DRINKING WATER -- BACTERIA
It is EPA's 1988 contention that there are only 4 of the coliform bacterial group in sludge biosolids, and only one is of some small
concern. Furthermore, EPA only tests for the thermotolerant bacteria in the fecal coliform group
1. Campylobacter jejuni ------------------------- Gastroenteritis.
2. Escherichia coli (pathogenic strains): ---------Gastroenteritis.
3. Salmonella sp ------------------------------------ Gastroenteritis and enteric fever
4. Shigella sp ----------------------------------------- Gastroenteritis.
5. Vibrio Cholerae -------------------------------------Cholera
Index to some pathogenic bacteria that are removed from sludge biosolids disposal sites by water runoff
and contaminate adjacent land, surface water as well as ground water. Drinking water treatment processes
do not remove or inactivate all bacteria and chemicals, and it would appear scientists have not evaluated
all bacteria that may pass through the treatment plant into your drinking water.
Drinking water Parasites and Viruses
AWWA M48 - 1999 did not address all bacteria
EFFECTIVENESS OF WATER TREATMENT PROCESSES OF A FEW WATERBORNE BACTERIA
Acinetobacter
Conventional treatment by coagulation and filtration removes between 76 and 99 percent (0.6 to 2 logs) and 50 and
99.5 percent (0.3 to 2.3 logs), respectively, of bacteria. Disinfection results during the treatment process can vary
appreciably depending on the disinfectant used and the relative resistance of the organism; however, typical removals
range from 99 to 99.99 percent (2 to 4 logs). The use of a disinfectant residual in the distribution system provides
additional microbial inactivation. Naturally-occurring Acinetobacter spp. were observed to have inactivation rates similar
to other heterotrophic bacteria, such as Moraxella, Aeromonas, Pseudomonas, and Alcaligenes, when exposed to
chloramines. Other studies, however, have indicated that acinetobacters can develop increased resistance to chlorine,
chloramines, and chlorine dioxide when grown under conditions favoring cell aggregation.
Aeromonads
Chlorination is sufficient to control aeromonads in public drinking water supplies with properly maintained distribution
systems, provided the free chlorine residual remains above 0.5 ppm at the distal ends of the system. Free chlorine
residuals below 0.5 ppm are associated with an increased number of positive water samples, and growth in filter beds,
softeners, and flocculation and sedimentation basins. Aeromonads colonize pipes and plumbing fixtures at the distal
ends of distribution systems in biofilms. Granular activated carbon (GAG) sequesters nutrients that promote growth of
aeromonads. Regular removal of sludge from sedimentation basins, and proper chlorination, filter maintenance,
backwashing procedures, and hydrant flushing are required to control Aeromonas colonization of public water supplies.
Campylobacters
Normal disinfection procedures using chlorine are sufficient to kill campylobacters in drinking water supplies and the
organisms appear to be somewhat more susceptible to chlorine than E. coli. In laboratory experiments, E. coli survived
better than campylobacters and is likely a good indicator for the potential presence of campylobacters. Campylobacters
are not found in water in the absence of E. coli. Water systems that are maintained free of E. coli will be free of
campylobacters.
Cyanobacteria -- (blue-green algae) creates deadly neurotoxins
For utilities using surface water supplies, cyanobacteria are well known for their association with taste-and-odor
problems, often regarded as a matter of aesthetics. Many utilities with seasonal taste-and-odor occurrences spend
millions of dollars on powdered activated carbon (PAC) to remove the offending compounds. In light of recent
information on cyanobacteria, PAC and granular activated carbon (GAG) may be very important to toxin removal.
Furthermore, for those water systems using disinfection as the only surface water treatment, there is always the threat
of a seasonal passage of cyanobacteria and deposition of their dead cells in the distribution pipe network. Such an
occurrence provides a source of assimilable organic carbon (AOC), which is a potential nutrient for bacterial regrowth.
E. coli -- the main coliform
Proper disinfection of drinking water should control pathogenic strains of E. coli. Various studies have shown that E. coli
is readily inactivated by chlorination, with C x Tgg values reported at 0.2 mg-min/L or less. In the United States, current
disinfection guidelines targeting protozoan and viral pathogens in surface water supplies are sufficient for controlling E.
coli. An adequate disinfectant residual must be maintained in all areas of the water distribution system.
Flavobacterium
Flavobacterium species appear to be chlorine-resistant. One strain was shown to survive a 10-minute exposure to 10
mg of chlorine per litre. During a five-month study of a New England metropolitan water supply, Flavobacterium species
were detected in the disinfected water from five of nine finished water reservoirs. In another study of the seasonal
occurrence of various pigmented bacteria (including Flavobacterium) in a treated municipal water system in the Midwest,
these organisms were detected not only in the raw water supply but thought to enter from soil in line breaks and
subsequent repairs to the distribution system. The predominant pigmented bacteria at most locations in the treatment
basins or from distribution sites were yellow and orange strains. A small number of pink organisms also occurred in
water collected at selected distribution sites.
Heterotrophic Bacteria all bacteria (including pathogens) that grow best a 20 C.- (Water is tested at 37 C. or 44.5°C)
HPC bacteria in drinking water are being used to gain better information on the effects of water treatment processes and
the bacteriological quality of distributed drinking water. HPC monitoring provides water quality information and bacterial
quality changes in water during treatment, storage, and distribution. Because of the large number of these bacteria,
especially at 20° C, HPC has been used to monitor the efficiency of water treatment processes, changes in water quality
during distribution and storage, microbial growth on materials, and bacterial regrowth or aftergrowth potential.
Conventional water treatment, including final disinfection with chlorine, reduces HPC bacteria to almost undetectable
levels. However, culturable bacteria constitute only a minor part of the total bacterial counts and they are able to grow in
low-nutrient environments. Thus, they will rapidly regrow in the absence of residual disinfectant or in treated water that
contains enough nutrients for their growth. Biologically stable treated drinking water (i.e., after biological filtration)
significantly reduces the potential for regrowth. Bacteriological quality changes may cause aesthetic problems involving
tastes and odors, discolored water, and slime growths, and treatment plant problems, including pipe corrosion and
biodeterioration of materials. Bacterial numbers tend to increase during distribution. The density reached is
influenced by a number of factors, including the bacterial quality of the finished water entering the distribution system,
temperature, residence time, presence or absence of disinfectant residual, construction materials, and availability of
nutrients for growth.
Klebsiella
Many of the water systems reporting coliform occurrences in their distribution networks have noted that the predominate
organism was a member of the Klebsiella genus. Although klebsiellae can be controlled effectively by adequate
disinfection in a clean pipe environment, these organisms can be protected by particulate material, porous pipe
sediments, biological debris, macroinvertebrates, and disinfection demand products. Furthermore,
Klebsiella can encapsulate, which provides some protection from disinfectants. As the organisms become
established in this type of environment, growth beyond meager subsistence can result in the periodic sloughing of cells
into water flowing past the sites. This condition can persist until elevated disinfectant residuals penetrate the protective
habitat and inactivate the microbes. Systematic flushing of the entire system, sanitizing of all new line extensions, cross-
connection control, cleaning of storage reservoirs and standpipes, and corrosion control in iron pipes are often effective
in suppressing the seasonal reoccurrence of these biofilm events.
Legionella
Strategies for prevention of legionellosis in the absence of disease are based on outbreak investigations and control.
Although routine maintenance procedures for water systems may not prevent legionellosis, the following measures have
been shown to reduce the prevalence of legionellae in water systems:
• maintain hot water at 50° C or higher in the return and cold water below 20° C
• limit thermal stratification in central hot-water storage equipment
• periodically clean and remove sediment in central hot-water storage tanks and cooling towers
• maintain hot-water tank temperature between 71 and 77° C
• remove obstructions to flow or conditions of stagnation
• consistently provide adequate maintenance and disinfection control procedures, especially for whirlpools and
cooling towers
Additional control measures used after outbreaks include the following: cleaning of scale or sediment accumulation or
replacement of faucets and showerheads, and supplemental chlorination of the heated water to achieve 1 to 2 mg/L of
free residual chlorine. If outbreaks of legionellosis are to be prevented, control methods must focus not just on
legionellae but the whole microbial community, particularly biofilm. The accumulation of microbial slime and sludge that
supports and protects Legionella bacteria in these systems must be reduced.
Mycobacteria
Most species of mycobacteria survive treatment with 1 mg/L free chlorine. Mycobacterium marinum was reported to
be resistant to 10 mg/L free chlorine. No reduction in mycobacterial numbers was found following
chlorination in the water treatment plant examined. Distribution system data suggest that use of chloramines as a
postdisinfectant may select for the presence of mycobacteria, although many systems that convert to chloramines do so
because of high levels of organic carbon in the water supply. Institutional plumbing systems (such as hospitals and
office buildings) can be disinfected for mycobacteria using hot water. Treatment of M. avium suspensions at 60° C for 4
minutes reduced viable counts by 90 percent (1 log).
Pseudomonas
Pseudomonas organisms may grow prodigiously in the water-air interfaces of process basins, sand filters,
granular activated carbon (GAG) beds, and distribution system sediments unless proper measures are
taken to control their colonization. Frequent removal of scum, careful control of backwashing procedures, and
sediment removal in the pipe network are essential. This implies that distribution systems must be adequately flushed to
maintain a disinfectant residual above 0.5 mg/L at the distal ends of the system. Home water treatment devices using
carbon filters or reverse osmosis and electrodialysis membranes can also be amplifiers of these organisms unless
attention is given to careful maintenance of these units.
Salmonella
The vast majority of waterborne outbreaks of salmonellosis are classified as acute gastrointestinal illness
of unknown etiology.
Disinfection is an important barrier in prevention of human exposure to pathogens in drinking water. Chlorination is
effective for inactivating Salmonella in properly maintained distribution systems using conventional treatment
(coagulation, sedimentation, filtration, and disinfection). Chlorine residuals need to be at least 0.2 mg/L at the distal
ends of the distribution system. Early studies have shown that S. typhi is as susceptible to chlorine disinfection as
Escherichia coli.
Serratia
Serratia frequently can be isolated from treated water because these organisms are more chlorine-
resistant than many nonpigmented aerobic, heterotrophic bacteria They may also enter the distribution system
via soil contamination during line breaks and their repairs. Since this organism passes through conventional
treatment barriers, control is best achieved by reducing sediment accumulations in pipe networks and water storage
reservoirs. Removing scum around process basins will suppress habitat sites for Serratia and many other organisms.
Shigella
Drinking water outbreaks occur year around, while recreational water outbreaks typically occur in summer
months between May and September. S. sonnei was implicated in 11 of 12 drinking water outbreaks, and 16
of 17 recreational water outbreaks. One outbreak each in drinking and recreational water was caused by S.
flexneri, and S. boydii was recovered from victims of one of the recreational water outbreaks (Mississippi
River near Dubuque, Iowa) caused by S. sonnei.
Isolation of cases, stool precautions, hand washing, and proper diaper and sewage disposal are the primary control
mechanisms for prevention of shigellosis. Water and wastewater treatment processes incorporating disinfection are
sufficient for inactivation of shigellae. ????????
Staphylococcus
Numerous reports suggest the staphylococci are more resistant to ultraviolet light (UV) radiation at ambient
temperature than Salmonella and Escherichia coli, and require 45 minutes or more contact time. Filtration of
surface waters may entrap significant numbers of these heterotrophic bacteria but some will pass through
water treatment barriers. Systematic flushing of distribution systems to reduce the nutrient source for these and other
opportunistic bacteria is important. Hospital maintenance crews must periodically flush the building water supply lines
and clean all water supply attachment devices on a scheduled basis to suppress colonization of staphylococci and other
opportunistic bacteria.
Vibro cholerae
As previously mentioned, virtually all waterborne outbreaks of cholera have been caused by untreated or improperly
treated waters. Chlorine disinfection, such as the one used during conventional drinking water treatment, is extremely
effective, as are other types of disinfection. However, post treatment contamination is still very dangerous. If the
population has access to chlorinated waters, and there is a boil water order issued, the heat actually will drive off
residual chlorine from the water and contamination by inserting contaminated hands into water vessels is still possible.
Although V. cholerae is very sensitive to low levels of chlorine, certain strains have been found to be more resistant.
Certain isolated strains with a "rugose" colony morphology seem to be more resilient to chlorine disinfection. Data are
still scant on this last point and more research needs to be done on the prevalence of these strains of V. cholerae.
Sewage treatment is effective in eliminating V. cholerae. Although chlorination of wastewater effluents is helpful, V.
cholerae has not been shown to survive for long periods of time under the conditions of treated effluents, thus, proper
treatment of the wastes is more important than disinfection.
Yersinias
Yersinias appear to have a similar sensitivity to chlorine as Escherichia coli, thus routine chlorination should be
adequate for control of the presence of yersinias in treated drinking water and distribution systems. Strain-to-strain
variation in chlorine sensitivity has been seen but this has not been shown to present a significant risk. As with other
bacteria, there is a relationship between chlorine concentration, water temperature, and rate of inactivation, with higher
temperatures resulting in more rapid cell death. Suboptimal chlorine treatment has been shown to yield cells that
will grow in liquid media but not on agar substrates. However, the chlorine susceptibility of these organisms
suggests that routine water treatment, including an adequate level of chlorination, is likely to prevent the risk of
Yersinia infection.