You Can Fix a Well with E Coli

If you find E colie or fecal coliform in your well the first step you should take is to protect your health then try and identify the source of the E coli and eliminate it.

1. If the sample tests positive for E coli then the first thing to do is chlorine shock not only the well, but also the inside piping and any treatment equipment to disinfect your home. 
2. Retest the water after the chlorine has left the system in about 10 days to two weeks see if E coli is present. 
3. If your well water tests positive again for total E coli, then the water must be treated to make it safe for consumption, while the source of is identified and eliminated if possible. 

Possible sources of E. coli contamination are septic tanks leaks, septic leach field or system failure, animal manure storage systems or in some areas with installed sewer systems and wells, sewer pipe leaks. There are instances when a neighborhood is hooked up to sewers, some of the homes do not pump out the old septic tanks and years later are found leaking.

Shallow groundwater is most easily contaminated by septic leaks, septic system failures, animal waste and sewer leaks. Nonetheless, in certain geology shallow sources of contamination can find their way into deeper groundwater. In fractured rock systems with limited overburden like we have here in the western portion of Prince William county, a fracture can carry contamination to deeper groundwater and spread the contamination.

Very shallow groundwater wells- dug or bored wells often become contaminated when the shallow aquifer becomes contaminated. These types of are prone to go dry during droughts and because they are shallow (less than 40 feet deep) are more subject to pollution. Drilled wells have more protection since they are more than 40 feet deep, typically more than 100 feet deep.

Well construction defects such as insufficient well casing depth, improper sealing of the space between the well casing and the borehole, corroded or cracked well casings, and poor well seals or caps can allow sewage, surface water, or insects to carry coliform bacteria into the well.

To prevent contamination to a well, regulations in Virginia and several other states have specified well construction standards since 1992. To provide the best natural protection these regulation require that the well should be 100 feet from the nearest edge of the septic drainfield and 50 feet from the nearest corner of the house. If the land area is small, the way to accomplish this is to separate the two as far as possible, with the septic drainfield downgradient of the well and go deep with the well. Obtaining the needed separation with vertical distance.

In Virginia (and most places) if a well is more than 100 feet deep the septic leach field need be only 50 feet away, but there are many wells like mine that have more than one water level and the shallower one is less than 100 feet deep (in my case 46 feet) making the well much more susceptible to contamination for the septic effluent leaching into the ground. You must make sure that the well is lined, grouted and the geology protects you from the drainfield to protect the well from the shallow ground water and being impacted by the septic system.

Septic drainfields also have a limited life. The life of a septic drainfield is dependent on how the system is managed, the frequency of septic tank pump outs, and the number of people living in a house, but 25-30 years is the typical life of those systems. After decades of use a septic drainfield can become a long term source of fecal or E coli contamination

Fecal coliform is the group of the total coliform that is considered to be present specifically in the gut and feces of warm-blooded animals. E. coli is considered to be the species of coliform bacteria that is the best indicator of fecal pollution and the possible presence of pathogens.

Back in the day we always recommended that a well that was contaminated with E coli be replaced with a new well. That is not always possible or desirable. I have observed several instances where E coli was eliminated from a well after repair of a failing septic system, but that takes time; so in the meantime the water must be treated to make it safe for consumption. Replacing a well can cost between $10,000 and $20,000, and cannot always be done.

Continuous disinfection of the water is necessary to protect you from fecal bacteria and E. coli. This is easily accomplished by installing either a UV (ultra violet) light or chlorine disinfection system. Your choice of systems should be based on personal preference and what other contaminants are present in your water. Both UV light and continuous chlorination do a good job of killing coliform bacteria including fecal coliform and E coli. However, chlorine treatment will control nuisance organisms such as iron, manganese, iron and manganese reducing bacteria and sulfate-reducing bacteria. Chlorine in water at the concentrations used for treatment is not poisonous to humans or animals. However, chlorine can impact the smell and/or taste of water even in very low concentrations. Household chlorination systems often use higher chlorine concentration than the typical 0.3 - 0.5 ppm (parts per million) concentration used for chlorination of public water supplies because the contact time is much shorter in home systems. UV light systems require filtration before the UV light maximize the functioning of the UV light system.

Both UV light and chlorine disinfection require additional treatment. Neither method of disinfection kills Giardia or Cryptosporidium, two microscopic parasites that can be found in surface water and groundwater that has been impacted by sewage. Both parasites produce cysts that cause illness and sometimes death. Giardia are often found in human, and dog feces. Cattle feces appear to be the primary source of Cryptosporidium, although these parasites have also been found in humans and other animals. Membrane filtration is the usual treatment for these parasites- a one micron or smaller membrane is required for this. There are new filter systems that combine carbon and one micron or smaller membrane a a special filter designed for this purpose.

Many manufacturers make whole house filters, typically they make a casings in 10, 20 or 30 inch and make different cartridges to address the various problems. To ensure that a filter removes Cryptosporidium, you can look for "NSF 53" or "NSF 58" and the words "cyst reduction" or "cyst removal." Reverse osmosis can also accomplish parasite removal, but typically only treats one sink rather than a whole house, wastes a lot of water, and if your water is at all hard requires a water softening system.