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 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.
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.
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.
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 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.
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.
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 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.
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.