How Minerals Affect Water Supplies
Groundwater with high amounts of minerals is common in both municipal and private North Dakota water supplies. Dissolved minerals can affect the usefulness of groundwater and surface water. If the problem is bad enough, chemical treatment may help. Sometimes another source of water is needed. The following is a brief description of how some common minerals affect water supplies.
Total Dissolved Solids
High concentrations of total dissolved solids can cause water to taste bad, forcing consumers to use other water sources. Highly mineralized water also deteriorates plumbing and appliances.
Waters containing more than 500 milligrams per liter (mg/l) of dissolved solids should not be used if other less mineralized supplies are available. This does not mean that any water in excess of 500 mg/l is unusable. People may eventually adjust to drinking water containing high total dissolved solids. With the exception of the Missouri River, Lake Sakakawea, a few fresh water lakes, and scattered wells, very few untreated water supplies in North Dakota contain less than the recommended 500 mg/l of total dissolved solids.
Hardness is the amount of calcium and magnesium dissolved in the water. Hard water has no adverse health effects and may even taste better than soft waters. But hard water is less desirable because it requires more soap for effective cleansing, forms scum and curd, causes yellowing of fabrics, toughens vegetables during cooking, and forms scales in boilers, hot water heaters, pipes, and on cooking utensils.
The hardness of good quality water should not exceed 270 mg/l (16 grams/gal.) measured as calcium carbonate (CaCO3). Water softer than 30-50 mg/l may be corrosive to piping, depending on pH, alkalinity and dissolved oxygen. Whether or not to soften hard water is a matter of personal preference and depends on the natural sodium level.
The most common types of commercial water softeners replace the calcium and magnesium ions with sodium. Water softened in this way may affect individuals on sodium-restricted diets. The treated water should be tested for sodium. A personal physician should be consulted about the results.
High nitrate concentrations can occur in wells located in or near feedlots, barnyards, sewage disposal systems or areas of high fertilizer application, and often indicate the presence of other forms of groundwater contamination. High nitrate water should never be used in infant feeding. In infants, nitrate can destroy the oxygen-carrying capacity of the blood, causing a condition known as methemoglobinemia. This results in an oxygen starvation condition and the infant appears blue. Serious poisonings, sometimes fatal, have occurred in infants less than six months old after drinking water containing nitrate as nitrogen at concentrations greater than 10 mg/l.
Iron and Manganese
The primary source of iron is the water bearing strata. Iron is typically dissolved in water and when brought to the surface, can form rust which may settle out. Another source of iron is iron-reducing bacteria, which depend upon iron to live. These bacteria add iron to the water by attacking the piping of the system. Removing naturally-occurring iron in the water may require special water treatment equipment. Iron-reducing bacteria may be controlled or eliminated by adequate chlorination. The most common water complaints are those of red water, laundry spotting, metallic tastes, and staining of plumbing fixtures. These are usually due to the presence of iron above 0.3 mg/l. Iron and manganese have similar adverse effects and frequently occur together in natural waters. Concentrations of manganese greater than 0.05 mg/l. may cause brown/black stains and deposits.
A person's intake of sodium is mostly influenced by the use of salt, where its role in the body is to help maintain water balance. Normally, the contribution of sodium from drinking water is small in comparison to other sources. Commercial water softeners may significantly increase the amount of sodium in drinking water. Sodium-restrictive diets are essential in treating congestive heart failure, hypertension, renal disease, cirrhosis of the liver, toxemias of pregnancy, and Meniere's disease. A diet for someone who must restrict sodium intake can be designed to allow for sodium from the water supply. The person can also use another source of drinking water. High concentrations of sodium may also make water less suitable for irrigation purposes by altering soil chemistry and absorption properties. With continued use, the soil will eventually be unable to absorb moisture. Although no evidence has shown that high sodium levels affect healthy individuals, recommended levels have been set at 100-200 mg/l.
Three reasons for limiting the concentration of sulfates in drinking water are: a) sulfates can cause laxative effects with high intake, especially in combination with magnesium or sodium; b) water containing large amounts of sulfate tends to form hard scales in boilers and heat exchangers; and c) sulfates can impact taste. The laxitive effect is commonly noted by people not used to water high in sulfates. These effects vary from one person to another and appear to fade with time. For these reasons, the recommended limit is 250-500 mg/l.
Alkalinity is a measure of the water's ability to neutralize acids. Natural waters usually contain carbonates, bicarbonates, and hyroxides. The bicarbonate ion is ususally the most common. The ratio of these ions is a funciton of pH, mineral composition, temperature, and ionic strength. Water may have low alkalinity but a relatively high pH value, so alkalinity alone is not of major importance as a measure of water quality. Alkalinity is not considered harmful to humans but may cause a distinct unpleasant taste.
Excess chloride in drinking water can have two effects. First, it can affect the taste. Second, the water may corrode hot water pipes. Consumers can decrease chloride levels by treating the water or by finding another water supply. A recommended limit of 250 mg/l has been set for chloride. For many years, chloride has been used as an indicator of pollution of the water source. Any sudden increase in the chloride content of a water supply should be investigated as a possible indication of pollution.
Varying amounts of fluoride are found in water supplies throughout the United States. Fluoride can affect teeth during the period when permanent teeth are being formed. When the concentration is best, 1.2 mg/l, no ill effects will result. The tooth decay rate will be 60-65 percent below the rate in areas where water supplies have little or no fluoride. High fluoride (more than 4.0 mg/l) in water can cause a brown color on teeth.
General mineral chemistry analyses of water samples are performed by the North Dakota Department of Health, Division of Chemistry, 2635 E. Main Ave, P.0. Box 937, Bismarck, ND 58506. For a chemical analysis, a sample of at least one quart should be submitted in any clean glass or plastic container (do not use metal). When submitting the sample, complete an information form or enclose information regarding the water source, type of well, depth, location, and other pertinent facts. If you plan to submit a sample, we recommend that you contact the Division of Chemistry prior to sampling your well. For more information, call (701) 328-6140 or write to the above address.
Carl Anderson - ND Dept. of Health