Is the replication of somatic coliphages in water environments significant?

Somatic coliphages are amid several groups of bacteriophages that have been suggested as indicators in water quality assessment. One of the limitations frequently endorsed to somatic coliphages as indicators is that they can replicate in the water environment. This review intends to evaluate the significance of this potential replication. In view of: the threshold densities of somatic coliphages and host bacteria needed for productive infection to occur, the densities of both host cells supporting somatic coliphages replication and these phages in water environments, and the poor contribution of lysogenic induction to the free somatic coliphage numbers in water, it can be concluded that replication of somatic coliphages in waters is very unlikely. Consequently, the contribution of replication in the environment of somatic coliphages is expected to have a non-noticeable influence on the numbers of somatic coliphages detected in water environments. Thus, the replication in the environment should not be argued as a limitation to the use of somatic coliphages as indicators.     

Potential usefulness of bacteriophages that infect Bacteroides fragilis as model organisms for monitoring virus removal in drinking water treatment plants.

The presence of bacteriophages at different stages in three drinking water treatment plants was evaluated to study the usefulness of phages as model organisms for assessing the efficiency of the processes. The bacteriophages tested were somatic coliphages, F-specific coliphages, and phages infecting Bacteroides fragilis. The presence of enteroviruses and currently used bacterial indicators was also determined. Most bacteriophages were removed during the prechlorination-flocculation-sedimentation step. In these particular treatment plants, which include prechlorination, phages were, in general, more resistant to the treatment processes than present bacterial indicators, with the exception, in some cases, of clostridia. Bacteriophages infecting B. fragilis were found to be more resistant to water treatment than either somatic or F-specific coliphages or even clostridia. Enteric viruses were found only in untreated water in low numbers, and consequently, the efficiency of the plants in the removal of viruses could not be evaluated with precision. The numbers and frequencies of detection of the various microorganisms in water samples taken in the distribution network served by the three plants confirm the results found in the finished water at the plants.     

Bacteriophage ecology in a small community sewer system related to their indicative role in sewage pollution of drinking water

In view of various studies looking for the merit of coliphages as indicators of water pollution with viruses originating from faecal material, a small agricultural community (population of approximately 1500 inhabitants of all ages, 2-3 km from Haifa) was selected in order to understand these bacteriophage ecology (F-RNA and somatic coliphages) in its sewer and oxidation pond system. Along the sewer lines, it was possible to isolate constantly both bacteriophage types (F-RNA and somatic coliphages) at 10(2)-10(4) plaque-forming units (pfu) ml(-1). The average numbers of somatic and F-RNA phages isolated from oxidation pond were 10(3)-10(4) pfu ml(-1); however, somatic coliphages were undetectable for several months (April-August). Significant high correlation (0.944 < R(2) < 0.99) was found between increased anionic detergent concentrations and F-RNA coliphage numbers. Infants less than 1 year old excreted both phage types and few only F-RNA coliphages (at high numbers > 10(5) pfu g(-1)) for up to 1 year. The excretion of F-RNA coliphages was highly linked to Escherichia coli F(+) harborage in the intestinal track as found in their faecal content. Finally, three bacterial hosts E. coli F(+), F(-) and CN(13) tested for survivability in sewage filtrate revealed that E. coli F(+) had the highest survivability under these conditions. Presence of somatic and F male-specific phages in sewer lines of a small community are influenced by several factors such as: anionic detergents, nutrients, temperature, source (mainly infants), shedding and survival capability of the host strain. Better understanding of coliphages ecology in sewer systems can enhance our evaluation of these proposed indicator/index microorganisms used in tracking environmental pollution of water, soil and crop contamination with faecal material containing enteric viruses.     

Coliphages and indicator bacteria in birds around Boston Harbor

Droppings from feral populations of pigeons, geese and herring gulls from the urban/suburban environment around Boston Harbor, MA, USA contained up to 10⁶ somatic coliphages, 10⁸ enterococci, 10⁹ thermotolerant coliforms and 10² F-specific coliphages per gram of feces. Somatic coliphages, enterococci and thermotolerant coliforms were common in the feces of all three kinds of birds but F-specific coliphages were found in droppings from only three of 32 gulls. Thus these sources of bacterial and viral indicators should be considered when dealing with the ecology of fecal pollution indicators. Moreover, microbial indicators of fecal or sewage pollution originating from bird droppings may be mistaken for indicators that come from humans. This may cause an overestimate of the hazard from human pathogens in water and confound attempts to locate sources of fecal or sewage pollution. Received 12 May 1998/ Accepted in revised form 15 July 1998     

Factors influencing the replication of somatic coliphages in the water environment

The potential replication of somatic coliphages in the environment has been considered a drawback for their use as viral indicators, although the extent to which this affects their numbers in environmental samples has not been assessed. In this study, the replication of somatic coliphages in various conditions was assayed using suspensions containing naturally occurring somatic coliphages and Escherichia coli WG5, which is a host strain recommended for detecting somatic coliphages. The effects on phage replication of exposing strain WG5 and phages to a range of physiological conditions and the effects of the presence of suspended particles or other bacteria were also assayed. Phage replication was further tested using a strain of Klebsiella terrigena and naturally occurring E. coli cells as hosts. Our results indicate that threshold densities of both host bacterium and phages should occur simultaneously to ensure appreciable phage replication. Host cells originating from a culture in the exponential growth phase and incubation at 37 degrees C were the best conditions for phage replication in E. coli WG5. In these conditions the threshold densities required to ensure phage replication were about 10(4) host cells/ml and 10(3) phages/ml, or 10(3) host cells/ml and 10(4) phages/ml, or intermediate values of both. The threshold densities needed for phage replication were higher when the cells proceeded from a culture in the stationary growth phase or when suspended particles or other bacteria were present. Furthermore E. coli WG5 was more efficient in supporting phage replication than either K. terrigenae or E. coli cells naturally occurring in sewage. Our results indicate that the phage and bacterium densities and the bacterial physiological conditions needed for phage replication are rarely expected to be found in the natural water environments.     

Sunlight inactivation of fecal indicator bacteria and bacteriophages from waste stabilization pond effluent in fresh and saline waters

Sunlight inactivation in fresh (river) water of fecal coliforms, enterococci, Escherichia coli, somatic coliphages, and F-RNA phages from waste stabilization pond (WSP) effluent was compared. Ten experiments were conducted outdoors in 300-liter chambers, held at 14C (mean river water temperature). Sunlight inactivation (k(S)) rates, as a function of cumulative global solar radiation (insolation), were all more than 10 times higher than the corresponding dark inactivation (k(D)) rates in enclosed (control) chambers. The overall k(S) ranking (from greatest to least inactivation) was as follows: enterococci > fecal coliforms greater-than-or-equal E. coli > somatic coliphages > F-RNA phages. In winter, fecal coliform and enterococci inactivation rates were similar but, in summer, enterococci were inactivated far more rapidly. In four experiments that included freshwater-raw sewage mixtures, enterococci survived longer than fecal coliforms (a pattern opposite to that observed with the WSP effluent), but there was little difference in phage inactivation between effluents. In two experiments which included simulated estuarine water and seawater, sunlight inactivation of all of the indicators increased with increasing salinity. Inactivation rates in freshwater, as seen under different optical filters, decreased with the increase in the spectral cutoff (50% light transmission) wavelength. The enterococci and F-RNA phages were inactivated by a wide range of wavelengths, suggesting photooxidative damage. Inactivation of fecal coliforms and somatic coliphages was mainly by shorter (UV-B) wavelengths, a result consistent with photobiological damage. Fecal coliform repair mechanisms appear to be activated in WSPs, and the surviving cells exhibit greater sunlight resistance in natural waters than those from raw sewage. In contrast, enterococci appear to suffer photooxidative damage in WSPs, rendering them susceptible to further photooxidative damage after discharge. This suggests that they are unsuitable as indicators of WSP effluent discharges to natural waters. Although somatic coliphages are more sunlight resistant than the other indicators in seawater, F-RNA phages are the most resistant in freshwater, where they may thus better represent enteric virus survival.     

Removal of micro-organisms in a small-scale hydroponics wastewater treatment system

Aims: To measure the microbial removal capacity of a small-scale hydroponics wastewater treatment plant. Methods and Results: Paired samples were taken from untreated, partly-treated and treated wastewater and analysed for faecal microbial indicators, i.e. coliforms, Escherichia coli, enterococci, Clostridium perfringens spores and somatic coliphages, by culture based methods. Escherichia coli was never detected in effluent water after >5.8-log removal. Enterococci, coliforms, spores and coliphages were removed by 4.5, 4.1, 2.3 and 2.5 log respectively. Most of the removal (60-87%) took place in the latter part of the system because of settling, normal inactivation (retention time 12.7 d) and sand filtration. Time-dependent log-linear removal was shown for spores (k = -0.17 log d(-1), r(2) = 0.99). Conclusions: Hydroponics wastewater treatment removed micro-organisms satisfactorily. Significance and Impact of the Study: Investigations on the microbial removal capacity of hydroponics have only been performed for bacterial indicators. In this study it has been shown that virus and (oo)cyst process indicators were removed and that hydroponics can be an alternative to conventional wastewater treatment.     

Occurrence and levels of indicators and selected pathogens in different sludges and biosolids

AIMS: Determine the occurrence and levels of pathogens and indicators in raw and treated sludges and compare their persistence after two different treatments. METHODS AND RESULTS: Helminth ova, Cryptosporidium spp., Salmonella spp., enteroviruses, and bacterial and viral indicators were determined in raw sludges and biosolids produced after mesophilic and thermophilic treatments. Except Salmonella, all of the parameters were quantified. Helminth ova were found at very low concentrations even in raw sludges. Viable Cryptosporidium oocysts were still present in most samples of treated sludges. Faecal coliforms, spores of sulphite-reducing clostridia (SSRC), and somatic coliphages were the only indicators with values above their detection limits in most of the samples. CONCLUSIONS: Pathogens were still detected in some treated sludge samples. SSRC were the most resistant micro-organisms to treatments and hence may be an indicator for the reduction of protozoan oocysts. Somatic coliphages constitute an alternative as viral indicators due to their detection in sludges before and after treatment. SIGNIFICANCE AND IMPACT OF THE STUDY: Because of the persistence of some pathogens after sludge treatments, additional indicators are needed. SSRC and somatic coliphages are good candidates. Easy and inexpensive methods for the determination of these indicators are feasible both in industrialized and developing countries.     

Bacterial host strains that support replication of somatic coliphages

Somatic coliphages detected by Escherichia coli strain WG5 have been proposed as potential indicators of water quality. Their potential replication in the water environment is considered a drawback for their use as indicators. However, the contribution of replication outside the gut to the total numbers has never been quantified. It has not been determined either the fraction of bacterial strains that might support replication of phages detected by strain WG5 in the water environment. We examined the sensitivity of 291 host strains to 25 phages by streaking slants of the presumptive host strain onto an agar layer that contains bacteriophages, which gives a total of 7275 combinations (sensitivity tests). Only a 3.02% of the tests showed sensitivity. Additionally, six environmental strains were used as hosts to count phages in sewage and seawater. Phages isolated on these strains were used to infect strain WG5. The environmental strains detected 1 log₁₀ fewer phages than strain WG5 in sewage and seawater. The fraction of phages that were detected by the six strains and that also infected strain WG5 ranged from < 0.07% to < 2.0% of the total amount of bacteriophages detected by strain WG5 in the same samples. Our results confirm that less than 3% of naturally occurring hosts support replication of phages infecting E. coli. We conclude that the contribution of replication to the number of somatic coliphages detected in the aquatic environment is negligible. This revised version was published online in June 2006 with corrections to the Cover Date.     

Sunlight inactivation of fecal bacteriophages and bacteria in sewage-polluted seawater.

Sunlight inactivation rates of somatic coliphages, F-specific RNA bacteriophages (F-RNA phages), and fecal coliforms were compared in seven summer and three winter survival experiments. Experiments were conducted outdoors, using 300-liter 2% (vol/vol) sewage-seawater mixtures held in open-top chambers. Dark inactivation rates (k(D)s), measured from exponential survival curves in enclosed (control) chambers, were higher in summer (temperature range: 14 to 20 degrees C) than in winter (temperature range: 8 to 10 degrees C). Winter k(D)s were highest for fecal coliforms and lowest for F-RNA phages but were the same or similar for all three indicators in summer. Sunlight inactivation rates (k(S)), as a function of cumulative global solar radiation (insolation), were all higher than the k(D)s with a consistent k(S) ranking (from greatest to least) as follows: fecal coliforms, F-RNA phages, and somatic coliphages. Phage inactivation was exponential, but bacterial curves typically exhibited a shoulder. Phages from raw sewage exhibited k(S)s similar to those from waste stabilization pond effluent, but raw sewage fecal coliforms were inactivated faster than pond effluent fecal coliforms. In an experiment which included F-DNA phages and Bacteroides fragilis phages, the k(S) ranking (from greatest to least) was as follows: fecal coliforms, F-RNA phages, B. fragilis phages, F-DNA phages, and somatic coliphages. In a 2-day experiment which included enterococci, the initial concentration ranking (from greatest to least: fecal coliforms, enterococci, F-RNA phages, and somatic coliphages) was reversed during sunlight exposure, with only the phages remaining detectable by the end of day 2. Inactivation rates under different optical filters decreased with the increase in spectral cutoff wavelength (50% light transmission) and indicated that F-RNA phages and fecal coliforms are more susceptible than somatic coliphages to longer solar wavelengths, which predominate in seawater. The consistently superior survival of somatic coliphages in our experiments suggests that they warrant further consideration as fecal, and possibly viral, indicators in marine waters.     

Sunlight Inactivation of Fecal Indicator Bacteria and Bacteriophages from Waste Stabilization Pond Effluent in Fresh and Saline Waters

Sunlight inactivation in fresh (river) water of fecal coliforms, enterococci, Escherichia coli, somatic coliphages, and F-RNA phages from waste stabilization pond (WSP) effluent was compared. Ten experiments were conducted outdoors in 300-liter chambers, held at 14°C (mean river water temperature). Sunlight inactivation (k_S) rates, as a function of cumulative global solar radiation (insolation), were all more than 10 times higher than the corresponding dark inactivation (k_D) rates in enclosed (control) chambers. The overall k_S ranking (from greatest to least inactivation) was as follows: enterococci > fecal coliforms ≥ E. coli > somatic coliphages > F-RNA phages. In winter, fecal coliform and enterococci inactivation rates were similar but, in summer, enterococci were inactivated far more rapidly. In four experiments that included freshwater-raw sewage mixtures, enterococci survived longer than fecal coliforms (a pattern opposite to that observed with the WSP effluent), but there was little difference in phage inactivation between effluents. In two experiments which included simulated estuarine water and seawater, sunlight inactivation of all of the indicators increased with increasing salinity. Inactivation rates in freshwater, as seen under different optical filters, decreased with the increase in the spectral cutoff (50% light transmission) wavelength. The enterococci and F-RNA phages were inactivated by a wide range of wavelengths, suggesting photooxidative damage. Inactivation of fecal coliforms and somatic coliphages was mainly by shorter (UV-B) wavelengths, a result consistent with photobiological damage. Fecal coliform repair mechanisms appear to be activated in WSPs, and the surviving cells exhibit greater sunlight resistance in natural waters than those from raw sewage. In contrast, enterococci appear to suffer photooxidative damage in WSPs, rendering them susceptible to further photooxidative damage after discharge. This suggests that they are unsuitable as indicators of WSP effluent discharges to natural waters. Although somatic coliphages are more sunlight resistant than the other indicators in seawater, F-RNA phages are the most resistant in freshwater, where they may thus better represent enteric virus survival.     

Clostridium perfringens and somatic coliphages as indicators of the efficiency of drinking water treatment for viruses and protozoan cysts.

To find the most suitable indicator of viral and parasitic contamination of drinking water, large-volume samples were collected and analyzed for the presence of pathogens (cultivable human enteric viruses, Giardia lamblia cysts, and Cryptosporidium oocysts) and potential indicators (somatic and male-specific coliphages, Clostridium perfringens). The samples were obtained from three water treatment plants by using conventional or better treatments (ozonation, biological filtration). All samples of river water contained the microorganisms sought, and only C. perfringens counts were correlated with human enteric viruses, cysts, or oocysts. For settled and filtered water samples, all indicators were statistically correlated with human enteric viruses but not with cysts or oocysts. By using multiple regression, the somatic coliphage counts were the only explanatory variable for the human enteric virus counts in settled water, while in filtered water samples it was C. perfringens counts. Finished water samples of 1,000 liters each were free of all microorganisms, except for a single sample that contained low levels of cysts and oocysts of undetermined viability. Three of nine finished water samples of 20,000 liters each revealed residual levels of somatic coliphages at 0.03, 0.10, and 0.26 per 100 liters. Measured virus removal was more than 4 to 5 log10, and cyst removal was more than 4 log10. Coliphage and C. perfringens counts suggested that the total removal and inactivation was more than 7 log10 viable microorganisms. C. perfringens counts appear to be the most suitable indicator for the inactivation and removal of viruses in drinking water treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Virus occurrence in municipal groundwater sources in Quebec, Canada

A 1 year study was undertaken on groundwater that was a source of drinking water in the province of Quebec, Canada. Twelve municipal wells (raw water) were sampled monthly during a 1 year period, for a total of 160 samples. Using historic data, the 12 sites were categorized into 3 groups: group A (no known contamination), group B (sporadically contaminated by total coliforms), and group C (historic and continuous contamination by total coliforms and (or) fecal coliforms). Bacterial indicators (total coliform, Escherichia coli, enteroccoci), viral indicators (somatic and male-specific coliphages), total culturable human enteric viruses, and noroviruses were analyzed at every sampling site. Total coliforms were the best indicator of microbial degradation, and coliform bacteria were always present at the same time as human enteric viruses. Two samples contained human enteric viruses but no fecal pollution indicators (E. coli, enterococci, or coliphages), suggesting the limited value of these microorganisms in predicting the presence of human enteric viruses in groundwater. Our results underline the value of historic data in assessing the vulnerability of a well on the basis of raw water quality and in detecting degradation of the source. This project allowed us to characterize the microbiologic and virologic quality of groundwater used as municipal drinking water sources in Quebec.     

Integrated analysis of established and novel microbial and chemical methods for microbial source tracking

Several microbes and chemicals have been considered as potential tracers to identify fecal sources in the environment. However, to date, no one approach has been shown to accurately identify the origins of fecal pollution in aquatic environments. In this multilaboratory study, different microbial and chemical indicators were analyzed in order to distinguish human fecal sources from nonhuman fecal sources using wastewaters and slurries from diverse geographical areas within Europe. Twenty-six parameters, which were later combined to form derived variables for statistical analyses, were obtained by performing methods that were achievable in all the participant laboratories: enumeration of fecal coliform bacteria, enterococci, clostridia, somatic coliphages, F-specific RNA phages, bacteriophages infecting Bacteroides fragilis RYC2056 and Bacteroides thetaiotaomicron GA17, and total and sorbitol-fermenting bifidobacteria; genotyping of F-specific RNA phages; biochemical phenotyping of fecal coliform bacteria and enterococci using miniaturized tests; specific detection of Bifidobacterium adolescentis and Bifidobacterium dentium; and measurement of four fecal sterols. A number of potentially useful source indicators were detected (bacteriophages infecting B. thetaiotaomicron, certain genotypes of F-specific bacteriophages, sorbitol-fermenting bifidobacteria, 24-ethylcoprostanol, and epycoprostanol), although no one source identifier alone provided 100% correct classification of the fecal source. Subsequently, 38 variables (both single and derived) were defined from the measured microbial and chemical parameters in order to find the best subset of variables to develop predictive models using the lowest possible number of measured parameters. To this end, several statistical or machine learning methods were evaluated and provided two successful predictive models based on just two variables, giving 100% correct classification: the ratio of the densities of somatic coliphages and phages infecting Bacteroides thetaiotaomicron to the density of somatic coliphages and the ratio of the densities of fecal coliform bacteria and phages infecting Bacteroides thetaiotaomicron to the density of fecal coliform bacteria. Other models with high rates of correct classification were developed, but in these cases, higher numbers of variables were required.     

Bacteriophages of enteric bacteria in drinking water, comparison of their distribution in two countries

The presence of bacteriophages infecting enteric bacteria was tested in more than 1500 drinking water samples in Israel and Spain. Bacteriophages tested were somatic coliphages, F-specific bacteriophages and Bacteroides fragilis bacteriophages. The three groups of bacteriophage were isolated in 100 ml water samples by the presence/absence test with similar frequencies, which ranged from 4·4% for somatic coliphages to 6·1% for bacteriophages infecting Bact. fragilis. In contrast, the frequency of isolation of bacteriophages was significantly higher than the frequency of isolation of faecal coliforms, which averaged only 1·9%. No significant differences were observed between the frequencies of isolation between the samples tested in Spain and those tested in Israel. The percentage of groundwater samples containing faecal coliforms and somatic coliphages was reduced significantly by chlorination, despite known deficiencies. However, there was no effect on the occurrence of F-specific bacteriophages and Bact. fragilis bacteriophages.     

Sunlight Inactivation of Fecal Bacteriophages and Bacteria in Sewage-Polluted Seawater

Sunlight inactivation rates of somatic coliphages, F-specific RNA bacteriophages (F-RNA phages), and fecal coliforms were compared in seven summer and three winter survival experiments. Experiments were conducted outdoors, using 300-liter 2% (vol/vol) sewage-seawater mixtures held in open-top chambers. Dark inactivation rates (k_Ds), measured from exponential survival curves in enclosed (control) chambers, were higher in summer (temperature range: 14 to 20°C) than in winter (temperature range: 8 to 10°C). Winter k_Ds were highest for fecal coliforms and lowest for F-RNA phages but were the same or similar for all three indicators in summer. Sunlight inactivation rates (k_S), as a function of cumulative global solar radiation (insolation), were all higher than the k_Ds with a consistent k_S ranking (from greatest to least) as follows: fecal coliforms, F-RNA phages, and somatic coliphages. Phage inactivation was exponential, but bacterial curves typically exhibited a shoulder. Phages from raw sewage exhibited k_Ss similar to those from waste stabilization pond effluent, but raw sewage fecal coliforms were inactivated faster than pond effluent fecal coliforms. In an experiment which included F-DNA phages and Bacteroides fragilis phages, the k_S ranking (from greatest to least) was as follows: fecal coliforms, F-RNA phages, B. fragilis phages, F-DNA phages, and somatic coliphages. In a 2-day experiment which included enterococci, the initial concentration ranking (from greatest to least: fecal coliforms, enterococci, F-RNA phages, and somatic coliphages) was reversed during sunlight exposure, with only the phages remaining detectable by the end of day 2. Inactivation rates under different optical filters decreased with the increase in spectral cutoff wavelength (50% light transmission) and indicated that F-RNA phages and fecal coliforms are more susceptible than somatic coliphages to longer solar wavelengths, which predominate in seawater. The consistently superior survival of somatic coliphages in our experiments suggests that they warrant further consideration as fecal, and possibly viral, indicators in marine waters.     

Occurrence of bacterial indicators and bacteriophages infecting enteric bacteria in groundwater in different geographical areas

AIMS: The aim of this research was to determine the suitability of coliphages (bacteriophages) for assessing the microbial quality of groundwater. METHODS AND RESULTS: The number of several bacterial indicators (faecal coliforms, Escherichia coli, enterococci and spores of sulfite-reducing clostridia) and bacteriophages (somatic coliphages, F-specific RNA bacteriophages and bacteriophages infecting Bacteroides fragilis) were determined in groundwater of aquifers in various geographical areas. Results show that the relative abundance, determined as percentages of positive detections, of the bacterial indicators and bacteriophages varies depending on the aquifer. CONCLUSIONS: A single bacterial indicator may not be enough to assess microbiological quality in certain aquifers. One bacterial indicator and a bacteriophage parameter provide more information than two bacterial indicators. SIGNIFICANCE AND IMPACT OF THE STUDY: Coliphages (CPH) provide different information from that provided by bacterial indicators on the microbial quality of groundwater in different geographical areas. Easy, fast and inexpensive methods for the detection of CPH are feasible in both industrialized and developing countries.     

Correlation between bacterial indicators and bacteriophages in sewage and sludge

The use of bacteriophages as potential indicators of faecal pollution has recently been studied. The correlation of the number of bacterial indicators and the presence of three groups of bacteriophages, namely somatic coliphages (SOMCPH), F-RNA-specific phages (FRNAPH) and phages of Bacteroides fragilis (BFRPH), in raw and treated wastewater and sludge is presented in this study. Raw and treated wastewater and sewage sludge samples from two wastewater treatment plants in Athens were collected on a monthly basis, over a 2-year period, and analysed for total coliforms, Escherichia coli, intestinal enterococci and the three groups of bacteriophages. A clear correlation between the number of bacterial indicators and the presence of bacteriophages was observed. SOMCPH may be used as additional indicators, because of their high densities and resistance to various treatment steps.