Drinking Water Risk Assessment Research Articles

Detecting Enteric Pathogens in Low-Risk Drinking Water in Dhaka, Bangladesh: An Assessment of the WHO Water Safety Categories.

The microbiological quality of water is usually assessed by fecal coliform bacteria, and the presence of E. coli as an indicator of fecal contamination is widely recommended by international guidelines. This study aimed to assess the prevalence of diarrheagenic pathogens, in both public and personal domain water sources and examine the reliance on the WHO drinking water risk assessment guidelines. This study was conducted in a low-income urban community in Dhaka, Bangladesh between September 2014 and October 2015. Polymerase chain reaction (PCR) was used to detect the marker and virulence genes of Escherichia coli, Vibrio cholerae, Salmonella species, and Campylobacter species, and the culture method was employed for the quantitative assessment of E. coli. According to the WHO guidelines, 48% of the public domain source water and 21% of the personal domain point-of-drinking water were classified in the low-risk group, i.e., 0 CFU of E. coli/100 mL. However, when using PCR, we detected pathogens in 39% (14/36) of the point-of-drinking water samples and 65% (74/114) of the public domain water source samples classified in the low-risk group. Our study showed that relying solely on E. coli detection as a measure of water quality may overlook the presence of other pathogens in the drinking water. In addition to the culture-based method, the detection of virulence genes by PCR should also be considered to add more scrutiny to the detection of diverse types of pathogens.

Water security and health risk assessment of an urban household-level drinking water and sanitation system, Punjab, India.

The water scarcity and deteriorating water quality are major issues of concern to the agrarian state of Punjab, India. The focus of the study is to assess the status of drinking water and sanitation systems of Punjab using an exhaustive dataset of 1575 drinking water samples from 433 sampling locations in 63 urban local bodies of Punjab. Water security index(WSI) indicate that out of 63 urban local bodies, 13 are categorized into good class, 31 fall under fair class, and 19 fall under poor class. The access indicator under sanitation dimension shows that Bathinda region has maximum sewerage network coverage relative to other regions, whereas ca. 50% of the ULBs in Amritsar region do not have sewerage facility. It is clearly depicted that the variation in WSI is mainly attributable to sanitation dimension (10-22.5) as variation in water supply dimension (29-35) is relatively less. Hence,emphasis on indicators and variables of sanitation dimension is required for the improvement of overall WSI. The assessment of qualitative aspects of drinking water and health risk depicts that the drinking water quality of southwest part of the state (i.e. Malwa region) is under good quality class contrary to its poor groundwater quality. Kapurthala district shows high health risk due to the presence of trace metals despite being classified into good class within water security index. The drinking water quality is better and health risks are minimal in regions where drinking water is supplied via treated surface water sources (e.g. Bathinda region). Furthermore, the results of health risk assessment correlate with M[Formula: see text]-WaterQualityIndex outcome owing to presence of trace metals in groundwater above permissible limits. These results will help in identification of shortcomings in water supply and sanitation infrastructure and its management in urban areas.

A cost-effective method for assessing groundwater well vulnerability to anthropogenic and natural pollution in the framework of water safety plans

Water abstraction is a key aspect when performing drinking water risk assessment within the scope of Water Safety Plan (WSP). In this context, evaluating aquifer vulnerability could be not exhaustive. Care must be taken to consider the well structure and dynamic behavior that can determine different water quality and vulnerability than those of the tapped aquifer. Here, a methodological approach to assess well vulnerability to natural and anthropogenic pollution is proposed. A data-driven hydrogeochemical conceptual modeling was performed through cluster analysis, supporting the identification of the main features determining well vulnerability. Well vulnerability was then assessed through a semi-quantitative method based on a well-specific analysis of the tapped aquifer type, water table depth, vadose zone permeability, natural redox conditions, and qualitative classification of the tapped groundwater age, considering evidence of mixing processes induced by the well dynamic behavior. Each feature was categorized into several classes, and a score was associated with each class according to the vulnerability induced by that specific condition. The method was applied to a dataset of ∼200 wells, in northern Italy. Each well was classified, and its vulnerability was assessed. The method was validated by analyzing the distribution of wells affected by natural or anthropogenic pollution in each of the vulnerability classes. Results of the chi-square test showed that the distribution of the polluted wells was associated with vulnerability classes, which is evidence of the robustness and reliability of the proposed method. This method was developed exploiting only hydrogeological information and raw water quality data, largely available to water managers from routine monitoring, which makes this approach widely applicable and cost-effective.

Development of a US national-scale, mixed-source, pesticide, rural well database for use in drinking water risk assessment: an atrazine case study.

For pesticide registrations in the USA under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), as implemented by the United States Environmental Protection Agency, drinking water risk assessments for groundwater sources are based on standard scenario modeling concentration estimates. The conceptual model for the drinking water protection goals is defined in terms of (1) a rural well in or near a relatively high pesticide use area, a shallow well (4-10m); (2) long-term, single-station weather data; (3) soils characterized as highly leachable; (4) upper-end or surrogate, worst-case environmental fate parameters; and (5) maximum, annual use rates repeated every year. To date, monitoring data have not been quantitatively incorporated into FIFRA drinking water risk assessment; even though considerable, US national-scale temporal and spatial data for some chemistries exists. Investigations into drinking water monitoring data development have historically focused on single-source efforts that may not represent wide geographies and/or time periods, whereas Safe Drinking Water Act groundwater monitoring data are focused on a community-level scale rather than an individual, shallow, rural well. In the current case study, US national-scale, rural well data for the herbicide atrazine was collected, quality controlled, and combined into a single database from mixed sources (termed the atrazine rural well database) to (1) characterize differences between exposure estimates from standard EPA modeling approaches for specific characterization, (2) evaluate monitoring data toward direct use in US drinking water risk assessments to compliment or supersede standard modeling approaches to define risk, and (3) evaluate monitoring trends a function of time relative to label changes implemented as part of the registration review process. Of the 75,665 drinking water samples collected from groundwater, atrazine was only detected in 3185, a 4% detection rate.

Geographic information system-based health risk assessment of rural drinking water in Central China: a case study of You County, Hunan.

This study assessed potential human health hazards posed by drinking water from centralized water supply systems in rural You County, along with its spatial distribution. While most previous studies have focused on source water or urban drinking water, this study evaluated the health risk posed by 20 common pollutants (arsenic, cadmium, chromium(VI), lead, mercury, selenium, cyanide, fluoride, nitrate nitrogen, trichloromethane, tetrachloromethane, chlorite, aluminum, iron, manganese, copper, zinc, ammonia nitrogen, chlorine dioxide, and volatile phenols) in rural terminal tap water. The assessment adopted the model recommended by the US Environmental Protection Agency (EPA) and was combined with the geographic information system (GIS) analysis to explore the spatial distribution of risk factors. Water samples were collected from 13 townships in You County across four quarters of 2019. The results indicated that the average carcinogenic risk of the rural drinking water was 2.45 × 10-5, ranging from 1.80 × 10-5 to 3.89 × 10-5, which never exceeded the maximum acceptable range recommended by the US EPA (1.0 × 10-4 ~ 1.0 × 10-6). The average hazard index (HI), which reflects noncarcinogenic risk levels, was 0.75 and ranged from 0.34 to 1.74. Throughout the year, some townships presented HI > 1, indicating a non-carcinogenic risk. The GIS analysis indicated that noncarcinogenic risks were mainly distributed in the north, followed by the east and west. This is generally consistent with the spatial distribution of chlorite concentrations, which contribute most strongly to noncarcinogenic risk levels. The northern You County should therefore be prioritized for health risk control, followed by the eastern and western regions. Chlorite is the priority pollutant for control.

Impact of DBPs on the fate of zebrafish; Behavioral and lipid profile changes

In recent years, the generation of disinfectant by-products (DBPs) in drinking water system has been highlighted for their potential negative impact on humans. A commonly used disinfectant, chlorine, produces a by-product which is highly hazardous and a known carcinogen. This study investigated the toxic effects of DBPs from several organic matter as a function of contact time with chlorine-based disinfectants were investigated using zebrafish. The results indicated that the generation of DBPs was dependent on the composition of dissolved organic matter (DOM) in water. Suwannee river natural organic matter and experimental site water sample (complex DOM) were almost 2.5 times higher than that of a single dissolved organic matter, such as microcystin-LR (MCLR) at 120 min. The behavior of zebrafish was significantly affected by complex composition DOM. In vivo biomarker analysis result from lipid profile analysis, reaction in vivo showed different depending on the composition of the DOM. Through this study, the effect of DBPs were observed via lipid metabolic and movement changes in aquatic organisms can be considered as a new biomarker for the drinking water risk assessment.

Escherichia coli as a Tool for Disease Risk Assessment of Drinking Water Sources.

Many diseases have been associated with poor drinking water quality including diseases caused by diarrheagenic pathogens, especially in developing countries where access to a consistent water supply is a problem. The objective of the study was to evaluate the health risks associated with the sources of drinking water in the Dangme West District of Ghana using E. coli as a measurement tool, aiming at ascertaining the paths leading to contamination of the water sources. A total of 464 water samples were obtained for analysis. Sampling covered a year across the dry and wet seasons in Ghana. Water samples were obtained from groundwater and surface water sources. E. coli counts were determined using the most probable number method (MPN). Disease risk assessment was carried out using the WHO drinking water risk assessment guidelines. Generally, the study revealed significantly higher E. coli counts in the wet season than in the dry season. Among the water samples analyzed, surface water, especially from the dams, was found to pose the highest disease risk as compared to the other water sources. Samples from groundwater sources, especially boreholes, posed the lowest disease risk. In conclusion, observations from the study implied that most water sources in the study district are highly polluted with bacteria pathogens beyond recommended safety guidelines. The main causes of faecal contamination in these water sources were purported to be anthropogenic. Therefore, there is a need to formulate a policy aimed at managing and improving rural water sources.

Occurrence of antibiotics in rural drinking water and related human health risk assessment

ABSTRACT Antibiotic residues in drinking water can have a negative impact on both human and environmental health. However, drinking water purification processes employed in rural areas are often less complicated than those used in urban areas. The occurrence of antibiotic residues in rural drinking water and their potential effects on residents’ health remains to be established. In this study, we measured antibiotic levels in rural drinking water using high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS), and evaluated the associated health risks based on Chinese population exposure parameters. Twenty-three antibiotics were detected in drinking water samples, of which fluoroquinolones and macrolides were the most common. The type and concentration of antibiotics in drinking water were affected both by the quality of the water source and by the water purification process used. The health risks associated with antibiotics in drinking water were within acceptable levels and likely to have little impact on human health. Of the antibiotics detected, salinomycin presented the greatest risk to human health. These findings can help to play a role in devising strategies to ensure drinking water safety.

Framework for shared drinking water risk assessment

Risk assessment plays a vital role in protecting our nation's critical infrastructure. Traditionally, such assessments have been conducted as a singular activity confined to the boarders of a particular asset or utility with little external sharing of information. In contrast other domains, e.g., disaster preparedness, cyber security, food-borne hazards, have demonstrated the benefits of sharing data, experiences and lessons learned in assessing and managing risk. Here we explore the concept of a Shared Risk Framework (SRF) in the context of critical infrastructure assessments. In this exploration, key elements of an SRF are introduced and initial instantiations demonstrated by way of three water utility assessments. Results from these three demonstrations were then combined with results from four other risk assessments developed using a different risk assessment application by a different set of analysts. Through this comparison we were able to explore potential challenges and benefits from implementation of a SRF. Challenges included both the capacity and interest of local utilities to conduct a shared risk assessment; particularly, wide scale adoption of any SRF will require a clear demonstration that such an effort supports the basic mission of the utility, adds benefit to the utility, and protects utility data from unintended access or misuse. In terms of benefits, anonymous sharing of results among utilities could provide the added benefits of recognizing and correcting bias; identifying ‘unknown, unknowns’; assisting self-assessment and benchmarking for the local utility; and providing a basis for treating shared assets and/or threats across multiple utilities.

Arsenic contamination of drinking water in Ireland: A spatial analysis of occurrence and potential risk.

The presence of arsenic in groundwater has become a global concern due to the health risks from drinking water with elevated concentrations. The Water Framework Directive (WFD) of the European Union calls for drinking water risk assessment for member states. The present study amalgamates readily available national and sub-national scale datasets on arsenic in groundwater in the Republic of Ireland. However, due to the presence of high levels of left censoring (i.e. arsenic values below an analytical detection limit) and changes in detection limits over time, the application of conventional statistical methods would inhibit the generation of meaningful results. In order to handle these issues several arsenic databases were integrated and the data modelled using statistical methods appropriate for non-detect data. In addition, geostatistical methods were used to assess principal risk components of elevated arsenic related to lithology, aquifer type and groundwater vulnerability. Geographic statistical methods were used to overcome some of the geographical limitations of the Irish Environmental Protection Agency (EPA) sample database. Nearest-neighbour inverse distance weighting (IDW) and local indicator of spatial association (LISA) methods were used to estimate risk in non-sampled areas. Significant differences were also noted between different aquifer lithologies, indicating that Rhyolite, Sandstone and Shale (Greywackes), and Impure Limestone potentially presented a greater risk of elevated arsenic in groundwaters. Significant differences also occurred among aquifer types with poorly productive aquifers, locally important fractured bedrock aquifers and regionally important fissured bedrock aquifers presenting the highest potential risk of elevated arsenic. No significant differences were detected among different groundwater vulnerability groups as defined by the Geological Survey of Ireland. This research will assist management and future policy directions of groundwater resources at EU level and guide future research focused on understanding arsenic mobilisation processes to facilitate in guiding future development, testing and treatment requirements of groundwater resources.

Manganese concentrations in drinking water from villages near banana plantations with aerial mancozeb spraying in Costa Rica: Results from the Infants' Environmental Health Study (ISA)

Elevated manganese (Mn) in drinking water has been reported worldwide. While, naturally occurring Mn in groundwater is generally the major source, anthropogenic contamination by Mn-containing fungicides such as mancozeb may also occur. The main objective of this study was to examine factors associated with Mn and ethylenethiourea (ETU), a degradation product of mancozeb, in drinking water samples from villages situated near banana plantations with aerial spraying of mancozeb. Drinking water samples (n = 126) were obtained from 124 homes of women participating in the Infants' Environmental Health Study (ISA, for its acronym in Spanish), living nearby large-scale banana plantations. Concentrations of Mn, iron (Fe), arsenic (As), lead (Pb), cadmium (Cd) and ethylenethiourea (ETU), a degradation product of mancozeb, were measured in water samples. Only six percent of samples had detectable ETU concentrations (limit of detection (LOD) = 0.15 μg/L), whereas 94% of the samples had detectable Mn (LOD = 0.05 μg/L). Mn concentrations were higher than 100 and 500 μg/L in 22% and 7% of the samples, respectively. Mn was highest in samples from private and banana farm wells. Distance from a banana plantation was inversely associated with Mn concentrations, with a 61.5% decrease (95% CI: −97.0, −26.0) in Mn concentrations for each km increase in distance. Mn concentrations in water transported with trucks from one village to another were almost 1000 times higher than Mn in water obtained from taps in houses supplied by the same well but not transported, indicating environmental Mn contamination. Elevated Mn in drinking water may be partly explained by aerial spraying of mancozeb; however, naturally occurring Mn in groundwater, and intensive agriculture may also contribute. Drinking water risk assessment for mancozeb should consider Mn as a health hazard. The findings of this study evidence the need for health-based World Health Organization (WHO) guidelines on Mn in drinking water.

Development and application of a catchment scale pesticide fate and transport model for use in drinking water risk assessment

This paper describes the development and application of IMPT (Integrated Model for Pesticide Transport), a parameter-efficient tool for predicting diffuse-source pesticide concentrations in surface waters used for drinking water supply. The model was applied to a small UK headwater catchment with high frequency (8h) pesticide monitoring data and to five larger catchments (479–1653km2) with sampling approximately every 14days. Model performance was good for predictions of both flow (Nash Sutcliffe Efficiency generally >0.59 and PBIAS <10%) and pesticide concentrations, although low sampling frequency in the larger catchments is likely to mask the true episodic nature of exposure. The computational efficiency of the model, along with the fact that most of its parameters can be derived from existing national soil property data mean that it can be used to rapidly predict pesticide exposure in multiple surface water resources to support operational and strategic risk assessments.

Drinking water risk assessment in practice: the case of Swedish drinking water producers at risk from floods

To achieve a safe and reliable drinking water supply, water producers need to manage a large range of risks regarding both water quality and quantity. A risk management approach where risks are systematically identified and handled in a preventive manner is promoted by the World Health Organization and supported by researchers and drinking water experts worldwide. Risk assessment is an important part of such a management approach, and a variety of tools for risk assessment are described in the literature. There is, however, little knowledge of how drinking water risk assessment is performed in practice, including which tools that are actually used. This study investigates the use of risk assessment tools, and the approach to risk management, on a local level in the Swedish water sector. It is based on interviews with key persons from a targeted selection of water producers. We find that the application of tools as well as the approach to risk assessment and management differs considerably between the water producers. The tools most frequently used are mainly the ones promoted or required by Swedish national organizations. Although many of the water producers have done some kind of risk assessment, most have not implemented a risk management approach. Furthermore, their knowledge of the concepts of risk and risk management is often limited. The largest challenge identified is to prioritize risk assessment, so that it is actually performed and then used as a basis for managing risk in a systematic way.

Reference pathogen numbers in urban stormwater for drinking water risk assessment

Targeted stormwater event-based monitoring of adenovirus, Cryptosporidium and Campylobacter, the human health reference pathogens of viruses, protozoa and bacteria, respectively, was undertaken to determine numbers prior to water recycling via an aquifer. This allowed the determination of a 95th percentile of reference pathogen numbers in stormwater (2 n/L for adenoviruses, 1.4 n/L for Cryptosporidium and 11 n/L for Campylobacter) and was used in a quantitative microbial risk assessment to determine the required microbial inactivation targets. Log10 removals through treatments and/or control measures to manage pathogen risks were determined for different end uses based on the 95th percentile numbers. Public open space irrigation was found to require 1.6 log10 reduction for viruses, 0.6 log10 for protozoa and 1.2 log10 for bacteria; third pipe systems which include potential exposure through toilet flushing and washing machine use require 2.7 log10 reduction for viruses, 1.8 log10 for protozoa and 2.3 log10 for bacteria; and drinking water requires 5.8 log10 reduction for viruses, 4.8 log10 for protozoa and 5.3 log10 for bacteria. These results are the first reported for an Australian urban stormwater site with sufficient data for a drinking water risk assessment.

Environmental and drinking water risk assessment of substances which are toxic to humans or aquatic organisms – examples and options

Reference EPFL-CONF-189320doi:10.1016/j.toxlet.2013.06.071View record in Web of Science Record created on 2013-10-01, modified on 2016-08-09

Bacterial invasion potential in water is determined by nutrient availability and the indigenous community

In drinking water (DW) and the distribution systems, bacterial growth and biofilm formation have to be controlled both for limiting taste or odour development and preventing clogging or biocorrosion problems. After a contamination with undesired bacteria, factors like nutrient availability and temperature will influence the survival of these invaders. Understanding the conditions enabling invaders to proliferate is essential for a holistic approach towards microbial risk assessment in DW. Pseudomonas putida was used as a model invader because this easy-growing bacterium can use a wide range of substrates. Invasion experiments in oligo- to eutrophic waters showed the requirement of both a carbon and phosphate source for survival of P. putida in DW. Addition of C, N and P enabled P. putida to grow in DW from 5.80 × 10(4) to 1.84 × 10(8) cells mL(-1) and survive for at least 12 days. However, in surface water with similar nutrient concentrations, P. putida did not survive, indicating the concomitant importance of the present indigenous microbial community of the specific water sample. Either extensive carbon or phosphate limitation can be used in water treatment design in order to obtain a DW which is not susceptible for unwanted bacterial growth.

Erratum: Cytotoxic drugs in drinking water: a prediction and risk assessment exercise for the Thames catchment in the United Kingdom

Rowney N, Johnson A, Williams R. 2009. Cytotoxic drugs in drinking water: a prediction risk assessment for the Thames catchment in the United Kingdom. Environ Toxicol Chem 28: 2733–2743. Table 5 on page 2747 has a calculation error in the ratio of exposure for the “Drinking water risk assessment at the Farmoor and Walton intakes on the Thames River during mean flow conditions.” The value should reflect the threshold divided by the exposure as presented in the ratio of exposure for “Drinking water risk assessment at the Farmoor and Walton intakes on the Thames River during 90th percentile flow conditions.” Table 5 is revised and presented below. The corresponding text in the original journal article is correct.

Incorporation of the Multiple Barrier Approach in drinking water risk assessment tools

A number of existing risk assessment tools make reference to, or incorporate, a Multiple Barrier Approach to drinking water safety. Three waterborne disease outbreaks that occurred in developed nations were used as case studies to test a selected set of risk assessment tools. The outbreaks were used to determine how well the risk assessment tools identify hazards and vulnerabilities associated with different barriers to drinking water contamination.

Chlorine disinfection of Francisella tularensis

To determine the range of free available chlorine (FAC) required for disinfection of the live vaccine strain (LVS) and wild-type strains of Francisella tularensis. Seven strains of planktonic F. tularensis were exposed to 0·5 mg·l(-1) FAC for two pH values, 7 and 8, at 5 and 25°C. LVS was inactivated 2 to 4 times more quickly than any of the wild-type F. tularensis strains at pH 8 and 5°C. Free available chlorine residual concentrations routinely maintained in drinking water distribution systems would require up to two hours to reduce all F. tularensis strains by 4 log10. LVS was inactivated most quickly of the tested strains. This work provides contact time (CT) values that are useful for drinking water risk assessment and also suggests that LVS may not be a good surrogate in disinfection studies.

Inactivation of Adenoviruses, Enteroviruses, and Murine Norovirus in Water by Free Chlorine and Monochloramine

Inactivation of infectious viruses during drinking water treatment is usually achieved with free chlorine. Many drinking water utilities in the United States now use monochloramine as a secondary disinfectant to minimize disinfectant by-product formation and biofilm growth. The inactivation of human adenoviruses 2, 40, and 41 (HAdV2, HAdV40, and HAdV41), coxsackieviruses B3 and B5 (CVB3 and CVB5), echoviruses 1 and 11 (E1 and E11), and murine norovirus (MNV) are compared in this study. Experiments were performed with 0.2 mg of free chlorine or 1 mg of monochloramine/liter at pH 7 and 8 in buffered reagent-grade water at 5 degrees C. CT values (disinfectant concentration x time) for 2- to 4-log(10) (99 to 99.99%) reductions in virus titers were calculated by using the efficiency factor Hom model. The enteroviruses required the longest times for chlorine inactivation and MNV the least time. CVB5 required the longest exposure time, with CT values of 7.4 and 10 mg x min/liter (pH 7 and 8) for 4-log(10) inactivation. Monochloramine disinfection was most effective for E1 (CT values ranged from 8 to 18 mg x min/liter for 2- and 3-log(10) reductions, respectively). E11 and HAdV2 were the least susceptible to monochloramine disinfection (CT values of 1,300 and 1,600 mg-min/liter for 3-log(10) reductions, respectively). Monochloramine inactivation was most successful for the adenoviruses, CVB5, and E1 at pH 7. A greater variation in inactivation rates between viruses was observed during monochloramine disinfection than during chlorine disinfection. These data will be useful in drinking water risk assessment studies and disinfection system planning.