Volume 1, Issue 1, September-October 2012
Available Online at www.gpublication.com/crbps
©Genxcellence Publication 2012, All Rights Reserved
REVIEW ARTICAL
Microbiological Aspects of Water: Key Criteria of Quality
Pankaj Goyal, Abhishek Chauhan, M.L. Aggarwal*, K.M. Chacko
Department of Microbiology, Shriram Institute for Industrial Research 19, University Road, Delhi (110007) India
[email protected]
Abstract
Water can be defined as safe if it does not cause any significant hazard to health over a lifetime of consumption. Safe drinking
water is thus suitable for all purposes, including personal hygiene. Many people do not have access to clean and safe drinking
water and many die of water-borne bacterial infections. This article thus focuses on microbiological quality of drinking water,
packaged drinking water, mineral water, natural mineral water etc. Different microflora associated with various types of water
has been discussed in detail along with their transmission pathways. General characterization of bacterial diseases transmitted
through drinking Water like Cholera, Gastroenteritis, and Typhoid fever bacillary dysentery are also discussed. Typical
concentrations of selected bacteria in raw and treated domestic wastewater are also discussed in brief. Microbiological water
analysis is based on the concept of faecal indicator bacteria. Permitted values of various microbiological parameters like E.coli,
Coliforms, Salmonella, S.aureus, P. aeruginosa, Shigella etc. have also been mentioned as per the various national as well as the
international guidelines.
Keywords
Drinking water, Microflora, Water-borne disease, Index microbes, Microbiological analysis, Quality parameters
INTRODUCTION
Sustainability of life directly depends on the availability
of adequate, safe and accessible water. Safe drinking
water is of utmost importance to provide tangible
benefits to health and active efforts should be made to
achieve the quality of drinking water (Cabral, 2010).
Water can be defined as safe if does not cause any
significant hazard to health over a lifetime of
consumption. Safe drinking water is thus suitable for all
purposes, including personal hygiene. Although several
definitions and guidelines are available for packaged
drinking water as well as water for human consumption,
there are several other quality parameters intended to be
used for some other purposes like water in food
production, in pharmaceutical or other industrial uses.
Access to safe and quality water is very difficult to be
obtained by a number of populations throughout the
world. According to the WHO, the mortality of water
associated diseases exceeds 5 million people per year.
From these, more that 50% are microbial intestinal
infections, with cholera standing out in the first place
(Fenwick, 2006; WHO, 2008).
Water can defined in several ways on the basis of their
origin or use. Some of the definitions are as follows (IS
14543:2004; IS 13428:2005):
Drinking Water (other than Natural Mineral Water):
Water from any potable source including public
drinking water.
Packaged Drinking Water (other than Packaged
Natural Mineral Water): Packaged drinking water
means water derived from any source of potable water
which may subjected to treatments, such as,
decantation, filtration, aeration, demineralization,
reverse osmosis, remineralization or any other method
to meet the prescribed standard and packed. It may be
disinfected to reduce the number of microorganisms to
a level that will not lead to harmful contamination in the
drinking water and does not compromise safety and
quality. It shall be filled in sealed containers of various
compositions, forms and capacities that is suitable for
direct consumption without further treatment.
Natural Mineral Water: It is obtained directly from
natural or drilled sources from underground waterbearing strata for which all possible precautions should
be taken within the protected parameters to avoid any
pollution on the chemical and physical qualities. It is
consistent in its composition and contains certain
mineral salts and trace elements. Microbiological purity
and chemical composition is absolute. It is packaged
close to the point of emergence of the source with
particular hygienic precautions, thus and it does not
require any specific treatment.
Naturally Carbonated Natural Mineral Water: Natural
mineral water which after possible treatment and reincorporation of gas from the same source and after
packaging taking into consideration usual technical
tolerance, has the same content of carbon dioxide
spontaneously and visibly given off under normal
conditions of temperature and pressure.
Non-carbonated Natural Mineral Water: Natural
mineral water which, by nature and after possible
treatment and after packaging taking into consideration
usual technical tolerance, does not contain free carbon
dioxide in excess of the amount necessary to keep the
hydrogen carbonate salts present in the water dissolved.
Decarbonated Natural Mineral Water: Natural mineral
water which, after possible treatment and after
packaging, has less carbon dioxide content that that at
emergence and does not visibly and spontaneously give
off carbon dioxide under normal conditions of
temperature and pressure.
Natural Mineral Water Fortified with Carbon Dioxide
from the Source: Natural mineral water which after
possible treatment and after packaging, has more carbon
dioxide content than that at emergence.
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M.L. Aggarwal et al, Current Research in Biological and Pharmaceutical Sciences, 1 (1), Sept-Oct 2012, 57-66
Carbonated Natural Mineral Water: Natural mineral
water which, after possible treatment and after
packaging, has been made effervescent by the addition
of carbon dioxide from another origin.
Packaged Natural Mineral Water: Natural mineral
water filled into hermetically sealed containers of
various compositions, forms and capacities that is
suitable for direct consumption without further
treatment.
WATER MICROBIOLOGY: DEFINITION AND
SCOPE
Microbiology can be defined as the study of living
organisms of microscopic size. They are categorized in
five groups’ viz. bacteria, protozoa, viruses, algae, and
fungi. These microbes live in a wide range of habitats
from hot springs to the human body and the depths of
the ocean. Microbes have a great impact on health, food
and environment and they play an important role in the
big issues like climate change, renewable energy
resources; healthier lifestyles and controlling diseases.
From microbiological point of view, the safety of water
depends on various aspects from its production to final
consumption in such a way so that either any microbial
contamination can be prevented or it will be reduced to
levels not harmful to health.
Water microbiology is concerned with the
microorganisms (Table 1-A) that live in water, or can
be transported from one habitat to another by water.
Water can support the growth of many types of
microorganisms. This can be advantageous, for
example, the chemical activities of certain strains of
yeasts provide us with beer and bread. Many
microorganisms are found naturally in fresh and
saltwater. These include bacteria, cyanobacteria,
protozoa, algae, and tiny animals such as rotifers. These
can be important in the food chain that forms the basis
of life in the water. For example, the microbes called
cyanobacteria can convert the energy of the sun into the
energy it needs to live. The plentiful numbers of these
organisms in turn are used as food for other life.
Biological examination is of value in determining the
causes of objectionable tastes and odors in water and
controlling remedial treatments, in helping to interpret
the results of various chemical analyses and in
explaining the causes of clogging in distribution pipes
and filters. The biological qualities of water are of
greater importance when the supply has not undergone
the conventional flocculation and filtration processes,
because increased growth of methane-utilizing bacteria
on biological slimes in pipes may then happen which
can cause operational difficulties.
Table I-A: Microflora of Different Types of Water
Unpolluted
Actinomycetes
Yeasts
Bacillus spores
Clostridium spores
Cellulose digesters
Autotrophic bacteria
Euglena
Paramecium
Polluted
Coliform bacteria
Escherichia coli
Desulfovibrio sp.
Clostridium sp.
Fecal streptococcci
Protozoan cysts
Blue-green algae
Enteric viruses
As well, the growth of some bacteria in contaminated
water can help digest the poisons from the water.
However, the presence of other disease causing
microbes in water is unhealthy and even life
threatening. For example, bacteria that live in the
intestinal tracts of humans and other warm blooded
animals, such as Escherichia coli, Salmonella, Shigella,
and Vibrio, can contaminate water if feces enter the
water. Contamination of drinking water with a type of
Escherichia coli known as O157:H7 can be fatal. The
intestinal tract of warm-blooded animals also contains
viruses such as rotavirus, enteroviruses, and
coxsackievirus that can contaminate water and cause
disease. Protozoans are the other group of microbes of
58
Marine
Halophilic organisms
Psychrophilic organisms
Diatoms
Dinoflagellates
Mold spores
Pseudomonas sp.
Forminiferans
Luminous microbes
concern in water microbiology. The two protozoa of the
most concern are Giardia and Cryptosporidium. They
live normally in the intestinal tract of animals such as
beaver and deer. Giardia and Cryptosporidium form
dormant and hardy forms called cysts during their life
cycles. The cyst forms are resistant to chlorine, which is
the most popular form of drinking water disinfection,
and can pass through the filters used in many water
treatment plants. If ingested in drinking water they can
cause debilitating and prolonged diarrhea in humans,
and can be life threatening to those people with
impaired immune systems. Figure 1 demonstrates
various modes of transmissions of water-borne
pathogens.
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M.L. Aggarwal et al, Current Research in Biological and Pharmaceutical Sciences, 1 (1), Sept-Oct 2012, 57-66
Figure 1: Transmission Pathways of Water Microorganisms
The greatest microbial risks are associated with
ingestion of water that is contaminated with human or
animal feces (George et al., 2001). Wastewater
discharges in fresh waters and costal seawaters are the
major source of fecal microorganisms, including
pathogens. Acute microbial diarrheal diseases (Table 1B) are a major public health problem in developing
countries (Grabow, 1996). People affected by diarrheal
diseases are those with the lowest financial resources
and poorest hygienic facilities (Seas et al., 2000).
Table II- B: Some Bacterial Diseases Transmitted Through Drinking Water (Cabral, 2010)
Disease
Cholera
Gastroenteritis caused by vibrios
Typhoid fever and other serious
salmonellosis
Causal bacterial agent
Vibrio cholerae, serovars O1 and O139
Vibrio parahaemolyticus
Salmonella enterica subsp. enterica serovar Paratyphi
Salmonella enterica subsp. enterica serovar Typhi
Salmonella enterica subsp. enterica serovar Typhimurium
Bacillary dysentery or shigellosis
Shigella dysenteriae, Shigella flexneri, Shigella boydii, Shigella sonnei
Acute diarrheas and gastroenteritis
Escherichia coli, particularly serotypes such as O148, O157 and O124
INDICATOR AND INDEX ORGANISMS
Owing to issues relating to complexity, cost and
timeliness of obtaining results, testing for specific
pathogens is generally limited to validation, where
monitoring is used to determine whether a treatment or
other process is effective in removing target organisms.
Very occasionally, pathogen testing may be performed
to verify that a specific treatment or process has been
effective. However, microbial testing included as part of
operational and verification (including surveillance)
monitoring is usually limited to that for indicator
organisms, either to measure the effectiveness of
control measures or as an index of faecal pollution.
The concept of using indicator organisms as signals of
faecal pollution is a well established practice in the
assessment of drinking-water quality. The criteria
determined for such indicators were that they should not
be pathogens themselves and should:
a. be universally present in faeces of humans and
animals in large numbers;
59
b.
c.
not multiply in natural waters;
persist in water in a similar manner to faecal
pathogens;
d. be present in higher numbers than faecal
pathogens;
e. respond to treatment processes in a similar
fashion to faecal pathogens; and
f. be readily detected by simple, inexpensive
methods.
These criteria reflect an assumption that the same
indicator organism could be used as both an index of
faecal pollution and an indicator of treatment/process
efficacy. However, it has become clear that one
indicator cannot fulfill these two roles. Increased
attention has focused on shortcomings of traditional
indicators, such as E. coli, as surrogates for enteric
viruses and protozoa, and alternative indicators of these
pathogens, such as bacteriophages and bacterial spores,
have been suggested. In addition, greater reliance is
being placed on parameters that can be used as
indicators for the effectiveness of treatments and
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M.L. Aggarwal et al, Current Research in Biological and Pharmaceutical Sciences, 1 (1), Sept-Oct 2012, 57-66
processes designed to remove faecal pathogens,
including bacteria, viruses, protozoa and helminths.
It is important to distinguish between microbial testing
undertaken to signal the presence of faecal pathogens or
alternatively to measure the effectiveness of
treatments/processes. As a first step, the separate terms
index and indicator have been proposed, whereby:
a. Index organism is one that points to the presence
of pathogenic organisms for example, as an index
of faecal pathogens such as E. coli as an index for
Salmonella and F-RNA coliphages as models of
human enteric viruses; and
b. Indicator organism is one that is used to measure
the effectiveness of a process, for example, a
process indicator or disinfection indicator.
a) Process indicator: A group of organisms that
demonstrates the efficacy of a process, such as
total heterotrophic bacteria or total coliforms for
chlorine disinfection.
b) Faecal indicator: A group of organisms that
indicates the presence of faecal contamination,
such as the bacterial groups thermotolerant
coliforms or E. coli. Hence, they only infer that
pathogens may be present.
MICROBIOLOGICAL WATER ANALYSIS
Microbiological examination of water is used to
monitor and control the quality and safety of various
types of water including potable waters i.e. water
intended for drinking or use in food preparation, treated
recreational waters such as swimming pools & spa
pools and untreated waters used for recreational
purposes such as sea, river, and lake water. This can be
achieved by proper protection of water recourses, and
suitable treatment strategies and also by maintaining the
water distribution system. Entry of pathogens into water
sources is also one of key strategy in this regard. Faecal
contamination of water is also a significant cause for
various infections caused by pathogenic bacteria, fungi,
viruses, protozoa, helminthes etc.
In 1914, the U.S. Public Health Service adopted the use
of coliform bacteria as “indicator microorganisms” to
indicate the presence of fecal contamination in water.
Ideally, if indicator microorganisms are detected in a
substance, it indicates the presence of fecal
contamination and therefore possible presence of
pathogenic microorganisms in the water. Indicator
microorganisms are tested for because they are easier
and cheaper to test for than all the possible pathogens
that might be present. The most common indicators are
total coliform bacteria, fecal coliforms, and Escherichia
coli (E. coli). It is very important to note the presence of
coliforms, fecal coliforms, or even Escherichia coli in
water does not mean that pathogenic microorganisms
are present. It only gives an indication that they might
be present. Presence of coliform or fecal coliform
bacteria does not determine whether a sample will make
someone ill. Although, there are a number of potential
pathogens which are associated with water; indicator
organisms especially of faecal origin such as coliforms
and E.coli, have been used as markers of risk (Hunter,
1997). Other species of microorganisms such as
enterococci, Clostridium perfringens, Klebsiella,
Enterobacter, and Citrobacter are also used in water
testing.
The faecal coliform test was developed as a marker of
faecal pollution when Salmonella typhi was the
commonest known cause of waterborne diseases. The
marker most closely associated with illness was the
enterococci count, although faecal coliforms were also
independently associated with illness. Total coliforms
and total counts were not independently associated with
illness (Barrell et al., 2000).
Table 2 represents different types of water and various
microbiological parameters along with their permitted
value associated with each type of water body. Water
should be tested routinely for the possible presence of
coliforms and E. coli. Coliforms must not be detected in
95% of samples when more than 50 samples are taken
from the same sampling point during a one year period.
The detection of E. coli in any one sample constitutes
an infringement of the regulations.
Table III: Different Types of Water and Their Microbiological Parameters (Barrell et al., 2000)
Type of water
Natural mineral waters
(samples any time up to
sale)
Natural mineral waters
(samples within 12 hours
of bottling)
Drinking
Water
containers
(at any time)
60
in
Parameters
coliforms/E. coli
enterococci
Pseudomonas aeruginosa
sulphite reducing clostridia
parasites/pathogens
coliforms/E. coli
enterococci
Pseudomonas aeruginosa
sulphite reducing clostridia
parasites/pathogens
colony count 22°C/72h
colony count 37°C/48h
coliforms/E. coli
enterococci
Pseudomonas aeruginosa
sulphite reducing clostridia
colony counts at 22°C and 37°C
Permitted value
0/250mL
0/250mL
0/250mL
0/50mL
Absent
0/250mL
0/250mL
0/250mL
0/50mL
Absent
100/mL
20/mL
0/100mL
0/100mL
0/100mL
0/20mL
Should show no appreciable increase after
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M.L. Aggarwal et al, Current Research in Biological and Pharmaceutical Sciences, 1 (1), Sept-Oct 2012, 57-66
Drinking
Water
in
containers
(samples within 12 hours
of bottling)
Mains water
(continuous sampling
recommended)
Private supplies
Swimming baths
Spa pools
coliforms/E. coli
enterococci
Pseudomonas aeruginosa
sulphite reducing clostridia
colony count 22°C/72h
colony count 37°C/48h
Presumptive coliforms
coliforms / E. coli
coliforms / E. coli
E. coli
coliforms
Pseudomonas aeruginosa
colony count 37°C / 24h
E. coli
coliforms
Pseudomonas aeruginosa
colony count 37°C / 24h
Cholera, salmonellosis and shigellosis are among the
major bacterial gastrointestinal diseases transmitted
through water contaminated with feces of patients. This
can lead to contamination of drinking water and this is
an issue of major concern. However, the biggest
problem associated is that the presence of pathogenic
bacteria in water is sporadic and levels are low thus the
isolation and culture of these bacteria is not very easy
task. For these reasons, routine water microbiological
analysis does not include the detection of pathogenic
bacteria. However, safe water demands that water is
free from pathogenic bacteria (George et al, 2002).
Natural microflora of the human intestine is also found
to be present in water contaminated with pathogenic
species.
A good bacterial indicator of fecal pollution should
fulfill the following criteria (Gauthier and Archibald,
2001; Wilkes et al., 2009):
a. exist in high numbers in the human intestine and
feces;
b. not be pathogenic to humans;
c. easily, reliably and cheaply detectable in
environmental waters;
d. does not multiply outside the enteric
environment;
e. in environmental waters, the indicator should
exist in greater numbers than eventual
pathogenic bacteria;
f. the indicators should have a similar die-off
behavior as the pathogens;
g. if human fecal pollution is to be separated from
animal pollution, the indicator should not be
61
bottling
0/100mL
0/100mL
0/100mL
0/20mL
100/mL
20/mL
0/100mL
0/100mL
0/100mL
0/100mL
≤10/100mL
0/100mL
≤100/mL
0/100mL
0/100mL
0/100mL
<100/mL
very common in the intestine of farm and
domestic animals.
The ratio of counts of fecal coliforms to fecal
streptococci has been proposed as a means to
differentiating between contamination from human and
animal sources (Table 3). Ratios greater than 4 have
been suggested to indicate a human source whereas
ratios less than 0.7 suggest an animal source. This
results from the fact that streptococcal concentrations in
human feces are generally less than coliforms.
In contrast, in animal feces fecal streptococci generally
outnumber fecal coliforms. In urban sewage, fecal
streptococci tend to be present in concentrations 10–100
times less than fecal coliforms. However, the
interpretation of this ratio should be cautious. It has
been observed a shift in the ratio with time and distance
from the fecal pollution source. This resulted from the
fact that both in surface and groundwaters, fecal
streptococci are more persistent than fecal coliforms
(Cabral, 2010).
Therefore increasing the distance from the pollution
point and with passing time, the ratio tends to decrease
without a change in the nature of the pollution source.
The ratio of fecal enterococci to fecal streptococci
differs among vertebrate species. Humans have a
predominance of enterococci, whereas animals contain
appreciable amounts of streptococci. However, since
enterococci are also present in animals and are more
persistent in the environment than other fecal
streptococci, the identification of the enterococci and
streptococci species present in polluted waters, and the
concomitant calculation of this ratio is generally
considered unreliable as an indicator of the source of
fecal
pollution
(Sinton
et
al.,
1998).
61
M.L. Aggarwal et al, Current Research in Biological and Pharmaceutical Sciences, 1 (1), Sept-Oct 2012, 57-66
Table IV: Bacteria in the feces of farm and domestic warm-blooded animals (Ashbolt et al., 2001)
Animal
Chicken
Duck
Horse
Pig
Sheep
Turkey
Cat
Dog
Log10 cells/g wet weight feces
Fecal coliforms
5.4
7.5
4.1
6.5
7.2
5.5
6.9
7.1
Fecal streptococci
6.1
7.7
6.8
7.9
7.6
6.4
7.4
9.0
MOST PROBABLE NUMBER METHOD
In 1914, the first US Public Health Service Drinking
Water Standard adopted a bacteriological standard that
was applicable to any water (Wolf, 1972). It specified
that not more than one out of five 10 ml portions of any
sample examined should show the presence of the
coliform group by the specified Multiple-Tube
Fermentation procedure (now referred to as the Most
Probable Number or MPN procedure). Although this
test is simple to perform, it is time-consuming,
requiring 48 hours for the presumptive results. There
are a number of isolation media each with its bias and
the bacteria enriched are not a strict taxonomic group.
Hence, the total coliforms can best be described as a
range of bacteria in the family Enterobacteriaceae
varying with the changing composition of the media.
Following presumptive isolation of coliforms, further
testing is required for confirmation of the coliform type.
Thermotolerant or ‘faecal’ coliforms are atypical
fermentors of lactose at 44°C and are indole-negative,
whereas E. coli was indole-positive. Confirmation of E.
coli with the indole test was undertaken in the UK, but
lactose fermentation at 44°C alone was used in the US
(Geldreich, 1966). Thus over a period of some 50 years,
water bacteriologists developed the concept of E. coli as
the indicator of faecal pollution, but continued to attach
significance to the total lactose fermenters, known
variously as ‘coli-aerogenes’ group, EscherichiaAerobacter group, colon group or generally referred to
as the ‘total coliforms’ group.
The range of non-faecal bacteria represented in the
coliform group and the environmental growth of
thermophilic (faecal) coliforms Klebsiella spp. and E.
coli (Ashbolt et al. 1997; Camper et al. 1991) have
concerned bacteriologists and sanitary engineers since
Clostridium perfringens
2.3
<0
3.6
5.3
7.4
8.4
the 1930s (Committee on Water Supply 1930). Despite
the obvious failings of the total coliform group to
indicate health risk from bacterial pathogens, they
provide valuable information on process efficiency
which is clearly important in relation to health
protection.
MEMBRANE FILTRATION METHOD
Membrane filters in conjunction with Endo-broth for
the analysis of potable waters for coliforms is an
exclusive method (Waite, 1985). The major drawback
of this method is the inability to demonstrate gas
production.
SOURCES OF SURFACE AND GROUNDWATER
CONTAMINATION
High numbers of intestinal bacteria are found to be
present in the sewage systems of urbanized areas
Treatment of sewage reduces the concentration of these
bacteria by 1–2 logs, but effluent still contains high
levels of intestinal bacteria (Table 4). Effluents from
sewage treatment plants can be a source of
contamination of surface waters with fecal bacteria.
Septic tanks, cesspools, latrines and other on-site
systems are widely used for wastewater storage and
treatment. The water percolating from these facilities
contains bacteria that may contaminate groundwater
supplies. Many farmers use cellars, tanks or landfills to
store manure. Water leaching from these storage sites
may also contaminate groundwater, especially during
periods of rainfall. The application of animal manure to
agricultural lands as fertilizer is common practice
throughout the world. Bacteria present in the manure
may
leach
into
the
groundwater.
Table V: Typical concentrations of selected bacteria in raw and treated domestic wastewater
Bacterial group
Salmonella
Total coliforms
Fecal coliforms
Enterococci
Clostridium perfringens
Raw sewage (cells/ml)
10–1 – 101
104 – 106
103 – 105
103 – 104
102 – 103
An important source of contamination of surface and
ground waters is runoff water from agricultural and
62
Treated effluent (cells/ml)
10–1 – 101
103 – 105
102 – 104
101 – 103
101 – 102
pasture lands, and urban areas. Fecal bacteria enter
surface water by direct deposit of feces and by overland
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M.L. Aggarwal et al, Current Research in Biological and Pharmaceutical Sciences, 1 (1), Sept-Oct 2012, 57-66
runoff. The movement of animal wastes into surface
waters can be a major factor contributing to the
pollution of available water in many regions. The
ability of fecal bacteria to survive in environmental
waters generally increases as the temperature decreases.
Others factors that influence survival include dissolved
organic carbon concentration, sunlight intensity and the
ability to enter the viable but non-culturable state
(Medema et al., 2003). The presence, persistence, and
possible naturalization of E. coli in these habitats can
confound the use of fecal coliforms as a reliable
indicator of recent fecal contamination of
environmental waters. It is therefore essential to
evaluate the microbiological quality of drinking water,
to complement the determination of Escherichia coli
with the assay of enterococci.
In this context, total coliforms should be determined on
daily basis. Only when these determinations are
repeatedly positive, it is mandatory to assess fecal
coliforms (Hecq et al., 2006; EPA, 2006). Although
total coliforms are not necessarily fecal bacteria, the
rationale behind this system is correct, because:
a. A positive test in fecal coliforms (which is our
target) is necessarily positive in the total coliform
procedure;
b. The inverse is not necessarily true;
c. Total coliforms are easily and cheaply assayed in
waters.
Simple and rapid in-field tests and automated and
continuous systems are available for the assay of
ammonia in environmental waters. More studies are
needed in order to confirm the use of ammonia as a
reliable parameter in a preliminary screening for
emergency fecal pollution outbreaks (Cabral, 2010).
TOTAL COLIFORM RULE (EPA, 1989):
The United States Environmental Protection Agency
(EPA) requires a maximum contaminant level (MCL)
goal of zero for total coliforms in a 100 mL sample of
drinking water. EPA defines total coliforms as both
coliforms and fecal coliforms. The total coliform rule
applies to all public water supplies. Private homeowners
are not regulated and therefore are NOT required to
monitor their wells for drinking water quality. An MCL
of less than 5 percent total coliform positive samples
applies to public water systems that analyze 40 or more
samples per month. If the system analyzes fewer than
40 samples per month, no more than one sample may be
positive for total coliforms. If coliforms are detected in
any sample, the system must collect three repeat
samples. In addition, any positive sample must be tested
for the presence of fecal coliforms or E. coli. When any
repeat sample is positive for fecal coliforms or E. coli,
the system is in acute violation of the MCL for total
coliforms and the public must be notified. If the repeat
sample shows the presence of total coliform bacteria,
the municipal water system is instructed to take steps to
kill the bacteria by disinfection. Systems with acute
threats to public health are placed on a “boil water
order” until testing indicates it is safe for human
consumption.
A “boil water order” is issued as a preventive measure
if there is a possibility of contamination of a drinking
63
water system with pathogenic microorganisms. During
a “boil water order,” any water for drinking, washing
foods, brushing teeth, or making ice, should be boiled
for at least 5 minutes. Water for cooking, washing
clothes, dishes, or bathing need not be boiled. If a
person believes that water is making them sick, they
need to consult a physician immediately.
Surface water quality is subject to frequent, dramatic
changes in microbial quality as a result of a variety of
activities. Discharges of municipal raw (untreated)
water, treated effluents from processing facilities, storm
water runoff, or other non-point source runoff all affect
surface waters. Typical levels of indicator
microorganisms in water are difficult to predict because
of the variability of surface waters and conditions.
Quality criteria for recreational waters have been
established since the 1950’s.
Primary Contact Recreational Water
a. Fecal coliforms not to exceed 500/100 mL at
any time.
b. Fecal coliforms not to exceed 200/100 mL in
more than 10 percent of total samples over 30
days.
Secondary Contact Recreational Water
a. Fecal coliforms not to exceed 800/100 mL at
any time.
b. Fecal coliforms not to exceed 400/100 mL in
more than 10 percent of total samples over 30
days.
VERIFICATION OF MICROBIAL QUALITY
Microbial quality of water in supply must be verified
properly to ensure the best possible chance of detecting
contamination. Sampling should therefore account for
potential variations of water quality in distribution by
taking account of locations and of times of increased
likelihood of contamination. Faecal contamination will
not be distributed evenly throughout a piped
distribution system. In systems where water quality is
good, this significantly reduces the probability of
detecting faecal indicator bacteria in the relatively few
samples collected.
Presence/absence (P/A) testing is the major tool for
detecting contamination for faecal indicator bacteria.
P/A testing is simpler, faster and less expensive than
quantitative methods. Comparative studies of the P/A
and quantitative methods demonstrate that the P/A
methods can maximize the detection of faecal indicator
bacteria. However, P/A testing is appropriate only in a
system where the majority of tests for indicators
provide negative results. The more frequently the water
is examined for faecal indicators, the more likely it is
that contamination will be detected. Frequent
examination by a simple method is more valuable than
less frequent examination by a complex test or series of
tests. The nature and likelihood of contamination can
vary seasonally, with rainfall and with other local
conditions. Sampling should normally be random but
should be increased at times of epidemics, flooding or
emergency operations or following interruptions of
supply or repair work.
63
M.L. Aggarwal et al, Current Research in Biological and Pharmaceutical Sciences, 1 (1), Sept-Oct 2012, 57-66
CURRENT APPLICABILITY
INDICATORS
OF
FAECAL
Many members of the total coliform group and some
faecal coliforms (e.g. Klebsiella and Enterobacter) are
not specific to feces, and even E. coli has been shown to
grow in some natural aquatic environments (Ashbolt et
al. 1997; Bermudez and Hazen 1988; Hardina and
Fujioka 1991; Niemi et al. 1997; Solo-Gabriele et al.
2000; Zhao et al. 1997). Hence, the primary targets
representing faecal contamination in temperate waters
are now considered to be E. coli and enterococci. For
tropical waters/soils, where E. coli and enterococci may
grow, alternative indicators such as Clostridium
perfringens may be preferable.
Numerous epidemiological studies of waterborne illness
in developed countries indicate that the common
etiological agents are more likely to be viruses and
parasitic protozoa than bacteria (Levy et al. 1998).
Fortunately, new index organisms such as Clostridium
perfringens and the phages for some pathogens look
promising as performance organisms in the HACCPtype management approaches (Ferguson et al. 1996).
Their resistance to disinfectants may also be an
advantage for indexing disinfectant resistant pathogens.
In Europe, the European Union (EU) recommends the
absence of C. perfringens in 100ml as a secondary
attribute to drinking waters (EU 1998). Also coliphages
or Bacteroides fragilis bacteriophages are preferred to
assess the removal or persistence of enteric viruses
(Calci et al. 1998; Puig et al. 1999; Shin and Sobsey
1998; Sinton et al. 1999). Extensive trials are necessary
for such type of index organisms before their general
acceptance in microbial risk assessment.
Pathogenicity of some of the indicator strains such as
toxigenic E. coli strains (ETEC) also lead to difficulties
during the analysis (Ohno et al. 1997). One of the
biggest example is E. coli O157:H7 which is
responsible for illness to recreational swimmers
(Ackman et al. 1997; Keene et al. 1994; Voelker 1996)
and several deaths have been documented through foodand waterborne outbreaks (Jones and Roworth 1996).
IMPLICATIONS
FOR
INTERNATIONAL
GUIDELINES AND NATIONAL REGULATIONS
Indicators have traditionally played a very important
role in guidelines and national standards. Increasingly,
however, they are being seen as an adjunct to
management controls, such as sanitary surveys, and
there is a move away from a specified indicator level
end product. In other words, indicators are being
replaced by on-line analyses, for example, chlorine
residual or particle sizes at critical control points. A
single indicator or even a range of indicators is unlikely
to be appropriate for every occasion and therefore it is
useful to tailor indicator choice to local circumstances
when translating international guidelines into national
standards. Additionally, with the change in management
paradigm, more indicators of process efficiency are
required rather than reliance on the ‘old-style’ faecal
indicators.
64
CONCLUSION
The objective of zero E. coli per 100 ml of water is the
goal for all water supplies and should be the target even
in emergencies; however, it may be difficult to achieve
in the immediate post-disaster period. This highlights
the need for appropriate disinfection. An indication of a
certain level of faecal indicator bacteria alone is not a
reliable guide to microbial water safety. Some faecal
pathogens, including many viruses and protozoal cysts
and oocysts, may be more resistant to treatment (e.g., by
chlorine) than common faecal indicator bacteria. More
generally, if a sanitary survey suggests the risk of faecal
contamination, then even a very low level of faecal
contamination may be considered to present a risk,
especially during an outbreak of a potentially
waterborne disease, such as cholera. Drinking-water
should be disinfected in emergency situations, and an
adequate disinfectant residual (e.g., chlorine) should be
maintained in the system. Turbid water should be
clarified wherever possible to enable disinfection to be
effective. Minimum target concentrations for chlorine at
point of delivery are 0.2 mg/litre in normal
circumstances and 0.5 mg/litre in high-risk
circumstances. Where there is a concern about the
quality of drinking-water in an emergency situation that
cannot be addressed through central services, then the
appropriateness of household-level treatment should be
evaluated, including, for example:
a. bringing water to a rolling boil and cooling before
consumption;
b. adding sodium or calcium hypochlorite solution,
such as household bleach, to a bucket of water,
mixing thoroughly and allowing to stand for about
30min prior to consumption; turbid water should
be clarified by settling and/or filtration before
disinfection;
c. vigorously shaking small volumes of water in a
clean, transparent container, such as a soft drink
bottle, for 20 s and exposing the container to
sunlight for at least 6h;
d. applying products such as tablets or other dosing
techniques to disinfect thewater, with or without
clarification by flocculation or filtration; and
e. end-use units and devices for field treatment of
drinking-water.
Emergency decontamination processes may not always
accomplish the level of disinfection recommended for
optimal conditions, particularly with regard to resistant
pathogens. However, implementation of emergency
procedures may reduce numbers of pathogens to levels
at which the risk of waterborne disease is largely
controlled.
Independent surveillance is a desirable element in
ensuring continued water safety within a large building
and should be undertaken by the relevant health agency
or other independent authority. In order to ensure safety
of drinking-water within buildings, supportive activities
of national regulatory agencies include the following:
a. specific attention to application of codes of good
practice (e.g., at commissioning and in contracting
construction and rehabilitation);
b. suitable training for engineers and plumbers;
64
M.L. Aggarwal et al, Current Research in Biological and Pharmaceutical Sciences, 1 (1), Sept-Oct 2012, 57-66
c.
d.
regulation of the plumbing community;
effective certification of materials and devices in
the marketplace; and
e. inclusion of WSPs as an essential component of
building safety provision.
To ensure and protect public health; specific attentions
should be given to implement water safety plans. If
these plans do not work effectively, the community may
be at the risk of various intestinal and other infectious
diseases. Following points should be kept in mind
before setting the qualitative value of water:
a) Safe drinking water for all is one of the major
challenges of the 21st century.
b) Microbiological control of drinking water should
be the norm everywhere.
c) Routine basic microbiological analysis of drinking
water should be carried out by assaying the
presence of Escherichia coli by the culture
methods. On-line monitoring of glucuronidase
activity is currently too insensitive to replace
culture based detection of E. coli but is a valuable
complementary tool for high temporal resolution
monitoring. Whenever financial resources are
available, coliform determinations should be
complemented with the quantification of
enterococci.
d) More studies are needed in order to check if
ammonia is reliable for a preliminary screening for
emergency fecal pollution outbreaks.
e) Financial resources should be devoted to a better
understanding of the ecology and behavior of
human and animal fecal bacteria in environmental
waters.
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