Drinking Water Standards

AESL Drinking Water Standards and Comments
EPA Drinking Water Contaminants – Standards and Regulations
Parameter	Secondary	Primary (MCL)	Comment

Other parameters

Conductivity	Conductivity is the measure of the ability of the water to conduct electricity. The units for conductivity are usually expressed either as micro-Siemens (S) or micro-mhos (mhos) per centimeter (S/cm = mhos/cm). Conductivity increases as the amount of dissolved ionic solids increases and is sometimes called "soluble salts". Dissolved inorganic compounds are relatively good conductors; conversely, dissolved organic compounds are poor conductors. The conductivity of distilled water usually ranges from 0.5 to 3 S/cm and most drinking water in the United States ranges from 50 to 1500 S/cm.
Hardness	The calculated hardness of this water sample exceeds 120 parts per million (ppm). The water is, therefore, considered hard. Water hardness is related to the amount of calcium, magnesium and other minerals in the water. Hard water does not pose a threat to health, but it can cause scale formation in pots, water pipes and water heaters. It can also interfere with the cleaning action of soaps and detergents, forming film on skin, clothing and fixtures. Water can be softened by installing an ion-exchange water softener which removes calcium, magnesium, etc. by exchanging them for sodium. Drinking softened water may not be recommended for individuals on sodium restricted diet because of the increased sodium concentrations.
pH	The pH of this water sample is below 6.5. Low pH is usually caused by dissolved carbon dioxide in the water and causes the water to be acidic. Low pH water is not harmful to drink but it can cause corrosion of metal pipes and other metal components in the plumbing system. If such corrosion is evident, the problem can usually be corrected by increasing the pH of the water before it enters the metal pipes. This can be accomplished by installing a calcium-based neutralizing tank.
Saturation Index	The saturation index is used to predict the corrosion or scaling property of this water. Corrosion of the pump, pipe, and fixtures can cause high metal levels in the water, especially copper and lead. Treatment for corrosion would consist of pH neutralization with a calcium or magnesium base (ie., calcite) filter bed. Corrosion problems can be reduced by using non-metal plumbing (ie., PVC). Treatment for scaling consists of water softening to reduce hardness. Scaling problems can be reduced by lowering the hot water temperature.
Silica (SiO₂)	Silica is an essential nutrient for animals and is related to bone development. The U. S. Environmental Protection Agency (USEPA) has not established a maximum contaminant level (MCL) for silica. In the presence of magnesium, silica can form scale in boilers and turbines. Concentrations greater than 30 ppm are considered high and could damage the membrane on a reverse osmosis (RO) water treatment system. Silica levels can be reduced by a strong anion exchange resin; however, as this resin becomes exhausted, high levels of silica will be released back into the water system.
Sodium (Na)	The concentration of sodium in this sample exceeds 20 parts per million (ppm). EPA has not set a maximum drinking water contaminant level for sodium; however, persons who consume this water regularly and have a history of heart problems or high blood pressure should consult their physician. Sodium can be removed from drinking water by using a point-of-use demineralization system such as distillation or reverse osmosis.