As part of the Virginia Household Water Quality Program the Virginia Cooperative Extension (VCE) holds an annual subsidized drinking water clinics for well owners. This year samples were analyzed for: iron, manganese, nitrate, lead, arsenic, fluoride, sulfate, pH, total dissolved solids, hardness, sodium, copper, total coliform bacteria and E. Coli bacteria at a cost of $55 to the well owner. These are mostly 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. Though this is not an exhaustive list of potential contaminants, these are the most common contaminants that effect drinking water wells. The chart below shows what we found in the 65 private wells tested in Prince William County in 2016.
In order to determine if treatment is necessary, water test results should be compared to a standard. The standard we use is the U.S.EPA Safe Drinking Water Act , SDW, private wells do not fall under the regulatory authority of the U.S. Environmental Protection Agency (EPA) or the Safe Drinking Water Act. The SDW act has primary and secondary drinking water standards. Primary standards are ones that can impact health and from the tested substances include: coliform bacteria, E. coli bacteria, nitrate, lead, and arsenic.
As in last year, the 2016 Prince William County water clinic found that almost a quarter of the wells tested present for coliform bacteria-this was a lower percentage than the overall program finds. 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.
None of the homes 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 water 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, failed grouting or surface drainage to the well. Shock chlorinate the well, repack the soil around the well pipe to flow away from the well and replace the well cap. Then after the next big rainstorm retest the well for coliform. If it 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.
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. 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 filtration system. Disinfection does not kill Giardia or Cryptosporidium, 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.
Membrane filtration is the usual treatment for these parasites- a one micron membrane is required after disinfection and can be accomplished at home with a reverse osmosis system. 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 that 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 65 samples had nitrate levels above the MCL. The MCL for nitrate is 10 mg/L. Infants below the age of six months who drink water containing nitrate in excess of the MCL could become seriously ill from blue-baby syndrome and, if untreated, may die. Symptoms include shortness of breath and a blue ting to the skin common in blue-baby syndrome. The NO3 dissolves and moves easily through soil which varies seasonally and over time as plants use up the nitrate over the summer. Testing in the spring will usually produce the highest levels. Nitrate may indicate contamination from septic tanks, but do not boil the water- boiling water reduces the water and actually INCREASES the concentration of nitrates. Reverse osmosis, or ion exchange is necessary to control the nitrate.
In years past the water clinic has found almost 20% of wells tested positive for lead. This year we had 13.8% of homes have first flush lead levels above the SDWA maximum contaminant level of 0.015 Mg/L. After the first flush only 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. In the homes that had elevated lead in the first draw, all but one case lead were the concentrations negatively correlated with pH values. Houses built before 1988 when the ban on lead went into effect and had low pH water had higher lead concentrations. Lead leaches into water primarily as a result of corrosion of plumbing and well components, but can also result from flaking of scale from brass fittings and well components unrelated to corrosion and corrosion control techniques such as adjusting pH or alkalinity that are commonly used to neutralize aggressive water will not work in those cases. For most instances, though, a neutralizing filter and lead removing activated carbon filters can be used to remove lead. Recently, some home water treatment companies are offering in home treatment systems that neutralize the water and add orthophosphate other phosphate solution to coat the piping to prevent further corrosion. It should work, but I have never seen such a home system and am not aware of any testing. It is important to note that elevated lead concentrations were still observed in homes built after 1988 and in one home with normal pH and built after 2000.
Iron and manganese are naturally occurring elements commonly found in groundwater in this part of the country. 9.2% of the wells tested exceed the iron standard and 1% 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 are easily 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 soluble form, thus causing precipitation and accumulation of 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. 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. Water softeners can remove low levels of iron, but are not recommended for just this purpose. 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 7.5. 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 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. The sodium based systems will increase the salt content in the water. 21.5% of the wells tested were found to have acidic water this year. High pH levels are not natural to groundwater and typically result from salt water intrusion or over treatment with water softening system and/acid neutralizing systems. There was one home where this turned out to be the case.
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. As the mineral level climbs, bath soap combines with the minerals and forms a pasty scum that accumulates on bathtubs and sinks. You either must use more soap and detergent in washing or use specially formulated hard water soap solutions. 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, 22% of the wells had hard water exceeding that level. This year we had a well test at 346.8 mg/L, but overall on 15.4% of homes tested had hard water. 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.
Water softening systems are used to address the problem are basically an ion exchange system. The water softening system consists of a mineral tank and a brine tank. The water supply pipe is connected to the mineral tank so that water coming into the house must pass through the tank before it can be used. The mineral tank holds small beads of resin that have a negative electrical charge. The calcium and magnesium ions 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 is often used to charge the resin beads. Water softeners can be used to remove small amounts of other metals like iron and some forms of arsenic. As the water is softened, the sodium ions are replaced and small quantities of sodium are released into the softened water, thus the salty taste of softened water. When the water softening system is recharged the excess sodium solution carrying the calcium and magnesium is flushed to the septic system which may shorten the life of the drain field.
At the present time the EPA guidance level for sodium in drinking water is 20 mg/L. This level was developed for those restricted to a total sodium intake of 500 mg/day and does not necessarily represent a necessary level for the rest of the population. Based on taste of the water levels of sodium should be below 30 to 60 mg/L based on individual taste. Water softeners ten to cost around $4,500 installed. They are often sold to solve every water quality problem because they have some ability to remove other contaminants. The resin bed used will determine specific contaminant removal. Softened water can have a low pH and high levels of chloride, corrosion control problems and softening systems can encourage the growth of reducing bacteria. Water softening systems add sodium. Reverse osmosis systems and distillation systems remove sodium and are safe for household use, but addressing hard water by using vinegar to descale pots and dishwashers, regularly draining hot water heaters, and using detergents formulated for hard water might be a better solution for you if your water like mine is only modestly hard.
For the second time this year we found a well 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 Prince William County. Arsenic can also be an indication of industrial or pesticide contamination and further testing should be done. Arsenic can be very tricky to remove depending on its form and the other contaminants present. Possible solutions for elevated levels of naturally occurring arsenic are reverse osmosis system, iron oxide filter system, or maybe a water softening system.
No comments:
Post a Comment