Which microbes lurk in the clear, crisp water that flows
from the tap? The potential answer to this question has spurred millions of
Americans to purchase point-of-use and point-of-entry removal technologies as a
preemptive strike. However, these units rely heavily on water utilities to
remove most, if not all, contaminants that pose a health threat. This article
provides a general overview of E. coli and drinking water as well as current
and emerging monitoring and decontamination technologies.
When sickness occurs from E. coli contamination, people
often think of food poisoning. Ingestion of E. coli tainted meat or dairy
products has received wide press coverage over the past 15 years, particularly
when mass outbreaks occurred from consuming fast-food hamburgers. Swimming in
infected ponds and beaches also has generated attention, and such public
information sites as the National Resources Defense Council (www.nrdc.org) list
U.S. beaches or entire states that either lack enforcement or regularly enforce
monitoring of such pathogens as E. coli.
E. coli is not synonymous with drinking water in most
Americans' minds. Occasionally, counties will advise residents to boil
their tap water as most in-home filters cannot filter E. coli out of drinking
water, according to the U.S. Environmental Protection Agency (EPA). Such
advisories result from an increased risk of contamination due to stormwater
runoff from creeks, groundwater, lakes or streams that flow into a town or
city's drinking water system. An outbreak in 1998 sickened 157 people
when deer and elk feces seeped into a Wyoming aquifier that provided a
town's drinking water. The incident highlighted treatment inadequacies in
small water systems--the water in this Wyoming system was unchlorinated.
E. coli poses a risk in any untreated water system,
particularly wells. In some rural parts of the United States, residents still
rely on these sources for their drinking water, and the consequences of
ingesting untreated water can be devastating. In 1999, 921 people who attended
the Washington County Fair in New York reported diarrhea; two people died.
While much of the fair was supplied with chlorinated water, a small section of
the fairground had drawn water from a well to boil food and make ice cubes. Environmental
cultures from this well revealed high levels of coliforms and E. coli.
E. coli is especially dangerous to children, the elderly and
immuno-suppressed, but even the healthiest person cannot ward off this
pathogen. While most strains of E. coli are harmless and live in the intestines
of healthy humans and animals, the strain O157:H7 produces a powerful toxin and
can cause abdominal cramps and severe diarrhea that often contains blood. In
rare cases, individuals may develop emolytic uremic syndrome, where the red
blood cells are destroyed and the kidneys fail.
The EPA long has recognized E. coli as a national health
threat. The Safe Drinking Water Act (SDWA) is the main federal law that ensures
the safety of U.S. drinking water and is overseen by the EPA. All public water
systems--defined as systems that operate at least 60 days per year and
serve 25 people or more or have 15 or more service connections--are
required under the SDWA to monitor for total coliform. Large public water systems
that serve millions of people must take 480 samples a month and smaller systems
must take at least five samples a month, unless the system has under gone a
sanitary survey within the last five years. The survey involves a state
inspector examining the system's components and ensuring they will
protect public health. Finally, the smallest water systems--those serving
only 25 to 1,000 people--typically take only one sample per month. (For
more information on E. coli and the SDWA, see the EPA's fact sheet on E.
coli in drinking water at www.epa.gov/safewater/ecoli.html.)
With the responsibility of public health squarely on their
shoulders, cash-strapped public water treatment systems must employ the most
cost-efficient monitoring and disinfection technology to meet regulations.
Common monitoring technologies include culture, enzyme-linked immunosorbent
assays, fluorescence in-situ hybridization/confocal laser scanning microscopy
and polymerase chain reaction (PCR).
EPA-approved analytical methods for coliform assay are published
in the Federal Register under the Total Coliform Rule. To comply with the
provisions of the rule, public water systems must conduct analyses using one of
seven analytical methods (these methods can be viewed at www.epa.gov/
OGWDW/methods/tcr_tbl.html).
Most water quality monitoring involves a multistep process
that cannot be conducted at the actual site from which the water sample is
taken. Instead, samples should be sent to your lab for an analyzation process
that involves culturing bacteria in an incubator or passing water through a
membrane filter, to see if the targeted bacteria such as E. coli and other
harmful fecal coliform are present in the water sample. This method can take
anywhere from six to 30 hours.
Real-time detection technologies are emerging from research
and development at universities, small companies and the Federal Small Business
Innovation Research (SBIR) program. (For more information on SBIR, visit
www.zyn.com/sbir.) Biosensors promise to detect live and dead bacteria, fungi,
viruses and more. Some employ several sensors to determine minute quantities of
biological materials such as protein or DNA to detect an array of pathogens.
Rugged, durable and reliable new technologies such as biosensors promise to
give accurate results in less time in both the laboratory and field settings.
There are a variety of treatment processes available to
remove contaminants from public water including flocculation/sedimentation,
filtration, ion exchange, adsorption and disinfection, used alone or in
combination. Under each of these processes are a number of products employing
different technology. For instance, disinfection of water can be achieved both
by chlorination and ozonation. Filtration enhances the effectiveness of
disinfection by removing remaining particles from the water supply.
Filtration technologies are becoming more sophisticated and,
eventually, may be used on their own to treat drinking water. Argonide
Nanomaterials, an Orlando-based manufacturer of nanoparticles and nanofiltration
products, has developed NanoCeram, which is capable of filtering 99.9 percent
of viruses at water flow rates several hundred times greater than virus-rated
ultra porous membranes. The product's performance is attributed to its
nano-size alumina and a highly electropositive surface that attracts and
retains sub-micron and nanosize particles more effectively than larger ones.
Tests have revealed successful attraction and adhesion of pathogens and
successful adsorption of viruses in the presence of salt and
sewage-contaminated water.
Specifically, chlorine, ultraviolet light or ozone can kill
or inactivate E. coli. Ion Physics Corp. of New Hampshire is developing a new
process to destroy or deactivate microbes. The process is similar to the pulsed
electric field (PEF) process but requires less energy at a lower cost because
equipment is correspondingly smaller and less expensive. The developers believe
this all-electric process will prove advantageous over chemical processes, as
it produces no toxic or carcinogenic byproducts. Its small size, ability to
treat quickly and robustness should surpass ozonation, UV treatment and
chorination.
Due to the vast array of products, treatment operators make
purchasing decisions based on highest effectiveness at lowest cost, making this
a best value market. Decisions regarding treatment also are made on a system by
system basis as size, location and source of water (groundwater or surface
water) affect a treatment system's needs. Regulations governing water systems
also force purchasers to choose technologies that meet standards, but
cash-strapped utilities rarely will pay more for a technology that treats
drinking water to lower than established EPA limits.
For those homeowners still concerned about E. coli, EPA
suggests boiling drinking water before consumption. There are several products
on the market today claiming to effectively remove E. coli and other
contaminants from home drinking water, employing different types of filter
technology. Some devices are NSF certified for reduction of bacteria including
E. coli. However, certification currently is limited to Class A UV devices,
said Tom Bruursema, general manager of the NSF Drinking Water Treatment Units
Program. It also is understood that distillation devices can reduce bacteria,
but there are none that are NSF certified today for a microbiological
performance claim. NSF still is working on microbiological standards for other
technologies (e.g., mechanical, ozone and halogen technologies).
The safety of the nation's drinking water continues to be a concern, and federal and state regulations as well as current and emerging technology promise to keep our drinking water virtually disease free.
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