Risk factors contributing to microbiological contamination of shallow groundwater in Kampala,Uganda

A study of water quality variation in shallow protected springs in Kampala was undertaken over a 12-month period to assess the causes of microbiological contamination. The microbiological quality of water was assessed using thermotolerant coliforms and faecal streptococci. Sanitary inspections and hazard assessments were undertaken to identify faecal sources (hazards), contaminant pathways and contributory factors. Data were collected on rainfall and population as additional factors potentially exerting an influence on microbiological quality. Initial analysis of the data showed a significant relationship between median level of contamination and rainfall, in particular to short-term rainfall events. Total sanitary risk score showed a significant relationship with median level of contamination, but population density may be a confounding factor. The raw microbiological data were transformed into five water quality targets: <1 and < or =10 cfu 100ml(-1) for faecal streptococci; and <1, < or =10 and < or=50 cfu 100 ml(-1) for thermotolerant coliforms. The presence of individual risk factors as well as variables for rainfall and population density were analysed with respect to failure to meet these water quality targets using contingency tables. Logistic regression models were developed for each of the five water quality targets. The analysis strongly suggested that there is rapid recharge of the springs after rainfall and this leads to microbiological contamination. On-site sanitation was less important than other sources of faecal matter, which was consistent with a low sanitation coverage in the study area. The study suggested that improving sanitary completion and local environmental hygiene was more important than controlling on-site sanitation in improving the quality of these springs.     

Monitoring of water quality from roof runoff: Interpretation using multivariate analysis

The quality of harvested rainwater used for toilet flushing in a private house in the south-west of France was assessed over a one-year period. Temperature, pH, conductivity, colour, turbidity, anions, cations, alkalinity, total hardness and total organic carbon were screened using standard analytical techniques. Total flora at 22 °C and 36 °C, total coliforms, Escherichia coli and enterococci were analysed. Overall, the collected rainwater had good physicochemical quality but did not meet the requirements for drinking water. The stored rainwater is characterised by low conductivity, hardness and alkalinity compared to mains water. Three widely used bacterial indicators - total coliforms, E. coli and enterococci - were detected in the majority of samples, indicating microbiological contamination of the water. To elucidate factors affecting the rainwater composition, principal component analysis and cluster analysis were applied to the complete data set of 50 observations. Chemical and microbiological parameters fluctuated during the course of the study, with the highest levels of microbiological contamination observed in roof runoffs collected during the summer. E. coli and enterococci occurred simultaneously, and their presence was linked to precipitation. Runoff quality is also unpredictable because it is sensitive to the weather. Cluster analysis differentiated three clusters: ionic composition, parameters linked with the microbiological load and indicators of faecal contamination. In future surveys, parameters from these three groups will be simultaneously monitored to more accurately characterise roof-collected rainwater.     

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.     

Concentrations of coprostanol that correspond to existing bacterial indicator guideline limits

Coprostanol is a faecal sterol that has been proposed as an alternative measure of faecal pollution. While the technique has been used successfully to trace sewage-derived organic matter in a range of environments, it has not been embraced for use as a water quality indicator. This is mostly because of a lack of epidemiological evidence relating coprostanol abundance to any health risk. However, there is a valuable reason why the concentration of coprostanol should be related as quantitatively as possible to the abundance of bacterial indicators currently used to measure faecal pollution. The measurement of coprostanol (and concurrently other faecal sterols) offers many diagnostic and quantitative advantages over traditional techniques for detecting human sewage pollution versus faecal contamination from animal sources. Knowing the amount of coprostanol expected given a certain amount of human sewage pollution would provide a measure against which water managers could quantitatively assess faecal pollution as a whole and relate that assessment to variables with which they are more familiar. This study determines the relationships between coprostanol concentrations and indicator bacterial counts and synthesises the results from several environments to propose coprostanol concentrations broadly equivalent to existing bacterial standards. Our data suggest that 60 and 400 ng L⁻¹ of coprostanol correspond to currently defined primary and secondary contact limits for bacteria measured as thermotolerant coliforms (commonly referred to as faecal coliforms) or enterococci.     

Monitoring source water for microbial contamination: evaluation of water quality measures

Watershed management programs often rely on monitoring for a large number of water quality parameters to define contaminant issues. While coliforms have traditionally been used to identify microbial contamination, these indicators cannot discriminate among potential contaminant sources. Microbial source tracking (MST) can provide the missing link that implicates the sources of contamination. The objective of this study was to use a weight-of-evidence approach (land use analysis using GIS, sanitary surveys, traditional water quality monitoring, and MST targets) to identify sources of pollution within a watershed that contains a raw drinking water source. For the study watersheds, statistical analyses demonstrated that one measure each of particulate matter (turbidity, particle counts), organic matter (total organic carbon, dissolved organic carbon, UV(254) absorbance), and indicator organisms (fecal coliforms, enterococci) were adequate for characterizing water quality. While these traditional parameters were useful for assessing overall water quality, they were not intended to differentiate between microbial sources at different locations. In contrast, the MST targets utilized (Rhodococcus coprophilus, sorbitol-fermenting Bifidobacteria, and male-specific coliphages) pinpointed specific sources of microbial pollution. However, these targets could not be used for routine monitoring due to a high percentage of non-detects.     

Investigation of bacterial removal during the filtration process in constructed wetlands

In this study, bacterial removal efficiencies of planted and unplanted subsurface vertical flow constructed wetlands are compared. Indicator organisms such as faecal coliforms (Escherichia coli, total coliforms) and enterococci, and a number of heterotrophic bacteria (heterotrophic plate counts) have been analysed from the influent and effluent of the constructed wetlands as well as at different depths (water and substrate samples). Furthermore dry matter content and total organic carbon (TOC) have been analysed and correlated. The investigated systems show a high removal rate for indicator organisms (a log removal rate of 2.85 for HPC, 4.35 for E. coli, 4.31 for total coliforms and 4.80 for enterococci was observed). In general no significant difference in the removal efficiency of planted and unplanted vertical flow beds could be measured. Only enterococci measured in the substrate samples of the main layer of the filter could a statistically significant difference be observed.     

Derivation of numerical values for the World Health Organization guidelines for recreational waters

In April 2001, draft ‘Guidelines’ for safe recreational water environments were developed at a World Health Organization (WHO) expert consultation. Later the same month, these were presented and discussed at the ‘Green Week’ in Brussels alongside the on-going revision of the European Union Bathing Water Directive 76/160/EEC. The WHO Guidelines cover general aspects of recreational water management as well as define water quality criteria for various hazards. For faecal pollution, these include faecal indicator organism concentrations and an assessment of vulnerability to faecal contamination. Central to the approach set out in the WHO Guidelines are: (i) the concept of beach profiling to produce a ‘sanitary inspection category’ which implies a priori hazard assessment as a core management tool and (ii) the prediction of poor water quality to assist in real time risk assessment and public health protection. These management approaches reflect a harmonized approach towards the assessment and management of risk for water-related infectious disease being applied by WHO. Numerical microbiological criteria for intestinal enterococci are proposed in the new Guidelines. These were developed using a novel approach to disease burden assessment, which has been applied to both recreational waters and urban air quality. This paper explains the scientific rationale and mathematical basis of the new approach, which is not presented in the WHO Guidelines for recreational waters.     

Study of the impact of land use and hydrogeological settings on the shallow groundwater quality in a peri-urban area of Kampala, Uganda

A study to assess the impacts of land use and hydrogeological characteristics on the shallow groundwater in one of Kampala's peri-urban areas (Bwaise III Parish) was undertaken for a period of 19 months. Water quality monitoring was carried out for 16 installed wells and one operational protected spring to ascertain the seasonal variation. The aspects of hydrogeological setting investigated in the study were the subsurface unconsolidated material characteristics (stratigraphy, lithology, hydraulic conductivity, porosity and chemical content), seasonal groundwater depths and spring discharge, topography and rainfall of the area. Both laboratory and field measurements were carried out to determine the soil and water characteristics. Field surveys were also undertaken to identify and locate the various land use activities that may potentially pollute. The results demonstrate that the water table in the area responds rapidly to short rains (48 h) due to the pervious (10(-5)-10(-3) ms(-1)) and shallow (<1 mbgl) vadose zone, which consists of foreign material (due to reclamation). This anthropogenically influenced vadose zone has a limited contaminant attenuation capacity resulting in water quality deterioration following the rains. There is widespread contamination of the groundwater with high organic (up to 370 mgTKN/l and 779 mgNO-3/l), thermotolerant coliforms (TTCs) and faecal streptococci (FS) (median values as high as 126E3 cfu/100 ml and 154E3 cfu/100 ml respectively) and total phosphorus (up to 13 mg/l) levels originating from multiple sources of contamination. These include animal rearing, solid waste dumping, pit latrine construction and greywater/stormwater disposal in unlined channels leading to increased localised microbial (faecal) and organic (TKN/NO-3) contamination during the rains. The spring discharge (range 1.22-1.48 m3/h) with high nitrate levels (median values of 117 and 129 mg/l in the wet and dry seasons) did not vary significantly with season (p=0.087) suggesting that this source is fed by regional base flow. However, the microbial quality deterioration observed in the spring discharge after a rain event (median values of 815TTCs cfu /100 ml and 433 FS cfu/100 ml) was attributed to the poor maintenance of the protection structure. Identification and selection of appropriate management solutions for the protection of shallow groundwater in informal settlements should not only be based on water quality problems and the causal physical characteristics as demonstrated by this study, but also institutional and socio-economic factors.     

Microorganisms in bioaerosol emissions from wastewater treatment plants during summer at a Mediterranean site

Measurements were conducted at a Mediterranean site (latitude 35 degrees 31' north and longitude 24 degrees 03' east) during summer, to study the concentration of microorganisms emitted from a wastewater treatment plant under intensive solar radiation (520-840 W/m2) and at elevated air temperatures (25-31 degrees C). Air samples were taken with the Air Sampler MAS 100 (Merck) at each stage of an activated-sludge wastewater treatment (pretreatment, primary settling tanks, aeration tanks, secondary settling tanks, chlorination, and sludge processors). Cultivation methods based on the viable counts of mesophilic heterotrophic bacteria, as well as of indicator microorganisms of faecal contamination (total and faecal coliforms and enterococci), and fungi were performed. During air sampling, temperature, solar radiation, relative humidity and wind speed were measured. The highest concentrations of airborne microorganisms were observed at the aerated grit removal of wastewater at the pretreatment stage. A gradual decrease of bioaerosol emissions was observed during the advanced wastewater treatment from the pretreatment to the primary, secondary and tertiary treatment (97.4% decrease of mesophilic heterotrophic bacteria, and 100% decrease of total coliforms, faecal coliforms and enterococci), 95.8% decrease of fungi. The concentration of the airborne microorganisms at the secondary and tertiary treatment of the wastewater was lower than in the outdoor control. At the same time, the reduction of the microbial load at the waste sludge processors was 19.7% for the mesophilic heterotrophic bacteria, 99.4% for the total coliforms, and 100% for the faecal coliforms and the enterococci, 84.2% for the fungi. The current study concludes that the intensive solar radiation, together with high ambient temperatures, as well as optimal wastewater treatment are the most important factors for low numbers of microbes in the air.     

Statistical study of the relationship between free chlorine levels and bacteriological checks on systems in the Paris area

The majority of French cities are supplied with treated surface water. The primary factor in determining the quality of this water concerns disinfection to ensure that the system is not contaminated with parasites, coliforms and streptococci; some of these organisms, especially coliforms, are capable of multiplying within the system. The presence of bacteria indicative of faecal contamination in water samples, which contains a significant amount of free chlorine, has revealed a possible link between the two. Based upon sampling points of the Parisian system (and in the suburbs for purposes of comparison), we show the existence of a linear relationship between the results of analyses for coliforms on a given day, D, and the content of free chlorine in the water on days D-2 and D-3. Subsequent ground tests confirm the explanations proposed regarding these phenomena.     

Lagged correlation in study of spatial pattern of wells contamination

The present communication summarizes and analyzes the results of an investigation conducted since 1977 in a section of South Windsor. Connecticut. A sanitary survey of drinking water wells in this area revealed that, out of 66 individual wells, 19 had counts of fecal and total coliforms in excess of what is recommended for potable water quality by guidelines set by the Public Health Code of the State of Connecticut. The data of this survey were subjected to lagged cross-correlation and spectral analysis in order to quantify spatial interactions between individual wells and, thus, to identify the pattern and the origin of contamination. Results indicated that there was a channeled flow of bacterial pollution through the study area with very little lateral diffusion. The study demonstrated that in some situations biological contaminants can travel large distances underground without substantial attenuation by the aquifer material.     

SEASONAL VARIATION OF BACTERIOLOGICAL AND CHEMICAL QUALITY OF DRINKING WATER: A CASE STUDY IN A PALESTINIAN DISTRICT

Evaluation of drinking water quality for Jenln district in Palestine was carried out for the years 1997, 1998, and 1999, respectively. Only 53.1 %, 85.4% and 69.6% of the drinking water samples tested for free chlorine residual, total coliforms and faecal coliforms, respectively are within the limits of the Palestinian and International standards. The seasonal variation of bacteriological and chemical quality of drinking water was investigated. It was found out that the summer season has the best quality and the winter has the worst. There remains some ignorance in testing the drinking water in the villages and towns in Jenin district. Huge efforts are required to improve the drinking water quality in Jenin district, as well as other Palestinian districts, through public awareness, training of governmental Inspectors, in addition to a strict monitoring system for water quality.     

Occurrence, molecular characterization and antibiogram of water quality indicator bacteria in river water serving a water treatment plant

Water pollution by microorganisms of fecal origin is a current world-wide public health concern. Total coliforms, fecal coliforms (Escherichia coli) and enterococci are indicators commonly used to assess the microbiological safety of water resources. In this study, influent water samples and treated water were collected seasonally from a water treatment plant and two major water wells in a Black Belt county of Alabama and evaluated for water quality indicator bacteria. Influent river water samples serving the treatment plant were positive for total coliforms, fecal coliforms (E. coli), and enterococci. The highest number of total coliform most probable number (MPN) was observed in the winter (847.5 MPN/100 mL) and the lowest number in the summer (385.6 MPN/100 mL). Similarly E. coli MPN was substantially higher in the winter (62.25 MPN/100 mL). Seasonal variation of E. coli MPN in influent river water samples was strongly correlated with color (R² = 0.998) and turbidity (R² = 0.992). Neither E. coli nor other coliform type bacteria were detected in effluent potable water from the treatment plant. The MPN of enterococci was the highest in the fall and the lowest in the winter. Approximately 99.7 and 51.5 enterococci MPN/100 mL were recorded in fall and winter seasons respectively. One-way ANOVA tests revealed significant differences in seasonal variation of total coliforms (P < 0.05), fecal coliforms (P < 0.01) and enterococci (P < 0.01). Treated effluent river water samples and well water samples revealed no enterococci contamination. Representative coliform bacteria selected by differential screening on Coliscan Easygel were identified by 16S ribosomal RNA gene sequence analysis. E. coli isolates were sensitive to gentamicin, trimethoprim/sulfamethazole, ciprofloxacin, vancomycin, tetracycline, ampicillin, cefixime, and nitrofurantoin. Nonetheless, isolate BO-54 displayed decreased sensitivity compared to other E. coli isolates. Antibiotic sensitivity pattern can be employed in microbial source tracking.     

Occurrence and densities of fungi from northern Greek coastal bathing waters and their relation with faecal pollution indicators

The objective of this study was to determine the frequency and densities of yeasts and filamentous fungi in coastal water samples as well as their correlation with the indicator bacteria of faecal pollution. The prevalence of fungi was investigated in parallel with the standard pollution indicator microorganisms in 197 marine water samples from six northern Greek prefectures during the bathing season May–October 1999. Filamentous fungi were isolated from all the examined samples and yeasts from 29 (14.7%) of them; among the positive samples, their mean counts were 90.9 and 38.4 cfu/100 ml, respectively. A total of 23 genera of filamentous fungi and four genera of yeasts were identified. Prevailing genera of filamentous fungi were Penicillium, Aspergillus and Alternaria spp., whereas Candida spp. was the most frequently isolated yeast. Counts of yeasts were significantly (p<0.01) correlated with those of total and faecal coliforms, whereas no correlation was found between filamentous fungi and the indicator bacteria of faecal pollution. Significantly higher counts of total and faecal coliforms (p<0.05), and enterococci (p<0.001), were found during the months with the higher water temperatures and bather numbers. In the six prefectures, significant differences were observed in the counts of filamentous fungi and yeasts as well as in the counts of all the faecal pollution indicators. The results of this study indicate that coastal water can be a path for contamination of swimmers with yeasts and filamentous fungi and that the pollution indicator microorganisms cannot always predict their presence.     

The Microbiological Quality of Private Water Supplies

This paper provides a detailed assessment of the microbiological quality of a selection of private water supplies. Samples were taken from 91 supplies and analyzed for total coliforms, faecal coliforms and faecal streptococci. The microbiological quality of the samples was generally poor, with almost 50% of the supplies failing to meet the required standards on at least one occasion. Given the high level of sanitary microbiological failures, there is the possibility that harmful microorganisms could be present and a significant risk to health cannot be discounted.     

The Microbiological Quality of Private Water Supplies

This paper provides a detailed assessment of the microbiological quality of a selection of private water supplies. Samples were taken from 91 supplies and analyzed for total coliforms, faecal coliforms and faecal streptococci. The microbiological quality of the samples was generally poor, with almost 50% of the supplies failing to meet the required standards on at least one occasion. Given the high level of sanitary microbiological failures, there is the possibility that harmful microorganisms could be present and a significant risk to health cannot be discounted.     

汨罗市饮用水安全保障体系的建设

汨罗市根据城市供水系统现状对城市生活饮用水安全保障体系建设进行了有益探索,制定了重大水源水质突发污染事件、供水设施发生事故及水源水质受到常规污染而超标时的三类应急保障措施。明确了应急备用水源建设目标年限、建设规模、应急保障时间、水源选择方案、强化处理措施、深度净化措施、工程建设投资等,从而为饮用水安全提供了保障。     

Distribution of indicator bacteria in Canyon Lake, California

The spatial and temporal distributions of indicator bacteria in a small, multiple-use source drinking water reservoir in Southern California, USA were quantified over the period August 2001-July 2002. High levels of total and fecal coliform bacteria were present in Canyon Lake (annual geometric mean concentrations+/-SEM of 3.93+/-0.02 and 3.02+/-0.03 log cfu/100mL, respectively), while comparatively low levels of enterococci and E. coli were found (1.16+/-0.02 log cfu/100mL and 0.30+/-0.03 log MPN/100mL, respectively). As a result, these different indicator bacteria yielded quite divergent indices of water quality, with 72.1% of all surface samples (n=294) exceeding the USEPA single-sample limit of 400 cfu/100mL fecal coliform bacteria, while none (0%) of the samples exceeded the single-sample limit for E. coli (n=194). Regression analyses found a positive correlation between total and fecal coliform bacteria (R=0.50, significant at p<0.001) and between enterococci and E. coli (R=0.51, significant at p<0.001), but no correlation or inverse correlations were found between coliform concentrations and enterococci and E. coli levels. External sources responsible for the high total and fecal coliform bacteria were not identified, although laboratory studies demonstrated growth of the coliform bacteria in lake water samples. Enterococci and E. coli were not observed to grow, however. Bacteria concentrations varied relatively little laterally across the lake, although strong vertical gradients in fecal coliform and enterococcus bacteria concentrations were present during summer stratification, with concentrations about 10x higher above the thermocline when compared with surface concentrations. In contrast, total bacteria, total virus and total coliform bacteria levels were unchanged with depth. Seasonal trends in bacteria concentrations were also present. This study shows that the choice of indicator bacteria and sampling depth can both strongly affect the apparent microbial water quality of a lake or reservoir.     

Bacterial source tracking from diverse land use catchments by sterol ratios

Water samples from sites potentially impacted by septic tanks, cattle, sewage treatment plant (STP) and natural forests were collected at regular monthly intervals and within 48 h of rainfall events between October 2004 and June 2006. All samples (n=296) were analysed for faecal coliforms and faecal sterols including coprostanol, epicoprostanol, cholestanol, cholesterol and 24-ethylcoprostanol. Faecal sterol ratios were used to assign human and/or herbivore contamination sources and to estimate their percentage relative contributions in water samples. The catchments had significantly different profiles of designated contamination origins (p<0.05), which were consistent with land use patterns. The STP impacted site had the highest incidence of human contamination assignations and the highest mean levels of coprostanol, whilst the forested site had the highest incidence of uncontaminated samples and the lowest mean concentration of coprostanol. Coprostanol concentrations were not always correlated with faecal coliform counts.     

Escherichia coli O157:H7 in drinking water from private water supplies in the Netherlands

The microbiological quality of drinking water from 144 private water supplies in the Netherlands was tested and additionally the occurrence of Escherichia coli O157 was examined. Faecal indicators were enumerated by using standard membrane filtration methods. The presence of E. coli O157 was determined using a specific enrichment method. Eleven percent of the samples contained faecal indicators whereas E. coli O157:H7 was isolated from 2.7% of the samples that otherwise met the drinking water standards. The E. coli O157 positive water supplies were located on camp-sites in agricultural areas with large grazer densities. Pulsed field gel electrophoresis (PFGE) analysis suggested that cattle might have been the cause of contamination. Our results indicate that compliance with microbiological quality standards obtained in routine monitoring does not always guarantee the absence of pathogens. The presence of pathogens such as E. coli O157 may suggest possible health consequences; however, a risk assessment process should be performed as the monitoring of both faecal indicator parameters and pathogens do not predict the effect of microbial contamination of drinking water on a population.