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Questions and Answers
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How can a cross-connection result in pollution of treated drinking water?
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Does the quality of drinking water in a distribution system tend to degrade over time?
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How does a Consumer Confidence Report (CCR) get distributed to the public?
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Is community water fluoridation a cost-effective method for disease prevention?
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How can nitrifying bacteria cause problems in a municipal water distribution system?
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How many types of drinking water customer categories are there for a community water system?
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Can distribution line flushing cause water quality problems?
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What is a normal rate of unaccounted for water loss from a public water system?
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Are there any benefits to installing automatic hydrant flushing units on water distribution systems?
What is a boil water order?
Public health
officials issue a Boil Water Order when there is a concern that a disaster or
other event has the potential to contaminate the water supply. Boiling your
water is a proven way to ensure that your water is safe to drink. When a Boil
Water Order is issued, you should make sure that any water used for drinking is
boiled at least three minutes (five minutes at higher altitudes) to make sure
that the water is safe. If you still have power, refrigerate the water after
boiling.
How
can a cross-connection result in pollution of treated drinking water?
A plumbing system
cross-connection is any existing or potential link between a potable (drinking)
water supply and any non-potable fluid. Any sudden loss of pressure on the
supply line can cause the contaminated fluid to be back-siphoned into the
treated water supply. Most connections to individual houses now have devices
installed at the water meter to prevent contaminated water from an individual
house from being pulled back into the potable water supply. Hoses in containers
of toxic chemicals have sometimes sucked the entire contents of the container
back into a well when the pump shut off and there was no check valve to prevent
back flow.
Does the quality of drinking water in a distribution system tend to degrade over
time?
Yes. The quality of
treated drinking water does begin to change to a certain amount as soon as it
leaves the water treatment plant. Reactions over time in the treated water and
between the treated water and the matter it comes in contact with during
distribution are continually occurring, and this can decrease the quality of the
water. Typical parameters indicating water quality changes in distribution
systems include: reduced chlorine residual, increase in heterotrophic plate
count, changes in pH, increased turbidity, increases in taste and/or odor
problems, and increases in disinfection byproducts.
How
does a Consumer Confidence Report (CCR) get distributed to the public?
One copy of the
report must be mailed to each customer, unless the governor of a state has
waived the mailing requirement for community water systems serving fewer than
10,000 persons. Systems for which the mailing requirement has been waived must:
inform their customers that the report will not be mailed; publish the report in
one or more local newspapers serving the area in which the system is located;
and make the reports available to the public upon request. A further exception
may apply to systems serving 500 or fewer persons. These systems may forego
publication of the report in a local newspaper if they provide notice by mail,
door-to-door delivery, or posting in an appropriate location that the report is
available.
Is
community water fluoridation a cost-effective method for disease prevention?
Yes. In 1999, an
estimated $56 billion was spent nationally on dental services, representing
about 5.6 percent of all expenditures for personal health care in the U.S.
during that year. The national average cost to restore one cavity with dental
amalgam is roughly $65—the approximate cost of providing fluoridation to an
individual for a lifetime.
How
can nitrifying bacteria cause problems in a municipal water distribution system?
These bacteria change
ammonia and other reduced forms of nitrogen to nitrate in water and moist soil
environments where oxygen is present. If present in treated drinking water,
these microbes can cause problems in those distribution systems where
chloramines are used for disinfection. Partial or incomplete nitrification may
produce excess nitrite, which accelerates the breakdown of chloramines and
reduces the effectiveness of the disinfection process. There is also some
concern for potential production of secondary amines and nitrosoamines, a
chemical group considered carcinogenic to humans.
Other than preventing the frequent occurrence of stagnant water, what are some
of the other advantages of having a looped distribution system instead of
dead-end distribution lines?
In the looped system,
water can flow from more than one direction when a high rate is required. A
fire-flow demand or large-demand use on a dead-end main can only draw water
through a single line, and the flow may be further restricted by the line length
and pipe size. When repairs are made on a dead-end line, the entire line has to
be taken out of service, which, without a bypass system, may mean that customers
will be out of water for a while and affected hydrants will hold little or no
water for fire protection. Also, the frequent flushing required to maintain
water quality on dead-end systems can be an excessive use of water, especially
where drought is taking its toll, or supply is at a premium.
How
many types of drinking water customer categories are there for a community water
system?
The four basic types
of customers for community drinking water systems include residential,
commercial, industrial and institutional. However, there are numerous subtypes.
For example, a public school system is an institutional subtype and a hospital
is another. It is not unusual for a consumer subtype to have its own public
water system. For example, an interstate highway rest stop or a school system
could have their own system. This however, does not exempt them from meeting
specific drinking water standards.
Can
distribution line flushing cause water quality problems?
Yes, especially if
flushing has not been performed properly. The flushing of dead-ends can lead to
dirty water complaints if sediment is stirred up and the line has not been
flushed enough to fully purge the materials. The flushing velocity should be
adequate to suspend loose sediment within the plumbing system and should
continue until the water has cleared and disinfectant residual has reached
normal expected levels.
What is a normal rate of unaccounted for water loss from a public water system?
In a properly managed
system, you can expect to have a 10 to 15 percent unaccounted for water loss
from un-metered uses, leaks, etc. If this value exceeds 20 percent, utility
managers need to become more concerned about illegal uses and leaks. Periodic
audits are recommended for all systems.
Are there any benefits to installing automatic
hydrant flushing units on water distribution systems?
Yes, most water
distribution systems that have installed them like them although they are not
completely trouble free. Special flushing units are now available or automatic
hydrant flushing attachments that connect to standard fire hydrants are
available. Advantages are savings in man-hours and travel expenses going to and
from the flushing points within the system. Since the units run on a timer they
can be set to flush in the early morning hours without the presence of a work
crew. Flushing when water demand is low has a number of advantages to include
reducing complaints associated with pressure drop and colored water that
customers sometimes experience with daytime flushing
What is the difference between surface and ground water?
Surface water is
found over the land surface in streams, ponds, marshes, lakes or other fresh
(not salty) water sources. Ground water is water occurring in the zone of
saturation in an aquifer or soil. Other than the location, one of the primary
differences between surface and ground water is that ground water moves much
slower than surface water. This is because ground water experiences far more
friction as it moves through the pores in soil than surface water experiences as
it flows over the earth’s surface. Surface water is more easily contaminated
that ground water.
How much does it cost to fluoridate drinking water?
The per person cost
of fluoridation varies by the size of the community population. The average cost
of providing fluoridated water to communities with more than 20,000 residents is
about 50 cents per year. For communities of 10,000 to 20,000 residents, the cost
is about $1, and for those living in communities of less than 5,000, the cost is
roughly $3 per year.
Is
ground water important?
Ground water, which
is found in aquifers below the surface of the Earth, is among the nation’s most
important natural resources. Ground water is the source of about 40 percent of
the water used for public supply. It provides drinking water for more than 97
percent of the rural population who do not have access t o public water–supply
systems. In addition, between 30 and 40 percent of the water used for
agriculture comes from ground water.
What is Nonpoint Source (NPS) pollution?
Nonpoint source (NPS) pollution, unlike pollution from industrial and sewage
treatment plants, comes from many different sources. NPS pollution is caused by
rainfall or snowmelt moving over and through the ground. As the runoff moves, it
picks up and carries away many natural and man-made pollutants, before
depositing them into lakes, rivers, wetlands, coastal waters, and even our
underground sources of drinking water. These pollutants often include: excess
herbicides, fertilizers, and insecticides from agricultural zones and
residential areas; oil, grease, and toxic chemicals from urban runoff and energy
production; sediment from improperly managed construction sites, crop and forest
lands, and eroding stream banks; salt from irrigation practices and acid
drainage from abandoned mines; and bacteria and nutrients from livestock, pet
wastes, and faulty septic systems. Atmospheric deposition and hydromodification
are also sources of nonpoint source pollution. (EPA-841-F-94-005, 1994 ).
What is Cryptosporidium?
Cryptosporidium is a parasite commonly found in lakes and rivers. It enters
water supplies through sewage and animal waste. It causes cryptosporidiosis, a
gastrointestinal disease. The largest water systems in the country are currently
participating in a testing program in which they check their source water for
Cryptosporidium each month for 18 months.
What are coliform bacteria?
Coliform bacteria are a class of rod shaped bacteria that can utilize lactose
(milk sugar) as a sole food source. Coliform bacteria are found essentially
everywhere, in soil, on skin, in lakes, streams, and rivers. Generally speaking,
coliform bacteria do not cause disease. The presence of coliform bacteria is
used as an indication that other disease causing organisms may be present in
drinking water.
What is the earliest record of a civilized society having a
sophisticated water and wastewater distribution system?
According to Dr. Jonathan Mark Kenoyer, professor of anthropology at the
University of Wisconsin at Madison, the ancient city of Harappa that was located
in the Indus Valley of Pakistan had both a city-wide drinking water system and
even a city sewer system. This preceded the record of such systems being
employed by the Roman Empire by over 2000 years. The Roman facilities were
limited primarily to upper-class neighborhoods. According to modern digs in the
Indus Valley region of Harappa, the city measured over 350 acres at its prime,
was fixed on three large raised mounds, had a supply of wells throughout the
city and most houses were equipped with bathing areas, latrines and sewage
drains. The sewage drains were linked to mains similar to modern sewer systems
of today and eventually emptied outside the city walls. It is believed that the
wastewater from the habitation areas was deposited on the surrounding
agricultural fields.
