As the individual molecules join together, characteristic rust color (often called "red water" or "rust water") appears. And, finally, a gelatinous precipitate of ferric hydroxide settles to the bottom of the container. In this way, the soluble ferrous ions convert into the insoluble ferric hydroxide.

When iron is found in surface supplies, the water may be extremely acidic, or the iron may be combined in various complex molecules, which resists oxidation. In some surface waters, iron may be present in an organic (gelated) form. Such water usually contains a great deal of color,

Iron bacteria frequently thrive in iron-bearing water, As they develop, these bacteria form reddish-brown growths, which may clog pipes and reduce flow rates. A decaying mass of these iron bacteria can cause bad tastes and odors in a water supply, as well as severe discoloration problems.

IRON REMOVAL

For medium concentrations of iron, the use of an oxidizing filter can be a most effective means of treatment. When used, such a filter should be placed in the water line ahead of the softener.

Oxidizing filters normally contain a base material that has been coated with manganese dioxide.

These manganic oxide deposits convert the soluble ferrous iron in the water into ferric iron. As the ferric hydroxide forms, it is filtered from the water by the granular material in the tank.

With high concentrations of iron, small pumps, eductors, or other devices may be used to feed chemical oxidizing agents such as household bleach (chlorine) or a permanganate solution in the water.

Like the manganese dioxide in an iron filter, these chemical oxidizing agents convert ferrous iron to the ferric state. The contaminant can be removed by running the water through a simple sand filter when chlorine is used and through an iron filter when permanganate is used.

The use of superchlorination-dechlorination is a means of removing iron from water. This variation of the oxidation-filtration concept uses two basic devices: one feeds chlorine into the water; the other removes any excess chlorine.

The injection of the full strength chlorine bleach into the water converts the ferrous iron into ferric iron. This insoluble gel is then removed from the water by simple filtration. A dechlorinator unit (usually an activated carbon filter) is then installed to remove excess chlorine, especially from drinking water.

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Manganese is akin to iron and is found in iron-bearing waters, but more rarely than iron. Chemically, it can be considered closely related to iron since it occurs in much the same forms. In low concentrations it causes objectionable stains.

U.S. Public Health Standards place a limit of 0.05 ppm on the manganese concentration in water.

MANGANESE REMOVAL

The same methods as those outlined for iron removal apply equally to the treatment of manganese problems. Managanese is much more difficult to oxidize than iron. Approximately twice as much oxidizing agent will be required as is used when treating a similar amount of iron.

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Hydrogen sulfide is a gas present in some waters. There is never any doubt as to when it is present due to its offensive "rotten egg" odor apparent in concentrations as low as 1 ppm.

HYDROGEN SULFIDE REMOVAL

There are several methods for removing hydrogen sulfide from water. Most of them involve converting the gas into elemental sulfur. This insoluble yellow powder can then be removed by filtration.

Low to moderate concentrations of hydrogen sulfide can be eliminated through use of an oxidizing filter of the same type for iron removal. Because the elemental sulfur precipitate tends to clog the filter material, it is usually necessary to replace this material from time to time.

Chemical treatment is recommended for medium to high concentrations of hydrogen sulfide. In such cases, solutions of household bleach or potassium permanganate serve as satisfactory oxidizing agents.

An activated carbon filter alone will remove trace amounts of hydrogen sulfide. In this process the carbon simply absorbs the gas on its surface areas. The use of an activated carbon filter can be economical when extremely small amounts of the gas are present.

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Almost all natural waters contain chloride and sulfate ions. Their concentrations vary considerably according to the mineral content of the soil in any given area.

In small amounts they are not significant. In large concentrations they present problems.

Usually chloride concentrations are light.

Sulfates can be more troublesome because they generally occur in greater concentrations.

Low to moderate concentrations of both chloride and sulfate ions add palatability to water. In fact, they are desirable for this reason. Excessive concentrations of either, of course, can make water unpleasant to drink.

The U.S. Public Health Service Drinking Water Standards recommend the same maximum concentration --250-ppm - for each of the chloride and sulfate ions.

Water containing calcium sulfate ions is likely to have a characteristic taste ... somewhat bitter and astringent. In fact it has been compared to the way dissolved gypsum might taste in water.

When 30 to 40 grains per gallon of calcium sulfates are dissolved in water most people can detect the taste.

If equal amounts of magnesium sulfate or sodium sulfate were dissolved in water, the taste would not be noticeable. Both possess definite laxative effects in concentrations above 30 grains per gallon. In this way, they can be troublesome especially to people not accustomed to such water.

Chlorides give water a salty taste. At what concentrations this becomes noticeable depends on the individual. In large concentrations, chlorides cause a brackish, briny taste that definitely is undesirable.

Although chlorides are extremely soluble, they possess marked stability. This enables them to resist change and to remain fairly constant in any given water unless the supply is altered by dilution or by industrial or human wastes.

Both chlorides and sulfates contribute to the total mineral content of water. As indicated above, the total concentration of minerals may have a variety of effects in the home.

* See DE-CONTAMINATION BY REVERSE OSMOSIS for removal of chlorides and sulfates.

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Sodium salts are present to a greater or lesser degree in all natural waters. Their concentrations vary from a few parts per million in some surface supplies to several hundred grains per gallon in certain well supplies.

Extremely soluble, sodium salts do not form scale when water is heated, nor do they produce curd when combined with soap. High concentrations tend to increase the corrosive action of water and may give water an unpleasant taste. Sodium ions in large amounts also hamper the operation of ion exchange softeners. Where water contains much hardness and sodium, several grains of hardness may remain in the softened water.

Reverse osmosis and demineralization are effective ways to remove sodium salts from water.

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Fluorides in water can be detrimental or beneficial. It all depends on the concentration.

Surface water supplies are normally low in fluorides (less than 0.5 ppm). Some have no fluoride at all. Well waters may contain excessive amounts of fluoride (over 1.5 ppm). There are some wells which contain the recommended amount (about 1 ppm) for drinking water.

Fluorides are important because they have a definite relation to dental health.

Research has shown that a concentration of 1-ppm fluoride in drinking water reduces tooth decay.

On the other hand, when water contains over 1.5 ppm of fluorides, it causes a condition known as "endemic dental fluorosis.' Sometimes called "Colorado Brown Stain," this condition appears as a dark brown mottling or spotting of the teeth. In certain cases the teeth become chalky white in appearance.

* See DE-CONTAMINATION BY REVERSE OSMOSIS for removal of fluorides.

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Pick up a glass of water, and hold it to the light. Can you see any finely divided, insoluble particles suspended in water? Or does the water seem hazy? If so, the water is turbid.

When water has a large amount of such suspended particles, we lose our zest for it. While it may be safe to drink, it seems offensive.

The U.S. Public Health Service Drinking Water Standards recommends that turbidity of potable water be less than 5 units.

The suspended particles clouding the water may be due to such inorganic substances as clay, rock flour, silt, calcium carbonate, silica, iron, manganese, sulfur or industrial wastes.

Again, the clouding may be caused by organic substances such as various micro-organisms, finely divided vegetable or animal matter, grease, fat, oil and others.

While turbidity may be due to a single foreign substance in water, chances are it is probably due to a mixture of several or many substances.

Those particles, which quickly sink to the bottom, are usually called sediment. There are, however, no hard and fast rules for classifying such impurities. If you take water from a swiftly flowing river or stream, you generally find that it contains a considerable amount of sediment.

In contrast, you find that water taken from a lake or pond is usually much clearer. In these more quiet, non-flowing waters, there is greater opportunity for settling action. Thus, all but very fine particles sink to the bottom.

REMOVAL OF TURBIDITY

In most cases, filters containing specially graded and sized gravel and sand are effective in screening out turbid particles. With such units, a periodic backwashing to remove the filtered material is all the maintenance necessary.

Municipal and industrial systems frequently make use of the coagulation process to aid in the removal of turbidity.

In cases where turbid particles are very small, a coagulating agent, such as aluminum sulfate, is fed into the water. After rapid mixing, the coagulating agent forms a "floc".

As the floc forms, it tends to collect or entrap the turbid particles and form them into larger particles which can then be removed by the filter.

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pH indicates the intensity of a given water in terms of alkalinity or acidity. Acidity or alkalinity is measured on a scale that goes from 0 to 14. Seven, the mid-point, is the measure of neutral water, neither acid nor alkaline.

pH figures larger than 7 indicate alkaline solutions with the intensity of alkalinity increasing as the number becomes larger.

pH figures lower than 7 indicate acid solutions with the intensity of acidity increasing as the numbers get smaller. There are two important things to bear in mind when considering pH:

(1) Always it is an intensity measure, not one of quantity. A thermometer will tell how cold a room is, but not how much warm air is necessary to heat it.

(2) It is an exponential function. pH 10 is 10 times as alkaline as pH 9 and 100 times as alkaline as pH 8. Similarly, a pH 2 is 100 times as acid as pH4 and 1,000 times as acidic as pH 5.

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Alkalinity of water may be due to the presence of one or more of a number of ions. These include hydroxides, carbonates and bicarbonates.

Small amounts of carbonates are found in natural water supplies in certain sections of the country, rarely exceeding 3 or 4 gpg they may also be found in water after treatments, such as limesoda ash softening.

Bicarbonates are the most common sources of alkalinity. Almost all natural supplies have a measurable amount of this ion, ranging from 0 to about 50 gpg.

Moderate concentrations of alkalinity are desirable in most water supplies to balance the corrosive effects of acidity. However, excessive quantities cause a number of problems.

You probably will not notice an alkaline condition due to bicarbonate ions, except, when present in large amounts. In contrast, you should readily detect alkalinity due even to fairly small amounts of carbonate and hydroxide ions.

Strongly alkaline waters have an objectionable "soda" taste. The U.S. Public Health Service Drinking Water Standards limit alkalinity only in terms of total minerals (500 ppm) and the limitation on taste.

Highly mineralized alkaline waters also cause excessive drying of the skin due to the fact that they tend to remove normal skin oils.

REMOVAL OF ALKALINITY

Although troublesome amounts of alkalinity can be removed in several ways, none of these methods are normally satisfactory for household needs. These include:

An anion resin regenerated with sodium chloride does the job. This process removes substantially all the anions (carbonates, bicarbonates and sulfates). It replaces these anions with a chemically equivalent amount of chloride ions. The disadvantage of this process is that in almost all cases a high chloride ion concentration results. For household purposes, such results are almost as undesirable as the original alkalinity.

The feed of a mineral acid will neutralize the alkalinity of water. Hydrochloric acid, sulfuric acid or a combination of these can be used. This process converts the bicarbonates and carbonates present into carbonic acid. At this point, it is advisable to provide some method to permit the gas to escape into the atmosphere,

The disadvantage of this acid feed technique is obvious. There are needs for precise control of the process and caution in handling the strong acid.

Distillation and demineralization are omitted here, as they are not normally suitable for home needs.

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Almost all natural waters contain some carbon dioxide which they gain in several ways.

Carbon dioxide gas (CO2] is present in the air to the extent of 0.03 per cent by volume and 0.05 per cent by weight, As rain falls through the air, it absorbs some of this gas.

On reaching the earth the rainwater -- now slightly acid -- will absorb additional amounts of carbon dioxide if it flows through decaying vegetation. At the same time the carbon dioxide becomes carbonic acid.

If the water now passes through limestone formations, its carbonic acid content will react with the limestone to form soluble calcium bicarbonate. In this process the carbonic acid is partially neutralized.

On the other hand, if water passes through rock formations, such as granite, no such reaction occurs. The carbonic acid is not neutralized. It continues as carbonic acid until drawn to the surface where it can then cause corrosion if not neutralized.

If nature or chemical agents do not neutralize carbonic acid, it will cause corrosion of both copper and galvanized plumbing systems. In those parts of the country where the problem is prevalent it is serious, for it can lead to serious damaging of plumbing equipment.

Carbon dioxide, together with carbonic acid, is primarily a problem in water containing relatively low concentrations of minerals. In such water there are not sufficient alkaline salts to buffer the effect of the carbonic acid.

REMOVAL OF ACIDITY

The simplest method for removal of carbonic acid is to pass the water through a tank containing limestone chips. A neutralizing filter of this type affects the carbonic acid just as does the underground limestone formation. The limestone in the filter reacts with the carbonic acid to produce calcium bicarbonate.

Where high carbon dioxide concentrations are encountered, a solution of soda ash-sodium carbonate (Na2CO~) -- may be fed into the water.

This method, as we have seen, has the disadvantage of requiring more attention in the preparation and maintenance of proper feeds.

Where water is obtained from a private well, a small positive displacement pump can be used to feed the soda ash solution into the water,

Normally such pumps are wired to act in conjunction with the operation of the well pump. This permits the proportioning of the solution with a good degree of accuracy.

It is important to feed soda ash solutions into the water in advance of some type of tank or mixing device, This is necessary to provide for reasonably consistent concentrations in the water to be treated. The type of pressure tank utilized in connection with most private water systems is adequate for this purpose.

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Some tastes and odors, especially those due to organic substances, can be removed from water simply by passing it through an activated carbon filter. Other tastes and odors may respond to oxidizing agents such as chlorine and potassium permanganate.

In any case you may have to try a number of methods in an attempt to rid water of objectionable tastes and odors. If the methods outlined do not work, it may be more economical to seek out a new source of drinking water. Removal of chlorine can be accomplished by the use of an activated carbon filter.

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Many ground waters contain small amounts of nitrate nitrogen. Concentrations range from 0.1 ppm to 3 or 4 ppm in most areas. The presence of nitrates in a water supply indicates possible pollution of the water.

In concentrations as low as 10 to 20 ppm nitrate nitrogen has caused illness and even death among infants under six months of age. Although this problem is serious, public health officials are primarily concerned with nitrates as a strong indicator of water pollution.

Certainly, where a ground water is known to contain little or no nitrate nitrogen naturally, the appearance of any significant increase is a probable indication of pollution.

Prevention of sewage contamination is the best possible treatment. Reverse osmosis and distillation are practical solutions for home needs, as well as bottled water.

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