Total coliform and Escherichia coli contamination in rural well water: analysis for passive surveillance

Development of a "big data" groundwater microbial contamination index and spatial comparisons with enteric infection rates in southern Ontario

Big data have become increasingly important for policymakers and scientists but have yet to be employed for the development of spatially specific groundwater contamination indices or protecting human and environmental health. The current study sought to develop a series of indices via analyses of three variables: Non-E. coli coliform (NEC) concentration, E. coli concentration, and the calculated NEC:E. coli concentration ratio. A large microbial water quality dataset comprising 1,104,094 samples collected from 292,638 Ontarian wells between 2010 and 2021 was used. Getis-Ord Gi* (Gi*), Local Moran's I (LMI), and space-time scanning were employed for index development based on identified cluster recurrence. Gi* and LMI identify hot and cold spots, i.e., spatially proximal subregions with similarly high or low contamination magnitudes. Indices were statistically compared with mapped well density and age-adjusted enteric infection rates (i.e., campylobacteriosis, cryptosporidiosis, giardiasis, verotoxigenic E. coli (VTEC) enteritis) at a subregional (N = 298) resolution for evaluation and final index selection. Findings suggest that index development via Gi* represented the most efficacious approach. Developed Gi* indices exhibited no correlation with well density, implying that indices are not biased by rural population density. Gi* indices exhibited positive correlations with mapped infection rates, and were particularly associated with higher bacterial (Campylobacter, VTEC) infection rates among younger sub-populations (p < 0.05). Conversely, no association was found between developed indices and giardiasis rates, an infection not typically associated with private groundwater contamination. Findings suggest that a notable proportion of bacterial infections are associated with groundwater and that the developed Gi* index represents an appropriate spatiotemporal reflection of long-term groundwater quality. Bacterial infection correlations with the NEC:E. coli ratio index (p < 0.001) were markedly different compared to correlations with the E. coli index, implying that the ratio may supplement E. coli monitoring as a groundwater assessment metric capable of elucidating contamination mechanisms. This study may serve as a methodological blueprint for the development of big data-based groundwater contamination indices across the globe.

Nitrate removal rates, isotopic fractionation, and denitrifying bacteria in a woodchip-based permeable reactive barrier system: a long-term column experiment

This study evaluated the effectiveness of using organic carbon materials (i.e., woodchips) to remove nitrate from groundwater. The results of our flow-through column experiment, which was conducted over 1.6 years, suggested that denitrifying bacteria reduce nitrate by using it as an electron acceptor and woodchips as an electron donor. The nitrate removal rates were sufficiently high (0.39-1.04 mmol L-1 day-1) during the operation of the column. Denitrification process was supported by fractionation of nitrogen and oxygen isotopes (δ15N and δ18O), with the δ15N and δ18O values enriched from 7.4‰ and 22.3‰ to 21.2‰ and 30.4‰, respectively. Enrichment factors ([Formula: see text]) for 15 N and 18O were calculated using the Rayleigh fractionation model, with values of - 13.2‰ for ε15N and - 7.1‰ for ε18O. The fractionation ratio of 15 N to 18O was 1.9:1, confirming denitrification. The most abundant bacterial genera in the soil used for inoculation were Enterobacter (86.7%), Nitrospira (1.8%), and Arthrobacter (1.5%), while those in the column effluent were Macrococcus (37.1%), Escherichia (14.7%), and Shigella (14.6%), indicating that bacterial communities changed in response to geochemical conditions in the column. This study suggests that nitrate in groundwater can be effectively removed using woodchip-based passive treatment systems and that information on isotopic fractionation and denitrifying bacteria can be key tools to understand denitrification.

Proximity of Water Wells to Public Water Testing Facilities in Alberta Using Drive Times

Approximately 10% of Albertans rely on well water for domestic purposes. The responsibility of water testing and stewardship is left to private well owners. Few well water owners conduct routine testing of their well water supplies. Drive times to public water testing facilities may be an important factor limiting a well owner's ability to conduct routine water testing. The objective of this study is to describe the proximity of water wells, using drive times, to public water testing facilities and describe the availability of facilities based on hours of operation. Using network analysis, we determined the proportion of a sample of wells within 3 estimated drive times of public water testing facilities. 5872 wells were included in the sample. One hundred and seven water testing facilities were mapped within the province. Of the 5872 wells mapped, 89% were located within 30 minutes of a water testing facility, 15% were located within 0 to 10 minutes of a water testing facility, 48% were located between 10 and 20 minutes of a water testing facility and 37% were located within 20 to 30 minutes of a water testing facility. Further analysis revealed that access to water testing facilities may be influenced by the hours of operation of the facilities.

An assessment of total coliforms and associated thresholds as water quality indicators using a large Ontario private drinking water well dataset

A spatiotemporally static total coliform (TC) concentration threshold of five colony-forming units (CFU) per 100 mL is used in Ontario to determine whether well water is of acceptable quality for drinking. The current study sought to assess the role of TC and associated thresholds as microbial water quality parameters as the authors hypothesized that, since static TC thresholds are not evidence-based, they may not be appropriate for all well water consumers. A dataset containing the microbial water quality information of 795,023 samples (including TC and Escherichia coli (E. coli) counts) collected from 253,136 private wells in Ontario between 2010 and 2017 was used. To accurately assess the relationship between E. coli and non-E. coli TC, "non-E. coli coliform" (NEC) counts were calculated from microbial water quality data and replaced TC throughout analyses. This study analysed NEC and E. coli detection rates to determine differences between the two, and NEC:E. coli concentration ratios to assess links, if any, between NEC and E. coli contamination. Study findings suggest that spatiotemporally static NEC thresholds are not appropriate because seasonal, spatial, and well-specific susceptibility factors are associated with distinct contamination trends. For example, NEC detection rates exhibited bimodality, with summer (29.4 %) and autumn (30.2 %) detection rates being significantly higher (p < 0.05) than winter (21.9 %) and spring (19.9 %). E. coli detection rates also varied seasonally, but peaked in summer rather than autumn. As such, it is recommended that these factors be considered during the development of private well water guidelines and that static thresholds be avoided. Furthermore, the authors propose that, because NEC:E. coli concentration ratios change in the context of the aforementioned factors, they may have a role in inferring groundwater contamination mechanisms, with high ratios being associated with generalized aquifer contamination mechanisms and low ratios with localized contamination mechanisms.

Potentially pathogenic Escherichia coli from household water in peri-urban Ibadan, Nigeria

Feco-orally transmitted infectious diseases are common in Nigeria where the potable water access is poor. In the south-western Nigerian Ibadan metropolis, supply of municipal water is meagre as residents depend on household wells and boreholes. The likelihood of fecal contamination of household water sources in Ibadan was examined longitudinally to quantify and understand its impact. Well and borehole water samples aseptically collected from 96 households in Ibadan were assessed for total heterotrophic counts (THCs), total coliform counts (TCCs) and total Escherichia coli counts (TECs) using a pour plate technique. E. coli were identified by uidA and whole-genome sequencing using Illumina technology, whereas virulence factors were predicted using VirulenceFinder. There was season-independent abundance of THC and TCC in the well and borehole with a significant recovery of E. coli in the wells during the wet season compared to the dry season (P = 0.0001). Virulence genes associated with pathogenic E. coli were identified in 13 (52%) strains with one E. coli each classified as extra-intestinal E. coli, avian pathogenic E. coli and enteroaggregative E. coli. High heterotrophic and coliform counts, with rainfall-driven E. coli contamination revealed that the water sources evaluated in this study are unfit for consumption.

Development of a qPCR assay for the detection of naturalized wastewater E. coli strains

We recently demonstrated the presence of naturalized populations of Escherichia coli in municipal sewage. We wanted to develop a quantitative polymerase chain reaction (qPCR) assay targeting the uspC-IS30-flhDC marker of naturalized wastewater E. coli and assess the prevalence of these naturalized strains in wastewater. The limit of detection for the qPCR assay was 3.0 × 10^-8 ng of plasmid DNA template with 100% specificity. This strain was detected throughout the wastewater treatment process, including treated effluents. We evaluated the potential of this marker for detecting municipal sewage/wastewater contamination in water by comparing it to other human and animal markers of fecal pollution. Strong correlations were observed between the uspC-IS30-flhDC marker and the human fecal markers Bacteroides HF183 and HumM2, but not animal fecal markers, in surface and stormwater samples. The uspC-IS30-flhDC marker appears to be a potential E. coli-based marker for human wastewater contamination.

Prevalence, diversity of diarrhoeagenic Escherichia coli and associated risk factors in well water in Ile-Ife, Southwestern Nigeria

BACKGROUND

Diarrhoeagenic Escherichia coli (DEC) strains are common causes of morbidity and mortality worldwide. Waterborne DEC could pose a health risk to humans through domestic use of contaminated water. However, epidemiological studies on DEC in well water are scarce in Nigeria. This study determined the prevalence, diversity and factors associated with the presence of DEC in well water in Ile-Ife, southwestern Nigeria.

METHODS

We assessed 143 wells for safety and a questionnaire was administered. Contaminating isolates were identified as E. coli by amplifying their 16S rRNA gene. Five diarrhoeagenic E. coli pathotypes were sought using multiplex polymerase chain reaction (PCR). (GTG)5 repetitive PCR and Shannon diversity index were used to determine isolates diversity. Multivariate analysis was used to reveal the factors associated with the presence of DEC in  well water.

RESULTS

Fifty-six (39.2%) wells were contaminated by diarrhoeagenic E. coli. Wells with dirty platforms, undercut by erosion and sited near septic tanks significantly harboured DEC (p <  0.05). There was a preponderance of Shiga-toxin producing E. coli among the isolates with 10 (17.9%) wells contaminated by multiple DEC. The DEC isolates showed 45 unique fingerprints and were divided into six clades, with an overall diversity index of 18.87.

DISCUSSION

The presence of DEC in well water highlights the risk to human health associated with the use of untreated water. There was a high degree of genetic diversity among the isolates implying multiple sources of contamination. There is a need for periodic sanitation and inspection of wells for cracks to prevent seepages and possible outbreaks of waterborne diseases.

Increased Incidence of Pyogenic Liver Abscess in a Midwest System With Emphasis on Rural Impact

OBJECTIVE

To assess if hepatic abscess incidence in a Midwest cohort was higher in rural areas compared to metropolitan areas in relation to water infrastructure.

MATERIALS AND METHODS

All cases of hepatic abscesses from Jan 1, 2016 through Dec 31, 2019 at Avera McKennan Hospital in Sioux Falls, South Dakota (SD), were retrospectively collected. Chart review was completed for each case for risk factor analysis. Microbiology cultures and patient demographic data were collected including age, gender, hometown, and ethnicity. Risk factors assessed included a history of abdominal surgery, gallbladder disease, sepsis, diverticulitis, cancer, and diabetes. The incidence of hepatic abscesses was calculated using the Poisson rate test and confidence interval equation. Averages of each risk factor were calculated. Finally, hometown was utilized to create a heatmap of disease burden and compared to the density of private wells.

RESULTS

Our data yielded 116 confirmed adult hepatic abscesses between 2016 and 2019. The corrected incidence per 100,000 hospitalized patients per year is 95.66. The Poisson exact probability P-value was <0.01. Rural areas had a higher per capita incidence of abscesses and higher density of private wells.

CONCLUSIONS

The incidence of hepatic abscesses is higher than national averages in this single-center study of Avera McKennan Hospital. Demographics, especially geographic location, play an important role in abscess rates. Rural location may be affecting the incidence of hepatic abscesses, explaining the much higher than expected incidence in this study. Infrastructure could be a contributing factor as much of the rural area is reliant on untreated groundwater.

The prevalence and levels of enteric viruses in groundwater of private wells in rural Alberta, Canada

The prevalence and levels of enteric viruses in untreated groundwater of private wells used for drinking and/or agricultural practices in rural Alberta were studied using the qPCR panel assay, integrated cell culture with qPCR and cell culture in the volume of 500 liters per sample through serial sampling. Seven viruses were assessed including adenovirus, rotavirus, norovirus, astrovirus, sapovirus, reovirus and JC virus. Five viruses were detected with an overall positive detection rate of 6.33 % (45 of 711 samples). The most frequently detected virus was adenovirus (48.9%, 22/45) followed by rotavirus (44.4%, 20/45), reovirus (20%, 9/45), JC virus (6.7%, 3/45) and norovirus (6.7%, 3/45). There was no significant difference in the positive detection rates, ranging from 1.1% to 3.4% by various well settings used for broiler farms, cow/calf farms, feedlots and rural acreages. Effects of well characteristics (aquifer type, well depth, static level of water, well seal) and well completion lithology on potential viral contamination of groundwater of private wells were also analyzed upon available data. The findings demonstrate that occurrence of enteric viruses is low and viral contamination is sporadic in groundwater of private wells in rural Alberta. Conventional fecal bacterial indicators (coliform and/or E. coli) were not a representative marker for viral contamination in groundwater wells in rural Alberta.

Microbial Contamination of Drinking Water Supplied by Private Wells after Hurricane Harvey

Hurricane Hurricane Harvey made landfall on the Texas Gulf Coast on August 25, 2017, as a Category 4 hurricane and caused widespread flooding. We explored spatial and temporal distributions of well testing and contamination rates; relationships between contamination and system characteristics and recovery behaviors; and efficacy of mitigation strategies. We estimated that over 500 000 well users (∼130 000 to 260 000 wells) may have been affected, but only around 15 000 well users (∼3800 to 7500 wells) had inundated systems based on inundation maps. Local health departments and our team sampled 8822 wells in 44 counties in the 10 months that followed. Total coliform occurrence was 1.5 times and Escherichia coli was 2.8 times higher after Hurricane Harvey compared to baseline levels. Microbial contamination was more likely (1.7-2.5 times higher) when wells were inundated and/or residents felt their water was unsafe. Although more wells in urban counties were affected, E. coli rates were higher in wells in rural counties. Disinfection did not always eliminate contamination, highlighting concerns about the implementation and efficacy of chlorination procedures. Despite this extensive well testing conducted after Hurricane Harvey, we estimate that only 4.1% of potentially affected wells were tested, underscoring the magnitude of recovery assistance needed to assist well users after flooding events.

Quality Assessment of Groundwater Resources in the City of Al-Marj, Libya

This study aimed to assess and compare the quality of groundwater in the city of Al-Marj in Libya with the international standard guidelines for drinking water recommended by the World Health Organisation. An evaluation of the groundwater wells in the study area was conducted. Standard techniques, such as Minitab (v. 16) and ArcGIS (v.10.2), were used for the analytics of the physicochemical and biological parameters of the groundwater samples. An assessment of the calculation of groundwater quality was conducted on the basis of temperature, pH, turbidity, electrical conductivity, total dissolved solids, chloride, sulphate, bicarbonate, total hardness, calcium, potassium, magnesium, ammonia, ammoniacal nitrogen, nitrate, sodium, copper, iron, dissolved oxygen, biochemical oxygen demand, chemical oxygen demand, total suspended solids, Escherichia coli and total coliform bacteria. Results indicated that most groundwater wells in the study area display a higher concentration of several parameters compared with the permissible limits of drinking water; thus, the water in these wells is chemically and biologically unsafe for drinking purposes. On the basis of the above results, routine water quality monitoring should be performed and additional water filtration plants should be installed by the local government to obtain safe drinking water.

Exploring Well Water Testing Behaviour Through the Health Belief Model

Health problems can arise from consuming contaminated well water. Well water testing can help prevent negative health outcomes associated with consuming contaminated water. The aim of this study was to understand the factors influencing well owner decisions to conduct water testing through the theoretical lens of the Health Belief Model. We conducted semi-structured interviews with 20 well owners and used framework analysis to sort and analyse the data. The results demonstrated that well owners' perceived susceptibility to well water contamination was low, while the perceived severity of contamination, benefits of testing, and self-efficacy towards testing were high. Cues to action to promote testing focused on increasing well owner education and awareness through well stewardship programmes and reminders to test. Participants faced some barriers to water testing. Increasing education and awareness about well water contamination and water testing, while reducing logistical barriers to testing, may improve compliance with water testing.

Evaluating the risks associated with Shiga-toxin-producing Escherichia coli (STEC) in private well waters in Canada

Shiga-toxin-producing Escherichia coli (STEC) represent a major concern for waterborne disease outbreaks associated with consumption of contaminated groundwater. Over 4 million people rely on private groundwater systems as their primary drinking water source in Canada; many of these systems do not meet current standards for water quality. This manuscript provides a scoping overview of studies examining STEC prevalence and occurrence in groundwater, and it includes a synopsis of the environmental variables affecting survival, transport, persistence, and overall occurrence of these important pathogenic microbes in private groundwater wells used for drinking purposes.