Read Bacteriological quality text version

Federal-Provincial-Territorial Committee on Drinking Water

June 1988 (edited February 1991) Updated October 2001 (edited January 2002)

Bacteriological Quality

Guideline

The maximum acceptable concentration (MAC) for the bacteriological quality of public, semi-public and private drinking water systems is no coliforms detectable per 100 mL. However, because coliforms are not uniformly distributed in water and are subject to considerable variation in public health significance, drinking water that fulfils the following conditions is considered to conform to this MAC. Public Drinking Water Supply Systems (1) No sample should contain Escherichia coli (or thermotolerant coliforms, where applicable). If Escherichia coli (E. coli) is detected, the system owner should resample and test the positive site(s) immediately and notify all appropriate agencies. Depending on the extent of E. coli contamination in the first sampling, it may be prudent to notify consumers immediately to boil their drinking water or use an alternative safe source. If thermotolerant coliforms are detected, the system owner should immediately reanalyse the thermotolerant coliform-positive samples and retest the positive site(s) to confirm the presence or absence of E. coli. Some jurisdictions may take a more precautionary approach and issue a boil water advisory based upon the first indication of thermotolerant coliforms. If resampling and testing confirm the presence of E. coli (or thermotolerant coliforms, where applicable) in drinking water, the owner of the waterworks system should immediately issue a boil water advisory in consultation with the appropriate agencies, carry out the corrective actions described below and cooperate with the local health authority in any surveillance for possible waterborne disease outbreaks.

(2) No consecutive samples from the same site or not more than 10% of samples from the distribution system in a given sampling period should show the presence of total coliform bacteria. The ability of total coliforms to indicate the presence of faecal pollution is less reliable. However, because of its superior survival characteristics, the total coliform group is preferred as an indicator of the adequacy of treatment. The presence of any total coliform bacteria in water leaving the treatment plant is unacceptable and should be corrected immediately. The presence of total coliforms in the distribution system suggests regrowth or post-treatment contamination within the distribution system and should therefore be investigated. If condition (2) is exceeded, the system owner should notify all appropriate agencies and immediately reanalyse the coliform-positive sample(s) and resample and test the positive site(s) to confirm the presence or absence of E. coli (or thermotolerant coliforms, where applicable). Based on the past history of the waterworks system, the appropriate agencies may require the applicable corrective actions listed below. Corrective Actions If E. coli is confirmed, the owner of the waterworks system, in consultation with the appropriate agencies, should immediately: l verify the integrity of the treatment process and distribution system; l verify that the required disinfectant residual is present throughout the distribution system; l increase chlorine dosage, flush water mains and check for the presence of cross-connections and pressure losses; l sample and test sites adjacent to the site(s) of the positive sample(s). At a minimum, one sample upstream and one downstream of the original sample site(s) plus the finished water from the treatment plant as it enters the distribution system should be

Guidelines for Canadian Drinking Water Quality: Supporting Documentation

1

Bacteriological Quality (10/01)

tested. Other samples should be collected and tested following a sampling plan appropriate for the distribution system; conduct an investigation to identify the problem and l prevent recurrence, including a measure of raw water quality, variability and turbidity; and continue selected sampling and testing of all identil fied sites during the investigative phase to confirm the extent of the problem and to verify the success of the corrective actions. The boil water advisory may be rescinded only after a minimum of two consecutive negative results are obtained that demonstrate full system-wide integrity. Additional negative results may be required by the local health authority. If total coliforms in the absence of E. coli (or thermotolerant coliforms, where applicable) are confirmed, the degree of response should be discussed with the appropriate agencies and will depend on: a risk-based assessment of the significance and exl tent of the problem, taking the history of the entire system into account; the history and variability of the quality of the raw l water supply; and the documented historical treatment process effecl tiveness and integrity of the distribution system. Every public drinking water supply system will have a history of testing and operation documented over the years. An understanding of this history may allow a degree of comfort for appropriate personnel upon the detection of an occasional, specified, low level of total coliforms in the absence of E. coli (or thermotolerant coliforms, where applicable). This level and frequency of occurrence will vary according to the historical records for that system. If corrective actions are deemed necessary, the owner of the waterworks system, in consultation with the appropriate agencies, should consider those corrective actions listed above. Also, if enhanced health surveillance indicates that a waterborne outbreak may be occurring or if conditions exist that could result in a waterborne outbreak, then the necessity of issuing a boil water advisory should be immediately discussed with senior operations personnel at the water utility and the appropriate authority. In the event that an incident that may have contaminated the distribution system or interfered with treatment is known to the owner, consumers may be notified immediately to boil the drinking water. Barring system-specific exemptions, all public supplies should be disinfected. In addition, minimum treatment of all supplies derived from surface water sources and groundwater impacted by surface waters should include coagulation, sedimentation and filtration, or equivalent technologies. Semi-public* and Private Drinking Water Supply Systems (1) No sample should contain Escherichia coli or other coliform bacteria. The presence of E. coli in a semi-public or private drinking water system demonstrates that the source or the system has been impacted by recent faecal contamination, and therefore the water is unsafe to drink. The presence of other coliform bacteria in non-disinfected well water in the absence of E. coli means either that the well is prone to surface water infiltration and therefore at risk of faecal contamination or that a biofilm has developed within the well or plumbing system. In semipublic or private systems that include disinfection, the presence of total coliform bacteria indicates a failure in the disinfection process or the presence of a biofilm. The appropriate agency can be consulted for advice on specific water quality problems. If a sample contains E. coli, the drinking water should be immediately retested to confirm its presence. The owner should be advised to boil the drinking water or to use an alternative safe source in the interim. If resampling confirms that the well is contaminated with E. coli, the corrective actions described below should be taken immediately. As a precautionary measure, some jurisdictions may recommend immediate corrective actions without waiting for confirmatory results. If a sample contains other coliform bacteria, the drinking water should be retested immediately for E. coli. If resampling confirms that the well is contaminated with E. coli, the corrective actions described below should be taken immediately. Additional responses to total coliform-positive samples in the absence of E. coli can vary from jurisdiction to jurisdiction. As a precautionary measure, some jurisdictions will advise the owner to boil the drinking water or use an alternative safe source in the interim, regardless of concentrations of coliform bacteria present. In other jurisdictions, advice on interim measures will depend upon the concentrations of total coliform bacteria present.

* For purposes of this document, a semi-public water supply system is defined as a system with a minimal or no distribution system that provides water to the public from a facility not connected to a public supply. Examples of such facilities include schools, personal care homes, day care centres, hospitals, community wells, hotels and restaurants.

2

Guidelines for Canadian Drinking Water Quality: Supporting Documentation

Bacteriological Quality (10/01)

It should be noted that a single negative sample is not necessarily indicative of a safe water supply. Only a history of data can be used to confirm the long-term integrity of a supply when applied jointly with the verification of the suitability of the system design and its operation and maintenance. If the second sample does not contain E. coli or other coliform bacteria, a third sample should be collected. If the third sample contains E. coli or other coliform bacteria, the owner should be advised immediately to boil the drinking water and take corrective actions as described below. If the third sample is free of E. coli or other coliform bacteria, the water should be safe to drink; however, an additional test should be taken after 3­4 months to ensure that the contamination has not recurred. In general, all semi-public and private systems should be analysed periodically, especially when the risk of contamination is greatest -- for example, during spring thaw and during extended periods of heavy rains or drought. Corrective Actions for Non-disinfected Wells First, if not yet completed, conduct a sanitary survey to verify the safe condition of the well, well-head, pump, plumbing and surrounding area. Correct any identified faults before proceeding. If all the physical conditions are acceptable, then: shock chlorinate the well and plumbing system; l flush the system thoroughly and retest to confirm l that the water is safe to drink. This should be done no sooner than either 48 hours after confirmatory tests indicate the absence of a chlorine residual or 5 days after the well has been treated. Local conditions may determine acceptable practice; l if the water remains contaminated following shock chlorination, either an appropriate disinfection device or well reconstruction or replacement should be considered. Drinking water should be boiled or an alternative safe source of water should continue to be used in the interim. Corrective Actions for Surface Water Supplies and Wells Impacted by Surface Waters First, if not yet completed, conduct a sanitary survey to verify the safe condition of the drinking water system as applicable, including water intake, well, well-head, pump, treatment system, plumbing and surrounding area. Correct any identified faults before proceeding. If all the physical conditions are acceptable, then: l flush the system thoroughly and retest to confirm that the water is safe to drink; l drinking water should be boiled or an alternative safe source of water should continue to be used in the interim. Minimum treatment of all semi-public and private supplies derived from surface water sources or groundwater under the impact of surface waters should include adequate filtration and disinfection.

Introduction

Historically, water has played a significant role in the transmission of human disease. Typhoid fever, cholera, infectious hepatitis and many varieties of gastrointestinal disease can all be transmitted by water. The introduction of filtration and disinfection to water treatment and the implementation of bacteriological testing programs to verify the delivery of safe water have resulted in a dramatic decrease in the occurrence of water-related illness. The occasional waterborne disease outbreak, however, points to the importance of continuous strict supervision and control over the quality of public, semi-public and private water supplies. Of all contaminants in drinking water, human and/or animal faeces present the greatest danger to public health. Bacteriological testing provides a sensitive means for the detection and control of such pollution. Although modern microbiological techniques have made the detection of pathogenic bacteria, viruses and protozoa in sewage and sewage effluents possible, it is not practical to attempt to routinely isolate them from drinking water. Even during waterborne outbreaks, pathogens are greatly outnumbered by normal intestinal bacteria, which are easier to isolate and identify. The presence of non-pathogenic faecal indicator bacteria, such as Escherichia coli, indicates that pathogenic enteric bacteria could be present; if faecal indicator bacteria are absent, pathogenic enteric bacteria are probably also absent. It should be emphasized that no bacteriological analysis can replace a complete knowledge of the quality of the water at the source of supply, during treatment and throughout a distribution system. Contamination is often intermittent and may not be revealed by the examination of a single sample. A bacteriological water analysis shows only that at the time of examination, bacteria indicating faecal pollution did or did not grow under laboratory conditions from the sample of water tested. Therefore, if a sanitary inspection shows that an untreated supply is subject to faecal contamination or that treated water is subject to faecal contamination during storage or distribution or is inadequately treated, the water should be considered unsafe, irrespective of the results of bacteriological examination.

Guidelines for Canadian Drinking Water Quality: Supporting Documentation

3

Bacteriological Quality (10/01) Indicator Organisms

Escherichia coli and Other Coliforms In the late 19th century, E. coli was recognized as the definitive indicator of the bacteriological safety of drinking water. It is the only species in the coliform group that is exclusively found in the intestinal tract of humans and other warm-blooded animals and is excreted in large numbers in faeces.1 At this time, it was also recognized that most genera in the total coliform group occur naturally in soil, vegetation and water in addition to faeces and therefore are not suitable indicators of faecal contamination. Nevertheless, total coliforms were used as a surrogate for E. coli, primarily because routine methods to distinguish E. coli from other coliform bacteria were not available. It was not until the mid-20th century that more specific methods for the thermotolerant coliforms (previously referred to as faecal coliforms), which include E. coli and a few other species, were developed. By this time, however, the use of total coliforms was so widespread that they were not immediately replaced by E. coli, in spite of their limitations, as noted above. Within the last few years, many government and private water testing laboratories in Canada have switched to using a defined-substrate medium to test specifically for the presence of E. coli in drinking water. Although the sanitary significance of most genera in the total coliform group is questionable, some members of the group may be of faecal origin. Definitions Total coliforms have been defined in the 20th edition of Standard Methods for the Examination of Water and Wastewater2 as follows: (1) all facultative anaerobic, Gram-negative, non-sporeforming, rod-shaped bacteria that ferment lactose with gas and acid formation within 48 hours at 35EC; (2) many facultative anaerobic, Gram-negative, nonspore-forming, rod-shaped bacteria that develop red colonies with a metallic (golden) sheen within 24 hours at 35EC on an Endo-type medium containing lactose; or (3) all bacteria possessing the enzyme $-galactosidase, which cleaves a chromogenic substrate (for example, ortho-nitrophenyl-$-D-galactopyranoside), resulting in release of a chromogen (orthonitrophenol). These definitions are not to be regarded as identical; rather, they refer to three groups that are roughly equivalent. All three groups contain various species of the genera Escherichia, Klebsiella, Enterobacter and Citrobacter, but the latter group contains an additional 11 genera, most of which occur naturally in the environment. The cytochrome oxidase test may be used to exclude members of the genus Aeromonas, which can ferment lactose and, therefore, yield false-positive total coliform reactions. The thermotolerant coliform group includes that portion of the total coliform group capable of forming gas within 24 hours in EC medium at 44.5EC or that produces a blue colony on m-FC broth within 24 hours at 44.5EC.2 This group comprises the genera Escherichia and, to a lesser extent, Klebsiella, Enterobacter and Citrobacter. As most species within these genera are not exclusively associated with faeces, the more accurate term "thermotolerant coliforms" has replaced the term "faecal coliforms." This distinction refers to the fact that thermotolerant coliforms can tolerate elevated incubation temperatures during culturing. Incubation at higher temperatures is used to distinguish thermotolerant coliforms from total coliforms. Escherichia coli is the predominant coliform in faeces and the only member of the coliform (and thermotolerant coliform) group exclusively associated with faeces. Therefore, it is the most specific indicator of faecal pollution and the possible presence of pathogenic microorganisms. The confirmed presence of E. coli in treated drinking water should trigger an immediate boil water advisory. Escherichia coli can be distinguished from other coliform bacteria using the classical "IMViC " test2 or a defined-substrate test.3,4 The latter are based on the presence of $-glucuronidase, a unique constitutive enzyme found in E. coli, Shigella spp. and some Salmonella spp., but rarely present in other coliforms.5 The most publicized method is based on the ability of E. coli to hydrolyse 4-methylumbelliferyl-$-Dglucuronide to form 4-methylumbelliferone, which fluoresces under longwave ultraviolet light.3 Survival and Regrowth Although some members of the coliform group (specifically Escherichia, Klebsiella, Citrobacter and Enterobacter) are present in fresh faeces and in fresh pollution from faecal sources, they do not all persist in water for the same length of time.2 Escherichia coli, for example, is generally the most sensitive to environmental stresses and does not grow outside the human or animal gut.6 Klebsiella, Citrobacter and Enterobacter, on the other hand, are more likely to persist in the environment and, under certain conditions, multiply in water. They may also occur with other bacteria in biofilms in distribution systems that are resistant to disinfection and other eradication measures.7,8 The growth of coliforms in the distribution system can be problematic to water purveyors who rely solely on total coliforms to assess the bacteriological safety of drinking water. Sporadic positive coliform results may make it difficult to assess the true hygienic status of the

4

Guidelines for Canadian Drinking Water Quality: Supporting Documentation

Bacteriological Quality (10/01)

water. In such cases, total coliform bacteria should be identified to determine if E. coli is present. Nevertheless, the occurrence of coliforms apparently as a result of regrowth should not be ignored. Corrective action in such cases is required in order to maintain the usefulness of total coliforms as an indicator of the overall quality of the water and possible faecal pollution. Relationship with Pathogens Escherichia coli has been shown to be an indicator of the potential presence of enteric pathogens in water. Payment et al.9 collected microbiological data on the intakes of 45 water treatment plants in the St. Lawrence River basin. Logistic regression analysis of the data suggests that at high levels of thermotolerant coliforms, the probability of finding enteric protozoa and viruses is very high. Le Chevallier et al.10 also found positive relationships between Giardia and raw water quality parameters, including a significant correlation between levels of Giardia and thermotolerant coliforms. The authors concluded that increasing levels of pollution will increase the probability of higher numbers of protozoa. An outbreak of waterborne giardiasis in a town in northern Ontario was characterized by the presence of abnormally high levels of cysts and thermotolerant coliforms in the raw water supply.11 Therefore, utilities should evaluate raw water quality periodically to ensure that the appropriate level of treatment is in place. A relationship has also been demonstrated between thermotolerant coliform density and the frequency of Salmonella detection.12,13 At thermotolerant coliform densities of 1­200 colony-forming units (cfu) per 100 mL, Salmonella was detected in 28% of the water samples examined; this frequency rose to 98% in waters with a thermotolerant coliform count above 2000 cfu/100 mL. Studies on survival in river water,14 well water15 and septic tank water16 have shown that thermotolerant coliforms persist longer than Salmonella organisms. Because they are relatively specific for faecal contamination, tests for the presence of E. coli and, to a lesser degree, the thermotolerant coliforms are suitable for monitoring raw water for the potential presence of enteric pathogens and for monitoring treated drinking water for the presence of faecal contamination. The ability of total coliforms to indicate the presence of faecal pollution is less reliable. However, because of its superior survival characteristics, the total coliform group is preferred as an indicator of the adequacy of treatment. The presence of any total coliform bacteria in water leaving the treatment plant is unacceptable and should be corrected immediately. The presence of total coliforms in the distribution system, but not in the water leaving the treatment plant, suggests regrowth or post-treatment contamination within the distribution system and should therefore be investigated. If total coliforms are detected in the distribution system but not in the water leaving the plant, the system should be resampled to verify the absence of E. coli. The presence of coliform bacteria but not E. coli in the distribution system is usually an indication of bacterial regrowth and is of no immediate public health significance. Heterotrophic Plate Count Although the absence of coliform bacteria, in particular E. coli, is considered to satisfy the bacteriological requirements for potable water, many types of environmental bacteria, such as those in the genera Alcaligenes, Acinetobacter, Flavobacterium and Pseudomonas, can be present in water and biofilms. The heterotrophic plate count (HPC, formerly known as standard plate count) provides an indication of the level of the general bacterial population. Effective treatment can reduce concentrations of HPC bacteria to less than 10 cfu/mL. The composition of species and their concentrations will vary depending on the physical and chemical characteristics of the water. Consequently, no single growth medium, temperature or incubation time will ensure the recovery of all organisms present in water. The 20th edition of Standard Methods for the Examination of Water and Wastewater2 does, however, specify requirements that will permit a meaningful estimate of selected members of the culturable bacterial population. These counts can be used for quality control in water treatment plants and as a measure of quality deterioration in wells, distribution lines and reservoirs.17­19 In the standard total coliform tests based upon lactose fermentation, elevated concentrations of the general bacterial population hinder the recovery of coliforms and may prevent the detection of a possible threat to public health. In these cases, the routine analysis for coliform bacteria should be supplemented by an HPC or by background colony counts on total coliform membrane filters. A sudden rise of an HPC or background count in drinking water collected from a site that has traditionally had low counts should give rise to concern, even in the absence of a concomitant rise in the total coliform count. Therefore, if a sample contains more than either 500 HPC colonies per millilitre or 200 background colonies on a total coliform membrane filter, the site should be resampled and the disinfectant residual verified. If there is a recurrence of an elevated HPC or background count, the system should be inspected to determine the cause. Remedial action should be taken, if deemed necessary. Inhibition of total coliforms by HPC bacteria does not occur with the defined-substrate coliform test. Therefore, it is not necessary to determine HPC or background colony counts when using this test for total coliform determinations. The growth of heterotrophs in biofilms in the distribution system can promote or cause corrosion of pipes, be responsible for foul-tasting or discoloured water, harbour secondary pathogens, such as 5

Guidelines for Canadian Drinking Water Quality: Supporting Documentation

Bacteriological Quality (10/01)

Legionella species, and increase the demand for disinfectant. In some jurisdictions, the background colony counts on total coliform membrane filters are used as a convenient and inexpensive surrogate for the HPC. Elevated background counts not only can be an indication of increased concentrations of the general bacterial population, but also, in tests based upon fermentation of lactose, can suppress the development of any coliform bacteria that may be present.17 In 1989, the U.S. Environmental Protection Agency (EPA) ruled that municipalities must maintain either a detectable level of disinfectant residual or an HPC of 500/mL or less at all sites in the distribution system.20 The general population of bacteria in potable water may include some genera that could, under special circumstances, constitute a health risk. Some species of Pseudomonas can become serious secondary pathogenic invaders in post-operative infections, in burn cases and in the very young.21­25 Flavobacterium has been reported as a primary pathogen for some surgical patients.26 The HPC is not a true indicator of potential pathogens of this type, as no constant relationship appears to exist between the HPC and the number of pathogens that might be present. Furthermore, elevated levels of HPC bacteria in drinking water have not been responsible for outbreaks of waterborne illness, nor have they been epidemiologically linked to endemic illness in the general population. potent toxins (verotoxins) related to Shigella toxins. The incubation period is 3­4 days, and the symptoms occur for 7­10 days.27,29 It is estimated that 2­7% of E. coli O157:H7 infections result in HUS, in which the destruction of erythrocytes leads to acute renal failure.29 The probability of becoming ill depends on the number of organisms ingested, the health status of the person and the resistance of the person to the organism or toxin.30 Children and the elderly are most susceptible to HUS complications. Evidence suggests that the incidence of E. coli O157:H7 infections and HUS has increased since the serotype was first recognized. Healthy cattle are the primary reservoir for E. coli O157:H7.31 Escherichia coli O157:H7 is primarily a foodborne pathogen, causing outbreaks of bloody diarrhoea through the consumption of contaminated food, particularly undercooked minced beef and unpasteurized juices or milk.28 Although E. coli O157:H7 is not usually a concern in treated drinking water, outbreaks involving consumption of drinking water contaminated with human sewage or cattle faeces have been documented.32,33 Although the tests for typical E. coli in drinking water inhibit the recovery of E. coli O157:H7, E. coli O157:H7 can be recovered using the common total coliform methods. Isolated colonies are cultured in Sorbitol-MacConkey medium.2,32 Presumptive E. coli O157:H7 isolates are confirmed serologically for O157 and H7 antigens, using standard slide agglutination and tube agglutination techniques. Verotoxin production is determined using commercially prepared assay kits. There is some indication that stressed cells may lose the O157 antigen and therefore possibly escape detection.34 Isolates can be further typed using pulsed field gel electrophoresis and nucleic acid amplification methods.33 The typical non-pathogenic E. coli, used to indicate recent faecal contamination, will always occur in greater concentration in faeces than the pathogenic strains, even during outbreaks. Studies have shown that the survival rate of E. coli O157:H7 approximates that of typical E. coli in the aquatic environment.27,30 Similarly, E. coli O157:H7 is as susceptible to disinfection as nonpathogenic E. coli.35,36 Multi-barrier treatment, based upon source protection, effective treatment and a secure storage and distribution system, will eliminate E. coli O157:H7 from drinking water. Salmonella and Shigella The survival characteristics of Salmonella and Shigella in water, and their susceptibility to disinfection, have been demonstrated to be similar to those of coliform bacteria.14,15 Therefore, routine monitoring to ensure the absence of coliforms should be adequate to protect drinking water from most contamination situations involving these organisms. However, instances have been reported in which these pathogens were isolated from drinking water in the absence of coliforms.37,38

Bacterial Pathogens Associated with Waterborne Disease Outbreaks

E. coli O157:H7 Escherichia coli is the predominant species within the thermotolerant coliform group of bacteria. The organism occurs exclusively in the digestive tract of warm-blooded animals, including humans. As such, it is the definitive indicator of recent faecal contamination of water. While most strains are non-pathogenic, some can cause serious diarrhoeal infections in humans. The pathogenic E. coli are divided into six groups based on serological and virulence characteristics: enterohaemorrhagic, enterotoxigenic, enteroinvasive, enteropathogenic, enteroaggregative and diffuse adherent.2,27 The enterohaemorrhagic strain E. coli serotype O157:H7 causes abdominal pain, bloody diarrhoea and haemolytic uraemic syndrome (HUS) and has been implicated in many foodborne and a few drinking water outbreaks. Escherichia coli O157:H7 was first recognized in 1982, when it was associated with two foodborne outbreaks of bloody diarrhoea and abdominal cramps.28 Studies have shown that the dose required to produce symptoms is lower than that for most other enteric pathogenic bacteria. Escherichia coli O157:H7 produces

6

Guidelines for Canadian Drinking Water Quality: Supporting Documentation

Bacteriological Quality (10/01)

Coliform suppression by elevated HPCs and poor recovery of stressed coliforms seem to be the most plausible explanations for these discrepancies. Total coliform and E. coli recoveries are not affected by elevated HPCs and environmental stress in the newer defined-substrate methods. Campylobacter and Yersinia Waterborne outbreaks of gastroenteritis involving Campylobacter jejuni and Yersinia enterocolitica have been recorded with increasing frequency over the past several years.39­45 In addition, many reports of their isolation from surface and well waters have also been presented.43,46­51 Since the realization that water can be a potential route of campylobacteriosis and yersiniosis, isolation and enumeration methods have been developed.2 Rollins and Colwell52 recently described the presence of viable but non-culturable states of C. jejuni in the aquatic environment. They suggested that this nonculturable type could be one reason why Campylobacter is not always isolated from water during a waterborne outbreak of campylobacteriosis. The findings of Wang and co-workers53 indicated that conventional water treatment and chlorination will probably destroy C. jejuni and Y. enterocolitica in drinking water. The survival characteristics of C. jejuni are similar to those of coliforms, but the frequency of isolation of Y. enterocolitica is higher in winter months, indicating that it can survive for extended periods and perhaps even multiply when water temperatures are low.54 In addition, the presence of Y. enterocolitica has been demonstrated to be poorly correlated with levels of coliforms and HPCs.55 A recent paper by Carter et al.56 sheds some doubt on the usefulness of indicator organisms to predict the presence of Campylobacter in surface raw water supplies. Campylobacter density was often negatively correlated with densities of total and thermotolerant coliforms, faecal streptococci and HPCs. Thus, coliforms may not be adequate indicators of the presence of both C. jejuni and Y. enterocolitica. Legionella pneumophila Legionella pneumophila, the causative agent of the respiratory diseases legionellosis and Pontiac fever, has been recovered in low concentrations in the drinking water of a number of Canadian cities.57,58 The bacterium is found in freshwater environments worldwide. However, it is not a major component of the bacterial populations of the relatively cold surface waters in Canada. Although chlorination appears to effectively control Legionella, the bacterium is an intracellular parasite of free-living amoeba and thus can be transported across treatment barriers. Legionella can colonize various niches in buildings (e.g., cooling towers, hot water tanks, shower heads, aerators) and contaminate potable water and air. This situation is particularly troublesome in hospitals, where susceptible human populations can be exposed to aerosols containing hazardous concentrations of L. pneumophila.59 In general, the presence of this organism is not sufficient evidence to warrant remedial action in the absence of disease cases.57,59 Legionella pneumophila are thermophilic organisms and have strict nutritional requirements. In biofilms, they can develop symbiotic relationships with other heterotrophic bacteria (Flavobacterium, Pseudomonas, Alcaligenes and Acinetobacter). Hence, elevated HPCs may indicate the presence of Legionella pneumophila. Coliforms are not suitable indicators of their presence. Emerging Pathogenic Bacteria Emerging infectious diseases have been defined as clinically distinct conditions whose incidence in humans has increased over the past two decades.60 This emergence or re-emergence may be due to the introduction of a new agent, recognition of an existing disease that has gone undetected or the reappearance of a known disease after a decline in its incidence. Three species of bacteria -- Aeromonas hydrophila, Helicobacter pylori and the non-tuberculous Mycobacterium avium -- have been recognized as emerging pathogenic bacteria. Aeromonas hydrophila Aeromonas hydrophila are Gram-negative, nonspore-forming, rod-shaped, facultative anaerobic bacilli belonging to the family Vibrionaceae. They are ubiquitous in the environment and have been isolated from drinking water distribution systems.6,61­64 Aeromonas hydrophila has gained increased public health recognition because it has been implicated as a potential agent of gastroenteritis, septicaemia, cellulitis, colitis and meningitis and is frequently isolated from wound infections sustained in aquatic environments.62,63 Gastrointestinal infection is thought to be due to the production of three enterotoxins.65 Humans become infected through ingestion of contaminated water or food or through a break in the skin.65 A greater risk of infection has been reported in children, the elderly and the immunocompromised.66 The risk of infection is highest in the summer months, because these microorganisms multiply rapidly in warm water.61 Although A. hydrophila is water-based, waterborne transmission has not been well established; however, various studies have suggested that drinking untreated water increases the risk of infection. Maintaining chlorine at or above 0.2 mg/L should provide adequate control of A. hydrophila in water.61 However, it is difficult to control its growth in biofilms.62 Further epidemiological studies are needed in order to fully evaluate the public health significance of A. hydrophila in drinking water. The European Community has established a drinking water standard for A. hydrophila of no more than 20 cfu/100 mL in water leaving the treatment plant and 200 cfu/100 mL in 7

Guidelines for Canadian Drinking Water Quality: Supporting Documentation

Bacteriological Quality (10/01)

distribution system water.67,68 Coliforms are not a suitable indicator of A. hydrophila, but elevated HPCs may indicate their presence. Helicobacter pylori Helicobacter pylori are small, Gram-negative, microaerophilic bacilli. When isolated from gastric biopsy samples, they appear coiled or spiral-shaped; on agar culture, they appear as singly curved rods. Infectious H. pylori has been linked to gastritis, duodenal ulcers and increased risk of gastric carcinoma in humans.69,70 Almost all patients with duodenal ulcers are infected with H. pylori.69 How the organism is transmitted is still not fully known, although the fact that it has been recovered from stomach and faecal samples strongly indicates oral­oral or faecal­oral transmission.70,71 Several studies have attempted to find the association between water and H. pylori infection. One such study in Peru concluded that transmission of H. pylori was due to poor hygiene or the consumption of contaminated water,72 whereas other epidemiological studies found little or no association between drinking water sources and transmission of H. pylori. Other suggested risk factors for transmission include the consumption of uncooked vegetables irrigated with untreated sewage.73 Water treatment practices that provide a chlorine residual of 1.1 mg/L and an exposure time of 45 minutes can inactivate H. pylori.74 Further studies are needed to confirm that H. pylori can be transmitted by water and to identify suitable surrogate organisms. Mycobacterium avium Mycobacteria are acid-fast, aerobic, non-sporeforming, non-motile, rod-shaped bacilli. Mycobacterium avium is one of the most important species of the nontuberculous or atypical mycobacteria. It has been isolated from surface water, aerosols and water distribution systems, including chlorinated hospital waters.75­77 Mycobacterium avium is an opportunistic pathogen frequently found in patients with acquired immunodeficiency syndrome (AIDS). It may cause systemic bacterial infections and pulmonary diseases in the elderly.78 How the organism is transmitted is not fully known; however, prolonged contact with contaminated water, inhalation of aerosolized organisms (from shower heads) and ingestion are thought to be the primary modes of transmission. Water filtration likely removes M. avium, but the bacilli are highly resistant to disinfection due to the high lipid content of the cell wall. Laboratory studies have shown that the organisms are more resistant to chlorine than yeasts, viruses and enteric bacteria.79 Additional data on the occurrence of M. avium in water systems, its resistance to disinfection and its potential to cause endemic waterborne disease are needed in order to better understand its public health significance. Mycobacteria are ubiquitous in the environment; hence, elevated HPCs may indicate the presence of M. avium.

Methodology

Coliforms In Canada, three methods are currently used to detect coliform organisms in water: presence­absence (P-A), membrane filter (MF) and multiple tube fermentation (MTF). A detailed description of the methods is given in Standard Methods for the Examination of Water and Wastewater.2 Lactose-based and/or defined-substrate media with incubation at 35EC for 24­48 hours are used to culture coliforms in these methods. The three methods do not give strictly comparable results. For example, the confidence limits for 10 coliform colonies per 100 mL range from 4.7 to 18 for the MF technique and from 3.5 to 27 for the MTF procedure.2 In both methods, clumping of coliforms can lead to an underestimation of their concentrations. The P-A procedure is a qualitative measure of contamination and is currently the preferred method for verifying the bacteriological safety of public drinking water supplies. Presence­Absence Procedure The P-A test was developed as a more sensitive, economical and efficient means of analysing drinking water samples.80 Essentially, it is a modification of the MTF procedure, in which only one analysis bottle per sample is used. It is therefore recommended only for the examination of a water supply for which a sequential or consecutive series of samples has been collected. Defined-substrate media have been developed for the simultaneous enumeration of both total coliforms and E. coli.81 Organisms can be detected and identified at 1 organism per 100 mL in 24 hours or less following incubation at 35EC. A chromogenic substrate, for example, ortho-nitrophenyl-$-D-galactopyranoside, is used to detect total coliforms. The enzyme $-galactosidase, produced by coliforms, hydrolyses ortho-nitrophenyl$-D-galactopyranoside and releases ortho-nitrophenol (yellow), which indicates a positive test. A fluorogenic substrate, such as 4-methylumbelliferyl-$-Dglucuronide, is used to detect E. coli. $-Glucuronidase, produced by E. coli, hydrolyses 4-methylumbelliferyl-$D-glucuronide and releases the compound 4-methylumbelliferone, which fluoresces under long-wavelength ultraviolet light. A distinct advantage of the definedsubstrate media is that non-coliform bacteria will not grow in the media and thus will not interfere with the recovery of coliforms. Various media have been approved by the U.S. EPA as an acceptable means for the detection of coliforms and E. coli in drinking water.82 Commercial kits are available for coliforms and E. coli based on $-galactosidase and $-glucuronidase activity.

8

Guidelines for Canadian Drinking Water Quality: Supporting Documentation

Bacteriological Quality (10/01)

In tests using lactose-based P-A broth, the formation of acid and/or gas following incubation constitutes a positive presumptive test for coliforms. Additional tests using a lactose-based broth or the chromogenic media described above are required to confirm the presence of coliforms and E. coli. In comparative tests, the P-A method was shown to be at least as sensitive as the MF technique for the recovery of coliforms in drinking water samples.83­85 Technically, the P-A test is also simpler than the MF and MTF procedures. Initial per-sample analysis time is less than 1 minute, and, since the majority of drinking water samples are negative, confirmatory tests are not usually required. The qualitative nature and the need to confirm positive results are the only shortcomings of the P-A test; consequently, samples giving a positive result will require an MF or MTF analysis if numbers of organisms are required. In the United States, a nationwide evaluation demonstrated no statistical difference in the number of coliform-positive samples obtained by either the standard MTF method or a defined-substrate medium used in a P-A mode.86 Membrane Filter Procedure The MF procedure was introduced to bacteriological water analysis in 1951, after its capacity to produce results equivalent to those obtained by the MTF procedure was demonstrated.87,88 With this technique, the water sample is passed through a filter that retains bacteria. The filter is then placed on an appropriate selective/ differential medium and incubated for 24 hours, and the coliform colonies are counted. The advantages of the technique were quickly recognized, as the technique made the examination of larger volumes of water practical. Sensitivity and reliability were increased, while significantly reducing time, labour, equipment, space and material requirements. There are some problems with the MF technique. The major concern, for this and other methods that use stressful selective media, is an inability to enumerate coliform bacteria that have been subjected to sublethal injury (e.g., chlorination) in the treatment plant or distribution system. Stressed organisms are often not able to grow on the selective coliform media but can recover through a resuscitation process. Experiments have shown that as many as 90% of the total coliforms present may be injured.87 False-negative findings such as these could lead to the acceptance of water of potentially hazardous quality. High turbidity can also interfere with the MF method. The retention of particulate matter by the filter can interfere with colony development and the production of surface sheens by coliform bacteria. One significant improvement in the MF technique has been the development of a new medium (m-T7) for the enhanced recovery of stressed coliforms in drinking water.89 In an evaluation of this medium,90 the m-T7 agar yielded 8- to 38-fold more coliforms than m-Endo LES agar. The m-T7 agar is also suitable for the enumeration of thermotolerant coliform bacteria. However, the medium should be extensively tested before being considered acceptable for recovering coliform bacteria. MF methods have been developed for the direct enumeration of E. coli,91,92 but they have not been extensively evaluated with drinking water. However, a differential coliform medium was developed and evaluated for the simultaneous recovery of coliforms and E. coli in drinking water by the MF technique.93 Escherichia coli can also be detected by transferring the membrane from a coliform-positive sample to a medium containing a defined substrate for E. coli. Non-coliform bacteria may interfere with the recovery of coliforms by the MF method when using a lactose-based medium. Data from the U.S. National Community Supply Survey17 showed that the recovery of total coliforms using the MF technique decreased as the concentration of HPC bacteria increased. The greatest reduction occurred when the HPC densities exceeded 500 cfu/mL. It was also shown that most water supplies maintaining a total chlorine residual of 0.2 mg/L had an HPC below 500 cfu/mL. In a study by Clark,83 a 24-hour HPC of more than 1000 cfu/mL produced a marked inhibition of total coliform recoveries, but a similar decline in recovery did not occur with the 24-hour total coliform background count or with the 48-hour HPC. Burlingame et al.94 demonstrated that Pseudomonas aeruginosa (30 cfu/mL) and A. hydrophila (2 cfu/mL) caused significant reductions in sheen production by coliforms on m-Endo LES agar. Flavobacterium sp. and Bacillus sp., in contrast, were not inhibitory, even at concentrations above 1000 cfu/mL. Standridge and Sonzogni95 evaluated two modifications of the MF technique for total coliforms in drinking water containing high background counts. In both cases, roughly 8% of the plates originally classified as coliform-negative but overgrown -- i.e., confluent growth or more than 100 background cfu/100 mL -- yielded coliforms. Additional methods for the verification of total coliforms recovered by the MF technique have been described.96­98 Many workers have shown the superiority of one filter manufacturer's product over another's; however, no brand emerges as clearly superior when the literature as a whole is considered.99­108 Variation has been attributed to filter sterilization procedures99,100 and the source of coliforms.101 It has been suggested that the most critical factors are the filter retention and the size of the surface opening.102,103 Clearly, a set of quality control specifications is needed that covers all parameters affecting the efficiency of recovery of organisms on membrane filters. Until such specifications are available, it will be

Guidelines for Canadian Drinking Water Quality: Supporting Documentation

9

Bacteriological Quality (10/01)

essential for MF users to do periodic comparative MF tests with the kinds of water normally encountered, to ensure acceptable results. The MF technique remains the method of choice in some jurisdictions for the routine enumeration of coliforms in drinking water. When used with the differential coliform medium or followed with a 4-methylumbelliferyl-$-D-glucuronide assay, it is an efficient means of determining the presence of E. coli in water. Multiple Tube Fermentation Procedure In the MTF procedure, 10-fold dilutions of the water to be tested are added to tubes containing the appropriate medium, as described above (5 or 10 tubes per dilution), and incubated. For drinking water, dilution should be unnecessary because of the expected low counts. Results are reported as a most probable number (MPN). The MPN is only a statistical estimate of the number of bacteria that, more probable than any other number, would give the observed result; it is not an actual count of the bacteria present. High densities of non-coliform bacteria and the inhibitory nature of some lactose-based MTF media may have an adverse influence on routine coliform monitoring procedures. Many species in the general bacterial population have been shown to inhibit the detection of E. coli.109­111 Seidler et al.112 showed that the recovery of total coliforms by MTF decreased as the concentration of HPC bacteria increased, with the greatest reduction occurring when the HPC densities exceeded 250 cfu/mL. Le Chevallier and McFeters113 hypothesized that competition for limiting organic carbon was responsible for the interference with total coliform recovery by HPC bacteria. The recovery of coliforms from gasnegative but turbid MTF tubes has demonstrated the presence of inhibitory compounds in the MTF media. When lauryl tryptose broth was the primary medium, coliform isolations from turbid gas-negative tubes increased the numbers of positive tubes in an MTF analysis by as much as 28%.114 Comparative studies using brilliant green lactose bile (BGLB) broth and m-Endo LES agar as confirmatory media also demonstrated that BGLB broth can inhibit the growth of some coliforms. Evans et al.115 developed a procedure to detect falsenegative reactions. Using a modified MTF technique, the incidence of coliform detection was twice that of the standard MTF technique for drinking water. In response to these findings, the current edition of Standard Methods for the Examination of Water and Wastewater2 recommends treating all tubes with turbidity, regardless of gas production, as presumptive coliform-positive tubes. The MTF procedure lacks precision, and results take longer than with the MF technique; because of this, the latter has largely replaced it for routine examinations of drinking water. However, the MTF procedure is still of value when conditions render the MF technique unusable -- for example, with turbid, coloured or grossly contaminated water -- and as a comparative procedure. Heterotrophic Plate Count Bacteria In the 20th edition of Standard Methods for the Examination of Water and Wastewater,2 four media are described for the enumeration of HPC bacteria. R2A agar and m-HPC agar are the most popular. R2A agar can be used for spread plate and MF methods, whereas m-HPC agar is recommended for MF use only. In comparative studies,18,19 R2A and m-HPC agar significantly improved the recovery of the general bacterial population compared with standard plate count agar. While incubation from 5 to 7 days at a temperature of 20­28EC will give the highest counts, a shorter incubation period of 48 hours at 35EC is recommended. HPC bacteria capable of rapid growth at 35EC are more likely to interfere with the recovery of coliforms.

Sampling for Bacteriological Examination

Sample Size A minimum volume of 100 mL of water should be examined by the MTF or MF procedures in order to obtain a reliable estimate of the number of coliform organisms at the expected low levels in treated drinking water. For the MTF method, a test series consisting of one 50-mL volume and five 10-mL volumes is suggested in the World Health Organization's International Standards for Drinking-Water for water expected to be of good quality.116 Examination of larger volumes, practical with the MF method, will increase both the test sensitivity and the test reliability. Smaller volumes, dilutions or other MTF combinations may be more appropriate for waters of doubtful quality. A 500-mL sample provides sufficient volume for a coliform determination by one of the three methods and also for an HPC. In addition, enough sample will remain if membrane filtration is required to complement a P-A determination. Frequency of Sampling The World Health Organization lists the following factors that should be taken into account when determining sampling frequency116,117: l past frequency of unsatisfactory samples; l source water quality; l the number of raw water sources; l the adequacy of treatment and capacity of the treatment plant; l the size and complexity of the distribution system; and l the practice of disinfection.

10

Guidelines for Canadian Drinking Water Quality: Supporting Documentation

Bacteriological Quality (10/01)

These variables preclude application of a universal sampling frequency formula. The frequency of sampling should therefore be established by the control agency after due consideration of local conditions and sampling history. It is recommended, however, that a minimum of four samples per month be examined for water supply systems. Advice on sampling of private wells may vary from jurisduction to jurisdiction but should include times when the risk of contamination is greatest. As a general guide, the World Health Organization recommends that one sample per 1000 persons served should be examined each month for supplies serving up to 100 000 persons. For supplies serving populations over 100 000, it is considered justifiable to reduce the sampling increment to one per 10 000 persons per month. In systems serving populations of this size, the interval between successive samples will be very short. The samples should be taken at regular intervals throughout the month. It must be emphasized that the above figures are only general guides. In water supplies with a history of high-quality water production, it may be possible to reduce the number of samples taken for bacteriological analysis. The laboratory resources thus liberated could then be applied to increasing the monitoring of supplies with known problems. The general practice of basing sampling requirements on the population served recognizes that smaller water supply systems may have limited resources available for surveillance. However, because small water supplies have more facility deficiencies118 and are responsible for more disease outbreaks than large ones,119 emphasis should also be placed on perceived problems based on sanitary surveys. Barring system-specific exemptions, all drinking water supply systems in Canada should receive continuous disinfection. Depending on source water turbidity, some systems may also require filtration. Failures in treatment could result in a serious health hazard. Routine verification of the concentration of the disinfectant residual and the bacteriological quality of the water is therefore necessary to ensure that immediate remedial action can be taken if water of doubtful quality enters the distribution system. The disinfection process and a bacteriological examination of water entering the distribution system should be checked daily.116,117 For supplies where such action is impractical (e.g., in the smallest supplies), residual disinfectant determinations should be relied upon. The daily sampling recommendation does not apply to supplies served by water sources of excellent quality in which disinfection is practised to increase the safety margin. Location of Sampling Points The location of sampling points in a distribution system must be decided by the surveillance agency. Samples should be taken at the point where the water enters the system and from representative points throughout the network, although not necessarily the same points on each occasion. If the water supply is obtained from more than one source, the location of sampling points in the distribution system should ensure that water from each source is periodically sampled. The majority of samples should be taken in potential problem areas: low-pressure zones, reservoirs, dead ends, areas at the periphery of the system farthest from the treatment plant and areas with a poor previous record. Although this practice is recommended, Pipes and Christian120 found no significant differences in the frequency of coliform occurrences between peripheral and non-peripheral sampling locations in a distribution system. Handling of Samples Proper procedures for collecting samples must be observed to ensure that the sample is representative of the water being examined. Detailed instructions on the collection of samples for bacteriological analysis are given in Standard Methods for the Examination of Water and Wastewater.2 Because the way in which samples are collected has an important bearing on the results of their examination, sample collectors should be properly trained for the work. To avoid unpredictable changes in the bacterial flora of the sample, examination should be started as soon as possible after collection. The sample should be transported to the laboratory in an iced cooler. Ideally, the interval between collection of the sample and the beginning of its examination should not exceed 24 hours, although up to 48 hours may be acceptable for samples collected from remote areas. When delays are anticipated, a delayed incubation procedure should be employed, or consideration should be given to on-site testing. The delayed incubation procedure, described in Standard Methods for the Examination of Water and Wastewater,2 is a modification of the standard MF technique, which permits transport of the membrane, after filtration, to a distant laboratory for incubation and completion of the test. Alternatively, if normal transportation time exceeds 24 or 48 hours (depending on circumstances noted above), the sample should be processed and arrangements made to have another sample collected as soon as the first sample is received. Thus, if the late sample contains coliforms, a repeat sample will already have been received or will be in transit. Some reports121,122 support the belief that samples should be stored under refrigeration to minimize changes in populations and concentrations. Samples should be labelled with the time, date, location and any special conditions. When examination will be delayed, it is particularly important to record the duration and temperature of storage, as this information should be taken into consideration when interpreting the results.

Guidelines for Canadian Drinking Water Quality: Supporting Documentation

11

Bacteriological Quality (10/01) Conclusions and Recommendations

Considerations for the Treatment of Raw Supplies Since modern water treatment technologies can produce high-quality drinking water from even heavily contaminated sources, numerical limits for the microbiological quality of raw supplies are not proposed. Nevertheless, the microbiological quality of raw water should be considered when selecting sites for new treatment plants or before performing major upgrades to existing plants. Similarly, close monitoring of the raw water quality is required so that existing treatment processes can be adjusted accordingly. In addition, measures to protect raw supplies from contamination should be implemented where feasible. When assessing the bacteriological quality of source water, the E. coli test and, to a lesser degree, the thermotolerant coliform test are preferred because they give a better indication of faecal contamination. The presence of total coliforms or thermotolerant coliforms when E. coli are absent is likely due to the presence of bacteria naturally associated with soil and vegetation. Raw water quality varies over time and between locations. The frequency of sampling for bacteriological examinations of a particular water supply should therefore be established by the surveillance agency in cooperation with the local control agency. Barring system-specific exemptions, all supplies should be disinfected. In addition, minimum treatment of all supplies derived from surface water sources and groundwater impacted by surface waters should include coagulation, sedimentation and filtration, or equivalent technologies. It should not be inferred that these guidelines will guarantee the production of drinking water of adequate quality from every raw water source. For example, protection of the supply or partial treatment may be necessary to reduce turbidity even when the coliform counts are low. In addition, satisfaction of other water quality criteria may dictate the use of unit processes not mentioned in the above scheme. Potable Water Quality E. coli, Coliforms, Coliform Background Counts and Heterotrophic Plate Counts Effective treatment including disinfection should yield water free of any coliform organisms, no matter how polluted the source water may have been. The presence of any type of coliform organism in treated water therefore suggests inadequate treatment and disinfection, regrowth or infiltration in the distribution system. Total coliforms do not necessarily indicate the presence of faecal contamination. Thermotolerant coliforms in drinking water may, however, indicate such contamination. The presence of E. coli -- one species in the thermotolerant coliform group -- is a definite indicator of the presence of human or animal faeces. Other species in the thermotolerant coliform group (e.g., Klebsiella pneumoniae and Enterobacter cloacae) are not restricted to faeces but occur naturally on vegetation and in soils. The routine analysis for coliform bacteria should be supplemented by HPCs or by background colony counts on the total coliform membrane filters when using lactose-based media. For an HPC, incubation at 35EC for 48 hours is preferred. A sudden rise of an HPC or background count that has been traditionally low should give rise to concern, even in the absence of a concomitant rise in the coliform count. This is particularly relevant to tests in which elevated concentrations of the general bacterial population hinder the recovery of coliforms and prevent the detection of a threat to public health. Based on the above discussion, the maximum acceptable concentration (MAC) for coliforms in public, semi-public and private drinking water systems is no organisms detectable per 100 mL. However, because coliforms are not uniformly distributed in water and are subject to considerable variation in public health significance, drinking water that fulfils the conditions described at the beginning of this document is considered to conform to the MAC. Pathogenic Microorganisms For some potential pathogenic bacteria (e.g., Salmonella, Shigella and C. jejuni), the absence of E. coli in treated water is a good indication that these pathogens are probably also absent. If, however, past experience has demonstrated that the raw water could harbour pathogens for which E. coli are not good indicators (e.g., C. parvum, G. lamblia, Y. enterocolitica, enteric viruses), then the water should receive treatment known to remove or inactivate these pathogens. Properly treated and distributed drinking water should be essentially free of pathogenic microorganisms. Nuisance Organisms Nuisance organisms, a morphologically and physiologically diverse group, include planktonic and sessile algae, fungi, crustaceans and free-living amoebae, actinomycetes and iron and sulphur bacteria. These organisms, not indicative of faecal contamination, can grow in water and may produce objectionable tastes, colour, odour and turbidity and may interfere with treatment processes by clogging strainers and filters. In addition, although not themselves pathogenic, certain planktonic organisms and protozoa may harbour pathogenic bacteria and viruses, thus protecting them from disinfection by chlorine. It is difficult, however, to specify any quantitative limit on nuisance organisms, because individual species differ widely in their ability to

12

Guidelines for Canadian Drinking Water Quality: Supporting Documentation

Bacteriological Quality (10/01)

produce undesirable effects. Most of these organisms can be controlled relatively easily by the usual operation and maintenance programs for all components of the system -- source, treatment, and distribution and storage. Furthermore, the problems of taste, odour, colour and turbidity that may be caused by these organisms are covered indirectly by the limits on the physical characteristics of water. The frequency of sampling and analysis for nuisance organisms should be determined by the control agency, based on the likelihood of significant kinds and concentrations of such organisms being present. Maintenance of a Chlorine Residual The purpose of treating drinking water is to provide a product that is microbiologically and chemically safe for consumption. In all municipal systems and semipublic systems applying disinfection, a disinfection residual should be maintained throughout the distribution system at all times. Maintenance and monitoring of a residual disinfectant offer two benefits. First, a trace of disinfectant will limit the growth of organisms within the system and may afford some protection against contamination from without; second, the disappearance of the residual provides an immediate indication of the entry of oxidizable matter into the system or of a malfunction of the treatment process. It is therefore recommended that a disinfectant residual be maintained and monitored daily throughout the entire system. It is recognized, however, that excessive levels of disinfectant may result in taste and odour problems. In these cases, the control agency may provide guidance as to the type and concentration of disinfectant residual to ensure that water remains microbiologically safe. When a residual concentration measured at a sampling point is less than that required by the control agency, another sample should be taken immediately. If this sample is also unsatisfactory, the line should be flushed and sampling continued until a satisfactory concentration is obtained. If the residual does not return to the allowable minimum, the disinfectant dosage should be increased. If increasing the dosage is ineffective or if excessive disinfection is required, a sanitary survey for potential sources of contamination should be made in cooperation with the responsible control agency. Special samples should be taken for coliform analysis. Should all these measures prove inadequate, the control agency should be consulted for further advice, and action should be taken as appropriate. Sampling and Sample Size The sampling frequency and location of sampling points should be decided by the control agency after due consideration of local conditions. In general, the number of samples for bacteriological testing should be increased in accordance with the size of the population served. The following table is offered as a guide:

Population served Up to 5000 5000­90 000 90 000+ Minimum no. of samples per month At least 4 1 per 1000 persons 90 + (1 per 10 000 persons)

The samples should be taken at regular intervals throughout the month. Chlorine residual tests should be made when bacteriological samples are taken. The majority of samples should be taken in potential problem areas. For private wells, samples should be collected at times when the risk of contamination is highest -- e.g., spring thaw, heavy rains or dry periods. New or renovated wells should also be sampled initially to confirm acceptable bacteriological quality. The sample volume should be sufficient to carry out all the tests required. For treated drinking water, a minimum volume of 100 mL should be examined for the coliform determination, regardless of which method is used. The maximum volume for analysis by the P-A test is usually 100 mL; however, 500 mL of sample should be collected, as an HPC and subsequent examination by the MF method may be required.

References

1. Department of National Health and Welfare. Microbiological quality of drinking water. Environmental Health Directorate Publication 77-EHD-2 (1977). 2. American Public Health Association/American Water Works Association/Water Pollution Control Federation. Standard methods for the examination of water and wastewater. 20th edition. Washington, DC (1998). 3. Feng, P.C.S. and Hartman, P.A. Fluorogenic assays for immediate confirmation of Escherichia coli. Appl. Environ. Microbiol., 43: 1320­1329 (1982). 4. Ley, A.N., Bowers, R.J. and Wolfe, S. Indoxyl-$-glucuronide, a novel chromogenic reagent for the specific detection and enumeration of Escherichia coli in environmental samples. Can. J. Microbiol., 34: 690­693 (1988). 5. Manafi, M., Kneifel, W. and Bascomb, S. Fluorogenic and chromogenic substrates used in bacterial diagnostics. Microbiol. Rev., 55: 335­348 (1991). 6. Geldreich, E.E. Microbial quality of water supply in distribution systems. Biological profiles in drinking water. CRC Press, Lewis Publishers, Boca Raton, FL. p. 128 (1996). 7. Martin, R.S., Gates, W.H., Tobin, R.S., Grantham, D., Sumarah, R., Wolfe, P. and Forestall, P. Factors affecting coliform bacteria growth in distribution systems. J. Am. Water Works Assoc., 74: 34­37 (1982). 8. Geldreich, E.E. and Rice, E.W. Occurrence, significance, and detection of Klebsiella in water systems. J. Am. Water Works Assoc., 79: 74­80 (1987).

Guidelines for Canadian Drinking Water Quality: Supporting Documentation

13

Bacteriological Quality (10/01)

9. Payment, P., Berte, A., Prevost, M., Menard, B. and Barbeau, B. Occurrence of pathogenic microorganisms in the Saint Lawrence River (Canada) and comparison of health risks for populations using it as their source of drinking water. Can. J. Microbiol., 46(6): 565­576 (2000). 10. Le Chevallier, M.W., Norton, W.D. and Lee, R.G. Occurrence of Giardia and Cryptosporidium spp. in surface water supplies. Appl. Environ. Microbiol., 57(9): 2610­2616 (1991). 11. Wallis, P.M., Primrose, B. and Robertson, W.J. Outbreak of waterborne giardiasis caused by sewage contamination of drinking water. Environ. Health Rev., 42(2): 44­51 (1998). 12. Geldreich, E.E. Applying bacteriological parameters to recreational water quality. J. Am. Water Works Assoc., 62: 113­120 (1970). 13. Van Donsel, D.J. and Geldreich, E.E. Relationships of salmonella to fecal coliforms in bottom sediments. Water Res., 5: 1079­1087 (1971). 14. Mitchell, D.O. and Starzyk, M.J. Survival of salmonella and other indicator microorganisms. Can. J. Microbiol., 21: 1420­1421 (1975). 15. McFeters, G.A., Bissonnette, G.K., Jezeski, J.J., Thomson, C.A. and Stuart, D.G. Comparative survival of indicator bacteria and enteric pathogens in well water. Appl. Microbiol., 27: 823­829 (1974). 16. Calabra, J.F., Cosenza, B.J. and Kolega, J.J. Recovery of gram-negative bacteria with hektoen agar. J. Water Pollut. Control Fed., 44: 491­493 (1972). 17. Geldreich, E.E., Nash, H.D., Reasoner, D.J. and Taylor, R.H. The necessity of controlling bacterial populations in potable waters: community water supply. J. Am. Water Works Assoc., 64: 596­602 (1972). 18. Reasoner, D.J. and Geldreich, E.E. A new medium for the enumeration and subculture of bacteria from potable water. Appl. Environ. Microbiol., 49: 1­7 (1985). 19. Fiksdal, L., Vik, E.A., Mills, A. and Staley, J.T. Non standard methods for enumerating bacteria in drinking water. J. Am. Water Works Assoc., 6: 313­318 (1982). 20. U.S. Environmental Protection Agency. Drinking water; national primary drinking water regulations; filtration, disinfection; turbidity, Giardia lamblia, viruses, Legionella and heterotrophic bacteria -- final rule. Fed. Regist., 54(124): 27485 (1989). 21. Hunter, C.A. and Ensign, P.R. An epidemic of diarrhea in a new-born nursery caused by P. aeruginosa. Am. J. Public Health, 37: 1166­1169 (1947). 22. Culp, R.L. Disease due to "non-pathogenic" bacteria. J. Am. Water Works Assoc., 61: 157 (1969). 23. Wilson, M.G., Nelson, R.C., Phillips, L.H. and Boak, R.A. New source of Pseudomonas aeruginosa in a nursery. J. Am. Med. Assoc., 175: 1146­1148 (1961). 24. Fierer, J., Taylor, P.M. and Gezon, H.M. Pseudomonas aeruginosa epidemic traced to delivery-room resuscitation. N. Engl. J. Med., 276: 991­996 (1967). 25. Lowbury, E.J.T., Thorn, B.T., Lilly, H.A., Babb, J.R. and Whitall, K. Sources of infection with Pseudomonas aeruginosa in patients with tracheostomy. J. Med. Microbiol., 3: 39­56 (1970). 26. Herman, L.S. and Himelsback, C.K. Detection and control of hospital sources of flavobacteria. Hospitals, 39: 72­76 (1965). 27. Rice, E.W. Escherichia coli. In: AWWA manual M48: Waterborne pathogens. American Water Works Association, Denver, CO. pp. 75­78 (1999). 28. Gugnani, H.C. Some emerging food and water borne pathogens. J. Communicable Dis., 31(2): 65­72 (1999). 29. Moe, C.L. Waterborne transmission of infectious agents. In: Manual of environmental microbiology. C.J. Hurst, G.R. Knudsen, M.J. McInerney, L.D. Stetzenbach and M.V. Walter (eds.). ASM Press, Washington, DC (1997). 30. AWWA Committee Report. Emerging pathogens -- bacteria. J. Am. Water Works Assoc., 91(9): 101­109 (1999). 31. Jackson, S.G., Goodbrand, R.B., Johnson, R.P., Odorico, V.G., Alves, D., Rahn, K., Wilson, J.B., Welch, M.K. and Khakhria, R. Escherichia coli O157:H7 diarrhoea associated with well water and infected cattle on an Ontario farm. Epidemiol. Infect., 120: 17­20 (1998). 32. Swerdlow, D.L., Woodruff, B.A., Brady, R.C., Griffin, P.M., Tippen, S., Donnell, H.D., Jr., Geldreich, E., Payne, B.J., Meyer, A., Jr., Wells, J.G., Greene, K.D., Bright, M., Bean, N.H. and Blake, P.A. A waterborne outbreak in Missouri of Escherichia coli O157:H7 associated with bloody diarrhea and death. Ann. Intern. Med., 17(10): 812­819 (1992). 33. Bruce-Grey-Owen Sound Health Unit. The investigative report on the Walkerton outbreak of waterborne gastroenteritis. May­June (2000). 34. Hara-Kudo, H., Miyahara, M. and Kumagai, S. Loss of O157 O antigenicity of verotoxin-producing Escherichia coli O157:H7 surviving under starvation conditions. Appl. Environ. Microbiol., 66(12): 5540­5543 (2000). 35. Kaneko, M. Chlorination of pathogenic E. coli O157. Water Sci. Technol., 38(12): 141­144 (1998). 36. Rice, E.W., Clark, R.M. and Johnson, C.H. Chlorine inactivation of Escherichia coli O157:H7. Emerg. Infect. Dis., 5(3): 461­463 (2000). 37. Seligmann, R. and Reitler, R. Enteropathogens in water with low Esch. coli titer. J. Am. Water Works Assoc., 57: 1572­1574 (1965). 38. Boring, J.R., III, Martin, W.T. and Elliott, L.M. Isolation of Salmonella typhimurium from municipal water, Riverside, California, 1965. Am. J. Epidemiol., 93: 49­54 (1971). 39. Eden, K.V., Rosenburg, M.L., Stoopler, M., Wood, B.T., Highsmith, A.K., Skaliy, P., Wells, J.G. and Feeley, J.C. Waterborne gastrointestinal illness at a ski resort. Public Health Rep., 92: 245­250 (1977). 40. McNeill, C.A., Out, K., Pagan, R.T., McMyre, P., Black, W.A. and Mathias, R.G. Possible waterborne Campylobacter outbreak -- British Columbia. Can. Dis. Wkly. Rep., 7: 226 (1981). 41. Mentzing, L.O. Waterborne outbreaks of Campylobacter enteritis in central Sweden. Lancet, ii: 352­354 (1981). 42. Vogt, R.L., Sours, H.E., Barrett, T., Feldman, R.A., Dickson, R.J. and Witherell, L. Campylobacter enteritis associated with contaminated water. Ann. Intern. Med., 96: 292­296 (1982). 43. Taylor, D.N., McDermott, K.T., Little, J.R., Wells, J.G. and Blaser, M.J. Campylobacter enteritis from untreated water in the Rocky Mountains. Ann. Intern. Med., 99: 38­40 (1983). 44. Lafrance, G., Lafrance, R., Roy, G.L., Ouellete, D. and Bourdeau, R. Outbreak of enteric infection following a field trip -- Ontario. Can. Dis. Wkly. Rep., 12: 171­172 (1986).

14

Guidelines for Canadian Drinking Water Quality: Supporting Documentation

Bacteriological Quality (10/01)

45. Sacks, J.J., Spencer, L., Baldy, L., Berta, S., Patton, C.M., White, M.C., Bigler, W.J. and Witte, J.J. Epidemic campylobacteriosis associated with a community water supply. Am. J. Public Health, 76: 424­428 (1986). 46. Blaser, M.J., Wells, J.H., Powers, B. and Wang, W.L. Survival of Campylobacter fetus subsp. jejuni in biological milieus. J. Clin. Microbiol., 11: 309­313 (1980). 47. Schiemann, D.A. Isolation of Yersinia enterocolitica from surface and well waters in Ontario. Can. J. Microbiol., 24: 1048­1052 (1978). 48. Caprioli, T., Drapeau, A.J. and Kasatiya, S. Yersinia enterocolitica: serotypes and biotypes isolated from humans and the environment in Quebec, Canada. Appl. Environ. Microbiol., 8: 7­11 (1978). 49. Ontario Ministry of the Environment. Yersinia enterocolitica in recreational lakes and sewage systems. Lakeshore Capacity Study, Laboratory Services Branch (1980). 50. Weagant, S.D. and Kaysner, C.A. Modified enrichment broth for isolation of Yersinia enterocolitica from non food sources. Appl. Environ. Microbiol., 45: 468­471 (1983). 51. El-Sherbeeny, M.R., Bopp, C., Wells, J.G. and Morris, G.K. Comparison of gauze swabs and membrane filters for isolation of Campylobacter spp. from surface water. Appl. Environ. Microbiol., 50: 611­614 (1985). 52. Rollins, D.M. and Colwell, R.R. Viable but non culturable stage of Campylobacter jejuni and its role in survival in the natural aquatic environment. Appl. Environ. Microbiol., 52: 531­538 (1986). 53. Wang, W.L.L., Powers, B.W., Blaser, M.J. and Leuchtefeld, N.W. Laboratory studies of disinfectants against Campylobacter jejuni. In: Proceedings of the Annual Meeting of the American Society of Microbiology, Washington, DC (1982). 54. Berger, P.S. and Argaman, Y. (eds.). Assessment of microbiology and turbidity standards for drinking water. EPA 570-9-83-001, U.S. Environmental Protection Agency, Washington, DC (1983). 55. Wetzler, T.F., Rea, J.R., Ma, G.J. and Glass, M. Non-association of Yersinia with traditional coliform indicators. In: Proceedings of the Annual Meeting of the American Water Works Association, Denver, CO (1979). 56. Carter, A.M., Pacha, R.E., Clark, G.W. and Williams, E.A. Seasonal occurrence of Campylobacter spp. in surface waters and their correlation with standard indicator bacteria. Appl. Environ. Microbiol., 53: 523­526 (1987). 57. Tobin, R.S., Ewan, P., Walsh, K. and Dutka, B. A survey of Legionella pneumophila in water in 12 Canadian cities. Water Res., 20: 495­501 (1986). 58. Dutka, B.J., Walsh, K., Ewan, P., El-Shaarawi, A. and Tobin, R.S. Incidence of Legionella organisms in selected Ontario (Canada) cities. Sci. Total Environ., 39: 237­249 (1984). 59. Dufour, A.P. and Jakubowski, W. Drinking water and Legionnaires' disease. J. Am. Water Works Assoc., 74: 631­637 (1982). 60. Lederberg, J., Shope, R.E. and Oaks, S.C., Jr. (eds.). Emerging infections: Microbial threats to health in the United States. Institute of Medicine, National Academy Press, Washington, DC. pp. 199­200 (1992). 61. Holmes, P. and Nicolls, L.M. Aeromonads in drinking-water supplies: Their occurrence and significance. J. Chart. Inst. Water Environ. Manage., 9(5): 464­469 (1995). 62. Gavriel, A.A., Landre, J.P.B. and Lamb, A.J. Incidence of mesophilic Aeromonas within a public drinking water supply in north-east Scotland. J. Appl. Microbiol., 84(3): 383­392 (1998). 63. Krovacek, K., Faris, A., Baloda, S.J., Lindberg, T., Peterz, M. and Mansson, I. Isolation and virulence profiles of Aeromonas spp. from different municipal drinking water supplies in Sweden. J. Food Microbiol., 9(3): 215­222 (1992). 64. Bernagozzi, M., Bianucci, F. and Sacchetti, R. Prevalence of Aeromonas spp. in surface waters. Water Environ. Res., 67(7): 1060­1064 (1995). 65. Schubert, R.H.W. Aeromonads and their significance as potential pathogens in water. J. Appl. Bacteriol. Symp. Suppl., 70: 131S­135S (1991). 66. Merino, S., Rubires, X., Knochel, S. and Tomas, J.M. Emerging pathogens: Aeromonas spp. Int. J. Food Microbiol., 28: 157­168 (1995). 67. Moyer, N.P. Aeromonas. In: AWWA manual M48: Waterborne pathogens. American Water Works Association, Denver, CO. pp. 63­66 (1999). 68. van der Kooij, D. Importance and assessment of the biological stability of drinking water in the Netherlands. In: Safety of water disinfection: Balancing the chemical and microbial risks. C. Craun (ed.). ILSI Press, Washington, DC. pp. 165­179 (1993). 69. Hunter, P.R. Waterborne disease: Epidemiology and ecology. John Wiley & Sons, London. pp. 160­164 (1997). 70. Jekel, P. Mode of transmission of Helicobacter pylori. Environ. Health Rev., J. Can. Inst. Public Health Inspect., 37(1): 22, 27 (1993). 71. Goodman, K.J., Correa, P., Aux, T.H.J., Ramirez, H., Delany, J.P., Pepinosa, O.G., Quinones, M.L. and Parra, T.C. Helicobacter pylori infection in the Colombian Andes: A population-based study of transmission pathways. Am. J. Epidemiol., 144(3): 290­299 (1996). 72. Klein, P.D., Graham, D.Y., Gaillour, A., Opekun, A.R. and Smith, O. Water source as risk factor for Helicobacter pylori infection in Peruvian children. Lancet, 337: 1503­1506 (1991). 73. Hopkins, R.J., Pablo, V.A., Ferreccio, C., Ovalle, J., Prado, P., Sotomayor, V., Russell, R.G., Wasserman, S.S. and Morris, J.G., Jr. Seroprevalence of Helicobacter pylori in Chile: Vegetables may serve as one route of transmission. J. Infect. Dis., 168: 222­226 (1993). 74. Johnson, C.H., Rice, E.W. and Reasoner, D.J. Inactivation of Helicobacter pylori by chlorination. Appl. Environ. Microbiol., 63(12): 4969­4970 (1997). 75. von Reyn, C.F., Waddell, R.D., Eaton, T., Arbeit, R.D., Maslow, J.N., Barber, T.W., Brindle, R.J., Gilks, C.F., Lumio, J., Lahdevirta, J., Ranki, A., Dawson, D. and Falkinham, J.O., III. Isolation of Mycobacterium avium complex from water in the United States, Finland, Zaire and Kenya. J. Clin. Microbiol., 31(12): 3227­3230 (1993). 76. Stottmeier, K.D. Waterborne Mycobacterium avium infection. J. Am. Med. Assoc., 261(7): 994 (1989). 77. Glover, N., Holtzman, T., Aronson, S., Froman, O.G.W., Berlin, P., Dominguez, K.A., Kunkel, K.A., Overturf, G., Stelma, G., Jr., Smith, C. and Yakrus, M. The isolation and identification of Mycobacterium avium complex (MAC) recovered from Los Angeles potable water, a possible source of infection in AIDS patients. Int. J. Environ. Health Res., 4: 63­72 (1994).

Guidelines for Canadian Drinking Water Quality: Supporting Documentation

15

Bacteriological Quality (10/01)

78. Wayne, L.G. and Sramek, H.A. Agents of newly recognized or infrequently encountered mycobacterial diseases. Clin. J. Rev., 5(1): 1­25 (1992). 79. Engelbrecht, R.S., Severin, B.F., Masarik, M.T., Farooq, S., Lee, S.H., Haas, C.N. and Lalchandani, A. New microbial indicators of disinfection efficiency. Technological Series No. EPA 600/ 2-77-052, U.S. Environmental Protection Agency, Washington, DC (1977). 80. Clark, J.A. and Vlassoff, L.T. Relationships among pollution indicator bacteria isolated from raw water and distribution systems by the presence­absence (P-A) test. Health Lab. Sci., 10: 163­172 (1973). 81. Edberg, S.C., Allen, M.J. and Smith, D.B. National field evaluation of a defined substrate method for the simultaneous evaluation of total coliforms and Escherichia coli from drinking water: comparison with the standard multiple tube technique. Appl. Environ. Microbiol., 54: 1595­1601 (1988). 82. U.S. Environmental Protection Agency. National primary drinking water regulations: analytical techniques; coliform bacteria -- final rule. Fed. Regist., 57(112): 24744 (1992). 83. Clark, J.A. The influence of increasing numbers of nonindicator organisms by the membrane filter and presence­absence test. Can. J. Microbiol., 26: 827­832 (1980). 84. Jacobs, N.J., Zeigler, W.L., Reed, F.C., Stukel, T.A. and Rice, E.W. Comparison of membrane filter, multiple-fermentation-tube, and presence­absence techniques for detecting total coliforms in small community water systems. Appl. Environ. Microbiol., 51: 1007­1012 (1986). 85. Pipes, W.O., Minnigh, H.A., Moyer, B. and Troy, M.A. Comparison of Clark's presence­absence test and the membrane filter method for coliform detection in potable water samples. Appl. Environ. Microbiol., 52: 439­443 (1986). 86. Edberg, S.C., Allen, M.J. and Smith, D.B. National field evaluation of a defined substrate method for the simultaneous detection of total coliforms and Escherichia coli from drinking water: comparison with presence­absence techniques. Appl. Environ. Microbiol., 55: 1003­1008 (1989). 87. Clark, H.F., Geldreich, E.E., Jeter, H.L. and Kabler, P.W. The membrane filter in sanitary microbiology. Public Health Rep., 66: 951­977 (1951). 88. Goetz, A. and Tsuneishi, N. Application of molecular filter membrane to bacteriological analysis of water. J. Am. Water Works Assoc., 43: 943­969 (1951). 89. Le Chevallier, M.W., Cameron, S.C. and McFeters, G.A. New medium for the improved recovery of coliform bacteria from drinking water. Appl. Environ. Microbiol., 45: 484­492 (1983). 90. McFeters, G.A., Kippin, J.S. and Le Chevallier, M.W. Injured coliforms in drinking water. Appl. Environ. Microbiol., 5: 1­5 (1986). 91. Dufour, A., Strickland, E. and Cabelli, V. Membrane filter method for enumerating Escherichia coli. Appl. Environ. Microbiol., 41: 1152­1158 (1981). 92. Ciebin, B.W., Brodsky, M.H., Eddington, R., Horsnell, G., Choney, A., Palmateer, G., Ley, A., Joshi, R. and Shears, G. Comparative evaluation of modified m-TEC media for membrane filter enumeration of Escherichia coli in water. Appl. Environ. Microbiol., 61(11): 3940­3942 (1995). 93. Ciebin, B.C., Schop, R.N. and Brodsky, M.H. DC medium: A differential coliform medium for simultaneous enumeration of coliforms and E. coli in water by membrane filtration. In: Proceedings of the Annual Meeting of the American Society of Microbiology, May 4­8 (1997). 94. Burlingame, G.A., McElhaney, J., Bennett, M. and Pipes, W.O. Bacterial interference with coliform colony sheen production on membrane filters. Appl. Environ. Microbiol., 47: 56­60 (1984). 95. Standridge, J.H. and Sonzogni, W.C. Evaluating modifications to the MF total coliform method for drinking waters with high non coliform backgrounds. J. Am. Water Works Assoc., 80: 90­91 (1988). 96. Evans, T.M., Seidler, R.J. and Le Chevallier, M.W. Impact of the verification media and resuscitation on accuracy of the membrane filter total coliform enumeration technique. Appl. Environ. Microbiol., 41: 1144­1151 (1981). 97. Standridge, J.H. and Delfino, J.J. Underestimation of the total coliform counts by the membrane filter verification procedure. Appl. Environ. Microbiol., 44: 1001­1003 (1982). 98. Le Chevallier, M.W., Cameron, S.C. and McFeters, G.A. Comparison of verification procedures for the membrane filter total coliform technique. Appl. Environ. Microbiol., 45: 1126­1128 (1983). 99. Presswood, W.G. and Brown, L.R. Comparison of Gelman and Millipore membrane filters for enumerating fecal coliform bacteria. Appl. Microbiol., 26: 332­336 (1973). 100. Dutka, B.J., Jackson, M.J. and Bell, J.B. Comparison of autoclaved and ethylene oxide sterilized membrane filters used in water quality studies. Appl. Microbiol., 8: 474­480 (1974). 101. Brodsky, M.H. and Schiemann, D.A. Influence of coliform source on evaluation of membrane filters. Appl. Microbiol., 30: 727­730 (1975). 102. Sladek, K.J., Suslavich, R.V., Sohn, B.C. and Dawson, F.W. Optimum membrane structures for growth of coliform and fecal coliform organisms. Appl. Microbiol., 30: 685­691 (1975). 103. Tobin, R.S. and Dutka, B.J. Comparison of the surface structure, metal binding and fecal coliform recoveries of nine membrane filters. Appl. Environ. Microbiol., 34: 69­79 (1977). 104. Hufham, J.B. Evaluating the membrane fecal coliform test by using Escherichia coli as the indicator organism. Appl. Microbiol., 27: 771­776 (1974). 105. Schaeffer, D.J., Long, M.C. and Janardan, K.G. Statistical analysis of the recovery of coliform organisms on Gelman and Millipore membrane filters. Appl. Microbiol., 28: 605­607 (1974). 106. Lin, S.D. Evaluation of Millipore HA and HC membrane filters for the enumeration of indicator bacteria. Appl. Environ. Microbiol., 32: 300­302 (1976). 107. Standridge, J.H. Comparison of surface pore morphology of two brands of membrane filters. Appl. Environ. Microbiol., 31: 316­319 (1976). 108. Tobin, R.S., Lomax, P. and Kushner, D.J. Comparison of nine brands of membrane filter and the most-probable-number methods for total coliform enumeration in sewage-contaminated drinking water. Appl. Environ. Microbiol., 40: 186­191 (1980). 109. Waksman, S.A. Antagonistic relations of microorganisms. Bacteriol. Rev., 5: 231 (1941). 110. Hutchison, D., Weaver, R.H. and Scherago, M. The incidence and significance of microorganisms antagonistic to Escherichia coli in water. J. Bacteriol., 45: 29 (1943).

16

Guidelines for Canadian Drinking Water Quality: Supporting Documentation

Bacteriological Quality (10/01)

111. Means, E.G. and Olson, B.H. Coliform inhibition by bacteriocin-like substances in drinking water distribution systems. Appl. Environ. Microbiol., 42: 506­512 (1981). 112. Seidler, R.J., Evans, T.M., Kaufman, J.R., Waarvick, C.E. and Le Chevallier, M.W. Limitations of standard coliform enumeration techniques. J. Am. Water Works Assoc., 73: 538­542 (1981). 113. Le Chevallier, M.W. and McFeters, G.A. Interactions between heterotrophic plate count bacteria and coliform organisms. Appl. Environ. Microbiol., 49: 1338­1341 (1985). 114. McFeters, G.A., Cameron, S.C. and Le Chevallier, M.W. Influence of diluents, media, membrane filters on detection of injured water-borne coliform bacteria. Appl. Environ. Microbiol., 43: 97­103 (1982). 115. Evans, T.M., Waarvick, C.E., Seidler, R.J. and Le Chevallier, M.W. Failure of the most probable number technique to detect coliforms in drinking water and raw water supplies. Appl. Environ. Microbiol., 41: 130­138 (1981). 116. World Health Organization. International standards for drinking-water. 3rd edition. Geneva (1971). 117. World Health Organization. Surveillance of drinking-water quality. World Health Organization Monograph Series No. 63, Geneva (1976). 118. McCabe, L.J., Symons, J.M., Lee, R.D. and Robeck, G.G. Survey of community water supply systems. J. Am. Water Works Assoc., 62: 670­687 (1970). 119. Taylor, A., Craun, G.F., Faich, G.A., McCabe, L.J. and Gangarosa, E.J. Outbreaks of waterborne disease in the United States, 1961­1970. J. Infect. Dis., 125: 329­331 (1972). 120. Pipes, W.O. and Christian, R.R. Sampling frequency -- microbiological drinking water regulations. EPA 570/9-83-001, U.S. Environmental Protection Agency (1982). 121. Dutka, B.J. and El-Shaarawi, A. Microbiological water and effluent sample preservation. Can. J. Microbiol., 26: 921­929 (1980). 122. McDaniels, A.E., Bordner, R.H., Gartside, P.S., Haines, J.R. and Kristen, P. Holding effects on coliform enumeration in drinking water samples. Appl. Environ. Microbiol., 50: 755­762 (1985).

Guidelines for Canadian Drinking Water Quality: Supporting Documentation

17

Information

Bacteriological quality

17 pages

Report File (DMCA)

Our content is added by our users. We aim to remove reported files within 1 working day. Please use this link to notify us:

Report this file as copyright or inappropriate

1340007


Notice: fwrite(): send of 203 bytes failed with errno=104 Connection reset by peer in /home/readbag.com/web/sphinxapi.php on line 531