Minerals, salts, metals, and cations/anions dissolve into the water from natural sources and can also be incorporated in water supplies due to urban-runoff, sewage, and industrial wastewater. Additionally, the chemicals used in the water treatment process contribute more dissolved solids. These contribute to the hardness and can leave spots on clean dishes or create a bad taste to the water.
In recent years, many people are taking medications for their health. Recent concerns have arisen about disposal methods of unused prescription medications; the EPA is investigating the impact of flushed pharmaceuticals on people's drinking water. As yet, no known impact has been noted for human consumption; it is suspected to be impacting breeding habits and hormone levels of natural wildlife.
In addition to Hardness and Dissolved Solids, well water comes with additional potential contaminants:
Some metals like Lead, Chromium, Arsenic, and Mercury, to name a few, can leech into ground water from agricultural, industrial, or domestic sources. While, in low doses, these metals are not harmful, if present in high quantities, these metals can pose health risks. Laboratory testing is required to isolate these components if they are suspected to be present. Those who live in close proximity to mines or industrial plants are more susceptible.
Noticeable as a strong rotten-egg smell, Sulfur is most often present as Hydrogen Sulfide gas. Decomposing plant material, sulfur reducing bacteria, and natural mineral deposits contribute to the increased levels of Hydrogen Sulfide in the water. Sulfate mineral also dissolves in the water from natural deposits and creates the same smell. In lower quantities, Sulfur is not harmful, however in rare cases of extremely high levels it can be poisonous or flammable.
Present in either dissolved or suspended states, Iron is notable as a brown staining that collects in the home. The iron builds up in piping and can restrict the flow of water. It is not unsafe to drink the iron, though it may be undesirable as it adds a metallic taste and smell to the water. Some bacteria feed on iron as well and will live in toilet tanks.
Small grit, clay, dirt, and rocks can filter into the water table and into the well from surface-runoff. Shallow wells are more susceptible to sediment issues. Sediment builds up in faucet screens and restricts flow throughout the home. Though typically harmless, sediment causes water to be brown and unappealingly muddy.
E-Coli and Coliform bacteria can cause serious illness. Typically, these kinds of bacteria get into the well from surface run-off and are present in fecal matter of humans and animals. Homes located nearby livestock farms and waste disposal sites are more susceptible to bacteria infection. Diarrhea and stomach ache are the common symptoms associated with bacteria consumption. Laboratory testing is highly recommended if bacteria is suspected.
Nitrates are typically introduced to the water table from the decomposition of plant matter and animal wastes. Fertilizers are a major contributor to excessive Nitrate levels. In small quantities, Nitrates are harmless; in excess, Nitrates can cause serious complications for infants leading to "blue baby syndrome". Laboratory testing is recommended if Nitrates are suspected.