Elimination of viruses and indicator bacteria at each step of treatment during preparation of drinking water at seven water treatment plants

Seven drinking water treatment plants were sampled twice a month for 12 months to evaluate the removal of indicator bacteria and cytopathogenic enteric viruses. Samples were obtained at each level of treatment: raw water, postchlorination, postsedimentation, postfiltration, postozonation, and finished (tap) water. Raw water quality was usually poor, with total coliform counts exceeding 105 to 106 CFU/liter and the average virus count in raw water of 3.3 most probable number of cytopathogenic units (MPNCU)/liter; several samples contained more than 100 MPNCU/liter. All plants distributed finished water that was essentially free of indicator bacteria as judged by analysis of 1 liter for total coliforms, fecal coliforms, fecal streptococci, coagulase-positive staphylococci, and Pseudomonas aeruginosa. The total plate counts at 20 and 35 degrees C were also evaluated as a measure of the total microbial population and were usually very low. Viruses were detected in 7% (11 of 155) of the finished water samples (1,000 liters) at an average density of 0.0006 MPNCU/liter the highest virus density measured being 0.2 MPNCU/liter. The average cumulative virus reduction was 95.15% after sedimentation and 99.97% after filtration and did not significantly decrease after ozonation or final chlorination. The viruses isolated from treated waters were all enteroviruses: poliovirus types 1, 2, and 3, coxsackievirus types B3, B4, and B5, echovirus type 7, and untyped picornaviruses.     

Virological examination of drinking water: a Canadian collaborative study

A collaborative virological survey of drinking water was initiated in three major Canadian urban areas, Montreal, Ottawa, and Toronto. In each selected area, three water purification plants were sampled monthly for up to 18 months. The total population served by all nine plants was about 1 500 000. Samples of raw (100 L) and treated (1000 L) water were examined by virus concentration procedures based on adsorption-elution. Sample concentrates were assayed for cytopathic viruses on BS-C-1 cells and the results were expressed as the most probable number of cytopathic units (MPNCU). Viruses were detected in 57% (0-15.35 MPNCU/L) of the raw water samples from Montreal, 37% (0-46.0 MPNCU/L) in Ottawa, and 33% (0-4.91 MPNCU/L) in Toronto. The majority of isolates were reoviruses, but picornaviruses were also found. All finished waters (177 samples) met bacteriological, turbidity, and residual chlorine standards and were free of detectable viruses.     

Removal of indicator bacteria, human enteric viruses, Giardia cysts, and Cryptosporidium oocysts at a large wastewater primary treatment facility

Pathogens and fecal indicator bacteria occurrence and removal were studied for a period of 6 months at the Montreal Urban Community wastewater treatment facility. With a capacity of about 7.6 million cubic metres per day (two billion U.S. gallons per day), it is the largest primary physico-chemical treatment plant in America. The plant discharges a nondisinfected effluent containing about 20 mg/L of suspended matter and 0.5 mg/L of total phosphorus on the basis of average annual concentrations. BDO5 (annual mean) is 75 mg/L before treatment and 32 mg/L after treatment. Samples were collected for a period of 6 months, and they demonstrated that the plant was not efficient at removing indicator bacteria and the pathogens tested. Fecal coliforms were the most numerous of the indicator bacteria and their removal averaged 25%. Fecal streptococci removal was 29%, while Escherichia coli removal was 12%. In untreated sewage, fecal coliforms, E. coli, and human enteric viruses were more numerous in summer and early autumn. Fecal streptococci counts remained relatively similar throughout the period. Clostridium perfringens removal averaged 51%. Giardia cysts levels were not markedly different throughout the study period, and 76% of the cysts were removed by treatment. Cryptosporidium oocyst counts were erratic, probably due to the methods, and removal was 27%. Human enteric viruses were detected in all samples of raw and treated wastewater with no removal observed (0%). Overall, the plant did not perform well for the removal of fecal indicator bacteria, human enteric viruses, or parasite cysts. Supplementary treatment and disinfection were recommended to protect public health. Various alternatives are being evaluated.     

Isolation of viruses from drinking water at the Point-Viau water treatment plant

Viruses were isolated from every sample of raw (100 L) and treated (1000 L) water collected at a water treatment plant drawing sewage-contaminated river water. Few plaque-forming isolates were formed but cytopathogenic viruses were isolated as frequently in drinking water as in raw water. In drinking water some samples contained more than 1 cytopathogenic unit per litre, but most contained 1-10/100 L. These viruses had not been inactivated or removed by prechlorination, flocculation, filtration, ozonation, and postchlorination. There were no coliforms present and a residual chlorine level had been maintained. Poliovirus type 1 was a frequent isolate but many isolates were nonpoliovirus. The presence of these viruses in drinking water raises questions about the efficacy of some water treatment processes to remove viruses from polluted water.     

Validity of fecal coliforms, total coliforms, and fecal streptococci as indicators of viruses in chlorinated primary sewage effluents.

Quantities of combined chlorine that usually destroyed more than 99.999% of the indigenous fecal coliforms, total coliforms, and fecal streptococci in primary sewage effluents destroyed only 85 to 99% of the indigenous viruses present. Viruses were recovered from five of eight chlorinated primary effluents from which fecal coliforms were not recovered by standard most-probable-number procedures. The limited volumes of such chlorinated effluents that can be tested for indicator bacteria with currently available multiple-tube and membrane filter techniques restrict the value of fecal coliforms, fecal streptococci, and even total coliforms as indicators of viruses in these effluents. Although fecal coliforms and fecal streptococci are useful indicators of viruses in effluents from which these bacteria are recovered, the absence of these bacteria and even total coliforms from disinfected effluents (in standard tests) does not assure that viruses are also absent.     

Validity of fecal coliforms, total coliforms, and fecal streptococci as indicators of viruses in chlorinated primary sewage effluents.

Quantities of combined chlorine that usually destroyed more than 99.999% of the indigenous fecal coliforms, total coliforms, and fecal streptococci in primary sewage effluents destroyed only 85 to 99% of the indigenous viruses present. Viruses were recovered from five of eight chlorinated primary effluents from which fecal coliforms were not recovered by standard most-probable-number procedures. The limited volumes of such chlorinated effluents that can be tested for indicator bacteria with currently available multiple-tube and membrane filter techniques restrict the value of fecal coliforms, fecal streptococci, and even total coliforms as indicators of viruses in these effluents. Although fecal coliforms and fecal streptococci are useful indicators of viruses in effluents from which these bacteria are recovered, the absence of these bacteria and even total coliforms from disinfected effluents (in standard tests) does not assure that viruses are also absent.     

F-specific RNA bacteriophages are adequate model organisms for enteric viruses in fresh water.

Culturable enteroviruses were detected by applying concentration techniques and by inoculating the concentrates on the BGM cell line. Samples were obtained from a wide variety of environments, including raw sewage, secondary effluent, coagulated effluent, chlorinated and UV-irradiated effluents, river water, coagulated river water, and lake water. The virus concentrations varied widely between 0.001 and 570/liter. The same cell line also supported growth of reoviruses, which were abundant in winter (up to 95% of the viruses detected) and scarce in summer (less than 15%). The concentrations of three groups of model organisms in relation to virus concentrations were also studied. The concentrations of bacteria (thermotolerant coliforms and fecal streptococci) were significantly correlated with virus concentrations in river water and coagulated secondary effluent, but were relatively low in disinfected effluents and relatively high in surface water open to nonhuman fecal pollution. The concentrations of F-specific RNA bacteriophages (FRNA phages) were highly correlated with virus concentrations in all environments studied except raw and biologically treated sewage. Numerical relationships were consistent over the whole range of environments; the regression equations for FRNA phages on viruses in river water and lake water were statistically equivalent. These relationships support the possibility that enteric virus concentrations can be predicted from FRNA phage data.     

Microbiological and virological analysis of water from two water filtration plants and their distribution systems

The microbial flora of the water produced by two water filtration plants and their drinking water distribution system were evaluated: the Pont-Viau (PV) and the Repentigny (RE) water filtration plants. Untreated water entering the plants contained 3.6 (PV) and 16.8 most probable number of infectious units (mpniu)/L (RE) enteric viruses and total coliform bacteria counts were 300,000 (PV) and 500,000 cfu/L (RE). Treated water leaving the plant was essentially free of all the bacterial indicators measured (total, stressed, and fecal coliforms; Aeromonas hydrophila; Pseudomonas aeruginosa; Clostridium perfringens; enterococci) as well as of human enteric viruses. Heterotrophic plate counts at 20 and 35 degrees C were low in the freshly treated water leaving the plants, but bacterial regrowth was observed in both distribution systems at all sampling sites. Average counts for the heterotrophic plate count (20 degrees C) were between 10(6) and 10(7) cfu/L and counts were clearly increased with the distance from the plant. The most numerous bacterial genera encountered were Bacillus, Flavobacterium, and Pseudomonas (nonaeruginosa).     

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.     

Destruction by Anaerobic Mesophilic and Thermophilic Digestion of Viruses and Indicator Bacteria Indigenous to Domestic Sludges

In raw sludges and in mesophilically and thermophilically digested anaerobic sludges, large variations in numbers of viruses occurred over narrow ranges of numbers of fecal coliforms, total coliforms, and fecal streptococci, demonstrating that the bacteria were poor quantitative reflectors of the numbers of the viruses detected. Mesophilic and thermophilic digestion of anaerobic sludges destroyed all three indicator bacteria more rapidly than such digestion destroyed the viruses. The relative rates for the destruction of viruses, fecal coliforms, and fecal streptococci in the digested sludges were consistent over the 17-month study. Fecal coliforms were 7 to 8 times more sensitive than the viruses to mesophilic digestion and 9 to 10 times more sensitive to thermophilic digestion. Total coliforms were even more sensitive. The rates at which fecal streptococci were destroyed by mesophilic and thermophilic digestion of anaerobic sludges approached those at which the viruses were destroyed by those processes; this suggested that the rates at which fecal streptococci in sludges are destroyed by those processes may serve as useful indicators for the rates at which viruses in sludges are destroyed by those processes.     

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)     

Detection of enteric viruses in treated drinking water

The occurrence of viruses in conventionally treated drinking water derived from a heavily polluted source was evaluated by collecting and analyzing 38 large-volume (65- to 756-liter) samples of water from a 9 m3/s (205 X 10(6) gallons [776 X 10(6) liters] per day) water treatment plant. Samples of raw, clarified, filtered, and chlorinated finished water were concentrated by using the filter adsorption-elution technique. Of 23 samples of finished water, 19 (83%) contained viruses. None of the nine finished water samples collected during the dry season contained detectable total coliform bacteria. Seven of nine finished water samples collected during the dry season met turbidity, total coliform bacteria, and total residual chlorine standards. Of these, four contained virus. During the dry season the percent removals were 25 to 93% for enteric viruses, 89 to 100% for bacteria, and 81% for turbidity. During the rainy season the percent removals were 0 to 43% for enteric viruses, 80 to 96% for bacteria, and 63% for turbidity. None of the 14 finished water samples collected during the rainy season met turbidity standards, and all contained rotaviruses or enteroviruses.     

Distribution and Significance of Fecal Indicator Organisms in the Upper Chesapeake Bay

Total viable aerobic, heterotrophic bacteria, total coliforms, fecal coliforms, and fecal streptococci were enumerated in samples collected at five stations located in the Upper Chesapeake Bay, December 1973 through December 1974. Significant levels of pollution indicator organisms were detected at all of the stations sampled. Highest counts were observed in samples collected at the confluence of the Susquehanna River and the Chesapeake Bay. The indicator organisms examined were observed to be quantitatively distributed independently of temperature and salinity. Counts were not found to be correlated with concentration of suspended sediment. However, significant proportions of both the total viable bacteria (53%) and fecal indicator organisms (>80%) were directly associated with suspended sediments. Correlation coefficients (r) for the indicator organisms examined in this study ranged from r = 0.80 to r = 0.99 for bottom water and suspended sediment, respectively. Prolonged survival of fecal streptococci in most of the sediment samples was observed, with concomitant reduction of the correlation coefficient from r = 0.99, fecal streptococci to total coliforms in water, to r = 0.01, fecal streptococci to fecal coliforms in sediments. The results of this study compared favorably with fecal coliforms: fecal streptococci ratios for the various sample types. Characterization of organisms beyond the confirmed most-probable-number procedure provided good correlation between bacterial indicator groups.     

Long-term variations in abundance and distribution of sewage pollution indicator and human pathogenic bacteria along the central west coast of India

Safe water quality criteria on the load and types of microbial populations are important for human use from fishery, tourism and navigational viewpoints. To understand the variations in sewage pollution indicator and certain human pathogenic bacteria, data collected from various locations along central west coast of India during 2002–2007 were analyzed. Water and sediment samples were examined for total viable counts (TVC), pollution indicator bacteria (total coliforms – TC, fecal coliforms – FC and Escherichia coli – EC) and potential pathogens (Vibrio cholerae – VC, Shigella – SH, and Salmonella spp. – SA). In both Mandovi and Zuari estuaries, where fishing and tourist-related activities are sizable and long-term data collection was regular, we observed high counts of TC, FC, VC, SH and SA in particular during monsoon due to increased land runoff. Further, the abundance of TC and FC has increased significantly over the years in the water column to much above either USEPA or India permissible limits. The concentrations of Vibrio cholerae, and Shigella correlated with those of coliforms. Pathogenic bacteria were detected even 20 km and/or 25 km offshore mainly due to dumping of raw or improperly treated sewage effluents either from land, fishing trawlers and/or ships in the anchorage. Higher concentrations of fecal coliforms and pathogenic bacteria in neretic waters signify threats to environmental and human health.     

Detection of enteric viruses in treated drinking water.

The occurrence of viruses in conventionally treated drinking water derived from a heavily polluted source was evaluated by collecting and analyzing 38 large-volume (65- to 756-liter) samples of water from a 9 m3/s (205 X 10(6) gallons [776 X 10(6) liters] per day) water treatment plant. Samples of raw, clarified, filtered, and chlorinated finished water were concentrated by using the filter adsorption-elution technique. Of 23 samples of finished water, 19 (83%) contained viruses. None of the nine finished water samples collected during the dry season contained detectable total coliform bacteria. Seven of nine finished water samples collected during the dry season met turbidity, total coliform bacteria, and total residual chlorine standards. Of these, four contained virus. During the dry season the percent removals were 25 to 93% for enteric viruses, 89 to 100% for bacteria, and 81% for turbidity. During the rainy season the percent removals were 0 to 43% for enteric viruses, 80 to 96% for bacteria, and 63% for turbidity. None of the 14 finished water samples collected during the rainy season met turbidity standards, and all contained rotaviruses or enteroviruses.     

Virus and bacteria removal from wastewater by land treatment.

Secondary sewage effluent and renovated water from four wells at the Flushing Meadows Wastewater Renovation Project near Phoenix, Arizona, in operation since 1967, were assayed approximately every 2 months in 1974 for viruses and enteric bacteria during flooding periods. No viruses of Salmonella sp. were detected in any renovated well water samples, and the numbers of fecal coliforms, fecal streptococci, and total bacteria were decreased by about 99.9% in the renovated well waters after the wastewater was filtered through about 9 m of soil.     

Coliphages as indicators of enteroviruses.

Coliphages were monitored in conjunction with indicator bacteria and enteroviruses in a drinking-water plant modified to reduce trihalomethane production. Coliphages could be detected in the source water by direct inoculation, and sufficient coliphages were detected in enterovirus concentrates to permit following the coliphage levels through different water treatment processes. The recovery efficiency by different filter types ranged from 1 to 53%. Statistical analysis of the data indicated that enterovirus isolates were better correlated with coliphages than with total coliforms, fecal coliforms, fecal streptococci, or standard plate count organisms. Coliphages were not detected in finished water.     

Coliphages as indicators of enteroviruses

Coliphages were monitored in conjunction with indicator bacteria and enteroviruses in a drinking-water plant modified to reduce trihalomethane production. Coliphages could be detected in the source water by direct inoculation, and sufficient coliphages were detected in enterovirus concentrates to permit following the coliphage levels through different water treatment processes. The recovery efficiency by different filter types ranged from 1 to 53%. Statistical analysis of the data indicated that enterovirus isolates were better correlated with coliphages than with total coliforms, fecal coliforms, fecal streptococci, or standard plate count organisms. Coliphages were not detected in finished water.     

Bacteriological water quality effects of hydraulically dredging contaminated upper Mississippi River bottom sediment.

Bacteriological effects of hydraulically dredging polluted bottom sediment in the navigation channel of the Upper Mississippi River (river mile 827.5 [about 1,332 km] to 828.1 [about 1,333 km]) were investigated. Bottom sediment in the dredging site contained high total coliform densities (about 6,800 most-probable-number total coliform index per g [dry weight] and 3,800 membrane filter total coliforms per g [dry weight]), and fecal coliforms comprised an average 32% of each total coliform count. Total coliform and fecal coliform densities in water samples taken immediately below the dredge discharge pipe were each approximately four times corresponding upstream values; fecal streptococcus densities were approximately 50 times corresponding upstream values. Correlation analysis indicated that mean turbidity values downstream to the dredging operation were directly and significantly (r greater than 0.94) related to corresponding total coliform, fecal coliform, and fecal streptococcus densities. Salmonellae and shigellae were not recovered from either upstream or downstream water samples. Turbidity and indicator bacteria levels had returned to predredge values within less than 2 km below the dredge spoil discharge area at the prevailing current velocity (about 0.15 m/s).     

Salmonellae and pollution indicator bacteria in municipal and food processing effluents and the Cornwallis River

A study was conducted to determine the incidence of fecal coliforms, fecal streptococci, Aeromonas hydrophilia, and Salmonella spp. in the waste discharges of seven sewage treatment plants, four fruit and vegetable canneries, a meat packing plant, a poultry processing plant, and a potato processing plant located along the Cornwallis River in Nova Scotia, Canada. Surface water samples were also collected from 13 locations in the river to assess the impact of these waste discharges on the receiving water quality. The results showed that the final effluents from most of the sewage treatment and processing plants were of very poor bacteriological quality, with the number of indicator bacteria comparable with those found in raw sewage. Salmonellae were isolated from the effluents of the meat and poultry plants and five of the seven sewage treatment plants surveyed. No salmonellae were detected in the effluents of the fruit and vegetable canneries. The impact of the discharge of untreated municipal and food processing wastes on the Cornwallis River water quality was evidenced by the recovery from river water of five Salmonella serotypes, and the high fecal coliform counts which exceeded recommended limit for bathing and shellfish harvesting.