©2016 Mahoning Valley Water Inc.  Bacteria and Water Wells Part I What Is Bacteria?      Bacteria are microscopic organisms.  They are so tiny that about 25,000 lined up would take about three inches.  Bacteria have existed for a very long time.  There are micro-fossils in the geologic record that show bacteria were in existence 3.2 billion years ago.  Some researchers believe that the first oxygen that appeared on Earth, 2 billion years ago, was created by bacteria.      Bacteria are highly resilient.  They can remain dormant when conditions are not ideal.  Some bacteria can even be frozen and become active when thawed.  Dried, but living, bacteria can be carried through the air.  Bacteria can excrete toxins or carry them inside their cell wall until they die and disintegrate.  The poisons are called exotoxins.  Some bacteria may invade a specific organ of the body, for example the brain, throat or bone.  Bacteria may produce enzymes that are responsible for illness.      Not all bacteria cause disease and harm living creatures.  In fact, most bacteria are beneficial.  Bacteria are the beginning of the world's food chain, and as decomposers, bacteria play a critical role in recycling organic materials essential to plants and animals.  Great numbers of bacteria live on human skin surfaces; there are millions in one drop of saliva.  Bacteria are an essential part of the digestive process of animals and insects.  Bacteria are used to clean up environmental contamination.  Septic systems and most waste water treatment facilities are designed to allow the work of bacteria to naturally break down harmful components. Viruses And Protozoa      In addition to bacteria, two other types of pathogenic (disease producing) organisms can affect water quality, viruses and protozoa.  The disease causing organisms usually leave an infected person via the feces.  They may cause illness in anyone drinking the contaminated water. Bacteriologic and protozoic pathogens are known to cause typhoid, dysentery, cholera, and some types of gastroenteritis.  Viruses are the smallest microorganisms known to scientists.  They differ from bacteria in that they have no distinct metabolism of their own and live in the cells of their living hosts.  Viruses account for more than 100 human diseases including polio and infectious hepatitis. Coliform Bacteria      Coliform bacteria is the name most associated with water quality.  The EPA standard for safe drinking water is total coliform count of zero.  Coliform bacteria occur naturally in the intestines of warm-blooded animals.  Coliform can be easily cultured in a laboratory and therefore, they are a good indicator species.  While coliform bacteria are not in themselves harmful, their presence in a water sample indicates that sewage water may be present and that if sewage is present, more harmful disease causing organisms may also be present. Iron Bacteria      Some bacteria that occur in wells, while not themselves harmful, can cause problems.  Iron bacteria can cause staining of plumbing fittings and laundry, can provide a place in wells for other bacteria to live, can increase corrosion, and can cause encrustation of well screen and pumps.  Iron and sulphur bacteria cause a build-up of a biofilm in wells.  By providing an environment for other more harmful bacteria to live, the slime reduces the effectiveness of chlorine in removing bacteria problems.       Another negative effect of iron bacteria is that they can cause electrons from ferrous iron (dissolved) to be converted to ferric iron (particulate).  This results in increased oxidation (corrosion) of pipes and pumps.  An additional problem is that the free ferric iron can bind with other chemicals to cause clogging of pump intakes, well screens and water filters.  A reduction in the inflow spaces to a well will cause and increase in speed of water flow in the remaining spaces; this turbulent flow causes the release of even more minerals to clog the well and water system. How Can Bacteria Get Into A Well?      A properly constructed and adequately cased (lined) and grouted (sealed) water well usually obtains its water at a depth at which bacteria is no longer present.  Bacteria are usually filtered out, or they die off, as water infiltrates and slowly moves in the subsurface ground water environment.  However, ground water can become bacteriologically affected when there is insufficient filtration or travel time between the land surface and the ground water.      Bacteria occur in upper soil layers and in most streams, lakes, and ponds; in addition, there can be concentrated bacteria sources such as inefficient septic systems, farm animals and storm run-off.  There are several ways in which bacteria actually get into a well.      Any shallow or dug well that is constructed from boards, bricks, stone, or tile, is vulnerable to surface water contamination.  Dug wells, with their water in  contact with saturated soil layers, are particularly at risk because bacteria affected water can seep straight into the well.  Insect infestation is very difficult to prevent in large diameter wells.      If a drilled or bored well has a casing that has not been properly sealed with grouting around the metal casing to a depth of 10-20 feet (or the original grout seal has deteriorated over time), it is possible for bacteria from the upper soil layers to leak down into the well.  In such cases, surface water or contaminated ground water may move vertically downward contaminating high quality aquifers. Surface water can enter the top of the well during a flood or from storm runoff, if the casing does not extend far enough above the ground or if there is no water-tight seal on the well casing.  Wells that are in pits below ground level may be especially vulnerable to the effects of bacteria.  Over time, well casing may rust through, leaving holes near the ground surface where water can seep in and contaminate deeper ground water.      Earthquakes, subsidence and settling around the well, or impact damage from farm implements or snow plows, can make a well susceptible to contamination.  Bacteria from the ground surface can be introduced into the well when it is drilled, or when a pump is installed or serviced.  Unsealed abandoned water wells and geotechnical drill holes can be conduits for bacteriologically affected surface water to reach aquifers and subsequently, other normally bacteria free wells.      Back-flow prevention devices are essential to prevent any risk of contamination from being siphoned into the well.  An example of this problem could occur if a power failure stopped a pump while a garden hose was filling a fish pond.  Without a back-flow device, water from the fish pond could be siphoned back down the well.      Wells may become infected when ground water levels rise above normal and extend up to soil levels where bacteria are present.  This can occur 1) in times of exceptional rainfall, 2) if major long-term water use by a nearby irrigation or municipal well ceases, or 3) when road construction, mining construction or dam construction lead to water level changes in wells. 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