E. Coli
Current and emerging
monitoring and decontamination technologies
This article provides a general
overview of E. coli and drinking water as well as current and
emerging monitoring and decontamination technologies.
- Danielle Duclos
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.
Danielle Duclos is with
Foresight Science & Technology
© 2005 Scranton Gillette Communications, Inc. All rights reserved.
Source: Water Quality Products
May 2003 Volume: 8 Number: 5
Copyright © 2005 Scranton Gillette Communications
|