Earlier this month the well owners who participated in the 2023 Prince William County Well Water Clinic received their results by email. Below you can see the summary of what was found in the 106-water analyses performed. VA Tech tested for the naturally occurring contaminants and common sources of contamination: a poorly sealed well or a nearby leaking septic system, or indications of plumbing system corrosion. These are the most common contaminants that affect drinking water wells.
To determine if treatment is necessary, water test results should be compared to a standard-usually the U.S.EPA Safe Drinking Water Act (SDW) limits. Though private wells are not regulated by the U.S. Environmental Protection Agency (EPA) or the Safe Drinking Water Act, the SDW act has primary and secondary drinking water standards that we use for comparison. Primary standards are ones that can impact health and from the tested substances include coliform bacteria, E. coli bacteria, nitrate, lead, and arsenic. Secondary standards impact taste or the perceived quality of the water.
Just because your water appears clear does not mean it is safe to drink. The 2023 Prince William County water clinic found that 22.6% of the wells tested present for coliform bacteria. This is lower than some previous years. Coliform bacteria are not a health threat itself; it is used to indicate other bacteria that may be present and identify that a well is not properly sealed from surface bacteria. The federal standard for coliform bacteria is zero, but the federal standard allows that up to 5% of samples can test positive for coliform during a month.
One of the bacteria contaminated wells tested positive for E
coli. Fecal coliform and E. coli are bacteria whose presence indicates that the
water is contaminated with human or animal wastes. Disease-causing microbes
(pathogens) in these wastes can cause diarrhea, cramps, nausea, headaches, or
other symptoms. These pathogens may pose a special health risk for infants, young
children, and those with compromised immune systems. However, people can drink
water contaminated with fecal bacteria and not notice.
If your well is contaminated with coliform but not fecal coliform or E. coli, then you have a nuisance bacteria problem, and the source may be infiltration from the surface from rain or snow melt. Typical causes are improperly sealed well cap, well repairs performed without disinfecting or adequately disinfecting the well, failed grouting or surface drainage to the well. Very low levels of coliform (1-5 MPN) may appear in an older well during extremely wet periods.
If your well was found to have coliform bacteria present you should shock chlorinate the well (according to the procedure from VA Tech), repack the soil around the well pipe to flow away from the well and replace the well cap. Then after at least two weeks and the next big rainstorm retest the well for coliform. If coliform bacteria is still present then a long-term treatment should be implemented: using UV light, ozonation, or chlorine for continuous disinfection. These systems can cost up to $2,000 installed more with supply interruptions.
If you have fecal coliform in the well or E. coli, your well
is being impacted by human or animal waste and you are drinking dilute sewage.
If there is not a nearby animal waste composting facility, then you are
probably drinking water from a failed septic system- yours or your nearest
neighbors or in some areas a leaking sewer line. To solve this problem you need
to fix or replace the septic system that is causing the contamination, replace
the well or install a disinfection and micro filtration or reverse osmosis
system. Giardia or Cryptosporidium are two microscopic parasites that can be
found in groundwater that has been impacted by surface water or sewage. Both
parasites produce cysts that cause illness and sometimes death. Chlorine can
work against Giardia but not Cryptosporidium. Ultraviolet (UV) light works
against both Giardia and Cryptosporidium so it is the preferred method of
treating this problem.
The failing septic systems can often be identified by using tracer dyes. While continuous disinfection will work to protect you from fecal bacteria and E. coli, be aware that if your well is being impacted by a septic system, then the well water might also have present traces of all the chemicals and substances that get poured down the drain. Long term treatment for disinfection, and micro-filtration should be implemented: using UV light, ozonation, or chlorine for continuous disinfection, carbon filtration, and anything that is used for drinking should be further treated with a reverse osmosis systems or micro membrane system both work by using pressure to force water through a semi-permeable membrane. Large quantities of wastewater are produced by reverse osmosis systems and need to bypass the septic system or they will overwhelm that system creating more groundwater problems. Reverse osmosis systems produce water very slowly, a pressurized storage tank and special faucet needs to be installed so that water is available to meet the demand for drinking and cooking.
Nitrate can contaminate well water from fertilizer use; leaking from septic tanks, sewage and erosion of natural deposits. None of the wells in our group of 102 samples had nitrate levels above the MCL. The regulatory limit for nitrate in public drinking water supplies, 10 mg/L, was set to protect against infant methemoglobinemia, but other health effects were not considered and are emerging as problems.
Dr. Mary Ward of the Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute has lead several important studies comparing all the research on the health impacts from exposure to nitrate in water. The first review was of studies published before 2005. In 2018 Dr. Ward was lead author on a review of more than 30 epidemiologic studies on drinking water nitrate and health outcomes.
This year they found 7.5% of homes had first draw lead levels above the SDWA maximum contaminant level of 0.015 Mg/L. After flushing the tap for at least one minute one home had lead levels above the 0.15 mg/L level; however, many scientists do not believe that any level of lead is safe to drink over an extended period of time. Often homes that have elevated lead in the first draw, have lower pH values.
Houses built before 1988 when the ban on lead went into effect and have low pH water typically have higher lead concentrations. Lead leaches into water primarily as a result of corrosion of plumbing and components in the well itself but can also result from flaking of scale from brass fittings and well components. Corrosion control techniques such as adjusting pH or alkalinity that are commonly used to neutralize aggressive water will not work in to reduce lead being leached from well components. For most instances, though, a neutralizing filter and lead removing activated carbon filters can be used to remove lead leaching from plumbing pipes, solder and fixtures. Recently, some home water treatment companies are offering home treatment systems that neutralize the water and add orthophosphate other phosphate solution to coat the piping to prevent further corrosion of metal pipes. It should work, but I have never seen such a home system and am not aware of any testing. Public water distribution systems typically use orthophosphate to coat pipes and prevent corrosion an release of lead.
Iron and manganese are naturally occurring elements commonly found in groundwater in this part of the country. 3.8% of the wells tested exceed the iron standard and 8.5% exceeded the manganese standard. At naturally occurring levels iron and manganese do not present a health hazard. However, their presence in well water can cause unpleasant taste, staining and accumulation of mineral solids that can clog water treatment equipment and plumbing and discolored water. The standard Secondary Maximum Contaminant Level (SMCL) for iron is 0.3 milligrams per liter (mg/L or ppm) and 0.05 mg/L for manganese. This level of iron and manganese can be detected by taste, smell, or appearance. In addition, some types of bacteria react with soluble forms of iron and manganese and form persistent bacterial contamination in a well, water system and any treatment systems. These organisms change the iron and manganese from a soluble form into a less black or reddish brown gelatinous material (slime). Masses of mucous, iron, and/or manganese can clog plumbing and water treatment equipment.
All systems of removing iron and manganese essentially involve oxidation of the soluble form or killing and removal of the iron bacteria. When the total combined iron and manganese concentration is less than 15 mg/l, an oxidizing filter is the recommended solution. (Iron bacteria, hydrogen sulfide and tannins can also be removed with pre-chlorination.) An oxidizing filter supplies oxygen to convert ferrous iron into a solid form which can be filtered out of the water. Higher concentrations of iron and manganese can be treated with an aeration and filtration system. This system is not effective on water with iron/ manganese bacteria but is very effective on soluble iron and manganese, so you need to do further testing to determine what type of iron/manganese you have before you install a treatment system. Newer iron filters have an option to add an ozone generator to kill reducing bacteria. Water softeners can remove low levels of iron and manganese and are widely sold for this purpose because they are very profitable but are now being banned in some locations due to rising sodium and chloride levels, what is known as inland salinization. Also, water softeners are easily clogged by iron bacteria.
Chemical oxidation can be used to remove high levels of dissolved or oxidized iron and manganese as well as treat the presence of iron/manganese (or even sulfur) bacteria. The system consists of a small pump that puts an oxidizing agent into the water before the pressure tank. The water will need about 20 minutes for oxidation to take place so treating before a holding tank or pressure tank is a must. After the solid particles have formed the water is filtered. The best oxidizing agents are chlorine or hydrogen peroxide. If chlorine is used, an activated carbon filter is often used to finish the water and remove the chlorine taste. The holding tank or pressure tank will have to be cleaned regularly to remove any settled particles.
The pH of water is a measure of the acidity or alkalinity. The pH is a logarithmic scale from 0 – 14 with 1 being very acidic and 14 very alkaline. Drinking water should be between 6.5 and 8.5. For reference and to put this into perspective, coffee has a pH of around 5 and salt water has a pH of around 9. Corrosive water, sometimes also called aggressive water is typically water with a low pH. (Alkaline water can also be corrosive.) Low pH water can corrode metal plumbing fixtures causing lead and copper to leach into the water and causing pitting and leaks in the plumbing system. The presence of lead or copper in water is most commonly leaching from the plumbing system or well rather than the groundwater. Acidic water is easily treated using an acid neutralizing filter. Typically these neutralizing filters use a granular marble, calcium carbonate or lime. If the water is very acidic a mixing tank using soda ash, sodium carbonate or sodium hydroxide can be used. The acid neutralizing filters will increase the hardness of the water because of the addition of calcium carbonate. 7.5% of the wells tested were found to have acidic water this year. Two wells had too high a pH. This is usually from over treating with a water softener.
Water that contains high levels of dissolved minerals is commonly referred to as hard. Groundwater very slowly wears away at the rocks and minerals picking up small amounts of calcium and magnesium ions. Water containing approximately 125 mg/L can begin to have a noticeable impact and is considered hard. Concentrations above 180 mg/L are considered very hard. Hard water can be just a minor annoyance with spotting and the buildup of lime scale, but once water reaches the very hard level 180 mg/L or 10.5 grains per gallon, it can become problematic. Overall 20.8% of homes tested had very hard water. (It is to be noted that 45.3% of homes reported having a water softener.)
Two methods are commercially available (and certified) to treat hard water. A water softener and a water system that work through a process called template assisted crystallization (TAC), have been certified by DVGW-W512 and are available in whole house units. In template assisted crystallization, water flows through a tank of TAC media. When the hard water comes into contact with the media, the magnesium and calcium ions are caught by the nucleation sites. As more calcium and magnesium ions build up within the sites, small micro-crystals form and flow through your plumbing. They do not attach themselves to your water pipes as scale.
The ubiquitous water softening system is an ion exchange
system consisting of a mineral tank and a brine tank. The mineral tank holds
small beads of resin that have a negative electrical charge. The calcium and
magnesium ions (along with small amounts of other minerals) are positively
charged and are attracted to the negatively charged beads. This attraction
makes the minerals stick to the beads as the hard water passes through the
mineral tank. Sodium from salt is used to charge the resin beads. The brine
tank is flushed out when the resin beads are recharged carrying the salty
solution to the environment. Inland salinization of surface waters and
groundwater is an emerging environmental concern. Research has shown that
salinization has affected over a third of the drainage area of the contiguous
United States even in areas without road salt. At the present time the EPA
guidance level for sodium in drinking water is 20 mg/L. Given the number of
homes with elevated sodium and our local geology, it is probably a reflection
of the number of homes with water softeners-54.7% of the wells tested had
One of wells was found that had arsenic exceeding the EPA MCL for drinking water of 10 ppm. While arsenic is a naturally occurring element found in soil and groundwater it is not typically found at significantly elevated levels in this geology. Arsenic is best removed by water treatment methods such as reverse osmosis, ultra-filtration, distillation, or as a last choice ion exchange (water softeners). Typically, these methods are used to treat water at only one faucet. Though anionic exchange systems (water softeners) are whole house systems, they may not be the best choice.