The Virginia Cooperative Extension (VCE) Offices in
Virginia occasionally holds drinking water clinics for well, spring and cistern
owners as part of the Virginia Household Water Quality Program. The VCE
subsidizes the analysis cost for these clinics. Currently, samples are 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 $49 to the well owner. This is far from an exhaustive
list of potential contaminants, but with one or two exceptions these are the
most common contaminants that effect drinking water wells. 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.
There are other contaminants that can be found in ground
water in certain regions that can cause illness when exposed to small amounts
over long periods of time Uranium is an example. There are also nuisance
contaminants for which there is not an approved EPA methodology, iron bacteria
is an example. A through water analysis should be performed before any
treatment is considered to make sure the selected treatment is necessary and
appropriate. Wells should be tested annually for bacteria and every 1-3 years
for other common contaminants especially if you install treatment systems.
Groundwater is dynamic and can change over time, and it is important to make sure
that any treatment is still appropriate and effective. Water treatment systems are not an install
and forget piece of equipment, they are more systems to maintain, adjust and
control to keep the water within ideal parameters. Improperly treated water can
be as problematic as not treating water.
In order to determine if treatment is necessary, water
test results should be compared to a standard. The standard we use if the
U.S.EPA Safe Drinking Water Act in the list to the left. There are primary and secondary
drinking water standards. Primary standards are ones that can impact health and
from the list above include: coliform bacteria, E. coli and fecal coliform
bacteria, nitrate, lead, and arsenic. Groundwater can sometimes be contaminate
from nearby or historic land use. Before a home is purchased a much more
comprehensive water analysis should be performed to ensure that groundwater is
not contaminated with hydrocarbons, solvents, fuels, heavy metals, pesticides.
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. New coliform standards are
anticipated to be promulgated shortly. 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.
If you have fecal coliform in the well or E. coli, your
well is being impacted by human or animal waste. 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 either fix or replace the septic system that is causing the contamination
or replace the well. 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. This is the
type of system that is used to desalinate water. 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. 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. So if your water is being impacted by a septic
system and you do not replace the well; distillation, reverse osmosis, or ion
exchange is necessary to control the nitrate.
The EPA guidance for sulfate is 250 ppm for taste. Sulfates can
clog plumbing and stain clothing and excessive levels can have a laxative
effect. If you have hydrogen sulfate above 0.5 ppm you can probably smell the
rotten egg smell in your water especially when the water is heated. Hydrogen
sulfide naturally occurs in shale, sandstone, and near coal or oil fields.
Sulfate and hydrogen sulfide are not regulated by the EPA for drinking water,
they are a secondary contaminant and though extremely unpleasant, harmless to
animals, but not to plumbing equipment. There is a related problem (for which
there are limited methods of testing) of sulfur reducing bacteria. According to
the EPA, sulfur-reducing bacteria and sulfur-oxidizing bacteria pose no known
health risks. Sulfur-reducing bacteria live in oxygen-deficient environments
such as deep wells, plumbing systems, water softeners, and water heaters. These
bacteria usually flourish in hot water tanks and pipes. Sulfate reduction can
occur over a wide range of pH, pressure, temperature, and salinity conditions
and produce the rotten egg smell and the blackening of water and sediment by
iron sulfide. Sulfate-reducing bacteria can cause the corrosion of iron in
pipes and water systems.
The treatment method selected depends on many factors
including the level of sulfate in the water, the amount of iron and manganese
in the water, and if bacterial contamination also must be treated. High
concentrations of dissolved hydrogen sulfide also can foul the resin bed of an
ion exchange water softener. When a hydrogen sulfide odor occurs in treated
water (softened or filtered) and no hydrogen sulfide is detected in the
non-treated water, it usually indicates the presence of some form of
sulfate-reducing bacteria in the system. Water softeners provide an environment
for these bacteria to grow. “salt-loving” bacteria, that use sulfates as an
energy source, may produce a black slime inside water softeners. If you have
modest sulfate, but no rotten egg smell, installing a water softening system
may create additional problems, especially if the system is not meticulously
maintained. If you have a rotten egg smell associated with the hot water and
elevated levels of sulfate on the cold water side, your hot water tank may be
fouled with sulfur reducing bacteria, or the tank’s corrosion control rod may
be causing the sulfur to react in the heated environment.
Iron and manganese are naturally occurring elements
commonly found in groundwater in this part of the country. 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. 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.
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.
Fluoride occurs naturally in groundwater and in certain
parts of Eastern Virginia there are very high naturally occurring levels.
Fluoride is a primary water contaminant and the EPA MCL 4.0 mg/L and SMCL 2.0
mg/L. Fluoride is typically added in small quantities to public water supplies
the optimum concentrations for public systems 0.8 - 1.2 mg/L. Excessive levels
of fluoride can cause fluorosis or bone cancer over long term exposure. Treatment
for excessive levels of fluoride in water is typically reverse osmosis which
will remove all fluoride and minerals from water.
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.
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. Concentration 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. Hard water spots appear on
everything that is washed in and around the home from dishes and silverware to
the floor tiles and cars. When heated calcium carbonate and magnesium carbonate
are removed from the water and form a scale (lime scale) in cookware, hot water
pipes, and water heaters.
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. 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 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.
Arsenic is not a common contaminant in groundwater that
has not been impacted from surface runoff. Arsenic can be caused by erosion of
natural deposits, but is more typically caused by runoff from orchards, runoff
from glass & electronics production wastes, or leaching from coal ash disposal
of or agricultural chemical mixing
areas. The EPA standard for arsenic is
0.01 mg/L. Arsenic removal depends on the type of arsenic (there are two types)
and the other contaminants present in water. Arsenic removal methods or systems include anion exchange, reverse
osmosis, activated alumina, and other types of adsorptive media filters. Each
method has its limitations, advantages and disadvantages and should be chosen
based on additional analysis.
