The primary components of hardness are the alkaline salts calcium and magnesium. Dissolved iron and manganese also constitute hardness but typically make up only a very small fraction of total hardness. As water moves through rocks and soils, it dissolves small amounts of naturally-occurring minerals and transports them into the water supply. Hardness is normally considered an aesthetic water quality factor and there is no EPA standard for hardness. See the hardness classification below (Sources: U.S. Geological Survey and Water Quality Association).

Classification	mg/L or ppm	gpg
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

Mg/L (ppm) / 17.1 = gpg
Dissolved mineral material contributes to the taste drinking water. At higher concentrations hard water leaves white mineral deposits ("scale") on dishes, glasses and flatware, results in soap residue in showers and tubs and reduces the efficiency of electrical appliances and water heaters.

Total Dissolved Solids (TDS) consist of inorganic salts (principally calcium, magnesium, potassium, sodium, bicarbonates, chlorides and sulfates) and some small amounts of organic matter that are dissolved in water. It is expressed in milligrams per liter (mg/L; equivalent to parts per million, or ppm). TDS in drinking-water originates from natural sources, sewage, urban run-off, industrial wastewater and chemicals used in the water treatment process, and the nature of the plumbing used to convey the water.

In general, the total dissolved solids concentration is the sum of the cations (positively charged) and anions (negatively charged) ions in the water. Therefore, the total dissolved solids test provides a qualitative measure of the amount of dissolved ions, but does not tell us the nature or ion relationships or indicate specific water quality issues and is used as an indicator test to determine the general quality of the water.

Although the EPA does not consider TDS to be a health issue, TDS is of concern for several reasons. Some level of TDS is desirable in drinking water and contributes to a pleasant taste, but as levels increase beyond 500 mg/l many people complain of the taste. For this reason, the EPA has set a secondary (voluntary) drinking water standard for TDS of 500 mg/L, which is generally considered the maximum for household use. TDS can give water a murky appearance and detract from the taste quality of the water. TDS can also interfere with treatment equipment and is an important consideration when choosing a treatment system. Water softeners do not reduce TDS.

The presence of bacteria in drinking water is usually a result of a problem with the treatment system or the pipes which distribute water, and indicates that the water may be contaminated with germs that can cause disease. Coliform bacteria are common in the environment and are generally not harmful but are present in the digestive systems of humans and animals and can be found in their wastes. Coliforms are also present in the soil and plant material.

Bacterial contamination cannot be detected by sight, smell or taste. The only way to know if a water supply contains bacteria is to have it tested. The Environmental Protection Agency (EPA) requires that all public water suppliers regularly test for coliform bacteria and deliver water that meets the EPA standards (no more than 500 bacterial colonies per millimeter). If you have a positive result for total coliform the sample is automatically tested for the presence or absence of Escherichia coli (E. coli).

Human and animal wastes are a primary source of bacteria in water. These sources of bacterial contamination include runoff from feedlots, pastures, dog runs, and other land areas where animal wastes are deposited. Additional sources include seepage or discharge from septic tanks and sewage treatment facilities. Bacteria from these sources can enter wells that are either open at the land surface, or do not have water-tight casings or caps, or do not have a grout seal in the annular space (the space between the wall of the drilled well and the outside of the well casing).

Coliform bacteria do not cause disease, but fecal coliform and E. coli are bacteria whose presence indicates that the water may be contaminated with human or animal wastes. Microbes in these wastes can cause short-term effects, such as diarrhea, cramps, nausea, headaches, or other symptoms.

The Heterotrophic Plate Count (HPC), or standard plate count, is an analytical procedure used to estimate the number of live heterotrophic bacteria that are present in a water sample. A heterotroph is any organism that cannot make its own food and is therefore dependent on other substances for nutrition. HPC results are generally reported as CFU/ml (or Colony-Forming Units per milliliter). The upper limit for potable water is usually 500 colony-forming-units or cfu/mL.

The presence of iron and manganese in household water does not itself present a health hazard, but rather causes nuisance problems such as staining and objectionable taste. When ground water percolates through soil and rocks, minerals containing iron and manganese are dissolved and transported by the water. There are EPA Secondary Standards for iron (0.3 mg/L) and manganese (0.5 mg/L) because of staining, but these are not health-related and are not enforceable. At high concentration (> 0.3ppm) the iron will cause the water to have a metallic taste and odor. Iron and manganese are also prone to bacteria and odor and are often accompanied by hydrogen sulfide gas (H₂S).

In order to treat water for iron and manganese, it is essential to know if the metal is bivalent or trivalent. Simple changes to the water supply such as oxygen content, temperature, pressure or even a change of pH affect water testing and subsequent treatment.

Hydrogen sulfide gas odor (common described as a "rotten egg" smell) is a very difficult contaminant to quantify because it is a gas and escapes very quickly from the water. On-site testing is the only option for testing as the gas quickly precipitates out of solution. Concentrations as low as 0.5ppm can be detected by smell. Concentrations above 2-3ppm will all smell the same. Because of this lack of difference in smell at high concentrations, odor is not a good indication of how much is in the water but only presence or absence.

Hydrogen sulfide gas may be formed in several ways. Sulfur-reducing bacteria thrive in oxygen-deficient environments and are the primary producers of large quantities of hydrogen sulfide gas. These bacteria chemically change natural sulfates in water to hydrogen sulfide. Hydrogen sulfide may also be formed by the decomposition of underground deposits of organic matter such as decaying plant material. Occasionally, a hot water heater is a source of hydrogen sulfide odor because 1) the warm environment is conducive to sulfate-reducing bacteria if sulfates are present in the water and 2) the magnesium corrosion control (anode) rod present in many hot water heaters can chemically reduce naturally occurring sulfates to hydrogen sulfide.

High sulfate content detected in a water test is a good indicator of susceptibility to H₂S. The EPA has a Secondary Standard (non-enforceable guideline regulating contaminants that may cause cosmetic effects or aesthetic effects including odor) of 250 mg/L for sulfate concentration. There is no EPA guideline for hydrogen sulfide (H₂S), which clients find to be one of the most annoying contaminants.

Nitrates are water-soluble molecules made up of nitrogen and oxygen and are formed when nitrogen combines with oxygen in water. Although nitrate occurs naturally in drinking water, elevated levels in groundwater usually result from human activities such as overuse of chemical fertilizers and improper disposal of human and animal wastes. Septic systems are a common source of nitrate contamination. Short-term exposure to drinking water with a nitrate level at or just above the health standard of 10 mg/L nitrate-N is a potential health problem, primarily for infants.

Nitrates have no detectable taste, odor or smell at the concentrations involved in drinking water supplies. They do not color the water or discolor plumbing fixtures, so they remain undetectable to our senses. Nitrates are extremely soluble in water and can move easily through soil into the drinking water supply. Geological formations, depth to groundwater, and directions of groundwater flow influence the possibilities of nitrate contamination from a particular source.

The U.S. Environmental Protection (EPA) has established the Maximum Contamination Level (MCL) for nitrate at 10 milligrams per liter (10mg/L or 10ppm). This standard is mandatory for public water supplies and is used as a guide for private water supplies. The EPA recommends that private wells be tested once a year for coliform bacteria, nitrates, and other constituents of concern. Good Water Company recommends testing every year if the well has previously tested for elevated nitrate levels or if the well is located in a nitrate-prone area.

Nitrates in groundwater are of concern not only because of their toxic potential, but also because they are an indicator of other possible contamination of the groundwater. If the source of contamination is animal waste or effluent from septic tanks, bacteria, viruses, and protozoa may also be present. Contamination of groundwater by fertilizers may also indicate the presence of other agricultural chemicals such as pesticides.

Arsenic occurs naturally in rocks and soil, water, air, and plants and animals. There are several possible sources of arsenic, but in the western United States, the major source of arsenic in groundwater is through the natural weathering, erosion and transportation of materials from arsenic-bearing rocks. It can be further released into the environment through natural activities such as volcanic action, erosion of rocks, and forest fires, or through human actions. Approximately 90 percent of industrial arsenic in the U.S. is currently used as a wood preservative, but arsenic is also used in paints, dyes, metals, drugs, soaps, and semi-conductors. Agricultural applications, mining, and smelting also contribute to arsenic release in the environment.

Arsenic does not generally impart color, taste, or smell to water; therefore it can only be detected by a chemical analytical test. Naturally-occurring arsenic found in many groundwaters in one of two valences or oxidation states: pentavalent arsenic (also known as As(V), As(+5), As+5, or arsenate) and trivalent arsenic (also known as As(III), As(+3), As+3 or arsenite). In natural groundwater, arsenic may exist as trivalent arsenic, pentavalent arsenic, or a combination of both with variance of the relative proportions of each through time. Although both forms of arsenic are potentially harmful to human health, trivalent arsenic is considered more harmful than pentavalent arsenic. The key to successful arsenic removal is knowing the valence of arsenic present (if any), because proper treatment is based on arsenic speciation.

Introduction
Naturally-occurring radioactive contaminants are commonly detected in New Mexico, particularly in northern Santa Fe County. The concentration of these contaminants in some areas exceeds the concentration maximums established in public drinking water standards. Uranium, radon, and radium are of primary concern with respect to safe drinking water. Although anthropogenic radionuclide contamination is documented near Los Alamos, isotopic analyses of radionuclide contamination in northern Santa Fe County, by various State agencies and the U.S. Geological Survey, demonstrate that the sources of the contamination are naturally-occurring.

Will it be obvious if there is radioactive contamination in my water?
No. When dissolved in water, radionuclides are colorless, odorless, and tasteless and typically cannot be detected by our senses (unlike many other contaminants that may cause an undesirable color, odor or taste).

How do radioactive contaminants enter aquifers?
Radioactive contaminants leach into groundwater from natural mineral deposits and are transported by water. The amount of radionuclides (if any) in groundwater is dependent on the provenance (point of origin, chemistry and transportation pathway) of the water.

Are radioactive contaminants in private wells regulated by the EPA?
No. EPA has established MCL's for public drinking water systems, which may be publicly- or privately-owned, serve at least 25 people or 15 service connections for at least 60 days per year, but private wells are not subject to these EPA standards.

Containment	MCL
(Adjusted) Gross Aplha†	15 pCi/L†† (not including radon or uranium) (1976)
Uranium	30 µg/L ‡ (2000)
Radon	Proposed 300 pCi/L (Code of Fed. Reg. 11/99)
Radium 226 and Radium 228 (combined)	5 pCi/L

^† Compliance gross alpha equals the concentration of analytical gross alpha (in pCi/L) minus the concentration of uranium (in pCi/L) ^†† pCi/L (picocuries per liter) ^‡ µg/L (micrograms per liter; or parts per billion, ppb) µg/L can be converted to pCi/L by multiplying µg/L x 0.67 (MCL for uranium expressed in pCi/L = 20.1 pCi/L)
pCi/L can be converted to µg/L by multiplying pCi/L x 1.49

Can radioactive contamination be reduced or eliminated from drinking water?Yes, in most cases. But depending on which contaminants are present, more than one type of treatment may be required.

Is radionuclide treatment affected by the presence of other, non-radioactive contaminants?Yes. Comprehensive lab testing is essential because some metals may need to be removed prior to radionuclide treatment.

What is the most reliable method to determine if radioactive contaminants are present and, if present, at what levels?It is essential to have a properly collected sample analyzed by an EPA-approved laboratory.

Can Good Water Company provide assistance in testing for radionuclides?Yes, we not only can recommend what contaminants might be present, but we can guide you down the rather convoluted EPA pathway of sequential testing for radionuclides based on the combination of your water chemistry and treatment objectives.

EPA links to radionuclides
public wells
private wells
drinking water standards
radionuclides in drinking water


Uranium
Certain geographic areas in Santa Fe County are more prone than others for having water with radioactive contamination. Although radioactive contaminants are documented in wells throughout Santa Fe County (including within the city limits), high radioactive levels (primarily from uranium) are found between Tesuque and Española. Over half the wells tested for uranium in the Nambé area have uranium levels in excess of the EPA's Maximum Contamination Level (MCL).

Precambrian crystalline rocks underlying and cropping out in the mountains east of Santa Fe are the primary source of uranium, which may directly enter wells drilled in granite, or may be eroded and deposited downslope in younger rock formations. Some aquifers in the Tesuque Formation, a widespread aquifer in northern Santa Fe County, are well known for their high uranium content and are well documented to contain vitric (glassy) volcanic ash, which can release metals, including uranium, into groundwater.


Radon
Radon is a colorless, odorless radioactive gas that occurs naturally as a byproduct of uranium decay. Radon is detectable in all New Mexico groundwater, but occurs at generally higher levels in areas with an abundance of uranium mineralization such as northern Santa Fe County, which is well known for indoor radon problems. The source of uranium is naturally occurring mineral deposits which are mobilized and migrated in ground water.

The most abundant isotope of radon is Radon-222, which is a naturally occurring, colorless, odorless radioactive gas that is soluble in water and is produced during the radioactive decay of Radium-226 (Uranium-238 natural decay series) in soil, rock, and water. Radon-222 has a half-life of 3.8 days and emits alpha particle radiation. Radon-222 is the radon commonly found in ground water.

On a state map jointly developed by the EPA and the USGS, Santa Fe County (and most of northern New Mexico) is included in a Zone 1 classification (highest potential for high overall levels of radon). The map is not specifically related to the occurrence of radon in water but does provide evidence of the overall susceptibility of the area to radon.
New Mexico Radon Zone Map

The concentration of radon measured in a house depends on many factors, including the design of the house, local geology and soil conditions, and the weather. The average indoor radon concentration is about 1.3 pCi/L of air. Elevated indoor radon concentrations are most often caused by radon in soil gas, not radon in household water. In fact, only in a few areas of the United States would radon from well water be expected to make a significant contribution to radon in air concentrations. It should be noted that the majority of the health risk from radon is associated with inhalation, not ingestion, and drinking or cooking with water that contains some radon is not known to pose a significant health risk.

Since uranium decay is the source of radon, uranium testing is recommended for on-site private domestic wells that supply households having excessive indoor radon (levels greater than 4 pCi/L). If these wells are located in areas of particularly high radionuclide bedrock and soil content, homeowners may be exposed to higher levels of radon and should test their water for radon and consider taking action to reduce the radon if the concentration in the water exceeds recommended contamination levels.



Radium
Radium occurs naturally in the environment, as a decay product of both uranium and thorium and is widely distributed in the earth's crust. It is present in all uranium and thorium minerals. Radium is soluble in water. As a result, groundwater in areas where concentrations of radium are high in underlying bedrock typically has relatively high radium content. All isotopes of radium are radioactive. As they decay, they emit radiation and form new radioactive elements, until they reach stable lead.

In order to effectively test for radium, it is critical to understand the Uranium-238 and Thorium-232 decay series, the decay type (alpha or beta emission) and the half-lives. Radium-226 and Radium-228 are the radium isotopes of primary environmental concern in water because their half-lives are long enough to promote substantial environmental accumulation. EPA classifies Radium-226 and Radium-228 as human carcinogens (cancer-causing). Radium reduction is based on eliminating the "parents" of radioactive decay.