Health-based targets for greywater reuse in residential schools in Madhya Pradesh,India

In line with developments in the water reuse sector, this paper applied quantitative microbial risk assessment (QMRA) techniques to seven greywater reuse systems used for recycling shower water for toilet flushing. The objective of the study was to establish a scientific basis for health-based greywater targets for India. It involved qualitative risk assessments and quantitative microbiological analysis using Enterococci, thermotolerant coliforms (TTC) and coliphage indicator organisms. Four conclusions are drawn from this study. Firstly, the systems indicated a low risk and high quality, and secondly that low levels of risk were present in systems, resulting in the recommendation of guideline of 5000 cfu/100 mL rather than 10 000 cfu/100 mL for greywater utilised for direct toilet flushing. Thirdly, disability adjusted life years (DALYs) are a useful indicator of risk for evaluating the performance of a greywater reuse system in addition to chemical/microbiological indicators DALYs, and finally that TTC are a useful surrogate microbial indicator for analysis of greywater in developing countries with limited analytical facilities.     

Bacteria,viruses, and parasites in an intermittent stream protected from and exposed to pasturing cattle: Prevalence,densities, and quantitative microbial risk assessment

Over 3500 individual water samples, for 131 sampling times, targeting waterborne pathogens/fecal indicator bacteria were collected during a 7-year period from 4 sites along an intermittent stream running through a small livestock pasture system with and without cattle access-to-stream restriction measures. The study assessed the impact of cattle pasturing/riparian zone protection on: pathogen (bacterial, viral, parasite) occurrence, concentrations of fecal indicators, and quantitative microbial risk assessments (QMRA) of the risk of Cryptosporidium, Giardia and Escherichia coli O157:H7 infection in humans. Methodologies were developed to compute QMRA mean risks on the basis of water samples exhibiting potentially human infectious Cryptosporidium and E. coli based on genotyping Crytosporidium, and E. coli O157:H7 presence/absence information paired with enumerated E. coli. All Giardia spp. were considered infectious. No significant pasturing treatment effects were observed among pathogens, with the exception of Campylobacter spp. and E. coli O157:H7. Campylobacter spp. prevalence significantly decreased downstream through pasture treatments and E. coli O157:H7 was observed in a few instances in the middle of the unrestricted pasture. Densities of total coliform, fecal coliform, and E. coli reduced significantly downstream in the restricted pasture system, but not in the unrestricted system. Seasonal and flow conditions were associated with greater indicator bacteria densities, especially in the summer. Norovirus GII was detected at rates of 7–22% of samples for all monitoring sites, and rotavirus in 0–7% of samples for all monitoring sites; pasture treatment trends were not evident, however. Seasonal and stream flow variables (and their interactions) were relatively more important than pasture treatments for initially stratifying pathogen occurrence and higher fecal indicator bacteria densities. Significant positive associations among fecal indicator bacteria and Campylobacter spp. detection were observed. For QMRA, adjusting for the proportion of Cryptosporidium spp. detected that are infectious for humans reduces downstream risk estimates by roughly one order of magnitude. Using QMRA in this manner provides a more refined estimate of beneficial management practice effects on pathogen exposure risks to humans.     

Microbial quality assessment of household greywater

A monitoring program was undertaken to assess the microbial quality of greywater collected from 93 typical households in Melbourne, Australia. A total of 185 samples, comprising 75 washing machine wash, 74 washing machine rinse and 36 bathroom samples were analysed for the faecal indicator Escherichia coli. Of these, 104 were also analysed for genetic markers of pathogenic E coli and 111 for norovirus (genogroups GI and GII), enterovirus and rotavirus using RT-PCR. Enteric viruses were detected in 20 out of the 111 (18%) samples comprising 16 washing machine wash water and 4 bathroom samples. Eight (7%) samples were positive for enterovirus, twelve (11%) for norovirus genogroup GI, one (1%) for norovirus genogroup GII and another (1%) for rotavirus. Two washing machine samples contained more than one virus. Typical pathogenic E. coli were detected in 3 out of 104 (3%) samples and atypical enteropathogenic E. coli in 11 (11%) of samples. Levels of indicator E. coli were highly variable and the presence of E. coli was not associated with the presence of human enteric viruses in greywater. There was also little correlation between reported gastrointestinal illness in households and detection of pathogens in greywater.     

Evaluating the importance of faecal sources in human-impacted waters

Quantitative microbial risk assessment (QMRA) was used to evaluate the relative contribution of faecal indicators and pathogens when a mixture of human sources impacts a recreational waterbody. The waterbody was assumed to be impacted with a mixture of secondary-treated disinfected municipal wastewater and untreated (or poorly treated) sewage, using Norovirus as the reference pathogen and enterococci as the reference faecal indicator. The contribution made by each source to the total waterbody volume, indicator density, pathogen density, and illness risk was estimated for a number of scenarios that accounted for pathogen and indicator inactivation based on the age of the effluent (source-to-receptor), possible sedimentation of microorganisms, and the addition of a non-pathogenic source of faecal indicators (such as old sediments or an animal population with low occurrence of human-infectious pathogens). The waterbody indicator density was held constant at 35 CFU 100 mL⁻¹ enterococci to compare results across scenarios. For the combinations evaluated, either the untreated sewage or the non-pathogenic source of faecal indicators dominated the recreational waterbody enterococci density assuming a culture method. In contrast, indicator density assayed by qPCR, pathogen density, and bather gastrointestinal illness risks were largely dominated by secondary disinfected municipal wastewater, with untreated sewage being increasingly less important as the faecal indicator load increased from a non-pathogenic source. The results support the use of a calibrated qPCR total enterococci indicator, compared to a culture-based assay, to index infectious human enteric viruses released in treated human wastewater, and illustrate that the source contributing the majority of risk in a mixture may be overlooked when only assessing faecal indicators by a culture-based method.     

Fates of bacteriophages and bacterial indicators in the Moselle river (France)

It has been suggested that bacteriophages can provide useful information about the pathogenic microorganisms, particularly enteric viruses, present in water. This information is complementary to that obtained from bacterial indicators of faecal contamination, which would be of great value for evaluating the risks associated with the use of certain types of water. Before bacteriophages can be used as indicators of faecal contamination, we need to confirm that bacteriophages give a different response to that given by the well-known bacteria indicators and to determine what happens to bacteriophages in river water. Indeed, drinking water is often produced from river water, either by natural filtration through the soil or after undergoing various treatments. We collected 96 river water samples from six different sites between February and November 2000. The samples were analysed for three faecal indicator bacteria (thermotolerant coliforms, enterococci and spores of sulphite-reducing anaerobes) and three types of bacteriophages (somatic coliphages, F-specific phages and Bacteroides fragilis phages). The densities of thermotolerant coliforms and enterococci depended mainly on physical factors such as flow rate and water temperature. High temperature and low flow rate led to a decrease in the density of these microorganisms, especially in the absence of a major input of faecal pollution. Conversely, the densities of somatic coliphages, F-specific phages and spores of sulphite-reducing anaerobes remained constant regardless of the flow rate and temperature. The density of Bacteroides fragilis phages was too low for unambiguous determination of their fate in river water.     

Efficiency of removal of coliforms, faecal coliforms and coliphages in the tubli sewage treatment plant, bahrain

Total coliforms, faecal coliforms and coliphages in the raw sewage were detected in high numbers during the months averaging a maximum temperature of 20°C. The secondary and tertiary effluents show a 99–100% removal of the three indicators of faecal pollution. A direct correlation between the faecal coliforms and coliphages suggests that coliphages alone may be used as an indicator for the presence of pathogenic bacteria in contaminated waters.     

Coliphages as an indicator of faecal pollution in water. Its relationship with indicator and pathogenic microorganisms

The study was designed to test the proposal that Escherichia coli specific bacteriophages might serve as universal faecal pollution indicators in water. A highly specific, sensitive and rapid technique for the detection and quantification of these virus particles was developed. The numerical relationship between E. coli and its parasitic phages was investigated in three different aqueous ecosystems such as sea water in the vicinity of sewage outfalls, river water contaminated by domestic and industrial sewage discharges, and estuarine waters, and found to be very close. In addition, the results obtained indicate that the coliphages are good indicators of the presence of the pathogenic microorganisms studied. In nearly all the water samples tested, the results suggest that coliphages are better indicators of faecal pollution than the classical indicator systems currently employed.     

Microbial risks associated with exposure to pathogens in contaminated urban flood water

Urban flood incidents induced by heavy rainfall in many cases entail flooding of combined sewer systems. These flood waters are likely to be contaminated and may pose potential health risks to citizens exposed to pathogens in these waters. The purpose of this study was to evaluate the microbial risk associated with sewer flooding incidents. Concentrations of Escherichia coli, intestinal enterococci and Campylobacter were measured in samples from 3 sewer flooding incidents. The results indicate faecal contamination: faecal indicator organism concentrations were similar to those found in crude sewage under high-flow conditions and Campylobacter was detected in all samples. Due to infrequent occurrence of such incidents only a small number of samples could be collected; additional data were collected from controlled flooding experiments and analyses of samples from combined sewers. The results were used for a screening-level quantitative microbial risk assessment (QMRA). Calculated annual risks values vary from 5 × 10⁻⁶ for Cryptosporidium assuming a low exposure scenario to 0.03 for Giardia assuming a high exposure scenario. The results of this screening-level risk assessment justify further research and data collection to allow more reliable quantitative assessment of health risks related to contaminated urban flood waters.     

Performance of UV disinfection and the microbial quality of greywater effluent along a reuse system for toilet flushing

This paper examines the microbial quality of treated RBC (Rotating Biological Contactor) and MBR (Membrane Bioreactor) light greywater along a continuous pilot-scale reuse system for toilet flushing, quantifies the efficiency of UV disinfection unit, and evaluates the regrowth potential of selected microorganisms along the system. The UV disinfection unit was found to be very efficient in reducing faecal coliforms and Staphylococcus aureus. On the other hand, its efficiency of inactivation of HPC (Heterotrophic Plate Count) and Pseudomonas aeruginosa was lower. Some regrowth occurred in the reuse system as a result of HPC regrowth which included opportunistic pathogens such as P. aeruginosa. Although the membrane (UF) of the MBR system removed all bacteria from the greywater, bacteria were observed in the reuse system due to “hopping phenomenon.” The microbial quality of the disinfected greywater was found to be equal or even better than the microbial quality of “clean” water in toilet bowls flushed with potable water (and used for excretion). Thus, the added health risk associated with reusing the UV-disinfected greywater for toilet flushing (regarding P. aeruginosa and S. aureus), was found to be insignificant. The UV disinfection unit totally removed (100%) the viral indicator (F-RNA phage, host: E. coli F_amp⁺) injected to the treatment systems simulating transient viral contamination. To conclude, this work contributes to better design of UV disinfection reactors and provides an insight into the long-term behavior of selected microorganisms along on-site greywater reuse systems for toilet flushing.     

Efficiency of natural systems for removal of bacteria and pathogenic parasites from wastewater

A combined constructed wetland formed by a facultative pond (FP), a surface flow wetland (SF) and a subsurface flow wetland (SSF) was studied from December 2004 until September 2005 in north-western Spain in order to evaluate their efficiency in the removal of pathogenic and indicator microorganisms and to determine their relationships. Microbial removal ranged from 78% for coliphages to over 99% for helminth eggs, depending on the treatment system. The highest removal of indicator bacteria (total coliforms, E. coli, faecal streptococci and Clostridium perfringens) occurred in the stabilization pond, reaching 84%, 96%, 89% and 78%, respectively. However, the greatest removal of protozoan pathogens (Cryptosporidium and Giardia) and coliphages was found in the SSF wetland, 98%, 97% and 94%, respectively. In contrast, the SF wetland was most efficient in the removal of pathogenic parasites when considering superficial removal rates. Seasonal differences in organism removal were not statistically significant during the study period. First-order removal rate constants ranged from 0.0027 to 0.71 m/d depending on the microorganism and type of wetland. Significant correlations were found between pathogenic parasites and faecal indicators in the influent of the treatment system but not in the other sampling points suggesting that such relations varied along the system due to the different survival rates of the microorganisms.     

Detection of somatic phages, infectious enteroviruses and enterovirus genomes as indicators of human enteric viral pollution in surface water

In the present study, we aimed to determine whether the concentrations of somatic coliphages, infectious enteroviruses or the detection of enterovirus genomes were associated with the detection of human pathogenic viruses in surface water. Four French rivers were sampled monthly or semimonthly for the quantitative detection of somatic coliphages, infectious enteroviruses and the qualitative RT-PCR detection of enterovirus, hepatitis A virus, Norwalk I viruses, Norwalk II viruses, astrovirus and rotavirus genomes over 12 months. All the 68 water samples tested were positive for the quantitative detection of somatic coliphages (range of concentrations: 4 x 10(2) to 1.6 x10(5) FUl(-1)). Infectious enteroviruses were isolated by a cell culture system in only two (3%) of the 68 concentrated water samples tested, whereas enterovirus genomes were detectable in 60 (88%) of the same samples. A positive RT-PCR detection of the genome of hepatitis A virus, Norwalk-like virus genogroup II, astrovirus, rotavirus and Norwalk-like virus genogroup I was demonstrated, respectively, in 1.5% (1/68), 1.5% (1/68), 3% (2/68), 0% and 0% of the 68 concentrated water samples tested. All of these four water samples were positive for the detection of enterovirus genomes, whereas only one of them was positive for the isolation of enteroviruses on cell culture. Moreover, the genomic detection of human pathogenic viruses appeared not to be statistically associated with the concentration levels of somatic coliphages in the 68 concentrated water samples tested (Wilcoxon rank test; P=0.14). Taken together, our findings indicate that the quantitative detection of somatic coliphages and the isolation of enteroviruses on cell culture are not suitable parameters for the control of the viral contamination in surface water, whereas the detection of enterovirus genomes may be useful for predicting the presence of waterborne viruses.     

Estimating the primary etiologic agents in recreational freshwaters impacted by human sources of faecal contamination

Epidemiology studies of recreational waters have demonstrated that swimmers exposed to faecally-contaminated recreational waters are at risk of excess gastrointestinal illness. Epidemiology studies provide valuable information on the nature and extent of health effects, the magnitude of risks, and how these risks are modified or associated with levels of faecal contamination and other measures of pollution. However, such studies have not provided information about the specific microbial agents that are responsible for the observed illnesses in swimmers. The objective of this work was to understand more fully the reported epidemiologic results from studies conducted on the Great Lakes in the US during 2003 and 2004 by identifying pathogens that could have caused the observed illnesses in those studies. We used a Quantitative Microbial Risk Assessment (QMRA) approach to estimate the likelihood of pathogen-induced adverse health effects. The reference pathogens used for this analysis were Norovirus, rotavirus, adenovirus, Cryptosporidium spp., Giardia lamblia, Campylobacter jejuni, Salmonella enterica, and Escherichia coli O157:H7. Two QMRA-based approaches were used to estimate the pathogen combinations that would be consistent with observed illness rates: in the first, swimming-associated gastrointestinal (GI) illnesses were assumed to occur in the same proportion as known illnesses in the US due to all non-foodborne sources, and in the second, pathogens were assumed to occur in the recreational waters in the same proportion as they occur in disinfected secondary effluent. The results indicate that human enteric viruses and in particular, Norovirus could have caused the vast majority of the observed swimming-associated GI illnesses during the 2003/2004 water epidemiology studies. Evaluation of the time-to-onset of illness strongly supports the principal finding and sensitivity analyses support the overall trends of the analyses even given their substantial uncertainties.     

Enterovirus and coliphage inactivation during activated sludge treatment

The inactivation rates of poliovirus 1, coxsackievirus B-1 and wastewater indigenous coliphages were determined during activated sludge treatment in a large volume reactor. Virus and phage inactivation closely approximated first order kinetics and the inactivation rates were independent of mixed liquor flow rates. The inactivation rates for the enterovirus and coliphages were not significantly different, suggesting that phage inactivation could be used as an indicator for enterovirus inactivation during activated sludge treatment. Total virus removal from mixed liquor and virus inactivation were determined, and a method is presented predicting the fate of viruses during activated sludge treatment.     

Adenovirus-associated health risks for recreational activities in a multi-use coastal watershed based on site-specific quantitative microbial risk assessment

We used site-specific quantitative microbial risk assessment (QMRA) to assess the probability of adenovirus illness for three groups of swimmers: adults with primary contact, children with primary contact, and secondary contact regardless of age. Human enteroviruses and adenoviruses were monitored by qPCR in a multi-use watershed and Adenovirus type 40/41 was detected in 11% of 73 samples, ranging from 147 to 4117 genomes per liter. Enterovirus was detected only once (32 genomes per liter). Seven of eight virus detections occurred when E. coli concentrations were below the single sample maximum water quality criterion for contact recreation, and five of eight virus detections occurred when fecal coliforms were below the corresponding criterion. We employed dose-harmonization to convert viral genome measurements to TCID₅₀ values needed for dose–response curves. The three scenarios considered different amounts of water ingestion and Monte Carlo simulation was used to account for the variability associated with the doses. The mean illness risk in children based on adenovirus measurements obtained over 11 months was estimated to be 3.5%, which is below the 3.6% risk considered tolerable by the current United States EPA recreational criteria for gastrointestinal illnesses (GI). The mean risks of GI illness for adults and secondary contact were 1.9% and 1.0%, respectively. These risks changed appreciably when different distributions were fitted to the data as determined by Monte Carlo simulations. In general, risk was at a maximum for the log-logistic distribution and lowest for the hockey stick distribution in all three selected scenarios. Also, under default assumptions, the risk was lowered considerably when assuming that only a small proportion of Adenovirus 40/41 (3%) was as infectious as Adenovirus type 4, compared to the assumption that all genomes were Adenovirus 4. In conclusion, site-specific QMRA on water-borne adenoviruses in this watershed provided a similar level of protection against public health risks as would be obtained by enumeration of fecal indicator bacteria under the new U.S. EPA guidelines.     

Elimination of enteric bacteria in biological-chemical wastewater treatment and tertiary filtration units

The occurrence and removal of salmonellae and faecal indicators in four conventional municipal wastewater treatment plants (MWTP) were investigated. In addition, we tested the efficiency of a semi-technical scale biological nutrient removal process and three pilot-scale tertiary filtration units in microbial removal. All influent samples collected from MWTPs contained salmonellae from 93 to 11,000 MPN/100 ml and indicator bacteria from about 10(7) to 10(8) CFU/100 ml. The reductions in salmonella numbers achieved in full-scale biological-chemical wastewater treatment and semi-technical scale biological nutrient removal processes were usually between 94% and virtually 100% (99.9%) and indicator bacteria reductions between 2 and 3 log units. Microbial numbers in MWTP effluents could be modelled as a function of effluent residual organic matter, suspended solids and total phosphorus concentrations. Pilot-scale tertiary treatment by rapid sand contact filter, chemical contact filter and biological-chemical contact filter reduced salmonella numbers below the detection limit and faecal coliform numbers on average by 99%, 39% and 71%, respectively. A total of 32 Salmonella serovars were identified among 197 Salmonella isolates from municipal wastewaters. Of the isolates, 32% were resistant to nalidixic acid, indicating reduced sensitivity to ciprofloxacin, the drug of choice in the treatment of salmonellosis. In addition, 18% of the isolates were multiresistant. Our results, especially antibiotic resistant Salmonella strains, indicate that conventional municipal wastewater treatment without efficient tertiary treatment, like filtration or disinfection, may constitute a risk for public health.     

Evaluation of a portable in-house greywater treatment system for potential water-reuse in urban areas

This study aims at improving greywater reuse potential. An advanced physical filtration system named as GAC-MI-ME was developed to attain multi-grade effluents for versatile reuse of greywater. It consists of a matrix of treatment trains including coarse filtration, microfiltration, activated carbon, ultrafiltration, ultraviolet, and reverse osmosis. A preliminary set of experiments were conducted to characterize the greywater originating from shower, washbasin, and laundry. The samples were subsequently treated through GAC-MI-ME system. It was observed that the activated carbon along with microfiltration and coarse filtration played vital roles as pre-filtration for ultrafiltration and reverse osmosis. The contaminant load distributions of GAC-MI-ME system were observed with an average of 90.4% turbidity and 53.2% of biochemical oxidation demand (BOD₅₎ as the pre-filtration, whereas the effluents at ultrafiltration and reverse osmosis showed unrestricted water reuse possibilities. The GAC-MI-ME system can be envisioned as advancement to the conventionally applied greywater treatments.     

Guidelines for Greywater Re-Use: Health Issues

This paper discusses the potential threat to health associated with the microbial contamination of grey-water. Although it has been shown that greywater may contain large numbers of potentially pathogenic microorganisms, the incidence of disease is dependent upon more than just the concentration of organisms. Other factors include the degree of exposure and the health and age of affected individuals. Proposed guidelines for the re-use of greywater focus upon faecal coliform contamination and suggest limits based upon the end use of recycled water.
The paper (a) proposes modifications to the guidelines to better represent the delicate balance between protection of public health and the levels of risk posed by greywater re-use within the context of everyday human activity, and (b) attempts to identify areas where there is either an expectation for responsibility or a personal acceptance of responsibility with regard to public or personal health.     

Bacterial pathogen incidences in sludge from Swedish sewage treatment plants

This study surveyed the presence of bacterial pathogens in eight Swedish sewage treatment plants (STPs), with four different treatment methods, focusing on detection of zoonotic bacteria in raw and treated sludge. Salmonella spp., Listeria monocytogenes, Campylobacter coli and jejuni, Escherichia coli O157 and indicator bacteria were investigated. Samplings were performed from July 2000 to June 2002, resulting in 64 raw sludge samples and 69 treated sludge samples. The samples from raw sludge (67%) and treated sludge (55%) were positive for Salmonella; 49 different serotypes were detected. Restriction enzyme analysis and pulsed field gel electrophoresis of Salmonella serotypes indicated that Salmonella persists in STPs and that there is a continuous supply of new strains. There are differences in treatment methods concerning the reduction of pathogens and indicator bacteria. If spread on arable land, sludge increases the environmental load of pathogens; this increases the risk for spreading diseases to people and animals.     

Survival of infectious Poliovirus-1 in river water compared to the persistence of somatic coliphages, thermotolerant coliforms and Poliovirus-1 genome

The microbiological quality of water is currently assessed by search for fecal bacteria indicators. There is, however, a body of knowledge demonstrating that bacterial indicators are less resistant to environmental factors than human pathogenic viruses and therefore underestimate the viral risk. As river water is often used as a resource for drinking water production, it is particularly important to obtain a valid estimation of the health hazard, including specific viral risk. This work was conducted to compare the survival of infectious Poliovirus-1 used as a pathogenic virus model to the persistence of, on the one hand, thermotolerant coliforms commonly used as indicators and on the other hand, to somatic coliphages and Poliovirus-1 genome considered as potential indicators. We studied the behavior of infectious Poliovirus-1 and the three (potential) indicators of viral contamination in river water at three different temperatures (4 degrees C,18 degrees C and 25 degrees C). This experiment was performed twice with river water sampled at two different periods, once in winter and once in summer. Our results showed that the survival of thermotolerant coliforms can be 1.5-fold lower than infectious Poliovirus-1. In contrast, under all our experimental conditions, somatic coliphages and Poliovirus-1 genome persisted longer than infectious Poliovirus-1, surviving, respectively, 2-6-fold and about 2-fold longer than infectious Poliovirus-1. According to our results exclusively based on survival capacity, somatic coliphages and viral genome, unlike thermotolerant coliforms appear to be better indicators of viral contamination in river water. Moreover, the disappearance of viral genome is well-correlated to that one of infectious virus irrespective of the conditions tested.     

Microorganism removal from wastewater by rapid mixed media filtration

Reuse of domestic sewage effluents in Arizona requires that certain microbiological standards be met. The purpose of this project was to determine the effectiveness of rapid mixed media filtration in the removal of enteric viruses, fecal coliforms and roundworm eggs from sewage destined for reuse as irrigation water. Two surrogate viruses, the simian rotavirus SA-11, used in place of human rotavirus which is pathogenic to man, and f2 coliphage, known to adsorb poorly to surfaces, were used to evaluate filter performance. No significant removal of coliphages occurred by the filters. Addition of ferric chloride and anionic polymer did not enhance virus removal. When small amounts of alum and polymer were added, removal of colliphage increased to 37–40%. Average removal of rotavirus ranged from 21 to 27% after addition of alum and polymer. Mixed media filtration effectively reduced coliform numbers. The removal of Ascaris ova by filtration was essentially complete.