Water supplies, whether obtained from municipal reservoirs or private wells, contain dissolved mineral salts and other materials. The amounts present determine various characteristics which affect water quality or usability.
In order to provide quality water for use, those impurities that surpass acceptable levels must be identified. No water treatment equipment on a private supply should be selected or installed without a water analysis. In most cases, a portable water analysis kit that tests for hardness, iron, and pH will give sufficient information. However, for problems of taste, order, severe corrosion, or blue or black staining, a more complete laboratory analysis should be obtained.
In the following paragraphs, common water problems, suggested corrections, and the recommended limits on levels of impurities are discussed.
HARDNESS
Hardness in water is due to the presence of calcium and magnesium compounds, which exist to some degree in all natural water supplies. Most supplies range from 3 grains per gallon (gpg) to 50 gpg of hardness. There are extreme cases where hardness may reach 100 gpg. The hardness of well water is usually higher than that of surface supplies. Shallow wells (025 ft.) can vary from season to season, but deep wells are usually quite constant. Soft water is defined as water not exceeding one grain per gallon.
Soft 0 to 0.5 gpg
Slightly Hard 0.5 to 3.5 gpg
Moderately Hard 3.5 to 7.0 gpg
Hard 7.0 to 10.5 gpg
Very Hard over 10.5 gpg
Hard water is responsible for the formation of lime scaling in pipes, water heaters, boilers, air conditioning systems, etc., causing inefficiency and sometimes permanent damage. One-sixteenth of an inch of scale may lower efficiency of a water heater as much as 15%. Scale acts as an insulating material, thus lowering heat transmission and often causing premature heater failure due to overheating of the metal. Hardness in water increases soap consumption, wasting from 50% to 90% of the soap used, depending on the amount of hardness. It also causes the formation of soap curd, which adheres to cloth fibers, hair, glassware and dishes. Soap curd causes poor results in laundering and may hold pathogenic bacteria.
When hardness appears as the only substantial water problem, the installation of a water softener is recommended.
IRON AND MANGANESE
Iron, mostly found in ground water supplies, usually appears in quantities less than 5 parts per million, but occasionally can be found in concentrations as high as 60 ppm. Water containing dissolved "ferrous" iron is usually clear when drawn, but on exposure to air it becomes cloudy, converting the iron to its "ferric" state, which in time, will deposit a rust-colored precipitate stain. The change occurs because oxygen from the air oxidizes the dissolved iron.
Iron in water, at quantities as low as 0.3 ppm, imparts a metallic or astringent taste, and causes rust colored stains on plumbing fixtures, tableware and laundry. Iron combines with tannin in tea, coffee, and alcoholic beverages to produce an unpleasant gray to black appearance. Iron-bearing waters favor the growth of iron bacteria, slime-forming organisms that cause clogging of pipes, and a foul taste and odor.
Manganese, seldom found alone in a water supply, is usually accompanied by iron. Concentrations as low as 0.2 part per million of manganese will produce dark brown or black staining. Fabrics washed in manganese-bearing waters are almost invariably stained. Deposits collect in plumbing, and tap water frequently contains a black sediment and turbidity. Manganese bacteria often causes clogging of pipes.
Because iron appears in different forms and mixes with a variety of other materials, there are a variety of methods of iron removal. A conventional water softener can remove up to 5 ppm of ferrous iron. Specialized water softeners/iron removers, oxidizing and colloidal type iron filters, chlorination and filtration systems, and sediment filters are all effective in reducing iron levels above 5 ppm in given types of water, and are available to meet your specific need.
Oxidizing Type Iron Filters Oxidizing filters can remove up to 10 ppm of both ferric (oxidized) and ferrous (clear) iron. They work well with all types of private water system pressure tanks. Sulphur removal is also possible when levels are 2.0 ppm or less. In cases where both iron and sulphur are present it is suggested that a sediment filter/water softener combination be installed for removal of all iron. The sulphur can then be removed by an oxidizing filter installed after the softener. Oxidizing filters require frequent backwashing and regeneration with a chemical, potassium permanganate. Birm media filters use the oxygen present in the water and eliminate the need for potassium permanganate. Automatic and manual types are available. Do not use oxidizing filters on water supplies that have a pH of 6.8 or less, sulphur in excess of 2.0 ppm or iron amounts exceeding 5 ppm.
Colloidal Type Iron Filters Colloidal filters can remove up to 25 ppm of both ferric (oxidized) and ferrous (clear) iron. It is preferred that they are installed in conjunction with permanent air head type pressure tanks. Colloidal filters are generally backwashed once every 4 days and require no chemicals to regenerate.
They require a water source capable of delivering flows in excess of 5.0 gpm. Successful iron removal is possible within the pH range of 5.5 thru 9.5. Colloidal filters will not work properly on waters that contain tannins or sulphur.
Chlorination and filtration systems This is a means of iron removal that is recommended only when a sulphur, extreme iron bacteria, or taste and odor problem also exists. Use a chemical solution pump to feed chlorine (household bleach) into the line ahead of the pressure tank. Chlorine causes iron in the water to form particles which can be filtered. On low pH waters and acid neutralizing compound should be added to the chlorine solution to facilitate iron removal. Use an activated carbon filter following the pressure tank to remove the iron particles as well as any excess chlorine.
NOTE - THE SUCCESS OF THIS METHOD OF IRON REMOVAL DEPENDS UPON AT LEAST 5 MINUTES OF CONTACT TIME FOR THE CHLORINE TO FULLY REACT WITH THE IRON. THIS CONTACT TIME CAN BE PROVIDED BY A BLENDING TANK SIZED AT A VOLUME OF 4 TIMES THE DRAWDOWN OF THE INSTALLED PRESSURE TANK.
pH VALUE
The pH scale is used to express the intensity of the acidity or alkalinity of a solution. As commonly used, this scale ranges from 0 to 14. A pH of 7.0 is neutral, indicating a balance between acidity and alkalinity. Values ranging below 7.0 indicate increasing acid strength. Values ranging above 7.0 indicate increasing alkaline strength.
Waters with pH below 7.0 (acid waters) tend to cause iron or copper pick-up in piping systems and contribute to staining problems. Blue to green staining will result if the piping is copper, or red staining if the piping is iron. The lower the pH, the greater the corrosive tendency of the water. Waters with pH less than 6.8 contain sufficient acidity to cause significant corrosion and should always be treated.
Excess acidity in water is treated by neutralizing the acidity through the addition of alkaline materials. This is most often accomplished by installing a neutralizing filter, which contains a mineral that reacts with acidity to raise the pH of the water. This process slowly dissolves the mineral and adds a few grains of hardness to the water. Because of the increased hardness, installation of a water softener following the acid neutralizer filter is recommended. In some cases, for use with an electrically operated well or water pump, a chemical solution pump can be used to feed a solution of acid neutralizer into the water system.
TURBIDITY AND SEDIMENT
Turbidity (fine particles) and sediment (coarse particles) may be caused by sand, scale, rust, organic matter, or clay. In addition to an objectionable, cloudy appearance, these substances may cause plugged piping or fouled water treatment equipment. Turbidity does not settle out readily, but remains suspended for several hours. It is normally present in pond, lake, or river water supplies. Turbidity levels should be less than 5 NTU's (turbidity units) for clear, acceptable water. Sediment/turbidity filters are available to handle such problems and bring water into usable ranges. Ordinary filtration does not generally remove turbidity, but by obtaining an individual water analysis, the best method of treatment may be determined.
Sediment, particles which settle to the bottom of a container within a few minutes, can be removed with an agraclear or sand type filter. When sand is determined to be present in water, a sand type filter should be used.
TASTE AND ODOR
Tastes and odors are generally considered as one and the same problem, except for taste caused by mineral salts. For example, water with high chloride content will have a salty taste but may be odorless. A quality water should contain no trace of objectionable taste or odor.
There are a variety of tastes and odors that may exist in a water supply. Common examples include chlorine odor, musty or moldy taste or odor, oil or gas odor, and rotten egg odor. Each characteristic indicates certain distinct problems and treatments. Tastes and odors, especially if caused by dissolved gases or other volatile matter are best identified at the source since they are often destroyed by oxidation.
Chlorine, musty or moldy tastes and odors, and oil or gas odors are commonly treated by carbon filtration. Rotten egg odor is caused by dissolved hydrogen sulfide gas. Hydrogen sulfide is not only unpleasant to smell, but is corrosive to most metals and tarnishes silver readily. Hydrogen sulfide levels of up to 2 ppm can be removed by an oxidizing type sulphur filter. Levels in excess of 2 ppm are treated by oxidation.
NITRATES
The presence of nitrates in water may indicate pollution of the water by organic matter. Although most of the polluted water is found in shallow wells, deep wells may also be affected. It is for this reason that the Board of Health has specifications governing the construction of wells and their location with respect to septic tanks, barns and other sources of contamination.
An acceptable level is less than 10 ppm. Concentrations of nitrates above 10 parts per million in the drinking water of infants can cause cyanosis ("blue baby"), a poisoning of the blood which results in a decreased ability to carry oxygen, which can prove fatal.
Because of these factors, well waters containing nitrates should be checked by the authorities, and the location and construction of th well thoroughly inspected. Nitrates can be substantially removed from water by a reverse osmosis system using a thin film composite membrane with a 50 psi minimum, preferably combined with a water softener.
DISSOLVED SOLIDS
notal dissolved solids (TDS) are the sum total of all mineral compounds dissolved in the water. They consist primarily of salts of calcium, magnesium or sodium usually in the form of chlorides, sulfates, or bicarbonates.
Excessive dissolved solids decrease the effectiveness of a water softener. While softening will greatly improve water for laundering and bathing purposes, high TDS content in water will exhibit a salty or brackish taste. In cases where water is high in TDS or chlorides (over 250 ppm), only reverse osmosis, demineralization, or distillation will significantly improve water quality.
FLUORIDES
Fluorides in water can be detrimental or beneficial depending upon the concentration. If the water contains over 1.5 parts per million of fluorides, use during the period of tooth formation causes a condition known as "endemic dental fluorosis", a dark brown stain on the teeth. It is therefore necessary to remove fluorides present in such high concentrations. Fluorides are not removed by softening, but a number of methods, including the installation of a reverse osmosis drinking water system, are available for fluoride reduction.
Recent work has shown that low concentrations of fluoride taken during tooth formation can minimize tooth decay. Concentrations on the order of 1 part per million are considered optimum.
SODIUM
Modium is present to some degree in all water supplies. Low concentrations have little or no effect, but high concentrations increase the corrosive effect on the water. An unpleasant taste can be noted when the concentration is over 500 ppm. High sodium content slightly reduces the capacity of a water softener. Sodium can be removed from a water supply only by processes such as reverse osmosis, demineralization, or distillation.
SULFATES
ater with a sulfate concentration in excess of 40 gpg may have a medicinal taste and a laxative effect. Sulfates are removed from a water supply by processes such as reverse osmosis, demineralization or distillation.
CARBON DIOXIDE
Carbon dioxide concentrations vary in most water supplies from almost zero to about 50 parts per million. Surface waters generally contain larger amounts than do ground waters. Carbon dioxide combines with water to form carbonic acid, a weak acid that accelerates corrosion, particularly when heated. Excessive concentrations of carbon dioxide are generally indicated by low pH values. Acid waters of this type can be treated by aeration or acid neutralization.
OXYGEN
Mater containing appreciable amounts of oxygen tends to be corrosive. Treatment involves treating the metal surfaces of a water system with polyphosphate, rather than treating the water itself. This forms a protective film which insulates the metal from attack by oxygen and other corrosive elements.
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Water & Water Quality
Absolutely pure water is a rarity and a chemical curiosity. It can be made by burning pure hydrogen in an atmosphere of pure oxygen. Water, being the greatest of all solvents, immediately dissolves a little of everything it contacts. Water is a tough, resilient substance which never wears out, but it does become contaminated.
In theory, water can be re-used endlessly. However, there is considerable public concern about, and a growing interest in water supplies - in the amount, future sources, and methods of treatment. Public health authorities, industrial firms, commercial firms, hospitals and institutions, farmers and homemakers all have special requirements in terms of water quality and availability. Major problems result when these fundamental needs are not met.
The difficulty in obtaining sufficient water does not stem from the lack of water in general. Over 97% of the world's water is in its oceans, but sea water is not usable for most purposes without extensive treatment. The difficulty, then, is due to the fact that the remaining 3%, which is fresh water, is not evenly distributed and often unaccessible.
Two-thirds of the world's fresh water is tied up in the polar ice caps and glaciers. The remaining one-third is in ground waters, surface water, the atmosphere, and soil moisture. The only two sources of water supply available to man are ground waters - wells and springs, and surface water - lakes, rivers, streams, and reservoirs.
In providing the right water for any demand, one must consider both a precise analysis of the raw water supply, and the end use of the water. Analysis of a water can show the existence and amount of dissolved minerals and gases, sediment, color and organic matter, taste and odor, and/or microorganisms. Whether any of these impurities could be harmful depends on (a) the nature and amount of the impurities, (b) the tolerance permissible for each of these impurities, and (c) to what use the water will be put.
A given quality of water that is unacceptable for one function may prove satisfactory for another. For example, exceptionally hard water that may be objectionable for laundering and bathing may be satisfactory for sprinkling the lawn. Both the quality of a raw water and its end use must always be determined before it can be treated economically.
It is almost impossible to find a source of water that will meet basic requirements for a public water supply without requiring some form of treatment. Generally, these requirements are that it be free of disease-producing organisms, that it be colorless, clear, odorless and good tasting, that it be non-corrosive and free of objectionable gases and staining minerals, and that it be plentiful and low in cost.
The source of any water supply determines the kinds and amounts of its impurities. There are tremendous variations in the quality of water from area to area. In some cases there are variations in quality even on a day to day basis.
HYDROLOGICAL CYCLE
The Earth's water cycle, or hydrological cycle, is the continuous circulation of moisture and water on our planet. Radiation from the sun evaporates water from the ocean into the atmosphere. The water vapor rises, then collects to form clouds. Under certain conditions, the cloud moisture condenses and falls back to earth. Precipitation that falls upon land areas is the source of essentially all our fresh water supply. Approximately 70% of precipitation is returned to the atmosphere by evaporation and transpiration.
The 30%, of precipitation which is not quickly evaporated either seeps deep into the soil or finds its way into lakes and rivers and eventually flows into the oceans. Surface topography and vegetation, porosity of the soil, the degree of its saturation at the time of a rainfall, and atmospheric conditions are all factors that help to determine the distribution of water after precipitation.
METEORIC CYCLE
When suspended in the atmosphere, water vapor approximates distilled water. It's free from impurities and remains so as long as it stays aloft. When water vapor condenses sufficiently to fall to earth, it comes into contact with atmospheric dust, which may contain minute particles of silica, oxides of iron and other materials, pollen, and some microorganisms. It also absorbs amounts of atmospheric gases in the surrounding air - nitrogen, oxygen, and carbon dioxide. Water dissolves and collects the carbon dioxide to produce carbonic acid. Water's solvent action which permits it to have a cleansing action on the atmosphere continues after it reaches the earth.
SURFACE WATER
Normally when this water reaches the earth, it is slightly acid, corrosive and relatively soft. Once on the ground, it may pick up additional amounts of carbon dioxide from decaying vegetable matter. Equipped with this booster action it acquires even greater potential for dissolving any other impurities on or below the surface.
Surface water contain many impurities - silt, sand and clay - which give them a muddy or cloudy appearance. If run-off to them passes over agricultural land, it may also absorb chemical wastes and toxic refuse from animals. Where water flows sluggishly through swamp land, it may acquire objectionable taste, odor, and plant color. During periods of flooding, these swamps may discharge their decayed vegetation, color, and microorganisms into moving streams and rivers. Surface waters are relatively low in mineral content, but possess a high degree of contamination and are unsafe to use for human consumption unless properly treated.
GROUNDWATER
Water must travel through various strata before becoming groundwater. Below the surface it moves first through the subsoil, the intermediate layer, the capillary fringe, and finally into the groundwater bed. As water seeps into the soil and passes through a limestone stratum, the carbonic acid content, which increases the solvent power of water, becomes neutralized. During this process, however, the water dissolves a certain amount of the mineral matter of the soil or rock with which it comes in contact. Groundwater supplies are usually higher in mineral content than surface waters in the same area. The nature and kinds of impurities vary widely indifferent sections of the country, as the rocks and sand in the soil consist of many kinds of minerals and chemical substances.
Usually, shallow wells will not contain as high an amount of hardness and other dissolved materials as deep wells. Shallow wells may, at times, be turbid and there is the - danger that water may become contaminated with human and animal wastes. Groundwater from deep wells typically contains high concentrations of dissolved minerals. It's usually clear and colorless due to filtration through rock and sand, but may contain various types of pollution, including detergents and industrial wastes, which can travel a considerable distance in water.
Springs provide another source of groundwater. It's a popular belief that spring waters are clear, sparkling, and absolutely pure. In fact, spring waters contain rather large amounts of mineral matter and often show a marked degree of turbidity. As for potability, no spring water should be considered safe to drink unless it is given periodic bacterial examinations.
CONCLUSION
A water supply is the product of its environment. The amount of vegetation and presence of limestone and other minerals directly affect a water supply's hardness and corrosiveness. The sources of water in any given area can serve as a guide to the nature and amounts of impurities which may occur. To further understand why water from different sources varies in quality, it is helpful to know something about basic water chemistry.
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Water Softeners
ION EXCHANGE - THE THEORY
As rain falls through the atmosphere, it often dissolves traces of acidic gases from the air (carbon dioxide, sulfur dioxide, etc.). When the water reaches the ground, it percolates through the soil and dissolves certain components of the soil; the greater the acidity of the rain water, the more soil material it dissolves. Ground waters (wells, springs) as well as surface waters (rivers, lakes, oceans) both contain a certain amount of dissolved matter. Most of these substances are electrolytes, which dissolve in water to form electrically charged particles called ions.
Two of the most commonly occurring ions in natural waters are calcium and magnesium. Both are positively charged ions, called cations, and each carries two unit charges. The presence of these two minerals in natural water causes hardness, which produces a scum or curd with soap, and forms a hard scale in piping, water heaters, steam irons, and even pots and pans. Other cations present in natural waters may include sodium, potassium, iron and other metallic components, but only calcium and magnesium make hard water.
Softening of water by ion exchange consists essentially of passing hard water through a bed of ion exchanger. The exchange rate is so rapid that water can be easily softened at normal flow rates regardless of hardness. However, reasonably clear water must be applied to the exchanger to avoid coating its particles with colloidal or suspended material from the water. Water containing very high amounts of chlorides, sulphates, or iron should be pretreated before applied to a softener.
The most common method used is the sodium cycle operation, in which the calcium and magnesium ions are removed and replaced in solution by sodium. Since the ions involved are all positively charged, the process is known as positive ion exchange or cation exchange. Negatively charged ions remain in the softened water, and softening does not reduce the total dissolved solids.
ION EXCHANGE - THE PROCESS
The cation exchange material used most often is polystyrene resin, which takes the form of spheres or beads; they are insoluble in water and have a negative electrical charge. The standard resin bead is less than 1/32 of an inch in diameter, and is the site where the exchange of ions actually occurs. Cation resin beads attract positively charged ions and hold them until the beads encounter some other cations for which they have a greater affinity.
In the beginning of the water softening cycle, the resin beads are covered with soft sodium (Na+) ions by washing them in a rich sodium chloride brine solution. These beads are contained in a pressurized vessel called a resin tank. The untreated hard water enters the resin tank and passes through the bed of resin.
The negatively charged resin beads have a greater attraction for the two positive charges in each ion of calcium (Ca++) and magnesium (Mg++) than they do for the single positive charge of the sodium (Na+) ion. Therefore, sodium ions on the resin beads will be displaced by the calcium and magnesium ions. In effect, the resin beads exchange the sodium ions for the "hard water" ions, allowing "soft" water to flow from the resin tank.
A softener will continue to give soft water only as long as there are sufficient sodium ions remaining on the resin beads. After a vast number of calcium and magnesium ions from the water have become attached to the resin beads, the exchanger will become exhausted. Before the regeneration cycle begins, the resin bed is backwashed.
In backwashing, water is passed through the resin bed in the opposite direction of normal flow, which flushes suspended matter out of the tank, reducing the possibility of fouling the bed. Backwashing also loosens the resin bed which becomes compacted during the softening cycle.
In the regeneration process, the resin beads are washed with a strong solution of salt water, known as brine solution. Although the resin beads prefer calcium and magnesium ions, the overwhelming concentration of sodium ions overcomes this affinity. the sodium ions in the brine solution force the calcium and magnesium ions off the beads to be discharged as waste. The resin bed is then rinsed to remove the excess brine solution from the tank, and the resin beads are ready to produce soft water again. The frequency of this regeneration process is determined by the capacity of the softener, the hardness of the water, and the water usage.
SOFT WATER QUALITY
The definition of "soft water" allows for trace elements of hardness (less than one grain per gallon of dissolved calcium and magnesium salts). The quality of the softened water, then, refers to the amount of hardness actually remaining.
The amount of salt used to regenerate the exchange material governs both its hardness removal capacity and the water quality. Generally, a salt dosage of 15 pounds per cubic foot of softening material will fully regenerate the mineral. Lesser salt dosages provide only partial regeneration, leaving some hardness in the mineral bed. As the unit is used, the water softened in the upper part of bed exhibits a regenerating effect on the bed below by displacing the calcium and magnesium ions from the beads. The resulting trace of hardness is called "hardness leakage." Since the residual hardness in the bed increases as the salting level decreases, hardness leakage occurs more readily with low salt dosages.
The total dissolved salts (TDS) content of the water also influences the effective softening capacity of a water softener and the hardness leakage. TDS content is the sum of the calcium, magnesium, and sodium salts present in the water, and varies for each water supply. Highly mineralized waters (high TDS) tend to reduce the efficiency of a softener and, therefore should be considered when selecting the salt setting. If the TDS limitations are not observed, excessive hardness leakage can occur.
In situations where the conditioned water is used for general purposes, soft water quality is not critical. Slight traces of hardness don't influence the overall operation and are ignored. When the TDS level is low, lower salt dosages are recommended for general use to provide the greatest operating economy. Although more frequent regenerations would be required, this is of little consequence when the operation is fully automatic.
COMMON CONCERNS REGARDING WATER SOFTENING
Perhaps the most common misconception regarding water conditioning in general is that water is naturally good and is best in an untreated form as nature provides it. While a bubbling spring emitting cool, clear water evokes an image of purity and health, such water often harbors millions of disease-causing bacteria. In fact, only a very small percentage of the earth's fresh water supply is drinkable without some sort of treatment.
Water supports our environment and water treatment aids in providing a healthful, efficient supply. The following questions and answers address some common concerns about the use of conditioned water.
Will drinking water softened by ion exchange be lacking in minerals necessary to good health? No. Primarily, the human body gains the minerals necessary to good health from foods, not from drinking water. The body may absorb the minerals in water, but in most cases, the amount is insignificant. In order to obtain sufficient minerals from water, it would be necessary to drink many gallons a day. In general, water with a high mineral content can't be considered a significant source of minerals.
Is the sodium in softened water harmful to people on restrictive salt diets? This depends on the strictness of the diet itself. In normal dietary considerations, the additional sodium produced by softening is insignificant. In an extremely restrictive diet, one should drink neither hard nor soft water, but demineralized or distilled water. Ultimately, if a patient is on a very restricted regimen, he should follow the physician's instructions regarding water intake.
Does a water softener have any harmful effect in the operation of a septic tank? The backwash and brining effluents from a softener can be discharged into a septic tank that is properly installed and of adequate size. Many states recommend units with a minimum of 500-gallon capacity, but even smaller units may provide adequate in relation to the amount of salt in the water. Tests show that mixtures of sodium, calcium, and magnesium salts as found in regeneration wastes do not hamper the digestion of sludge. Bacteria in the septic tank can become acclimated to the salt environment, with mixed salt concentrations up to 1 having no adverse effects. Even at concentrations of 1.2%, the digestive process slackens but returns to normal in a short time.
Is soft water safe for tropical fish? Yes, soft water is satisfactory for most tropical fish. According to several authorities, both fully soft water and municipally softened water have no toxic effect in an aquarium. When making the change from hard to soft water, it's necessary to make the substitution on a gradual basis. Drastic changes constitute a shock to the delicate systems of tropical fish and would result in fatalities. By replacing about one-fourth of the water in the aquarium at weekly intervals, the fish will suffer no ill effects as a result of the change.
Should softened water be used for watering houseplants or sprinkling the garden or lawn? In watering houseplants, distilled water or rainwater is the best choice. While softened water is not the best for houseplants, it can still be used safely. It is important to water heavily each time so that the minerals deposited in the soil during the previous watering are washed away. This means that containers should be equipped with holes or bottom drains.
For outside sprinkling, the use of softened water is, first and foremost, wasteful. It could also be harmful, especially where the concentration of hardness minerals is heavy. The sodium salts replacing them when the water is softened could retard the growth or even kill the grass.
CONCLUSION
Water softening by ion exchange is the process of removing hard calcium and magnesium ions from water and replacing them with soft sodium ions. This is done by passing the hard water by a resin known as an ion exchanger, which is originally covered with the sodium ions. After a period of use, these sodium ions are depleted, being replaced by calcium and magnesium. The ion exchange material regains its water softening capacity by regeneration, a process in which the extracted hardness ions are replaced by sodium ions.
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Reverse Osmosis Drinking Water
PRINCIPLE
Water in nature is never really perfect and comes to us with impurities from living organisms, suspended substances, and dissolved gases and solids. All of these can affect the taste and appearance of water, not to mention its degree of both safety and hardness. The reverse osmosis process is the same process that many hospitals throughout the country have used to make certain that their pharmaceutical water is of the highest quality.
Your drinking water comes from two main sources: ground waters (wells and springs), and surface water (lakes, streams, rivers, ponds). Both sources are replenished by rain, which dissolves and carries contaminants into surface and underground aquifiers. Some of these contaminants are dioxin, THM's, arsenic, temik, and others which can be dangerous even when measured in the parts-per-billion range.
Over 40 million Americans need to restrict their intake of salt because of high blood pressure, yet almost every water supply has sodium chloride in it. Nitrates and phosphates from fertilizers enter our water supplies as run-off during rain storms and irrigation. Nitrates over 10 parts-per-million may cause intestinal and stomach cancer.
Industrial wastes containing acids, caustics, hydrocarbons, PCB's, TCE's, lead, mercury, and chromium enter our water supplies from dump sites. Excess amounts in our drinking water can lead to nervous disorders, heart disease, and other medical problems. Waste from private septic systems and public disposal plants can lead to dangerous bacteria levels causing virus and bacteriological diseases. You can't see, smell, or taste most dangerous contaminants in your water supply. Although it may take -15 to 20 years before you develop cancer, heart disease, or nervous disorders, perhaps we should take preventive measures to better protect ourselves.
A home R.O. system can substantially reduce dissolved metals such as calcium, magnesium, sodium, and manganese as well as brackish mineral salts, chlorides, and other tastes. The result is cleaner, healthier drinking water
PROCESS
Water contains total dissolved solids. TDS is the measurement by weight of dissolved materials in a given volume of water. If a material will completely dissolve and is not visible in the water, it is part of the total dissolved solids. Reverse osmosis helps to lower the TDS content of water (such as brackish water, saline water, or seawater) since substances such as calcium, magnesium, and sodium cannot readily pass through the semi-permeable membrane, while water can. With the assistance of water pressure, impurities are removed and sent down
the drain.
R.O. is a membrane process that acts as a molecular filter to remove up to 99% of all dissolved minerals. Water passes through the membrane while the dissolved and particulate materials are left behind. As pressure is applied to the concentrated solution, the flow is reversed and water is forced through the membrane from the concentrated side to the dilute side.
Water molecules penetrate the thin cellulose acetate layer of membrane and diffuse through it molecule by molecule. Dissolved salt ions would also diffuse through this layer, except that the solubility of the salt ions in the acetate is much less than that of the water. Thus, the water moves through more rapidly with the result that a separation occurs. The driving force is furnished by both the pressure and the concentration differentials across the thin layer For water, the pressure effect is the most important, and for dissolved mineral ions the concentration difference is most important. Therefore, increases in pressure increase the water flux without a corresponding increase in salt flux.
This process removes most of the dissolved mineral salts, almost all of the particulate matter, and most of the dissolved organic compounds. With reverse osmosis systems, water pressure must be maintained at 40-70 PSI to keep a driving force across the membrane to produce a high clarity, low mineral content water Most R.O. systems operate in the 75-80% conversion range. This means that at 75% conversion, 100 gallons of feed water will produce 75 gallons of pure water and 25 gallons of brine.
Other methods of water treatment, such as water softening and deionization, are also important and it is a combination of these along with R.O. that will normally produce the highest quality water It should be noted that an R.O. system is not a solution for all water problems and that water must be potable-safe for human consumption-before it is put through an R.O. system.
OPERATION
The central part of the R.O. system is the module, which is a pressurized container housing the semi-permeable membrane. Cellulose Triacetate (CTA) membranes are used for chlorinated supplies. Thin Film Composite (TFC) long-life membranes are used for non-chlorinated water supplies. Here, the feedwater will be separated into usable product, called permeate, and waste product, called concentrate. On either side of the module may be two carbon filters, one which pretreats the feedwater, the other which post-treats the permeate.
The product water may then pass into a diaphragm pressure tank which holds the water until it is taken from the discharge faucet by the user. Countertop units, however, normally omit a pressurized storage tank and discharge directly into a non-pressurized container. Most of these systems have a one to five gallon capacity, usually more than adequate for drinking and cooking purposes. Unlike the larger commercial systems, a pump is not required to provide additional pressure. The home R.O. system operates on line or system pressure. No electricity is needed. Its compactness allows the system to fit easily in a small area, often under the kitchen sink or in a cabinet.
The home low pressure R.O. system is designed for use on a potable drinking water supply. In addition, the water should be clear in appearance, not turbid or cloudy, and without offensive taste. If these conditions have not been met, the water will require treatment before putting it through the R.O. system. Good quality feedwater is essential if the system is to function properly and produce a satisfactory product. This is why the carbon filter system is important; it can treat the feedwater for chlorine removal, as well as reduce suspended solids.
Reasonable care must be taken to prevent damage to the R.O. membrane. Factors which can shorten the life of the membrane include scaling, excessive pressure or temperature, and bacteria and chlorine degradation. By exercising care, avoiding extremes in feedwater impurities, and occasionally cleaning and monitoring the system, these problems may be prevented. However, periodically changing the membrane will be necessary.
SIZING
To properly size an R.O. system, determine the water temperature and TDS level and mutiply the percent of loss by the gallon rating of the unit.
A sample of the customer's water is a must when sizing the R.O. system. The main water tests that must be considered are:
Iron content of water- both clear and colored
Total hardness content of the water
Total dissolved solids level in ppm
Chlorine level if present
Source: private well or municipal supply; if municipal, is it surface water?
Water pressure available
SUMMARY
As you know, there are many different contaminants in water - small and large virus particles, pollen particles, metals, dissolved salts, and many, many others. The home reverse osmosis system will remove most of these particles and significantly reduce TDS levels.
The R.O. system provides protection against chemicals and bacteria that enter water supplies at a cost that can be remarkably low much lower than that of bottled water In the final analysis, there are few residences, small businesses or offices, that could not benefit from the installation of a convenient, economical low pressure R.O. system.
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Water Filters
In its passage from the clouds to the tap, water comes in contact with many different substances, including gases, minerals, and organic matter, which are carried either as solid particles or are completely dissolved in water.
A wide variety of filters are available to remove the numerous different contaminants found in water. The specific type of filter required in the home depends, of course, on the kinds of impurities in the water and the amounts present. Basically, filters provide a screening which traps the contaminants in the water as it flows through the filter. If the contaminated particles are large enough, the filter simply traps them. In other cases, a chemical reaction may first be necessary to make the particles of sufficient size to permit their collection on the filter media.
IRON FILTERS (OXIDIZING FILTERS)
Iron/oxidizing filters are used for treatment of waters with medium concentrations of iron, manganese, or hydrogen sulfide. Iron appears in water in both a ferric (visible and insoluble) and a ferrous (dissolved) state. While ferric iron can be simply filtered from the water, ferrous iron must be oxidized, converting it to the suspended ferric state, in order to be filtered out. The media used in these iron filters is manganese green sand, which is capable of oxidizing dissolved iron and manganese, allowing them to be filtered out in the same tank.
Iron/oxidizing filters must be periodically backwashed, to flush away accumulated deposits, then regenerated with a potassium permanganate solution. After rinsing, the filter is again ready for operation. When such filters are used, they are, in most cases, placed ahead of a softener.
SAND FILTERS
The sand filter is used for the simple filtration from water of visible dirt or suspended matter (turbidity) due to silt, sand, organic matter, and rust type particles. These units use sand or gravel as the filter media, and are effective in removing sediment and cloudiness from water, except when such turbidity is due to extremely fine particles. Sand filters must be backwashed periodically to clean the suspended matter from the filter media and flush it down the drain.
ACTIVATED CARBON FILTERS
Activated carbon filters are primarily used to remove objectionable tastes and odors from water, and are effective in removing chlorine. These filters contain activated carbon, a form of charcoal with high adsorptive qualities. Adsorption is defined as the adhesion of a gas, vapor, or dissolved material on the surface of a solid. As water is brought into contact with these activated carbon particles, the taste and odor constituents are retained in the carbon, resulting in a taste and odor free water. Activated carbon filters have also proven effective in the removal of inorganics such as trihalomethanes. The granulated filters must be periodically backwashed, and the cartridges cleaned or replaced from time to time.
NEUTRALIZING FILTERS
To increase the pH value of a water, which is to decrease the acidity and thus its corrosive nature, a neutralizing filter is recommended. The presence of large amounts of free carbon dioxide gas in solution (carbonic acid) renders a water acid in character, which can cause corrosion damage to the metal components of a water system, including the water pump, piping (iron, galvanized brass, and even copper), tank, water heater, and fixtures. Neutralizing filters contain a bed of materials such as calcite and magnesia. As water passes through this bed, the carbonic acid is neutralized and a small amount of the bed is dissolved. As a result, the water becomes more alkaline (higher pH value) and thus less corrosive. A neutralizer requires occasional backwashing to loosen the material and clean the bed. From time to time, additional material must be added to the bed to replace that which is dissolved.
CHEMICAL FEED PUMPS
Chemical feed pumps are used to inject corrective solutions into a water supply. For example, soda ash, a highly alkaline compound, is often added in solution to a water supply as an alternate method for reducing acidity. Chemical feed pumps can be wired to operate in conjunction with an electrically operated well or water pump, and multiple solutions can be fed into a water system with a single pump unit when applicable. Chemical feed storage tanks are occasionally an attractive solution to water treatment problems because several chemicals can be mixed and fed together, thus solving several problems at once (e.g. chlorine for purification and acid neutralizer for pH control). Chemical feed storage tanks must be refilled with the chemical compound periodically.
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Water Chemistry
Water is a colorless, odorless, and tasteless substance which exists naturally as either solid, liquid, or gas. Water is a very stable compound which can withstand extreme temperatures before decomposing into individual atoms. In the universe there are two prime ingredients: matter and energy. All matter can be classified as compounds, elements, or mixtures. An element can be defined as a substance which cannot be decomposed chemically into a simpler substance. To understand water chemistry, it is important to know how atoms are held together to form compounds.
ATOM
A molecule may consist of one atom or two or more similar atoms. An atom is matter in its simplest form and is inconceivably small. Atoms consist of protons, neutrons, and electrons. Protons are positively charged particles, neutrons have no charge, and electrons are negatively charged and considerably smaller. Protons and electrons determine chemical properties of an atom, while neutrons merely add mass or weight to the atomic unit.
Most atoms have a nucleus formed by neutrons and protons. The number of protons in an atom equals the number of electrons. The number of neutrons equals the mass number minus the atomic number. An atom is electrically neutral. Hydrogen is the smallest and simplest atom, consisting of one proton and one electron orbiting around it. Other atoms have two or more orbiting electrons; the most complex natural element, uranium, has 92.
ELEMENTS AND ISOTOPES
The number of protons in an atom's nucleus is the atomic number, and determines which element it is. Atomic mass units relate all atoms to each other by mass and were adopted to simplify measurement of the atom's particles.
Not all atoms of a particular element are identical. Atoms may vary in their atomic weight (the number of protons and neutrons in the nucleus). Since atoms must remain electrically neutral, their atomic weight can change only by adding neutrons. Atoms of the same element, but with different atomic weights are called isotopes. All known elements exist in two or more isotopic forms. Hydrogen, for example, has three natural isotopes: protium, deuterium, and tritium. All three are common in water.
COMPOUNDS AND MIXTURES
A compound is a substance cornposed of two or more chemically bonded atoms or elements. It has a definite and unvarying composition. The chemical properties of a given compound are different from those of its constituent elements. Water, a typical compound, is composed of two elements, hydrogen and oxygen, in definite proportions. It is a uniform substance whether one is considering a drop, a glass, or a lake of it. Thus, a compound is homogenous.
In sharp contrast, a mixture will vary in the amounts of the ingredients it contains. No exact ratio of substances is necessary to constitute a mixture. At the same time, the ingredients in a mixture continue to
maintain their essential properties. A mixture may have varying proportions of its ingredients in different parts of the sample and is therefore heterogeneous.
Inert elements are those which may not combine with others. Their outermost orbits contain eight electrons, except for helium, which has two. These orbits are considered full. Atoms with "unfilled" orbits can form compounds, those with "filled" cannot. Helium and neon are examples of inert elements.
VALENCE
Atoms tend to form stable compounds by shifting their electronic structure. This is called valence bonding. An element's valance number tells how many of its electrons participate in forming a compound. An atom's valence electrons are those occurring beyond the last filled orbit (free electrons). These may participate in a chemical reaction. In a compound which is composed of two elements, one element will "give up" a free electron to another element and develop a positive charge. The element accepting an electron will develop a negative charge. These charged atoms are called ions.
CHEMICAL BONDING
toms are held together to form compounds by many types of chemical bonds. When atoms form compounds through electron transfer, they are held together by ionic bonds. Covalent bonding occurs when atoms "share" electrons. For example, oxygen needs two electrons to complete its outermost orbit, while hydrogen needs only one. Water, whose chemical formula is H2O is an example of covalent bonding. Common gases, such as oxygen, hydrogen, and nitrogen, form molecules by sharing electrons.
OXIDATION AND REDUCTION
Chemical reactions occur when atoms combine to form new elements or when elements break down into individual atoms. Originally, the term oxidation signified a chemical reaction involving the addition of oxygen to a compound. Similarly, the removal of oxygen was defined as reduction. Oxidation now means an increase in positive valence, a decrease in negative valence. Reduction, which goes on simultaneously, refers to a decrease in positive valence and an increase in negative valence. The substance that loses electrons is oxidized and is referred to as a reducing agent; the substance that gains electrons is reduced and is called the oxidizing agent. Oxidation and reduction always occur together and in equal amounts.
IONS
Water's chemical nature causes the splitting of many molecules. Certain substances called electrolytes, which dissolve in distilled water, increase its conductivity and form electrically charged particles called ions. An ion can be defined as an electrically charged atom or group of atoms in solution.
Because the solution as a whole is electrically neutral, there are two types of ions, one charged negative
ly, the other positively. Positively charged ions are called cations, negatively charged ions are called anions.
When a molecule dissociates (ionizes) in water, the total charge before and after the reaction must be the same. This condition is called electroneutrality. The sum of the positive charges equals the sum of the negative charges. A reaction not in equilibrium will adjust itself under stress until equilibrium is reestablished. Changing the temperature, pressure or concentration of elements in a compound will upset its equilibrium and set off a chemical reaction. Water treatment uses this principle to change the chemical nature of a particular water supply.
Many impurities exist as ions in natural waters (calcium, magnesium, sodium, iron, and manganese as cations, and bicarbonate, chloride, sulfate, nitrate, and carbonate as anions). These electrically charged dissolved particles make water a good conductor of electricity. Conversely, pure water has a high electrical resistance, which is frequently used as a measure of its purity.
A number of methods have been developed for the reduction of these ionic impurities from water because many of them interfere with the beneficial uses of water. These are: (a) distillation, (b) precipitation and separation, (c) ion exchange, and (d) membrane separation.
ACIDS, BASES, AND SALTS
Briefly, acids can be defined as compounds which release hydrogen ions in solution. All acids contain hydrogen. Bases are substances which can release hydroxide ions. Salts are substances containing both metallic and non-metallic ions, and are classified as normal, acid, and basic.
When equal weights of an acid are combined with a base, the free hydrogen and hydroxide ions will combine to form water until an equilibrium is achieved. This process, called neutralization, is important in water chemistry. Rain, an acid solution, is quickly neutralized as it reaches limestone in soil and bedrock. If rain were not neutralized by bases in the soil and rock, all water obtained from precipitation would be acidic.
Another important characteristic of a solution is its pH, which indicates the relative concentration of hydrogen ions; and that determines whether a substance is acidic or basic. The pH also gives the solution's relative acidity or alkalinity.
CONCLUSION
A solution consists of a solvent and a solute. A solvent promotes dissolving; the solute is the substance being dissolved. Water is the universal solvent, and an almost infinite variety of solute substances and concentrations can exist in water. Among the various contaminants to be found are hardness compounds, chlorides, sulfates, fluorides, iron, sodium, silica, and others. Each has unique properties, and will be discussed in further detail
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Water-Science Glossary of Terms
A
acequia--acequias were important forms of irrigation in the development of agriculture in the American Southwest. The proliferation of cotton, pecans and green chile as major agricultual staples owe their progress to the acequia system.
acid--a substance that has a pH of less than 7, which is neutral. Specifically, an acid has more free hydrogen ions (H+) than hydroxyl ions (OH-).
acre-foot (acre-ft)--the volume of water required to cover 1 acre of land (43,560 square feet) to a depth of 1 foot. Equal to 325,851 gallons or 1,233 cubic meters.
alkaline--sometimes water or soils contain an amount of alkali (strongly basic) substances sufficient to raise the pH value above 7.0 and be harmful to the growth of crops.
alkalinity--the capacity of water for neutralizing an acid solution.
alluvium--deposits of clay, silt, sand, gravel, or other particulate material that has been deposited by a stream or other body of running water in a streambed, on a flood plain, on a delta, or at the base of a mountain.
appropriation doctrine--the system for allocating water to private individuals used in most Western states. The doctrine of Prior Appropriation was in common use throughout the arid west as early settlers and miners began to develop the land. The prior appropriation doctrine is based on the concept of "First in Time, First in Right." The first person to take a quantity of water and put it to Beneficial Use has a higher priority of right than a subsequent user. Under drought conditions, higher priority users are satisfied before junior users receive water. Appropriative rights can be lost through nonuse; they can also be sold or transferred apart from the land. Contrasts with Riparian Water Rights.
aquaculture--farming of plants and animals that live in water, such as fish, shellfish, and algae.
aqueduct--a pipe, conduit, or channel designed to transport water from a remote source, usually by gravity.
aquifer--a geologic formation(s) that is water bearing. A geological formation or structure that stores and/or transmits water, such as to wells and springs. Use of the term is usually restricted to those water-bearing formations capable of yielding water in sufficient quantity to constitute a usable supply for people's uses.
aquifer (confined)--soil or rock below the land surface that is saturated with water. There are layers of impermeable material both above and below it and it is under pressure so that when the aquifer is penetrated by a well, the water will rise above the top of the aquifer.
aquifer (unconfined)--an aquifer whose upper water surface (water table) is at atmospheric pressure, and thus is able to rise and fall.
artesian water--ground water that is under pressure when tapped by a well and is able to rise above the level at which it is first encountered. It may or may not flow out at ground level. The pressure in such an aquifer commonly is called artesian pressure, and the formation containing artesian water is an artesian aquifer or confined aquifer.
artificial recharge--an process where water is put back into ground-water storage from surface-water supplies such as irrigation, or induced infiltration from streams or wells.
B
base flow--streamflow coming from ground-water seepage into a stream.
base--a substance that has a pH of more than 7, which is neutral. A base has less free hydrogen ions (H+) than hydroxyl ions (OH-).
bedrock--the solid rock beneath the soil and superficial rock. A general term for solid rock that lies beneath soil, loose sediments, or other unconsolidated material.
C
capillary action--the means by which liquid moves through the porous spaces in a solid, such as soil, plant roots, and the capillary blood vessels in our bodies due to the forces of adhesion, cohesion, and surface tension. Capillary action is essential in carrying substances and nutrients from one place to another in plants and animals.
commercial water use--water used for motels, hotels, restaurants, office buildings, other commercial facilities, and institutions. Water for commercial uses comes both from public-supplied sources, such as a county water department, and self-supplied sources, such as local wells.
condensation--the process of water vapor in the air turning into liquid water. Water drops on the outside of a cold glass of water are condensed water. Condensation is the opposite process of evaporation.
consumptive use--that part of water withdrawn that is evaporated, transpired by plants, incorporated into products or crops, consumed by humans or livestock, or otherwise removed from the immediate water environment. Also referred to as water consumed.
conveyance loss--water that is lost in transit from a pipe, canal, or ditch by leakage or evaporation. Generally, the water is not available for further use; however, leakage from an irrigation ditch, for example, may percolate to a ground-water source and be available for further use.
cubic feet per second (cfs)--a rate of the flow, in streams and rivers, for example. It is equal to a volume of water one foot high and one foot wide flowing a distance of one foot in one second. One "cfs" is equal to 7.48 gallons of water flowing each second. As an example, if your car's gas tank is 2 feet by 1 foot by 1 foot (2 cubic feet), then gas flowing at a rate of 1 cubic foot/second would fill the tank in two seconds.
D
desalinization--the removal of salts from saline water to provide freshwater. This method is becoming a more popular way of providing freshwater to populations.
discharge--the volume of water that passes a given location within a given period of time. Usually expressed in cubic feet per second.
domestic water use--water used for household purposes, such as drinking, food preparation, bathing, washing clothes, dishes, and dogs, flushing toilets, and watering lawns and gardens. About 85% of domestic water is delivered to homes by a public-supply facility, such as a county water department. About 15% of the Nation's population supply their own water, mainly from wells.
drainage basin--land area where precipitation runs off into streams, rivers, lakes, and reservoirs. It is a land feature that can be identified by tracing a line along the highest elevations between two areas on a map, often a ridge. Large drainage basins, like the area that drains into the Mississippi River contain thousands of smaller drainage basins. Also called a "watershed."
drip irrigation--a common irrigation method where pipes or tubes filled with water slowly drip onto crops. Drip irrigation is a low-pressure method of irrigation and less water is lost to evaporation than high-pressure spray irrigation.
drawdown--a lowering of the ground-water surface caused by pumping.
E
effluent--water that flows from a sewage treatment plant after it has been treated.
erosion--the process in which a material is worn away by a stream of liquid (water) or air, often due to the presence of abrasive particles in the stream.
estuary--a place where fresh and salt water mix, such as a bay, salt marsh, or where a river enters an ocean.
evaporation--the process of liquid water becoming water vapor, including vaporization from water surfaces, land surfaces, and snow fields, but not from leaf surfaces. See transpiration
evapotranspiration--the sum of evaporation and transpiration.
F
flood--An overflow of water onto lands that are used or usable by man and not normally covered by water. Floods have two essential characteristics: The inundation of land is temporary; and the land is adjacent to and inundated by overflow from a river, stream, lake, or ocean.
flood, 100-year--A 100-year flood does not refer to a flood that occurs once every 100 years, but to a flood level with a 1 percent chance of being equaled or exceeded in any given year.
flood plain--a strip of relatively flat and normally dry land alongside a stream, river, or lake that is covered by water during a flood.
flood stage--The elevation at which overflow of the natural banks of a stream or body of water begins in the reach or area in which the elevation is measured.
flowing well/spring--a well or spring that taps ground water under pressure so that water rises without pumping. If the water rises above the surface, it is known as a flowing well.
freshwater, freshwater--water that contains less than 1,000 milligrams per liter (mg/L) of dissolved solids; generally, more than 500 mg/L of dissolved solids is undesirable for drinking and many industrial uses.
G
gage height--the height of the water surface above the gage datum (zero point). Gage height is often used interchangeably with the more general term, stage, although gage height is more appropriate when used with a gage reading.
gaging station--a site on a stream, lake, reservoir or other body of water where observations and hydrologic data are obtained. The U.S. Geological Survey measures stream discharge at gaging stations.
geyser--a geothermal feature of the Earth where there is an opening in the surface that contains superheated water that periodically erupts in a shower of water and steam.
giardiasis--a disease that results from an infection by the protozoan parasite Giardia Intestinalis, caused by drinking water that is either not filtered or not chlorinated. The disorder is more prevalent in children than in adults and is characterized by abdominal discomfort, nausea, and alternating constipation and diarrhea.
glacier--a huge mass of ice, formed on land by the compaction and recrystallization of snow, that moves very slowly downslope or outward due to its own weight.
greywater--wastewater from clothes washing machines, showers, bathtubs, hand washing, lavatories and sinks.
ground water--(1) water that flows or seeps downward and saturates soil or rock, supplying springs and wells. The upper surface of the saturate zone is called the water table. (2) Water stored underground in rock crevices and in the pores of geologic materials that make up the Earth's crust.
ground water, confined--ground water under pressure significantly greater than atmospheric, with its upper limit the bottom of a bed with hydraulic conductivity distinctly lower than that of the material in which the confined water occurs.
ground-water recharge--inflow of water to a ground-water reservoir from the surface. Infiltration of precipitation and its movement to the water table is one form of natural recharge. Also, the volume of water added by this process.
ground water, unconfined--water in an aquifer that has a water table that is exposed to the atmosphere.
H
hardness--a water-quality indication of the concentration of alkaline salts in water, mainly calcium and magnesium. If the water you use is "hard" then more soap, detergent or shampoo is necessary to raise a lather.
headwater(s)--(1) the source and upper reaches of a stream; also the upper reaches of a reservoir. (2) the water upstream from a structure or point on a stream. (3) the small streams that come together to form a river. Also may be thought of as any and all parts of a river basin except the mainstream river and main tributaries.
hydroelectric power water use--the use of water in the generation of electricity at plants where the turbine generators are driven by falling water.
hydrologic cycle--the cyclic transfer of water vapor from the Earth's surface via evapotranspiration into the atmosphere, from the atmosphere via precipitation back to earth, and through runoff into streams, rivers, and lakes, and ultimately into the oceans.
I
impermeable layer--a layer of solid material, such as rock or clay, which does not allow water to pass through.
industrial water use--water used for industrial purposes in such industries as steel, chemical, paper, and petroleum refining. Nationally, water for industrial uses comes mainly (80%) from self-supplied sources, such as a local wells or withdrawal points in a river, but some water comes from public-supplied sources, such as the county/city water department.
infiltration--flow of water from the land surface into the subsurface.
injection well--refers to a well constructed for the purpose of injecting treated wastewater directly into the ground. Wastewater is generally forced (pumped) into the well for dispersal or storage into a designated aquifer. Injection wells are generally drilled into aquifers that don't deliver drinking water, unused aquifers, or below freshwater levels.
irrigation--the controlled application of water for agricultural purposes through manmade systems to supply water requirements not satisfied by rainfall.
irrigation water use--water application on lands to assist in the growing of crops and pastures or to maintain vegetative growth in recreational lands, such as parks and golf courses.
K
kilogram--one thousand grams.
kilowatthour (KWH)--a power demand of 1,000 watts for one hour. Power company utility rates are typically expressed in cents per kilowatt-hour.
L
leaching--the process by which soluble materials in the soil, such as salts, nutrients, pesticide chemicals or contaminants, are washed into a lower layer of soil or are dissolved and carried away by water.
lentic waters--ponds or lakes (standing water).
levee--a natural or manmade earthen barrier along the edge of a stream, lake, or river. Land alongside rivers can be protected from flooding by levees.
livestock water use--water used for livestock watering, feed lots, dairy operations, fish farming, and other on-farm needs.
lotic waters--flowing waters, as in streams and rivers.
M
maximum contaminant level (MCL)--the designation given by the U.S. Environmental Protection Agency (EPA) to water-quality standards promulgated under the Safe Drinking Water Act. The MCL is the greatest amount of a contaminant that can be present in drinking water without causing a risk to human health.
milligram (mg)--One-thousandth of a gram.
milligrams per liter (mg/l)--a unit of the concentration of a constituent in water or wastewater. It represents 0.001 gram of a constituent in 1 liter of water. It is approximately equal to one part per million (PPM).
million gallons per day (Mgd)--a rate of flow of water equal to 133,680.56 cubic feet per day, or 1.5472 cubic feet per second, or 3.0689 acre-feet per day. A flow of one million gallons per day for one year equals 1,120 acre-feet (365 million gallons).
mining water use--water use during quarrying rocks and extracting minerals from the land.
municipal water system--a water system that has at least five service connections or which regularly serves 25 individuals for 60 days; also called a public water system
N
nephelometric turbidity unit (NTU)--unit of measure for the turbidity of water. Essentially, a measure of the cloudiness of water as measured by a nephelometer. Turbidity is based on the amount of light that is reflected off particles in the water.
non-point source (NPS) pollution--pollution discharged over a wide land area, not from one specific location. These are forms of diffuse pollution caused by sediment, nutrients, organic and toxic substances originating from land-use activities, which are carried to lakes and streams by surface runoff. Non-point source pollution is contamination that occurs when rainwater, snowmelt, or irrigation washes off plowed fields, city streets, or suburban backyards. As this runoff moves across the land surface, it picks up soil particles and pollutants, such as nutrients and pesticides.
O
organic matter--plant and animal residues, or substances made by living organisms. All are based upon carbon compounds.
osmosis--the movement of water molecules through a thin membrane. The osmosis process occurs in our bodies and is also one method of desalinizing saline water.
outfall--the place where a sewer, drain, or stream discharges; the outlet or structure through which reclaimed water or treated effluent is finally discharged to a receiving water body.
oxygen demand--the need for molecular oxygen to meet the needs of biological and chemical processes in water. Even though very little oxygen will dissolve in water, it is extremely important in biological and chemical processes.
P
pH--a measure of the relative acidity or alkalinity of water. Water with a pH of 7 is neutral; lower pH levels indicate increasing acidity, while pH levels higher than 7 indicate increasingly basic solutions.
particle size--the diameter, in millimeters, of suspended sediment or bed material. Particle-size classifications are:
[1] Clay—0.00024-0.004 millimeters (mm);
[2] Silt—0.004-0.062 mm;
[3] Sand—0.062-2.0 mm; and
[4] Gravel—2.0-64.0 mm.
parts per billion--the number of "parts" by weight of a substance per billion parts of water. Used to measure extremely small concentrations.
parts per million--the number of "parts" by weight of a substance per million parts of water. This unit is commonly used to represent pollutant concentrations.
pathogen--a disease-producing agent; usually applied to a living organism. Generally, any viruses, bacteria, or fungi that cause disease.
peak flow--the maximum instantaneous discharge of a stream or river at a given location. It usually occurs at or near the time of maximum stage.
per capita use--the average amount of water used per person during a standard time period, generally per day.
percolation--(1) The movement of water through the openings in rock or soil. (2) the entrance of a portion of the streamflow into the channel materials to contribute to ground water replenishment.
permeability--the ability of a material to allow the passage of a liquid, such as water through rocks. Permeable materials, such as gravel and sand, allow water to move quickly through them, whereas unpermeable material, such as clay, don't allow water to flow freely.
point-source pollution--water pollution coming from a single point, such as a sewage-outflow pipe.
polychlorinated biphenyls (PCBs)--a group of synthetic, toxic industrial chemical compounds once used in making paint and electrical transformers, which are chemically inert and not biodegradable. PCBs were frequently found in industrial wastes, and subsequently found their way into surface and ground waters. As a result of their persistence, they tend to accumulate in the environment. In terms of streams and rivers, PCBs are drawn to sediment, to which they attach and can remain virtually indefinitely. Although virtually banned in 1979 with the passage of the Toxic Substances Control Act, they continue to appear in the flesh of fish and other animals.
porosity--a measure of the water-bearing capacity of subsurface rock. With respect to water movement, it is not just the total magnitude of porosity that is important, but the size of the voids and the extent to which they are interconnected, as the pores in a formation may be open, or interconnected, or closed and isolated. For example, clay may have a very high porosity with respect to potential water content, but it constitutes a poor medium as an aquifer because the pores are usually so small.
potable water--water of a quality suitable for drinking.
precipitation--rain, snow, hail, sleet, dew, and frost.
primary wastewater treatment--the first stage of the wastewater-treatment process where mechanical methods, such as filters and scrapers, are used to remove pollutants. Solid material in sewage also settles out in this process.
prior appropriation doctrine--the system for allocating water to private individuals used in most Western states. The doctrine of Prior Appropriation was in common use throughout the arid West as early settlers and miners began to develop the land. The prior appropriation doctrine is based on the concept of "First in Time, First in Right." The first person to take a quantity of water and put it to beneficial use has a higher priority of right than a subsequent user. The rights can be lost through nonuse; they can also be sold or transferred apart from the land. Contrasts with riparian water rights.
public supply--water withdrawn by public governments and agencies, such as a county water department, and by private companies that is then delivered to users. Public suppliers provide water for domestic, commercial, thermoelectric power, industrial, and public water users. Most people's household water is delivered by a public water supplier. The systems have at least 15 service connections (such as households, businesses, or schools) or regularly serve at least 25 individuals daily for at least 60 days out of the year.
public water use--water supplied from a public-water supply and used for such purposes as firefighting, street washing, and municipal parks and swimming pools.
R
rating curve--A drawn curve showing the relation between gage height and discharge of a stream at a given gaging station.
recharge--water added to an aquifer. For instance, rainfall that seeps into the ground.
reclaimed wastewater--treated wastewater that can be used for beneficial purposes, such as irrigating certain plants.
recycled water--water that is used more than one time before it passes back into the natural hydrologic system.
reservoir--a pond, lake, or basin, either natural or artificial, for the storage, regulation, and control of water.
return flow--(1) That part of a diverted flow that is not consumptively used and returned to its original source or another body of water. (2) (Irrigation) Drainage water from irrigated farmlands that re-enters the water system to be used further downstream.
returnflow (irrigation)--irrigation water that is applied to an area and which is not consumed in evaporation or transpiration and returns to a surface stream or aquifer.
reverse osmosis--(1) (Desalination) The process of removing salts from water using a membrane. With reverse osmosis, the product water passes through a fine membrane that the salts are unable to pass through, while the salt waste (brine) is removed and disposed. This process differs from electrodialysis, where the salts are extracted from the feedwater by using a membrane with an electrical current to separate the ions. The positive ions go through one membrane, while the negative ions flow through a different membrane, leaving the end product of freshwater. (2) (Water Quality) An advanced method of water or wastewater treatment that relies on a semi-permeable membrane to separate waters from pollutants. An external force is used to reverse the normal osmotic process resulting in the solvent moving from a solution of higher concentration to one of lower concentration.
riparian water rights--the rights of an owner whose land abuts water. They differ from state to state and often depend on whether the water is a river, lake, or ocean. The doctrine of riparian rights is an old one, having its origins in English common law. Specifically, persons who own land adjacent to a stream have the right to make reasonable use of the stream. Riparian users of a stream share the streamflow among themselves, and the concept of priority of use (Prior Appropriation Doctrine) is not applicable. Riparian rights cannot be sold or transferred for use on nonriparian land.
river--A natural stream of water of considerable volume, larger than a brook or creek.
runoff--(1) That part of the precipitation, snow melt, or irrigation water that appears in uncontrolled surface streams, rivers, drains or sewers. Runoff may be classified according to speed of appearance after rainfall or melting snow as direct runoff or base runoff, and according to source as surface runoff, storm interflow, or ground-water runoff. (2) The total discharge described in (1), above, during a specified period of time. (3) Also defined as the depth to which a drainage area would be covered if all of the runoff for a given period of time were uniformly distributed over it.
S
saline water--water that contains significant amounts of dissolved solids.
Here are our parameters for saline water:
Fresh water - Less than 1,000 parts per million (ppm)
Slightly saline water - From 1,000 ppm to 3,000 ppm
Moderatly saline water - From 3,000 ppm to 10,000 ppm
Highly saline water - From 10,000 ppm to 35,000 ppm
secondary wastewater treatment--treatment (following primary wastewater treatment) involving the biological process of reducing suspended, colloidal, and dissolved organic matter in effluent from primary treatment systems and which generally removes 80 to 95 percent of the Biochemical Oxygen Demand (BOD) and suspended matter. Secondary wastewater treatment may be accomplished by biological or chemical-physical methods. Activated sludge and trickling filters are two of the most common means of secondary treatment. It is accomplished by bringing together waste, bacteria, and oxygen in trickling filters or in the activated sludge process. This treatment removes floating and settleable solids and about 90 percent of the oxygen-demanding substances and suspended solids. Disinfection is the final stage of secondary treatment.
sediment--usually applied to material in suspension in water or recently deposited from suspension. In the plural the word is applied to all kinds of deposits from the waters of streams, lakes, or seas.
sedimentary rock--rock formed of sediment, and specifically: (1) sandstone and shale, formed of fragments of other rock transported from their sources and deposited in water; and (2) rocks formed by or from secretions of organisms, such as most limestone. Many sedimentary rocks show distinct layering, which is the result of different types of sediment being deposited in succession.
sedimentation tanks--wastewater tanks in which floating wastes are skimmed off and settled solids are removed for disposal.
self-supplied water--water withdrawn from a surface- or ground-water source by a user rather than being obtained from a public supply. An example would be homeowners getting their water from their own well.
seepage--(1) The slow movement of water through small cracks, pores, Interstices, etc., of a material into or out of a body of surface or subsurface water. (2) The loss of water by infiltration into the soil from a canal, ditches, laterals, watercourse, reservoir, storage facilities, or other body of water, or from a field.
septic tank--a tank used to detain domestic wastes to allow the settling of solids prior to distribution to a leach field for soil absorption. Septic tanks are used when a sewer line is not available to carry them to a treatment plant. A settling tank in which settled sludge is in immediate contact with sewage flowing through the tank, and wherein solids are decomposed by anaerobic bacterial action.
settling pond (water quality)--an open lagoon into which wastewater contaminated with solid pollutants is placed and allowed to stand. The solid pollutants suspended in the water sink to the bottom of the lagoon and the liquid is allowed to overflow out of the enclosure.
sewage treatment plant--a facility designed to receive the wastewater from domestic sources and to remove materials that damage water quality and threaten public health and safety when discharged into receiving streams or bodies of water. The substances removed are classified into four basic areas:
[1] greases and fats;
[2] solids from human waste and other sources;
[3] dissolved pollutants from human waste and decomposition products; and
[4] dangerous microorganisms.
Most facilities employ a combination of mechanical removal steps and bacterial decomposition to achieve the desired results. Chlorine is often added to discharges from the plants to reduce the danger of spreading disease by the release of pathogenic bacteria.
sewer--a system of underground pipes that collect and deliver wastewater to treatment facilities or streams.
sinkhole--a depression in the Earth's surface caused by dissolving of underlying limestone, salt, or gypsum. Drainage is provided through underground channels that may be enlarged by the collapse of a cavern roof.
solute--a substance that is dissolved in another substance, thus forming a solution.
solution--a mixture of a solvent and a solute. In some solutions, such as sugar water, the substances mix so thoroughly that the solute cannot be seen. But in other solutions, such as water mixed with dye, the solution is visibly changed.
solvent--a substance that dissolves other substances, thus forming a solution. Water dissolves more substances than any other, and is known as the "universal solvent".
specific conductance--a measure of the ability of water to conduct an electrical current as measured using a 1-cm cell and expressed in units of electrical conductance, i.e., Siemens per centimeter at 25 degrees Celsius. Specific conductance can be used for approximating the total dissolved solids content of water by testing its capacity to carry an electrical current. In water quality, specific conductance is used in ground water monitoring as an indication of the presence of ions of chemical substances that may have been released by a leaking landfill or other waste storage or disposal facility. A higher specific conductance in water drawn from downgradient wells when compared to upgradient wells indicates possible contamination from the facility.
spray irrigation--an common irrigation method where water is shot from high-pressure sprayers onto crops. Because water is shot high into the air onto crops, some water is lost to evaporation.
storm sewer--a sewer that carries only surface runoff, street wash, and snow melt from the land. In a separate sewer system, storm sewers are completely separate from those that carry domestic and commercial wastewater (sanitary sewers).
stream--a general term for a body of flowing water; natural water course containing water at least part of the year. In hydrology, it is generally applied to the water flowing in a natural channel as distinct from a canal.
streamflow--the water discharge that occurs in a natural channel. A more general term than runoff, streamflow may be applied to discharge whether or not it is affected by diversion or regulation.
subsidence--a dropping of the land surface as a result of ground water being pumped. Cracks and fissures can appear in the land. Subsidence is virtually an irreversible process.
surface tension--the attraction of molecules to each other on a liquid's surface. Thus, a barrier is created between the air and the liquid.
surface water--water that is on the Earth's surface, such as in a stream, river, lake, or reservoir.
suspended sediment--very fine soil particles that remain in suspension in water for a considerable period of time without contact with the bottom. Such material remains in suspension due to the upward components of turbulence and currents and/or by suspension.
suspended-sediment concentration--the ratio of the mass of dry sediment in a water-sediment mixture to the mass of the water-sediment mixture. Typically expressed in milligrams of dry sediment per liter of water-sediment mixture.
suspended-sediment discharge--the quantity of suspended sediment passing a point in a stream over a specified period of time. When expressed in tons per day, it is computed by multiplying water discharge (in cubic feet per second) by the suspended-sediment concentration (in milligrams per liter) and by the factor 0.0027.
suspended solids--solids that are not in true solution and that can be removed by filtration. Such suspended solids usually contribute directly to turbidity. Defined in waste management, these are small particles of solid pollutants that resist separation by conventional methods.
T
tertiary wastewater treatment--selected biological, physical, and chemical separation processes to remove organic and inorganic substances that resist conventional treatment practices; the additional treatment of effluent beyond that of primary and secondary treatment methods to obtain a very high quality of effluent. The complete wastewater treatment process typically involves a three-phase process: (1) First, in the primary wastewater treatment process, which incorporates physical aspects, untreated water is passed through a series of screens to remove solid wastes; (2) Second, in the secondary wastewater treatment process, typically involving biological and chemical processes, screened wastewater is then passed a series of holding and aeration tanks and ponds; and (3) Third, the tertiary wastewater treatment process consists of flocculation basins, clarifiers, filters, and chlorine basins or ozone or ultraviolet radiation processes.
thermal pollution--a reduction in water quality caused by increasing its temperature, often due to disposal of waste heat from industrial or power generation processes. Thermally polluted water can harm the environment because plants and animals can have a hard time adapting to it.
thermoelectric power water use--water used in the process of the generation of thermoelectric power. Power plants that burn coal and oil are examples of thermoelectric-power facilities.
transmissibility (ground water)--the capacity of a rock to transmit water under pressure. The coefficient of transmissibility is the rate of flow of water, at the prevailing water temperature, in gallons per day, through a vertical strip of the aquifer one foot wide, extending the full saturated height of the aquifer under a hydraulic gradient of 100-percent. A hydraulic gradient of 100-percent means a one foot drop in head in one foot of flow distance.
transpiration--process by which water that is absorbed by plants, usually through the roots, is evaporated into the atmosphere from the plant surface, such as leaf pores. See evapotranspiration.
Tributary--a smaller river or stream that flows into a larger river or stream. Usually, a number of smaller tributaries merge to form a river.
turbidity--the amount of solid particles that are suspended in water and that cause light rays shining through the water to scatter. Thus, turbidity makes the water cloudy or even opaque in extreme cases. Turbidity is measured in nephelometric turbidity units (NTU).
U
unsaturated zone--the zone immediately below the land surface where the pores contain both water and air, but are not totally saturated with water. These zones differ from an aquifer, where the pores are saturated with water.
W
wastewater--water that has been used in homes, industries, and businesses that is not for reuse unless it is treated.
wastewater-treatment return flow--water returned to the environment by wastewater-treatment facilities.
water cycle--the circuit of water movement from the oceans to the atmosphere and to the Earth and return to the atmosphere through various stages or processes such as precipitation, interception, runoff, infiltration, percolation, storage, evaporation, and transportation.
water quality--a term used to describe the chemical, physical, and biological characteristics of water, usually in respect to its suitability for a particular purpose.
water table--the top of the water surface in the saturated part of an aquifer.
water use--water that is used for a specific purpose, such as for domestic use, irrigation, or industrial processing. Water use pertains to human's interaction with and influence on the hydrologic cycle, and includes elements, such as water withdrawal from surface- and ground-water sources, water delivery to homes and businesses, consumptive use of water, water released from wastewater-treatment plants, water returned to the environment, and instream uses, such as using water to produce hydroelectric power.
watershed--the land area that drains water to a particular stream, river, or lake. It is a land feature that can be identified by tracing a line along the highest elevations between two areas on a map, often a ridge. Large watersheds, like the Mississippi River basin contain thousands of smaller watersheds.
watthour (Wh)--an electrical energy unit of measure equal to one watt of power supplied to, or taken from, an electrical circuit steadily for one hour.
well (water)--an artificial excavation put down by any method for the purposes of withdrawing water from the underground aquifers. A bored, drilled, or driven shaft, or a dug hole whose depth is greater than the largest surface dimension and whose purpose is to reach underground water supplies or oil, or to store or bury fluids below ground.
withdrawal--water removed from a ground- or surface-water source for use.
X
xeriscaping--a method of landscaping that uses plants that are well adapted to the local area and are drought-resistant.
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