Hardness Minerals in Drinking Water Water described as "hard" is high in dissolved minerals, specifically calcium and magnesium. Hard water is not a health risk, but a nuisance because of mineral buildup on fixtures and poor soap and/or detergent performance. Water is a good solvent and picks up impurities easily. Pure water -- tasteless, colorless, and odorless -- is often called the universal solvent. When water is combined with carbon dioxide to form very weak carbonic acid, an even better solvent results. As water moves through soil and rock, it dissolves very small amounts of minerals and holds them in solution. Calcium and magnesium dissolved in water are the two most common minerals that make water "hard." The degree of hardness becomes greater as the calcium and magnesium content increases. Indications of Hard Water Hard water interferes with almost every cleaning task, from laundering and dishwashing to bathing and personal grooming. Clothes laundered in hard water may look dingy and feel harsh and scratchy. Dishes and glasses may be spotted when dry. Hard water may cause a film on glass shower doors, shower walls, bathtubs, sinks, faucets, etc. Hair washed in hard water may feel sticky and look dull. Water flow may be reduced by hard water deposits in pipes. Dealing with hard water problems in the home can be a nuisance. The amount of hardness minerals in water affects the amount of soap and detergent necessary for cleaning. Soap used in hard water combines with the minerals to form a sticky soap curd. Some synthetic deter- gents are less effective in hard water because the active ingredient is partially inactivated by hardness, even though it stays dissolved. Bathing with soap in hard water leaves a film of sticky soap curd on the skin. The film may prevent removal of soil and bacteria. Soap curd interferes with the return of skin to its normal, slightly acid condition, and may lead to irritation. Soap curd on hair may make it dull, lifeless and difficult to manage. When doing laundry in hard water, soap curds lodge in fabric during washing to make fabric stiff and rough. Incomplete soil removal from laundry causes graying of white fabric and the loss of brightness in colors. A sour odor can develop in clothes. Continuous laundering in hard water can shorten the life of clothes. In addition, soap curds can deposit on dishes, bathtubs and showers, and all water fixtures. Hard water also contributes to inefficient and costly operation of water-using appliances. Heated hard water forms a scale of calcium and magnesium minerals that can contribute to the inefficient operation or failure of water-using appliances. Pipes can become clogged with scale that reduces water flow and ultimately requires pipe replacement. Potential Health Effects Hard water is not a health hazard. In fact, the National Research Council (National Academy of Sciences) states that hard drinking water generally contributes a small amount toward total calcium and magnesium human dietary needs. They further state that in some instances, where dissolved calcium and magnesium are very high, water could be a major contributor of calcium and magnesium to the diet.
Researchers have studied water hardness and cardiovascular disease mortality. Such studies have been "epidemiological studies," which are statistical relationship studies. While some studies suggest a correlation between hard water and lower cardiovascular disease mortality, other studies do not suggest a correlation. The National Research Council states that results at this time are inconclusive and recommends that further studies should be conducted. Testing If you are on a municipal water system, the water supplier can tell you the hardness level of the water they deliver. If you have a private water supply, you can have the water tested for hardness. Most water testing laboratories offer hardness tests for a fee, including the Nebraska State Department of Health Laboratory. Many companies that sell water treatment equipment offer hardness tests. When using these water tests, be certain you understand the nature of the test, the water condition being measured, and the significance of the test results. An approximate estimate of water hardness can be obtained without the aid of outside testing facilities. Water hardness testing kits are available for purchase through water testing supply companies. If more accurate measurements are needed, obtain a laboratory test. Interpreting Test Results The hardness of your water will be reported in grains per gallon, milligrams per liter (mg/l) or parts per million (ppm). One grain of hardness equals 17.1 mg/l or ppm of hardness. The Environmental Protection Agency (EPA) establishes standards for drinking water which fall into two categories -- Primary Standards and Secondary Standards. Primary Standards are based on health considerations and Secondary Standards are based on taste, odor, color, corrosivity, foaming, and staining properties of water. There is no Primary or Secondary standard for water hardness. Water hardness is classified by the U.S. Department of Interior and the Water Quality Association as follows: Classification mg/l or ppm grains/gal Soft 0-17.1 0-1 Slightly hard 17.1-60 1-3.5 Moderately hard 60-120 3.5-7.0 Hard 120-180 7.0-10.5 Very Hard 180 & over 10.5 & over Other organizations may use slightly different classifications. Summary Hard water is not a health hazard, but dealing with hard water in the home can be a nuisance. The hardness (calcium and magnesium concentration) of water can be approximated with a home-use water testing kit, or can be measured more accurately with a laboratory water test. Water hardness can be managed with packaged water softeners or with a mechanical ion exchange softening unit.
Lead in Drinking Water Small quantities of lead can be a serious health concern, especially for children. Sources of lead in the environment include lead-based paint; lead contaminated soil, air and dust; lead contaminated food; imported food in leadsoldered cans; non-fda regulated ceramics with lead glazes; leaded crystal and lead contaminated drinking water. Lead rarely occurs naturally in water. Most lead contamination takes place at some point in the water delivery system. This occurs as a result of corrosion, the reaction between the water and lead in parts of the water delivery system. Materials in the water delivery system which may contain lead include service connections, pipes, solder and brass fixtures. Water's characteristics vary: some water is naturally more corrosive than others. Several factors cause water to be corrosive including acidity (low ph), high temperature, low total dissolved solids (TDS) content and high amounts of dissolved oxygen or carbon dioxide. Generally, naturally soft water is more corrosive than hard water, because it is more acidic and has low TDS. Softening naturally hard water with an ion exchange water softening unit does not appreciably change the corrosivity of the water, resulting in little, if any, effect on the water's ability to dissolve lead. Lead in drinking water from plumbing or fixtures is most often a problem in either very old or very new houses. Through the early 1900's it was common in some areas of the country to use lead pipes for interior plumbing. Lead piping was also used for the service connections used to join residences to public water supplies. Lead piping is most likely to be found in homes built before 1930. Copper piping replaced lead piping, but lead-based solder was used to join copper piping. It is likely lead-based solder was used in any home built before 1988. Today, brass materials are used in nearly 100 percent of all residential, commercial, and municipal water distribution systems. Many household faucets, plumbing fittings, check valves and well pumps are manufactured with brass parts. While brass contains some lead to make casting easier and the machining process more efficient, the lead content of brass plumbing components is now restricted to 8 percent. Even at this low level, however, lead can be leached from new brass faucets and fittings. Eventually, if the water is not corrosive, hard water minerals deposit on the interior of plumbing. These deposits form a calcium carbonate lining inside pipes and fittings which protects against lead contamination. It may take up to five years for an effective calcium carbonate lining to form. Softening naturally hard water with an ion exchange water softening unit can either prevent or dissolve the calcium carbonate scale, eliminating its possible protective effect. Some private wells may have submersible pumps containing brass or bronze capable of leaching lead. Some well screens also may contain lead or were installed with a "lead packing collar". Potential lead contamination also exists if the well is a driven, sandpoint well and has been "shot" to clear the screen. Lead shot was sometimes poured into a well to keep out sand. In other wells, lead wool was used. None of these practices are recommended and driven, sandpoint wells are not allowable under Nebraska well construction regulations. Older water coolers with lead-lined tanks are another possible source of lead in drinking water. The Lead Contamination Control Act of 1988 required the repair or recall of lead-lined tanks and prohibited manufacturing and sale of such coolers. As with any repair or recall notice, it is possible that less than 100 percent compliance was achieved and coolers with lead-lined tanks could remain in use. Indications of Lead Lead does not noticeably alter the taste, color or smell of water. The effects of low levels of lead toxicity in humans may not be obvious. There may be no symptoms present or symptoms may be mistaken as flu or other illnesses. Potential Health Effects As far as we know, lead has no benefits to humans or animals. Lead is a cumulative poison, meaning it accumulates in the body until it reaches toxic levels. It can be absorbed through the digestive tract, the lungs and the skin and is
carried by the blood throughout the body. The severity of the effects of lead poisoning varies depending on the concentration of lead in the body. This concentration can be determined with a blood test. Although lead has long been recognized as poisonous at high dosages, recent studies have shown it is damaging at lower levels than previously believed. As a result, lead exposure levels considered acceptable have been lowered. While some effects of lead poisoning may diminish if exposure is reduced, others are irreversible. Excess lead in the human body can cause serious damage to the brain, kidneys, nervous system and red blood cells. Young children, infants and fetuses are particularly vulnerable to lead poisoning. An amount of lead which would have little effect on an adult can greatly effect a child. Also, growing children more rapidly absorb any lead consumed. A child's mental and physical development can be irreversibly stunted by lead. Lead in drinking water is not the predominant source of lead poisoning, but it can increase total lead exposure, particularly the exposure of infants who drink baby formulas and juices which are mixed with water. On average, about 10 to 20 percent of a child's total lead exposure might come from drinking water. Infants who are fed formula could get 40 to 60 percent of their lead intake from water. The Centers for Disease Control and Prevention recommend all children be tested for lead with a blood test. Parents or guardians should consult with their physician. Testing To determine if lead is present in drinking water and to determine the possible source of the contamination, water must be tested using specific sampling procedures. Tests to determine the presence of lead in drinking water should be done by a laboratory certified specifically for lead testing. Carefully follow all directions provided by the laboratory and use provided containers when collecting water samples. Home test kits available on the market may not provide accurate results. To evaluate the household's highest level of lead exposure, collect a sample after water has sat motionless in the plumbing system for six or more hours. When collecting the sample, collect the first water from the faucet. Do not allow any water to run before collecting the sample. This is called a first-draw or first-flush sample. Because lead will continually dissolve into the water, the lead concentration will increase with time. This is why water drawn after any extended period of nonuse will contain the highest lead levels. Collect a second sample after the tap has run for at least five minutes. This is called a purged-line or flushed sample, which will indicate the lead concentration in water that has not been in contact with the plumbing system for an extended period of time. If the first-draw sample contains a higher amount of lead than the purged-line sample, the water is leaching lead from the plumbing system. If both samples contain nearly equal amounts of lead, the water is being contaminated by a source other than the household plumbing system. Although private water supplies are not subject to any regulations concerning lead contamination, users of private water supplies may want to test their water supply. This is especially true if a problem is suspected or if children use the water. Water supplied by Public Water Systems is regulated by the U.S. Environmental Protection Agency (EPA) and Nebraska Health and Human Services System's Department of Regulation and Licensure. Public water systems must complete a distribution system materials evaluation and/or review other information to target homes at high risk of lead contamination. At-risk homes are then monitored at the tap, with the number of tapsampling sites based on the population served. Additional monitoring for other water-quality parameters affecting corrosion is required to both optimize any required treatment and determine compliance with lead standards. All large systems (serving more than 50,000 persons), as well as small and medium-size water systems (serving less than 50,000 persons) exceeding the EPA's lead action level, are required to complete additional monitoring. The lead action level is discussed below in the "Interpreting Test Results" section.
A public water system exceeding the EPA action level in more than 10 percent of sampled homes is required to take action to reduce lead levels. The system must initiate corrosion control treatment, source water treatment and public education. If a system continues to exceed the lead action level following these three steps, lead service lines must be replaced over a 15 year period. Interpreting Test Results Interpreting water test results for lead involves considering both the magnitude of the lead concentration in the samples and comparing the first-draw and flushed samples. As discussed earlier, if results show higher levels of lead in the first-draw sample than the flushed sample, the lead is likely coming from components of the household plumbing (lead piping, lead-based solder or brass fixtures and fittings). On the other hand, if test results show nearly equal amounts of lead in both the first-draw and flushed samples, the lead is probably coming from a source outside the house. EPA's Maximum Contaminant Level Goals (MCLG) are desirable, non-enforceable, health-based goals established to assure a completely safe water supply. Water containing any chemical in an amount equal to or below its MCLG is not expected to cause any health problems, even over a lifetime of drinking this water. The MCLG for lead in drinking water is zero. EPA has established an enforceable lead concentration action level for public water supplies. The lead action level is 15 micrograms per liter (mg/l) = parts per billion (ppb) which is equivalent to 0.015 milligrams per liter (mg/l) = parts per million (ppm). When the lead concentration exceeds 15 ppb, the water supplier must initiate the actions described in the previous section. The 15 ppb concentration should also be used as an action level for private water supplies. Options If water tests indicate lead is present in drinking water and testing determines the source is household plumbing, first try to identify and eliminate the lead source. If it is neither possible nor cost-effective to eliminate the lead source, flushing the water system before using the water for drinking or cooking may be an option. Flushing the system means anytime the water in a particular faucet has not been used for several hours, water should be run until it becomes as cold as it will get. This could take as little as two minutes or longer than five minutes depending on your system. Flush each faucet individually before using the water for drinking or cooking. Water run from the tap during the flushing can be used for non-consumption purposes such as watering plants, washing dishes or clothes or cleaning. Flushing may be ineffective in high-rise buildings with large-diameter supply pipes joined with lead-based solder. Avoid cooking with or consuming water from hot-water taps. Hot water dissolves lead more readily than cold water. Especially avoid using water from a hot water tap for making baby formula.contamination. If the source of water is a private well, check both the well and the pump for potential lead sources. A licensed water well contractor may be able to help you determine if any of the well components are a source of lead. In addition to identifying potential lead sources, consider the corrosivity factor. One practice which may increase corrosion is the grounding of electrical equipment (including telephones) to water pipes. Electric current traveling through the ground wire accelerates the corrosion of lead in the pipes. In this case, a qualified electrician should be consulted. If at all possible and if cost-effective, eliminate the source of lead in drinking water. If that is not possible, consider water treatment or an alternative drinking water source (such as bottled water). There are several treatment methods suitable for removing lead from drinking water, including reverse osmosis, distillation and carbon filters specially designed to remove lead. Typically these methods are used to treat water at only one faucet. Reverse osmosis units can remove approximately 85 percent of the lead from water. Distillation can remove approximately 99 percent. A water softener can be used with either a reverse osmosis or distillation unit when water is excessively hard. Low flow rates are required when using lead selective carbon filters. Typically they have flow controllers which limit the system to 0.25 to 0.5 gallons per minute.
Summary Lead rarely occurs naturally in drinking water. It is more common for lead contamination to occur at some point in the water delivery system. Too much lead in the human body can cause serious damage to the brain, kidneys, nervous system and red blood cells. Young children, infants and fetuses are especially vulnerable to lead poisoning. To determine the presence of lead in drinking water and its possible source, a specific procedure must be used to collect samples and a certified laboratory used for testing. If test results indicate the presence of lead and the source is identified, appropriate steps should be taken. Options include removing the lead source and managing the water supply use for drinking and cooking by flushing water with high lead concentrations from the water system, using water treatment equipment or using an alternative water source. Options selected must be based on the specific situation.
Sources of Iron and Manganese in Drinking Water Iron and manganese are non-hazardous elements that can be a nuisance in a water supply. Iron and manganese are chemically similar and cause similar problems. Iron is the most frequent of the two contaminants in water supplies; manganese is typically found in iron-bearing water. Iron and manganese are common metallic elements found in the earth's crust. Water percolating through soil and rock can dissolve minerals containing iron and manganese and hold them in solution. Occasionally, iron pipes also may be a source of iron in water. Indications of Iron and Manganese In deep wells, where oxygen content is low, the iron/manganese-bearing water is clear and colorless (the iron and manganese are dissolved). Water from the tap may be clear, but when exposed to air, iron and manganese are oxidized and change from colorless, dissolved forms to colored, solid forms. Oxidation of dissolved iron particles in water changes the iron to white, then yellow and finally to red-brown solid particles that settle out of the water. Iron that does not form particles large enough to settle out and that remains suspended (colloidal iron) leaves the water with a red tint. Manganese usually is dissolved in water, although some shallow wells contain colloidal manganese (black tint). These sediments are responsible for the staining properties of water containing high concentrations of iron and manganese. These precipitates or sediments may be severe enough to plug water pipes. Iron and manganese can affect the flavor and color of food and water. They may react with tannins in coffee, tea and some alcoholic beverages to produce a black sludge, which affects both taste and appearance. Manganese is objectionable in water even when present in smaller concentrations than iron. Iron will cause reddish-brown staining of laundry, porcelain, dishes, utensils and even glassware. Manganese acts in a similar way but causes a brownish-black stain. Soaps and detergents do not remove these stains, and use of chlorine bleach and alkaline builders (such as sodium and carbonate) may intensify the stains. Iron and manganese deposits will build up in pipelines, pressure tanks, water heaters and water softeners. This reduces the available quantity and pressure of the water supply. Iron and manganese accumulations become an economic problem when water supply or water softening equipment must be replaced. There also are associated increases in energy costs from pumping water through constricted pipes or heating water with heating rods coated with iron or manganese mineral deposits. A problem that frequently results from iron or manganese in water is iron or manganese bacteria. These nonpathogenic (not health threatening) bacteria occur in soil, shallow aquifers and some surface waters. The bacteria feed on iron and manganese in water. These bacteria form red-brown (iron) or black-brown (manganese) slime in toilet tanks and can clog water systems. Potential Health Effects Iron and manganese in drinking water are not considered health hazards. Testing The method used to test water for iron and manganese depends on the form of the element. If water is clear when first drawn but red or black particles appear after the water sits in a glass, dissolved (ferrous) iron/manganese is present. If the water has a red tint with particles so small they cannot be detected nor do they settle out after a time, colloidal (ferric) iron is the problem. Typically, laboratory tests are needed only to quantify the extent of iron and manganese contamination, but testing of additional water parameters such as ph, silica content, oxygen content, hardness and sulfur may be necessary to determine the most appropriate water treatment system.
Iron and manganese testing is provided for a fee by the Nebraska Department of Health Laboratory and some commercial water testing laboratories. See NebGuide G89-907, Water Testing Laboratories, for a list of laboratories in Nebraska providing water testing. Select a laboratory and contact them to obtain a drinking water iron and/or manganese test kit. The kit will contain a sample bottle, an information form, sampling instructions and a return mailing box. The sampling instructions provide information on how to collect the sample. Follow these instructions to avoid contamination and to obtain a representative sample. Promptly mail the sample with the completed information form to the laboratory. Take the sample on a day when it can be mailed to arrive at the laboratory Monday through Thursday. Avoid weekends and holidays which may delay the mail or lab analysis. Samples may be taken from the inside surfaces of the plumbing system to confirm iron or manganese bacteria presence. The interior of the toilet tank is a good location for obtaining a bacteria sample. Check with the laboratory for further information on bacterial colony sampling. Interpreting Test Results The Environmental Protection Agency (EPA) standards for drinking water fall into two categories --- Primary Standards and Secondary Standards. Primary Standards are based on health considerations and are designed to protect people from three classes of pollutants: pathogens, radioactive elements and toxic chemicals. Secondary Standards are based on taste, odor, color, corrosivity, foaming and staining properties of water. Iron and manganese are both classified under the Secondary Maximum Contaminant Level (SMCL) standards. The SMCL for iron in drinking water is 0.3 milligrams per liter (mg/l), sometimes expressed as 0.3 parts per million (ppm), and 0.05 mg/l (ppm) for manganese. Water with less than these concentrations should not have an unpleasant taste, odor, appearance or side effect caused by a secondary contaminant. Options If excessive iron or manganese is present in your water supply, you have two basic options -- obtain an alternate water supply or use some type of treatment to remove the impurity. The need for an alternate water supply or impurity removal should be established before making an investment in treatment equipment or an alternate supply. Base the decision on a water analysis by a reputable laboratory. It may be possible to obtain a satisfactory alternate water supply by drilling a new well in a different location or a deeper well in a different aquifer. The Conservation and Survey Division of the University of Nebraska-Lincoln can provide general information on the possible location of a water supply with satisfactory quality. Several methods of removing iron and manganese from water are available. The most appropriate method depends on many factors, including the concentration and form of iron/manganese in the water, if iron or manganese bacteria are present, and how much water you need to treat. Generally speaking, there are five basic methods for treating water containing these contaminants. They are: (1) phosphate compounds; (2) ion exchange water softeners; (3) oxidizing filters; (4) aeration (pressure type) followed by filtration; and (5) chemical oxidation followed by filtration. Table I summarizes iron and manganese treatment options. These treatment techniques are effective in water that has an almost neutral ph (approximately 7.0). The phosphate compound treatment is an exception and is effective in the ph range of 5.0 to 8.0. Exceptions are noted for manganese removal.
Phosphate treatment Low levels of dissolved iron and manganese at combined concentrations up to 3 mg/l can be remedied using phosphate compound treatment. Phosphate compounds are a family of chemicals that can surround minerals and keep them in solution. Phosphate compounds injected into the water system can stabilize and disperse dissolved iron at this level. As a result, the iron and manganese are not available to react with oxygen and separate from solution. The phosphate compounds must be introduced into the water at a point where the iron is still dissolved in order to maintain water clarity and prevent possible iron staining. This should be before the pressure tank and as close to the well discharge point as possible. Phosphate compound treatment is a relatively inexpensive way to treat water for low levels of iron and manganese. Since phosphate compounds do not actually remove iron, water treated with these chemicals will retain a metallic taste. In addition, too great a concentration of phosphate compounds will make water feel slippery. Phosphate compounds are not stable at high temperatures. If phosphate compound-treated water is heated (for example, in a water heater or boiled water), the phosphates will break down and release iron and manganese. The released iron and manganese will then react with oxygen and precipitate. Adding phosphate compounds is not recommended where the use of phosphate in most cleaning products is banned. Phosphate, from any source, contributes to excess nutrient content in surface water. Ion exchange water softener Low to moderate levels of dissolved iron, at less than 5 mg/l concentrations, usually can be removed using an ion exchange water softener. Be sure to check the manufacturer's maximum iron removal level recommendations before you purchase a unit. Capacities for treating dissolved iron typically can range from 1 to 5 mg/l. Oxidized iron or levels of dissolved iron exceeding the manufacturer's recommendations will cause a softener to become plugged. The principle is the same as that used to remove the hardness minerals, calcium and magnesium; i.e., iron in the untreated water is exchanged with sodium on the ion exchange medium. Iron is flushed from the softener medium by backwashing (forcing sodium-rich water back through the device). This process adds sodium to the resin medium, and the iron is carried away in the waste water. Since iron removal reduces the softening capacity of the unit, the softener will have to be recharged more often. The manufacturer of the softener medium is able to make recommendations concerning the appropriate material to use for a particular concentration of iron. Some manufacturers recommend adding a "bed cleaning" chemical with each backwashing to prevent clogging. Not all water softeners are able to remove iron from water. The manufacturer's specifications should indicate whether or not the equipment is appropriate for iron removal. Water softeners add sodium to the water, a health concern for people on sodium-restricted diets. Consider installing a separate faucet to provide unsoftened water for cooking and drinking. Oxidizing filter An oxidizing filter treatment system is an option for moderate levels of dissolved iron and manganese at combined concentrations up to 15 mg/l. The filter material is usually natural manganese greensand or manufactured zeolite coated with manganese oxide, which adsorbs dissolved iron and manganese. Synthetic zeolite requires less backwash water and softens the water as it removes iron and manganese. The system must be selected and operated based on the amount of dissolved oxygen. Dissolved oxygen content can be determined by field test kits, some water treatment companies or in a laboratory.
Aeration followed by filtration High levels of dissolved iron and manganese at combined concentrations up to 25 mg/l can be oxidized to a solid form by aeration (mixing with air). For domestic water processing, the "pressure-type aerator" often is used. In this system, air is sucked in and mixed with the passing stream of water. This air-saturated water then enters the precipitator/aerator vessel where air separates from the water. From this point, the water flows through a filter where various filter media are used to screen out oxidized particles of iron, manganese and some carbonate or sulfate. The most important maintenance step involved in operation is periodic backwashing of the filter. Manganese oxidation is slower than for iron and requires greater quantities of oxygen. Aeration is not recommended for water containing organic complexes of iron/manganese or iron/manganese bacteria that will clog the aspirator and filter. Chemical oxidation followed by filtration High levels of dissolved or oxidized iron and manganese greater than 10 mg/l can be treated by chemical oxidation, using an oxidizing chemical such as chlorine, followed by a sand trap filter to remove the precipitated material. Iron or manganese also can be oxidized from the dissolved to solid form by adding potassium permanganate or hydrogen peroxide to untreated water. This treatment is particularly valuable when iron is combined with organic matter or when iron bacteria is present. The oxidizing chemical is put into the water by a small feed pump that operates when the well pump operates. This may be done in the well, but typically is done just before the water enters a storage tank. A retention time of at least 20 minutes is required to allow oxidation to take place. The resulting solid particles then must be filtered. When large concentrations of iron are present, a flushing sand filter may be needed for the filtering process. If organic-complexed or colloidal iron/manganese is present in untreated water, a longer contact time and higher concentrations of chemicals are necessary for oxidation to take place. Adding aluminum sulfate (alum) improves filtration by causing larger iron/manganese particles to form. When chlorine is used as the oxidizing agent, excess chlorine remains in treated water. If the particle filter is made of calcite, sand, anthracite or aluminum silicate, a minimum quantity of chlorine should be used to avoid the unpleasant taste that results from excess chlorine. An activated carbon filter can be used to remove excess chlorine and small quantities of solid iron/manganese particles. Any filtration material requires frequent and regular backwashing or replacement to eliminate the solid iron/manganese particles. Some units have an automatic backwash cycle to handle this task. The ideal ph range for chlorine bleach to oxidize iron is 6.5 to 7.5. Chlorination is not the method of choice for high manganese levels since a ph greater than 9.5 is required for complete oxidation. Potassium permanganate will effectively oxidize manganese at ph values above 7.5 and is more effective than chlorine oxidation of organic iron if that is a problem. Potassium permanganate is poisonous and a skin irritant. There must be no excess potassium permanganate in treated water and the concentrated chemical must be stored in its original container away from children and animals. Careful calibration, maintenance and monitoring are required when potassium permanganate is used as an oxidizing agent.
Table I. Treatment of iron and manganese in drinking water Indication Cause Treatment Water clear when drawn but red-brown or black particles appear as water stands; red-brown or black stains on fixtures or laundry Water contains red-brown particles when drawn; particles settle out as water stands Water contains red-brown or black particles when drawn; particles settle out as water stands Red-brown or black slime appears in toilet tanks or from clogs in faucets Reddish or black color that remains longer than 24 hours Dissolved iron or manganese Iron particles from corrosion of pipes and equipment Oxidized iron/manganese due to exposure of water to air prior to tap Iron or manganese bacteria Colloidal iron/manganese; organically complexed iron/manganese Phosphate compounds (< 3 mg/l iron) Water softener (<5 mg/l combined concentrations of iron and manganese) Oxidizing filter (manganese greensand or zeolite) (<15 mg/l combined concentrations of iron and manganese) Aeration (pressure) (<25mg/l combined concentrations of iron and manganese) Chemical oxidation with potassium permanganate or chlorine; followed with filtration (>10 mg/l combined concentrations of iron and manganese) Raise ph with neutralizing filter Particle filter (if quantity of oxidized material is high, use larger filter than inline; e.g., sand filter) Kill bacteria masses by shock treatment with chlorine or potassium permanganate, then filter; bacteria may originate in well, so it may require continuous feed of chlorine or potassium permanganate, then filter Chemical oxidation with chlorine or potassium permanganate; followed with filtration Adapted from "Iron and Manganese in Household Water," Water Treatment Notes. Fact Sheet 6, Cornell Cooperative Extension. (1989). Plumbing corrosion Corroded pipes and equipment may cause reddish-brown particles in the water that, when drawn from the tap, will settle out as the water stands. This can indicate oxidized iron or, in some cases, it may only be iron corrosion particles. Raising the water's ph and using a sediment filter is the simplest solution to this problem. Iron and manganese bacteria The most common approach to control of iron and manganese bacteria is shock chlorination. Shock chlorination procedures are described in NebGuide 95-1255, Shock Chlorination of Domestic Water Supplies. It is almost impossible to kill all the iron and manganese bacteria in your system. They will grow back eventually so be prepared to repeat the treatment from time to time. If bacteria regrowth is rapid, repeated shock chlorination becomes time consuming. Continuous application of low levels of chlorine may be less work and more effective. An automatic liquid chlorine injector pump or a dispenser that drops chlorine pellets into the well are common choices. Chlorine rapidly changes dissolved iron into oxidized (colored) iron that will precipitate. A filter may be needed to remove oxidized iron if continuous chlorination is used to control iron bacteria.
Multistage treatment If the water has high levels of iron and manganese and they are both the dissolved and solid forms, a multistage treatment operation is necessary. For example, a troublesome supply could be chlorinated to oxidize dissolved iron and kill iron bacteria, and filtered through a mechanical device to remove particles. This can be followed by activated carbon filtration to remove excess chlorine and a water softener for hardness control as well as removal of any residual, dissolved iron or manganese. Often hydrogen sulfide, iron and manganese contaminants can be removed using the same treatment. Summary Iron and manganese are common water contaminants that are not considered health hazards. Their presence in water results in staining as well as offensive tastes and appearances. Treatment of these elements depends on the form in which they occur in the untreated water. Therefore, accurate testing is important before considering options and/or selecting treatment equipment. A summary of treatment options is shown in Table I. Often the treatment for iron and manganese is the same for hydrogen sulfide, allowing removal of all three contaminants in one process.