Guidelines for Monitoring Public Drinking Water Supplies (Get Acrobat Reader)

ACIDIC WATER  

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.

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 health Canada as a carcinogen. The current acceptable limit for arsenic is 0.025 mg/l which was derived from toxicity considerations rather than carcinogenicity. See Map

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 95% 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 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 a recognized testing facility 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.. 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 and dysentery.

Treatment - Bacteria can be treated by microfiltration, Reverse Osmosis, ultrafiltration, 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 Health Canada standards. Reverse Osmosis will remove 99+ % of the bacteria in a drinking water system.

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.

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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, Ultrafiltration, 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.

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. Electrodialysis 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. Electrodialysis and Ultrafiltration also will remove calcium. Calcium can also be removed with the hydrogen form cation exchanger portion of a deionizer system.

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.

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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

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.

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

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 maximum acceptable concentration established for drinking water by Health Canada is 1.5 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.

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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.

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  

Source - Hard water is found over 80% of Canada's ground water. 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 ***
1. Calcium Carbonate (CaCO3) - Known as limestone, rare in water supplies. Causes alkalinity in water.
2. Calcium Bicarbonate [Ca(HCO3)2] - Forms when water containing CO2 comes in contact with limestone. Also causes alkalinity in water. When heated CO2 is released and the calcium bicarbonate reverts back to calcium carbonate thus forming scale.
3. Magnesium Carbonate (MgCO3) - Known as magnesite with properties similar to calcium carbonate.
4. Magnesium Bicarbonate [Mg(HCO3)2] - Similar to calcium bicarbonate in its properties.
*** Permanent Hardness Salts ***
1. Calcium Sulfate (CaSO4) - Know as gypsum, used to make plaster of paris. Will precipitate and form scale in boilers when concentrated.
2. Calcium Chloride (CaCl2) - Reacts in boiler water to produce a low pH as follows: CaCl2 + 2HOH ==> Ca(OH)2 + 2HCl
3. Magnesium Sulfate (MgSO4) - Commonly known as epsom salts, may have laxative effect if great enough quantity is in the water.
4. Magnesium Chloride (MgCl2) - Similar in properties to calcium chloride.
Sodium salts are also found in household water supplies, but they are considered harmless as long as they do not exist in large quantities.

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 can be treated with a air draw Birm Machine or chlorine injection which 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. The latter is the most efficient way to treat Hydrogen Sulfide.

IRON  

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 can be converted to ferric iron by contact with an 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. 

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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. Health Canada considers lead to be a highly toxic metal and a major health threat. The current level of lead allowable in drinking water is 0.010 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.

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 produce 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 Permanganate 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 enters the food chain through fish and comes primarily from industrial chemical manufacturing waste or from the leaching of coal ash. If inorganic mercury enters the body, it usually settles in the kidneys, whereas organic mercury attacks the central nervous system.

Treatment - Activated carbon filtration is very effective for the removal of mercury. Reverse osmosis will remove 95 - 97 % of it.

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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.

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.

Treatment - Nitrites are removed in the same manner as nitrates; reverse osmosis, anion exchange, or distillation.

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. 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.

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 Health Canada 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.

See Diagram

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 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.

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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. Health Canada suggests daily intake should not exceed 200 mg per day.

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.

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.

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, DISSOLVED bicarbonates, chlorides, sulfates, phosphates, nitrates, calcium, magnesium, SOLIDS 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. High levels of total dissolved solids can adversely affect 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. Health Canada has a suggested level of 500 mg/l listed in the drinking water guidelines.

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.

TURBIDITY 

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)..

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, Health Canada tends to classify it as a carcinogen. Uranium has been found to have a toxic effect on the human kidneys. See Map

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.

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