Julia Derx

Clostridium perfringens Is Not Suitable for the Indication of Fecal Pollution from Ruminant Wildlife but Is Associated with Excreta from Nonherbivorous Animals and Human Sewage

ABSTRACT During a 3-year study, Clostridium perfringens was investigated in defined fecal sources from a temperate alluvial backwater area of a large river system. The results reveal that using C. perfringens as a conservative water quality indicator for total fecal pollution monitoring is no longer justified but suggest that it can be used as a tracer for excreta from nonherbivorous wildlife and human sewage.

Effects of fluctuations in river water level on virus removal by bank filtration and aquifer passage — A scenario analysis

Riverbank filtration is an effective process for removing pathogenic viruses from river water. Despite indications that changing hydraulic conditions during floods can affect the efficacy of riverbank filtration to remove viruses, the impact on advection and dispersion of viruses in the riverbank is not well understood. We investigated the effects of fluctuations in river water level on virus transport during riverbank filtration, considering 3-D transient groundwater flow and virus transport. Using constant removal rates from published field experiments with bacteriophages, removal of viruses with distance from the riverbank was simulated for coarse gravel, fine gravel and fine sandy gravel. Our simulations showed that, in comparison with steady flow conditions, fluctuations in river water level cause viruses to be transported further at higher concentrations into the riverbank. A 1-5 m increase in river water levels led to a 2- to 4-log (log10 reduction in concentration relative to the initial concentration in the river) increase in virus concentration and to up to 30% shorter travel times. For particular cases during the receding flood, changing groundwater flow conditions caused that pristine groundwater was carried from further inland and that simulated virus concentrations were more diluted in groundwater. Our study suggests that the adverse effect of water level fluctuations on virus transport should be considered in the simulation of safe setback distances for drinking water supplies.

QMRAcatch: Microbial Quality Simulation of Water Resources including Infection Risk Assessment.

Given the complex hydrologic dynamics of water catchments and conflicts between nature protection and public water supply, models may help to understand catchment dynamics and evaluate contamination scenarios and may support best environmental practices and water safety management. A catchment model can be an educative tool for investigating water quality and for communication between parties with different interests in the catchment. This article introduces an interactive computational tool, QMRAcatch, that was developed to simulate concentrations in water resources of , a human-associated microbial source tracking (MST) marker, enterovirus, norovirus, , and as target microorganisms and viruses (TMVs). The model domain encompasses a main river with wastewater discharges and a floodplain with a floodplain river. Diffuse agricultural sources of TMVs that discharge into the main river are not included in this stage of development. The floodplain river is fed by the main river and may flood the plain. Discharged TMVs in the river are subject to dilution and temperature-dependent degradation. River travel times are calculated using the Manning-Gauckler-Strickler formula. Fecal deposits from wildlife, birds, and visitors in the floodplain are resuspended in flood water, runoff to the floodplain river, or infiltrate groundwater. Fecal indicator and MST marker data facilitate calibration. Infection risks from exposure to the pathogenic TMVs by swimming or drinking water consumption are calculated, and the required pathogen removal by treatment to meet a health-based quality target can be determined. Applicability of QMRAcatch is demonstrated by calibrating the tool for a study site at the River Danube near Vienna, Austria, using field TMV data, including a sensitivity analysis and evaluation of the model outcomes.

QMRAcatch: Human-Associated Fecal Pollution and Infection Risk Modeling for a River/Floodplain Environment

Protection of drinking water resources requires addressing all relevant fecal pollution sources in the considered catchment. A freely available simulation tool, QMRAcatch, was recently developed to simulate concentrations of fecal indicators, a genetic microbial source tracking (MST) marker, and intestinal pathogens in water resources and to conduct a quantitative microbial risk assessment (QMRA). At the same time, QMRAcatch was successfully applied to a region of the Danube River in Austria, focusing on municipal wastewater emissions. Herein, we describe extension of its application to a Danube River floodplain, keeping the focus on fecal sources of human origin. QMRAcatch was calibrated to match measured human-associated MST marker concentrations for a dry year and a wet year. Appropriate performance characteristics of the human-associated MST assay were proven by simulating correct and false-positive marker concentrations, as determined in human and animal feces. With the calibrated tool, simulated and measured enterovirus concentrations in the rivers were compared. Finally, the calibrated tool allowed demonstrating that 4.5 log enterovirus and 6.6 log norovirus reductions must be achieved to convert current surface water to safe drinking water that complies with a health-based target of 10 infections person yr. Simulations of the low- and high-pollution scenarios showed that the required viral reductions ranged from 0 to 8 log. This study has implications for water managers with interests in assessing robust catchment protection measures and water treatment criteria by considering the fate of fecal pollution from its sources to the point of abstraction.

Setback distances between small biological wastewater treatment systems and drinking water wells against virus contamination in alluvial aquifers.

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 calculated for alluvial sand and gravel aquifers for different vadose zone and aquifer thicknesses and horizontal groundwater gradients. This study applies to individual households and small settlements (1-20 persons) in decentralized locations without access to receiving surface waters but with the legal obligation of biological wastewater treatment. The calculations are based on Monte Carlo simulations using an analytical model that couples vertical unsaturated and horizontal saturated flow with virus transport. Hydraulic conductivities and water retention curves were selected from reported distribution functions depending on the type of subsurface media. The enteric virus concentration in effluent discharge was calculated based on reported ranges of enteric virus concentration in faeces, virus infectivity, suspension factor, and virus reduction by mechanical-biological wastewater treatment. To meet the risk target of <10-4infections/person/year, a 12 log10 reduction was required, using a linear dose-response relationship for the total amount of enteric viruses, at very low exposure concentrations. The results of this study suggest that the horizontal setback distances vary widely ranging 39 to 144m in sand aquifers, 66-289m in gravel aquifers and 1-2.5km in coarse gravel aquifers. It also varies for the same aquifers, depending on the thickness of the vadose zones and the groundwater gradient. For vulnerable fast-flow alluvial aquifers like coarse gravels, the calculated setback distances were too large to achieve practically. Therefore, for this category of aquifer, a high level of treatment is recommended before the effluent is discharged to the ground surface.

Evaluating the effect of temperature induced water viscosity and density fl uctuations on virus and DOC removal during river bank fi ltration - a scenario analysis

Riverbank fi ltration is considered an effi cient method for removing contaminants from infi ltrated surface water in the subsurface. Despite indications that changing water temperatures affect the biochemical and biological mediated removal processes of contaminants, the impact of temperature induced fl uid viscosity and density effects on contaminant removal during riverbank fi ltration is not well understood. This paper investigates the viscosity and density effects associated with seasonal changes in groundwater temperature on virus and dissolved organic carbon (DOC) removal during riverbank fi ltration. Hypothetical aquifer and fl ood wave scenarios were assumed. Data on groundwater temperature were taken from an Austrian fi eld site of the River Danube recorded during 2010/2011. Based on removal rates taken from previously published fi eld experiments, virus and DOC transport was simulated for highly permeable gravel, fi ne gravel and fi ne sandy gravel material. Our simulations indicate that for DOC and a wide range of virus types the viscosity and density effects induced by water temperature changes can counteract with temperature dependent decay and inactivation rates. For particular situations, however, such as for receding fl oods during colder periods, our simulations indicate that fl uid viscosity and density effects can result in a net de- crease in the virus removal effi ciency during colder periods. Persistent types of viruses (e.g. polio 1 or HAV ) can be reduced less effectively and may travel by up to 25 % faster during warmer than during colder periods. Our simula- tions indicate that viscosity and density effects induced by temperature changes should be considered for studying and simulating virus or DOC removal and transport during riverbank fi ltration. The effects may be important spe- cifi cally at fi eld sites with a high river-aquifer exchange and large variations in groundwater temperature.

Global Distribution of Human-Associated Fecal Genetic Markers in Reference Samples from Six Continents

Numerous bacterial genetic markers are available for the molecular detection of human sources of fecal pollution in environmental waters. However, widespread application is hindered by a lack of knowledge regarding geographical stability, limiting implementation to a small number of well-characterized regions. This study investigates the geographic distribution of five human-associated genetic markers (HF183/BFDrev, HF183/BacR287, BacHum-UCD, BacH, and Lachno2) in municipal wastewaters (raw and treated) from 29 urban and rural wastewater treatment plants (750–4 400 000 population equivalents) from 13 countries spanning six continents. In addition, genetic markers were tested against 280 human and nonhuman fecal samples from domesticated, agricultural and wild animal sources. Findings revealed that all genetic markers are present in consistently high concentrations in raw (median log10 7.2–8.0 marker equivalents (ME) 100 mL–1) and biologically treated wastewater samples (median log10 4.6–6.0 ME 100 mL–1) regardless of location and population. The false positive rates of the various markers in nonhuman fecal samples ranged from 5% to 47%. Results suggest that several genetic markers have considerable potential for measuring human-associated contamination in polluted environmental waters. This will be helpful in water quality monitoring, pollution modeling and health risk assessment (as demonstrated by QMRAcatch) to guide target-oriented water safety management across the globe.

Spatiotemporal resolved sampling for the interpretation of micropollutant removal during riverbank filtration

Riverbank filtration (RBF) systems along rivers are widely used as public water supplies. In these systems, many organic micropollutants (OMPs) are attenuated, but some compounds have shown to be rather persistent. Their fate and transport has been studied in RBF sites along lakes and small rivers, but not extensively along large and dynamic rivers. Therefore, the influence of flood events on OMP behavior in these large and dynamic RBF sites was investigated. Monthly samples were taken from surface- and groundwater up to a distance of 900 m from the riverbank of the Danube from March 2014 till May 2016. Two flood events were sampled more extensively nearby the river. Results showed that changes in flow conditions in the river not only caused changes in OMP concentrations, but also in their load. It was seen that the load of benzotriazole, carbamazepine and sulfamethoxazole in the river increased with increasing river discharges. After a relatively long, oxic groundwater passage, several OMPs were reduced. In contrast to previous work, we found that benzotriazole was almost fully removed under oxic conditions. When entering the aquifer, benzotriazole concentrations were significantly reduced and at a distance of 550 m from the river, >97% was degraded. Carbamazepine and sulfamethoxazole showed relatively persistent behavior in the aquifer. The concentrations measured during flood events were in the same range as seasonal sampling. Furthermore concentrations in the groundwater were higher during these events than in the Danube and can reach further into the aquifer. During flood events some highly degradable compounds (i.e. diclofenac) were found up to a distance of 24 m from the river. These results implied that drinking water utilities with RBF wells in oxic, alluvial aquifers located close to highly dynamic rivers need to consider a potential reduction in groundwater quality during and directly after flood events.

Poikilothermic animals as a previously unrecognized source of fecal indicator bacteria in a backwater ecosystem of a large river

The current fecal indicator concept is based on the assumption that the standard fecal indicator bacteria (SFIB) Escherichia coli, intestinal enterococci, and Clostridium perfringens multiply significantly only in the guts of humans and other homeothermic animals and can therefore indicate fecal pollution and the potential presence of pathogens from those groups. The findings of the present study showed that SFIB can also occur in high concentrations in poikilothermic animals (i.e., animals with body temperatures that vary with the ambient environmental temperature, such as fish, frogs, and snails) in an alluvial backwater area in a temperate region, indicating that a reconsideration of this long-standing indicator paradigm is needed. This study suggests that poikilotherms must be considered to be potential primary sources of SFIB in future studies. ABSTRACT Quantitative information regarding the presence of Escherichia coli, intestinal enterococci, and Clostridium perfringens in poikilotherms is notably scarce. Therefore, this study was designed to allow a systematic comparison of the occurrence of these standard fecal indicator bacteria (SFIB) in the excreta of wild homeothermic (ruminants, boars, carnivores, and birds) and poikilothermic (earthworms, gastropods, frogs, and fish) animals inhabiting an alluvial backwater area in eastern Austria. With the exception of earthworms, the average concentrations of E. coli and enterococci in the excreta of poikilotherms were equal to or only slightly lower than those observed in homeothermic excreta and were 1 to 4 orders of magnitude higher than the levels observed in the ambient soils and sediments. Enterococci reached extraordinarily high concentrations in gastropods. Additional estimates of the daily excreted SFIB (E. coli and enterococcus) loads (DESL) further supported the importance of poikilotherms as potential pollution sources. The newly established DESL metric also allowed comparison to the standing stock of SFIB in the sediment and soil of the investigated area. In agreement with its biological characteristics, the highest concentrations of C. perfringens were observed in carnivores. In conclusion, the long-standing hypothesis that only humans and homeothermic animals are primary sources of SFIB is challenged by the results of this study. It may be necessary to extend the fecal indicator concept by additionally considering poikilotherms as potential important primary habitats of SFIB. Further studies in other geographical areas are needed to evaluate the general significance of our results. We hypothesize that the importance of poikilotherms as sources of SFIB is strongly correlated with the ambient temperature and would therefore be of increased significance in subtropical and tropical habitats and water resources. IMPORTANCE The current fecal indicator concept is based on the assumption that the standard fecal indicator bacteria (SFIB) Escherichia coli, intestinal enterococci, and Clostridium perfringens multiply significantly only in the guts of humans and other homeothermic animals and can therefore indicate fecal pollution and the potential presence of pathogens from those groups. The findings of the present study showed that SFIB can also occur in high concentrations in poikilothermic animals (i.e., animals with body temperatures that vary with the ambient environmental temperature, such as fish, frogs, and snails) in an alluvial backwater area in a temperate region, indicating that a reconsideration of this long-standing indicator paradigm is needed. This study suggests that poikilotherms must be considered to be potential primary sources of SFIB in future studies.