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Contamination of groundwater by pathogenic viruses from small biological wastewater treatment system discharges in remote areas is a major concern. To protect drinking water wells against virus contamination, safe setback distances are required between wastewater disposal fields and water supply wells. In this study, setback distances are calculate...
Contexts in source publication
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... notations are given in Table 1. p in Eq. (1) was taken from the reciprocal of the minimum infectious dose of enteric viruses (Hurst, 2002). ...
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... to Table 1 for notations and Table 3A for input variables. The mean and standard deviation of C 0 were calculated using reported input values (Table 3A). ...
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... are listed in Table 1. The required mean enteric virus re- duction to achieve the water quality criterion of ≤ 3.4 × 10 −7 enteric virus particles/L is 12 log 10 . ...
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... was calculated by using the van Genuchten (1980) model with the parameters N, θ r , and θ s , ( Nielsen et al., 1986), refer to Table 1 for nota- tions. Eqs. ...
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... are listed in Table 1. This equation is for steady-state groundwater flow and virus transport conditions and was solved in the form of log 10 reduction of C relative to C 0 at a certain distance in the direction of groundwater flow. ...
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... results suggest that virus reduction is at least 12 log 10 in sand aquifers Log regression fit (sand) Fig. 2. Simulated required setback distances (95th percentiles) for achieving a 12 log 10 virus reduction in sand, gravel, and coarse gravel assuming the same lithology in both vadose zone and aquifer. Input parameters are given in Table 1. over 100 m and in gravel aquifers over 200 m, but it is only 1.6 log 10 in coarse gravel aquifers over 200 m. The vadose zone was shown to be ef- fective in reducing virus concentrations, in particular, for sandy media. ...
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... approach by Hurst Table 3 Input variables and ranges for simulating virus concentrations in effluent of small biological wastewater treatment systems and in groundwater. For notations see Table 1. ⁎ Based on a mean faeces production of 150 g and a mean wastewater production of 150 L/person/day and a faecal density of 1 g/cm 3 . ...
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... Table 3 for the input pa- rameters; the aquifer thickness was set to 3 m. A Groundwater gradient: 0.01 Table 1. grain sizes, dilution of wastewater is low, and thus chemical pollution and oxygen depletion can cause negative impacts on ground water quality. For loamy sand aquifers and sandy loam aquifers, for instance, setback distances should therefore also be determined based on these parameters. ...
Citations
... They are hence a significant source of contaminants, e.g., nutrient and pathogen leaks into aquifers. Viral concentrations of up to 10 9 viruses/L have been measured below conventional septic systems (Anderson and Weber, 2004;Blaschke et al., 2016). Under optimal operation conditions (i.e., correctly designed, installed, and maintained septic systems), viral removal in ISS is about 4 log (Lusk et al., 2017;Adegoke and Stenstrom, 2019;Eregno and Heistad, 2019;Blaschke et al., 2016). ...
... Viral concentrations of up to 10 9 viruses/L have been measured below conventional septic systems (Anderson and Weber, 2004;Blaschke et al., 2016). Under optimal operation conditions (i.e., correctly designed, installed, and maintained septic systems), viral removal in ISS is about 4 log (Lusk et al., 2017;Adegoke and Stenstrom, 2019;Eregno and Heistad, 2019;Blaschke et al., 2016). Additional removal of viruses subsequently occurs via natural attenuation mechanisms during subsurface transport through the aquifer. ...
... This distance is 50 m in Germany, and wells must be placed upgradient of septic systems (Law on Water Resources, Wasserhaushaltsgesetz WHG). Several modeling exercises have shown that regulatory setback distances are too low or too varied to be universally defined (Schijven et al., 2002;Van der Wielen et al. 2006Masciopinto et al., 2008;Trimper, 2010;Blaschke et al., 2016). Thus, the implementation of revised, nonarbitrary, and science-supported policies is imperative to ensure the protection of private water-production wells. ...
The transport of viruses in groundwater is a complex process controlled by both hydrodynamic and reaction parameters. Characterizing the transport of viruses in groundwater is of crucial importance for investigating health risks associated with groundwater consumption from private individual or residential pumping wells. Setback distances between septic systems, which are the source of viruses, and pumping wells must be designed to offer sufficient groundwater travel times to allow the viral load to degrade sufficiently to be acceptable for community health needs. This study consists of developing numerical simulations for the reactive transport of viruses in the subsurface. These simulations are validated using published results of laboratory and field experiments on virus transport in the subsurface and applying previously developed analytical solutions. The numerical model is then exploited to investigate the sensitivity of the fate of viruses in saturated porous media to hydraulic parameters and the coefficients of kinetic reactions. This sensitivity analysis provides valuable insights into the prevailing factors governing health risks caused by contaminated water in private wells in rural residential contexts. The simulations of virus transport are converted into health risk predictions through dose-response relationships. Risk predictions for a wide range of input parameters are compared with the international regulatory health risk target of a maximum of 10-4 infections/person/year and a 30 m setback distance to identify critical subsurface contexts that should be the focus of regulators.
... At a more general level, studies relied on literature values, e.g. for providing recommendation guidelines. Blaschke et al. (2016) used a wide range of reported hydraulic and virus transport parameters to model the virus removal by soil passage in the unsaturated and saturated soil zone. They modelled safe setback distances for drinking water at on-site disposal sites of biologically treated wastewater for different scenarios and types of aquifer media. ...
... The integration was approximated by dividing the time series into sampling intervals, of which it was assumed that the sample concentration was an average value for that time interval. The setback distance for the QMRA method was calculated by the 1D advection-dispersion equation coupled with the removal, λ, and inactivation rate (modified from Blaschke et al., 2016): ...
To guarantee proper protection from fecally transmitted pathogen infections, drinking water wells should have a sufficiently large setback distance from potential sources of contamination, e.g. a nearby river. The aim of this study was to provide insight in regards to microbial contamination of groundwater under different flow velocities, which can vary over time due to changes in river stage, season or pumping rate. The effects of these changes, and how they affect removal parameters, are not completely understood. In this study, field tracer tests were carried out in a sandy gravel aquifer near Vienna, Austria to evaluate the ability of subsurface media to attenuate Bacillus subtilis spores, used as a surrogate for Cryptosporidium and Campylobacter. The hydraulic gradient between injection and extraction was controlled by changing the pumping rate (1, 10 l/s) of a pumping well at the test site, building upon previously published work in which tracer tests with a 5 l/s pumping rate were carried out. Attachment and detachment rate coefficients were determined using a HYDRUS-3D model and ranged from 0.12 to 0.76 and 0–0.0013 h⁻¹, respectively. Setback distances were calculated based on the 60-day travel time, as well as a quantitative microbial risk assessment (QMRA) approach, which showed similar results at this site; around 700 m at the highest pumping rate. Removal rates (λ) in the field tests ranged from 0.2 to 0.3 log/m, with lower pumping rates leading to higher removal. It was shown that scale must be taken into consideration when determining λ for the calculation of safe setback distances.
... Bacterial hazard indicator removal rates determined over short distances in an experimental setting are often used in combination with worst-case hydrological assumptions to predict the longer-range bacterial fate and required set-back distances in alluvial aquifers between faecal pollution sources and points of exposure such as drinking water wells (Blaschke et al. 2016), or where the groundwater emerges (Pang et al. 2004). However, we found that such predictions using the removal rates observed in the one-meter-thick sand beds greatly overestimated the actual attenuation of bacterial hazard indicators in the alluvial sand aquifers below the settlement (Table 2). ...
... However, we found that such predictions using the removal rates observed in the one-meter-thick sand beds greatly overestimated the actual attenuation of bacterial hazard indicators in the alluvial sand aquifers below the settlement (Table 2). Such discrepancies could be caused by the rapid groundwater flow in response to the pumping along preferential pathways, or spatial variation in removal rates (Blaschke et al. 2016;Pang et al. 2004). It is for example likely that, in line with the observed decrease in total bacteria as indicated by 16S rRNA gene copy numbers, the number of bacterial predators such as bacteriophages is also reduced during groundwater transport (Pang et al. 2005), affecting Table 3 Quantitative microbial risk assessment outcomes for exposure in the informal settlement via consumption of groundwater, use of groundwater for gardening, and emptying of pit latrines. ...
Pit latrines provide essential onsite sanitation services to over a billion people, but there are concerns about their role in infectious disease transmission, and impacts on groundwater resources. We conducted fieldwork in an informal settlement in Dar es Salaam, where cholera is endemic. We combined plate counting with portable MinION sequencing and quantitative polymerase chain reaction (qPCR) methods for characterization of bacteria in pit latrine sludge, leachate, shallow and deep groundwater resources. Pit latrine sludge was characterized by log10 marker gene concentrations per 100 mL of 11.2±0.2, 9.9±0.9, 6.0±0.3, and 4.4±0.8, for total bacteria (16S rRNA), E. coli (rodA), human-host-associated Bacteroides (HF183), and Vibrio cholerae (ompW), respectively. The ompW gene observations suggested 5% asymptomatic Vibrio cholerae carriers amongst pit latrine users. Pit leachate percolation through one-meter-thick sand beds attenuated bacterial hazard indicators by 1 to 4 log10 units. But first-order removal rates derived from these data substantially overestimated the longer-range hazard attenuation in the sand aquifers. Cooccurrence of human sewage marker gene HF183 in all shallow groundwater samples testing positive for ompW genes demonstrated the human origin of Vibrio cholerae hazards in the subsurface. All borehole water samples tested negative for ompW and HF183 genes, but 16S rRNA gene sequencing data suggested ingress of faecal pollution into boreholes at the peak of the “long rainy season”. Quantitative microbial risk assessment (QMRA) predicted a gastrointestinal disease burden of 0.05 DALY per person per year for the community, well above WHO targets of 10⁻⁴-10⁻⁶ DALY for disease related to drinking water.
... At a more general level, studies relied on literature values, e.g. for providing recommendation guidelines. Blaschke et al. (2016) used a wide range of reported hydraulic and virus transport parameters to model the virus removal by soil passage in the unsaturated and saturated soil zone. They modelled safe setback distances for drinking water at on-site disposal sites of biologically treated wastewater for different scenarios and types of aquifer media. ...
Karst landscapes cover large parts of our globe. The aquifers laying below their surface are of high importance for global drinking water supply—although many of them being vulnerable to chemical and fecal pollution. This chapter intends to give an overview on the available knowledge on the microbiology of karst aquifers, typical sources of microbiological pollution, and available management strategies for the protection of karst water resources. Emphasis is also given to the environmental factors influencing the assembly of the planktonic fraction of the microbiome. These include the hydrogeology and biogeochemistry of karst aquifers, important influential catchment characteristics and the role of native microbes in karst aquifers. The main focus of the chapter is on the vulnerability of karst aquifers to fecal pollution, its sources and potential impacts on human health, as well as on the available approaches to study and manage karst water resources that are used for drinking water supply. In this context, a recently proposed strategy for the sustainable quality management of karst water resources based on a holistic analysis of fecal pollution and its sources is presented to support its safe and high quality use.
... At a more general level, studies relied on literature values, e.g. for providing recommendation guidelines. Blaschke et al. (2016) used a wide range of reported hydraulic and virus transport parameters to model the virus removal by soil passage in the unsaturated and saturated soil zone. They modelled safe setback distances for drinking water at on-site disposal sites of biologically treated wastewater for different scenarios and types of aquifer media. ...
Groundwater and riverbank filtrate are valuable resources for drinking water production. The presence of pathogens in the environment poses a threat to drinking water quality and human health. This chapter summarizes the current approaches for evaluating pathogen fate and transport in the environment, their removal during subsurface transport in porous aquifers and the needed infection protection to achieve safe drinking water. The focus is on whole-system concepts as proposed by the (WHO, 2017) considering potential fecal sources in water resource catchments towards the point of use. We explain how microbial pathogens move through groundwater and give an overview about the traditional and novel monitoring techniques to investigate fecal contamination in water. Modelling techniques are presented for estimating the required pathogen treatment reduction by riverbank filtration or subsequent disinfection steps to achieve safe drinking water or safe setback distances. The monitoring and modelling techniques include monitoring of natural and artificial fecal indicators and host-associated genetic fecal markers (microbial source tracking (MST) markers) in surface water and groundwater as surrogates for studying pathogen treatment and transport characteristics, experimental tracer tests, analytical and numerical transport models and quantitative microbial risk assessment (QMRA). We discuss the strengths and limitations of the presented approaches.
... According to the fitted curve, the www.nature.com/scientificreports/ increase in the thickness of the vadose zone would effectively extend the EOL of landfill 44 . As shown in Fig. 6c, the aquifer thickness has an approximately logarithmic relationship with the EOL; thus, increases in aquifer thickness will result in increases in the EOL 45 , with much greater growth occurring when the aquifer thickness increases from 5 to 10 m. ...
Mass construction and operation of hazardous waste landfill infrastructure has greatly improved China’s waste management and environmental safety. However, the deterioration of engineering materials and the failure of landfill may lead to the release of untreated leachate rich in persistent toxic pollutants to the soil and shallow groundwater. Accordingly, we develop the framework and process model to predict landfill life by coupling the landfill hydrological performance model and material degradation model. We found that the decrease rate of the concentration of persistent pollutants in leachate was significantly slower than the deterioration rate of the landfill engineering materials. As a result, when the materials failed, the leachate with high concentrations of persistent pollutants continued to leak, resulting in the pollutants concentration in surrounding groundwater exceeding the acceptable concentration at around 385 a, which is the average life of a landfill. Further simulation indicated that hydrogeological conditions and the initial concentration of leachate will affect landfill lifespan. The correlation coefficients of concentration, the thickness of vadose zone and the thickness of aquifer are − 0.79, 0.99 and 0.72 respectively, so the thickness of vadose zone having the greatest impact on the life of a landfill. The results presented herein indicate hazardous waste landfill infrastructure reinvestment should be directed toward long-term monitoring and maintenance, waste second-disposal, and site restoration.
... Significant acid-base and fluoride-pollution sources were not found, so the fluctuations of pH and F were inconspicuous and there was no significant correlation between COD Mn and NH 3 -N. Figure 6 shows that the COD Mn and NH 3 Certain hydrogeological parameters are indispensable for the establishment of hydrogeological numerical models of the studied site. Detailed information collection, geological investigation and in-situ hydrogeological tests provide the necessary inputs for modeling, such as hydraulic conductivity, specific storage, dispersion coefficient, effective porosity and total porosity. ...
A drinking-groundwater source protection technology system based on a three-dimensional finite-difference groundwater model was constructed and applied to the safe management of drinking groundwater in the first terrace of Fujiang River. In the study area, the main type of groundwater is the quaternary systemic alluvial deposit loose rock pore water and the aquifer thickness varies between 20 and 35 m. Groundwater is the main source of water and is used for various purposes through two exploitation wells. The water volumes of 1# exploitation well (1#) and 2# exploitation well (2#) are 10,000 m3/day and 5000 m3/day, respectively. An analysis of 22 indicators from 11 groundwater samples showed that a higher concentration of chemical-oxygen-demand (CODMn) and ammonia-nitrogen (NH3-N), and they had a high correlation with most of the other water-quality factors. Therefore, CODMn and NH3-N were selected as indicator factors for model calibration and prediction. Twenty-two hydraulic head observation wells were used for flow-model calibration. The flow model indicated that a drop funnel formed with a maximum depth of 12 m, and the particle-capture zone in the original downstream direction of the south side extended to 1100 m because of groundwater exploitation. The solute-transport model showed that industrial pollution sources were the main factors that led to a deterioration of water quality. To analyze the necessity and effectiveness of remediation measures for the safety of drinking-water sources, two scenarios were considered to predict the concentration of NH3-N and CODMn in groundwater exploitation wells over 20 years. Scenario I, which considered that current conditions were maintained, predicted that the NH3-N would exceed the drinking-water quality standard of 0.5 mg/L after 16 years. Scenario II, in which industrial sewage treatment plants were installed outside the particle-trapped zone of the exploitation wells and strict anti-seepage measures were implemented, predicted that the peak concentrations of NH3-N and CODMn in the exploitation wells would be 0.26 mg/L and 1.33 mg/L, respectively, after 3 years of model operation. This study provides a theoretical basis for drinking-groundwater source protection that can be applied to safety management practices.
... Previous bacterial research has focused on estimating the safe setback distance for protecting drinking water wells from the effluent of small biological wastewater treatment systems, including OSSs (Blaschke et al., 2016). In India, a previous study as well as local NGOs recommended the installation of toilets at least 10 m away from the nearest water supply resource (Banerjee, 2011;Sorensen et al., 2016). ...
... In this regard, fixed setback distances are practical and easy to implement. However, the scientific determination of setback distances is challenging due to the influences of complex hydrogeological and microbiological factors and the high spatial variability of subsurface media that act as natural filters and buffers (Blaschke et al., 2016;Martinez-Santos et al., 2017). In particular, previous studies have reported that static buffers may fail to prevent faecal contamination owing to the effects of complex hydrogeological and microbiological factors (Taylor et al., 2004). ...
We evaluated the hygienic influence of onsite sanitation systems (OSSs) on drinking water wells in rural Sri Lanka by determining the safe setback distance between wells and the management of OSSs. Although previous studies have used bacterial indicators such as E. coli to evaluate the OSS impact, these parameters cannot assess the hygiene risk for waterborne pathogenic viruses (e.g. rotaviruses). Therefore, pepper mild mottle virus was selected as an indicator of human-specific faecal virus contamination. From a viral perspective, not only can the horizontal distance between a well and the nearest OSS reasonably represent hygiene safety, but the OSS sludge management can mitigate the contamination of wells even at short distances from the OSSs. Quantitative microbial risk assessment suggests that the infection risk of rotavirus was extremely high compared to the international standard. As proper management of OSSs would be key to reducing viral risk, it is necessary to reach out to the residents who are unaware of the importance and necessity of such management.
... infectious doses (< 10-10 3 virus particles) [4], and higher persistence to environmental stressors (temperature and pH changes) compared with bacteria [5,6]. This emphasizes a significant and urgent need for efficient virus disinfection in water. ...
Waterborne human viruses, with ubiquitous prevalence in aquatic environments, extremely low infectious doses, and high resistance to common disinfection processes, pose a substantial threat to human health. Herein, for the first time, a photocatalytic membrane reactor (PMR) driven by visible light emitting diodes (Vis-LEDs) was applied for effective water disinfection of human adenoviruses. The photocatalyst used in the PMR was selected to be a metal-free heterojunction (named as CNO) with the advantages of visible-light-response, efficient virucidal effects, green properties and easy recovery via microfiltration. The disinfection performance of the Vis-LED PMR towards human adenoviruses was improved by adjusting operation with response surface methodology (RSM). Based on twenty sets of operating data, a semi-empirical model was established with a high accuracy of R2 = 0.9622 for predicting the final adenovirus inactivation after 300-min operation. The optimal operating solution was found to be 5.00-log MPN/mL, 320.30 mg/L and 502.65 min for initial virus concentration (IVC), photocatalyst loading (PL) and hydraulic retention time (HRT), respectively. Under the optimized operation, all human adenoviruses were completely inactivated without regrowth, accompanied by severe damage to capsids, within 600 min in the Vis-LED PMR. In addition, the CNO photocatalyst could be retained inside the reactor via low-energy microfiltration with excellent recovery (99.9 wt%) but without obvious chemical or structural changes. Our work can offer a simple, effective, economical and eco-friendly water disinfection device against resistant pathogenic microbes, with controllable efficiency by facilely varying operating solutions.
