ranging from 1100 to 3300
mg/day. Persons requiring restrictions on salt intake, usually have a sodium
limitation down to 500 mg/day. The amount of sodium obtained from drinking
softened water is insignificant compared to the sodium ingested in the normal
human diet. The amount of sodium contained in a quart of softened, 18 grain per
gallon water is equivalent to a normal slice of white bread. Sodium in the body
regulates the osmotic pressure of the blood plasma to assure the proper blood
volume. Sodium chloride is essential in the formation of the stomach acids
necessary for the digestive processes. The US EPA sponsored a symposium which
concluded that there is no relationship between soft water and cardiovascular
disease. There is also no MCL published for sodium,
however the US EPA suggests a level of 20 mg/l in drinking water for that
portion of the population on severe sodium restricted diets of 500 mg/day or
less.
Treatment - Sodium can
be removed with the hydrogen form cation exchanger portion of a deionizer.
Reverse Osmosis will reduce sodium by 94 - 98%. Distillation will also remove
sodium.
STRONTIUM
Source - Strontium (Sr) is in the same family as calcium and magnesium, and is
one of the polyvalent earth metals that shows up as
hardness in the water. The presence of strontium is usually restricted to areas
where there are lead ores, and its concentration in water is usually very low.
Strontium sulfate is a critical reverse osmosis membrane foulant,
dependent on its concentration. There is no MCL for strontium listed in the US
EPA Drinking Water Standards.
Treatment - Strontium
can be removed with strong acid cation exchange resin. It can be in sodium form
as in a water softener or the hydrogen form as in the cation portion of a
two-column deionizer. Reverse Osmosis will also reduce strontium but as stated
above strontium sulfate is a membrane foulant.
SULFATE
Source - Sulfate (SO4)
occurs in almost all natural water. Most sulfate compounds originate from the
oxidation of sulfite ores, the presence of shales,
and the existence of industrial wastes. Sulfate is one of the major dissolved
constituents in rain. High concentrations of sulfate in drinking water causes a
laxative effect when combined with calcium and magnesium, the two most common
components of hardness. Bacteria which attack and reduce sulfates, causes
hydrogen sulfide gas (H2S) to form. Sulfate has a suggested level of 250 mg/l
in the Secondary Drinking Water Standards published by the US EPA.
Treatment - Reverse
Osmosis will reduce the sulfate content by 97 - 98%. Sulfates can also be
reduced with a strong base anion exchanger, which is normally the last half of
a two-column deionizer.
TASTE
Source - Generally,
individuals have a more acute sense of smell than taste.
Taste
problems in water come from total dissolved solids (TDS) and the presence of
such metals as iron, copper, manganese, or zinc. Magnesium chloride and
magnesium bicarbonate are significant in terms of taste. Fluoride may also
cause a distinct taste. Taste and odor problems of many different types can be
encountered in drinking water. Troublesome compounds may result from biological
growth or industrial activities. The tastes and odors may be produced in the
water supply, in the water treatment plant from reactions with treatment
chemicals, in the distribution system, and /or in the plumbing of consumers.
Tastes and odors can be caused by mineral contaminants in the water, such as
the "salty" taste of water when chlorides are 500 mg/l or above.
Decaying vegetation is probably the most common cause for taste and odor in
surface water supplies. In treated water supplies chlorine can react with
organics and cause taste and odor problems. See "ODOR" for more
information.
Treatment - Taste and
odor can be removed by oxidation-reduction or by activated carbon adsorption.
Aeration can be utilized if the contaminant is in the form of a gas, such as
H2S (hydrogen sulfide). Chlorine is the most common oxidant used in water
treatment, but is only partially effective on taste and odor. Potassium
permanganate and oxygen are also only partially effective. Chloramines are not
at all effective for the treatment of taste and odor. The most effective
oxidizers for treating taste and odor, are chlorine
dioxide and ozone. Activated carbon has an excellent history of success in
treating taste and odor problems. The life of the carbon depends on the
presence of organics competing for sites and the concentration of the taste and
odor causing compound.
TOTAL DISOLVED
SOLIDS (TDS)
Source - Total Dissolved
Solids (TDS) consist mainly of carbonates, bicarbonates, chlorides, sulfates,
phosphates, nitrates, calcium, magnesium, sodium, potassium, iron, manganese,
and a few others. They do not include gases, colloids, or sediment. The TDS can
be estimated by measuring the specific conductance of the water. Dissolved solids in natural waters range from less than 10 mg/l for
rain to more than 100,000 mg/l for brines. Since TDS is the sum of all
materials dissolved in the water, it has many different mineral Sources. The
chart below indicates the TDS from various Sources.
Source
|
TDS - mg/l
|
|
Distilled Water |
0 |
|
Two-column Deionizer Water |
8 |
|
Rain and Snow |
10 |
|
Lake Michigan |
170 |
|
Rivers in U.S. (average) |
210 |
|
Missouri River |
360 |
|
Pecos River |
2600 |
|
Oceans |
35,000 |
|
Brine Well |
125,000 |
|
Dead Sea |
250,000 |
High
levels of total dissolved solids can adversely industrial applications
requiring the use of water such as cooling tower operations, boiler feed water,
food and beverage industries, and electronics manufacturers. High levels of
chloride and sulfate will accelerate corrosion of metals. The US EPA has a
suggested level of 500 mg/l listed in the Secondary Drinking Water Standards.
Treatment - TDS
reduction is accomplished by reducing the total amount in the water. This is
done during the process of deionization or with Reverse Osmosis. Electrodialysis will also reduce the TDS.
THM's
(Trihalomethanes)
Source - THM's
(Trihalomethanes) are produced when chlorine reacts with residual organic
compounds. The four common THM's are trichloro-methane
(chloroform), dibromochloromethane, dichlorobromomethane, and bromoform.
There have been studies that suggest a connection between chlorination
by-products and particularly bladder and possibly colon and rectal cancer. An
MCL of 0.10 mg/l for total THM's exists.
Treatment -
Trihalomethanes and other halogenated organics can be reduced by adsorption
with an activated carbon filter.
TOC (Total Organic
Carbon)
Source - TOC is a measurement
to track the overall organic content of water. The organic content of the water
will appear on the water analysis as C (carbon). The TOC test is the most
common test performed to obtain an indication of the organic content of the
water. Nonspecific tests utilized to determine the organic content of water are
given below.
BOD-
Biochemical oxygen demand - expressed as O2
CCE-
Carbon-chloroform extract - expressed in weight
CAE-
Carbon-alcohol extract (performed after CCE)
COD-
Chemical oxygen demand - expressed as O2
Color-
Color - reported as APHA units
IDOD-
Immediate dissolved oxygen demand - expressed as O2
LOI-
Loss of ignition - expressed in weight
TOC-
Total organic carbon - expressed as C
The
above tests are used to determine organic content of the water, for more
information about different types see
"ORGANICS".
Treatment - Procedures
and suggestions for reduction of TOC is given under the heading
"ORGANICS".
TURBIDITY - EPA Maximum Contaminant level: 0.5 -
1.0 NTU
Source - Turbidity is
the term given to anything that is suspended in a water supply. It is found in
most surface waters, but usually doesn't exist in ground waters except in
shallow wells and springs after heavy rains. Turbidity gives the water a cloudy
appearance or shows up as dirty sediment. Undissolved materials such as sand,
clay, silt or suspended iron contribute to turbidity. Turbidity can cause the
staining of sinks and fixtures as well as the discoloring of fabrics. Usually
turbidity is measured in NTUs (nephelometric turbidity units). Typical drinking
water will have a turbidity level of 0 to 1 NTU. Turbidity can also be measured
in ppm (parts per million) and it's size is measured
in microns. Turbidity can be particles in the water consisting of finely
divided solids, larger than molecules, but not visible by the naked eye;
ranging in size from .001 to .150 mm (1 to 150 microns). The US EPA has
established an MCL for turbidity to be 0.5 to 1.0 NTU, because it interferes
with disinfection of the water.
Treatment - Typically
turbidity can be reduced to 75 microns with a cyclone separator, then reduced
down to 20 micron with standard backwashable filter,
however flow rates of 5 gpm/ sq. ft. are recommended maximum. Turbidity can be
reduced to 10 micron with a multimedia filter while providing flow rates of 15
gpm/sq. ft. Cartridge filters of various sizes are also available down into the
submicron range. Ultrafiltration also
reduces the turbidity levels of process water.
URANIUM
Source - Uranium is a
naturally occurring radionuclide. Natural uranium combines uranium 234, uranium
235, and uranium 238; however, uranium 238 makes up 99.27 percent of the
composition. All radionuclides are considered
carcinogens; however, the organs each attacks is
different. Uranium is not a proven carcinogen but accumulates in the bones
similar to the way radium does. Therefore, the US EPA tends to classify it as a
carcinogen. Uranium has been found to have a toxic effect on the human kidneys.
Under the NIPDWR (national interim primary drinking water regulations), the MCL
(maximum contamination level) for uranium is set at 15 pCi/L (see radium for explanation of how radiation is
measured).
Treatment - Uranium can
be reduced by both cation or anion dependent upon its
state. Reverse Osmosis will reduce uranium by 95 to 98%. Ultrafiltration
will also reduce the amount of uranium. Activated alumina can also be utilized.
VIRUSES
Source - Viruses are
infectious organisms which range in size from 10 to 25 nanometers [1 nanometer
= one billionth (10-9) of a meter]. They are particles composed of an acidic
nucleus surrounded by a protein shell. Viruses depend totally on living cells
and lack an independent metabolism. There are over 100 types of enteric
viruses. Enteric viruses are the viruses which infect humans. Enteric viruses
which are of particular interest in drinking water are hepatitis A,
Norwalk-type viruses, rotaviruses,adenoviruses,
enteroviruses, and reoviruses.
The test for coliform bacterial is widely accepted as an indication whether or
not the water is safe to drink, therefore tests for
viruses are not usually conducted. The US EPA has established an MCL which
states that 99.99% reduction or inactivation for viruses. Major enteric viruses
and their diseases are shown below.
Treatment - Chemical
oxidation / disinfection is the preferred treatment. Chlorine feed with 30
minute contact time for retention, followed by activated carbon filtration is
the most widely used treatment. Ozone or iodine may also be utilized as
oxidizing agents. Ultraviolet sterilization or distillation may also be used
for the treatment of viruses
VOCs (Volatile Organic
Chemicals)
Source - VOCs pose a
possible health risk because many of them are known carcinogens. Volatile
organic chemicals are man-made, therefore the
detection of any of them indicates that there has been a chemical spill or
other incident.
Treatment - The best
choice for removal of volatile organic chemicals is Activated carbon
filtration. The adsorption capacity of the carbon will vary with each type of
VOC. The carbon manufacturers can run computer projections on many of these
chemicals and give an estimate as to the amount of VOC which can be removed
before the carbon will need replacement. Aeration may also be used alone or in
conjunction with the activated carbon. Reverse Osmosis will remove 70 to 80% of
the VOCs in the water. Electro dialysis and Ultra filtration are also capable
of reducing volatile organic chemicals