Both river bank filtration and dead‐end sand filtration are becoming increasingly applied in rural areas to improve the quality of fecally contaminated water. To evaluate the capacity of both ...treatments to remove E. coli, fecal streptococci, and somatic and K13‐phages, this study investigates their concentrations in diluted wastewater after short‐distance tangential sand filtration and dead‐end sand filtration. Bacteria were almost undetectable in both systems after 60 cm depth, and at a pore‐water velocity of 1 m/d. Both phages underwent removal of 2.5 logs by tangential filtration, whereas dead‐end filtration removed 5.1 logs and 3.9 logs of K13‐phages and somatic phages, respectively. After discounting removal by the schmutzdecke, observed only in the dead‐end filtration, both systems removed phages similarly. It is concluded that short‐distance river bank filtration, alone, does not meet WHO requirements for drinking water. However, the concomitant reduction of suspended solids renders the filtered water amenable to further treatment steps.
The aim of the present study was to estimate the performance of slow sand filtration (SSF) facilities, including the time needed for reaching stabilization (maturation), operated with surface water ...bearing high fecal contamination, representing realistic conditions of rivers in many emerging countries. Surface water spiked with wastewater was infiltrated at different pore water velocities (PWV) and samples were collected at different migration distances. The samples were analyzed for phages and to a lesser extent for fecal bacteria and enteric adenoviruses. At the PWV of 50 cm/d, at which somatic phages showed highest removal, their mean log10 removal after 90 cm migration was 3.2. No substantial differences of removal rates were observed at PWVs between 100 and 900 cm/d (2.3 log10 mean removal). The log10 mean removal of somatic phages was less than the observed for fecal bacteria and tended more towards that of enteric adenoviruses This makes somatic phages a potentially better process indicator than Escherichia coli for the removal of viruses in SSF. We conclude that SSF, and by inference in larger scale river bank filtration (RBF), is an excellent option as a component in multi-barrier systems for drinking water treatment also in areas where the sources of raw water are considerably fecally polluted, as often found in many emerging countries.
Exposure to human pathogenic viruses in recreational waters has been shown to cause disease outbreaks. In the context of Article 14 of the revised European Bathing Waters Directive 2006/7/EC (rBWD, ...CEU, 2006) a Europe-wide surveillance study was carried out to determine the frequency of occurrence of two human enteric viruses in recreational waters. Adenoviruses were selected based on their near-universal shedding and environmental survival, and noroviruses (NoV) selected as being the most prevalent gastroenteritis agent worldwide. Concentration of marine and freshwater samples was done by adsorption/elution followed by molecular detection by (RT)-PCR. Out of 1410 samples, 553 (39.2%) were positive for one or more of the target viruses. Adenoviruses, detected in 36.4% of samples, were more prevalent than noroviruses (9.4%), with 3.5% GI and 6.2% GII, some samples being positive for both GI and GII. Of 513 human adenovirus-positive samples, 63 (12.3%) were also norovirus-positive, whereas 69 (7.7%) norovirus-positive samples were adenovirus-negative. More freshwater samples than marine water samples were virus-positive. Out of a small selection of samples tested for adenovirus infectivity, approximately one-quarter were positive. Sixty percent of 132 nested-PCR adenovirus-positive samples analysed by quantitative PCR gave a mean value of over 3000 genome copies per L of water. The simultaneous detection of infectious adenovirus and of adenovirus and NoV by (RT)PCR suggests that the presence of infectious viruses in recreational waters may constitute a public health risk upon exposure. These studies support the case for considering adenoviruses as an indicator of bathing water quality.
We performed epidemiologic studies at public freshwater bathing sites in Germany to provide a better scientific basis for the definition of recreational water quality standards. A total of 2,196 ...participants were recruited from the local population and randomized into bathers and non-bathers. Bathers were exposed for 10 min and had to immerse their head at least three times. Water samples for microbiological analysis were collected at 20-min intervals. Unbiased concentration-response effects with no-observed-adverse-effect levels (NOAELs) were demonstrated for three different definitions of gastroenteritis and four fecal indicator organisms. Relative risks for bathing in waters with levels above NOAELs compared with nonbathing ranged from 1.8 (95% CI, 1.2-2.6) to 4.6 (95% CI, 2.1-10.1), depending on the definition of gastroenteritis. The effect of swallowing water provided additional evidence for true dose-response relationships. Based on the NOAELs, the following guide values for water quality are suggested: 100 Escherichia coli, 25 intestinal enterococci, 10 somatic coliphages, or 10 Clostridium perfringens per 100 mL. Recreational water quality standards are intended to protect the health of those consumers who are not already immune or resistant to pathogens that may be associated with indicator organisms. In contrast to current World Health Organization recommendations, we concluded that standards should be based on rates of compliance with NOAELs rather than on attributable risks determined above NOAELs, because these risks depend mainly on the unpredictable susceptibility of the cohorts. Although in theory there is no threshold in real concentration-response relationships, we demonstrated that a NOAEL approach would be a more robust and practical solution to the complex problem of setting standards.
Both river bank filtration and dead-end sand filtration are becoming increasingly applied in rural areas to improve the quality of fecally contaminated water. To evaluate the capacity of both ...treatments to remove E. coli, fecal streptococci, and somatic and K13-phages, this study investigates their concentrations in diluted wastewater after short-distance tangential sand filtration and dead-end sand filtration. Bacteria were almost undetectable in both systems after 60 cm depth, and at a pore-water velocity of 1 m/d. Both phages underwent removal of 2.5 logs by tangential filtration, whereas dead-end filtration removed 5.1 logs and 3.9 logs of K13-phages and somatic phages, respectively. After discounting removal by the schmutzdecke, observed only in the dead-end filtration, both systems removed phages similarly. It is concluded that short-distance river bank filtration, alone, does not meet WHO requirements for drinking water. However, the concomitant reduction of suspended solids renders the filtered water amenable to further treatment steps.
In an attempt to obtain a conservative estimate of virus removal during slow sand and river bank filtration, a somatic phage was isolated with slow decay and poor adsorption to coarse sand. We ...continuously fed a phage suspension to a 7-m infiltration path and measured the phage removal. In a second set of experiments, we fed the phage suspension to 1-m long columns run at different pore water velocities. Using the data obtained, a mathematical model was constructed describing removal vs. pore water velocity (PWV), assuming different statistical distributions of the adsorption coefficient λ. The bimodal distribution best fit the results for PWVs higher than 1 m/d. It predicted a removal of approximately 4 log10 after 50 days infiltration at 1 m/d. At PWVs below 1 m/d the model underestimated removal. Sand-bound phages dissociated slowly into the liquid phase, with a detachment constant kdet of 2.6 × 10⁻⁵. This low kdet suggests that river bank filtration plants should be intermittently operated when viral overload is suspected, e.g. during flooding events or at high water-marks in rivers, in order for viruses to become soil-associated during the periods of standstill. Resuming filtration will allow only a very slow virus release from the soil.
Human adenoviruses (HAdV) may be implicated in some disease outbreaks associated with recreational water exposures, typically in swimming pools. Modern molecular methods can be used to detect HAdV in ...environmental water samples. During the EU FP6 Project VIROBATHE a database of over 290 HAdV analyses with corresponding faecal indicator organism (FIO) determinations was gathered and used to explore statistical associations between HAdV and FIO results. The FIOs measured were Escherichia coli, intestinal enterococci and somatic coliphage. Statistically significant trends of increasing proportions of HAdV-positive results in categories of increasing FIO concentration were found in freshwater but not seawater samples. The analysis of these trends in freshwater samples was refined, the trends remaining statistically significant when using categories of 0.5 log10 intervals of FIO concentration. Logistic regression models were then developed to predict the probability of a HAdV-positive outcome from FIO concentration. Potential applications of these models to predict the probability of HAdV-positive outcomes from routine FIO determinations used to describe recreational water quality exposures and to classify recreational water quality are discussed.
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► Over 290 samples were collected from diverse European freshwater and marine sites. ► Samples were analyzed for the presence of human adenovirus using PCR. ► Concentrations of traditional faecal indicator organisms (FIOs) were also measured. ► Adenovirus presence was relatively high at low FIO concentrations. ► Adenovirus presence increased with FIO concentration in freshwater samples.
A novel and simple procedure for concentrating adenoviruses from seawater samples is described. The technique entails the adsorption of viruses to pre-flocculated skimmed milk proteins, allowing the ...flocs to sediment by gravity, and dissolving the separated sediment in phosphate buffer. Concentrated virus may be detected by PCR techniques following nucleic acid extraction. The method requires no specialized equipment other than that usually available in routine public health laboratories, and due to its straightforwardness it allows the processing of a larger number of water samples simultaneously. The usefulness of the method was demonstrated in concentration of virus in multiple seawater samples during a survey of adenoviruses in coastal waters.
The globalized nature of markets has provoked interest in whether cultural difference may affect how consumers process the information via websites. Language, as a vehicle for cultural values, is an ...important factor in their design and the messages they convey. The present study analyzes how language moderates the relationships between online perceived risk, perceived usability and satisfaction online. To fulfill the research aim, the work focuses on two languages that pertain to countries with markedly different cultural values. It employs a between-subjects experimental design, with the processing language (Spanish vs. English) as the independent variable. The study finds that online information-processing is moderated by the language in which users process information. It also demonstrates that firms can reduce the negative effect of perceived risk on perceived usability (and on satisfaction online) using the language known by the user that carries cultural values associated with a lower level of uncertainty avoidance.
Both river bank filtration and dead‐end sand filtration are becoming increasingly applied in rural areas to improve the quality of fecally contaminated water. To evaluate the capacity of both ...treatments to remove
E. coli
, fecal streptococci, and somatic and K13‐phages, this study investigates their concentrations in diluted wastewater after short‐distance tangential sand filtration and dead‐end sand filtration. Bacteria were almost undetectable in both systems after 60 cm depth, and at a pore‐water velocity of 1 m/d. Both phages underwent removal of 2.5 logs by tangential filtration, whereas dead‐end filtration removed 5.1 logs and 3.9 logs of K13‐phages and somatic phages, respectively. After discounting removal by the
schmutzdecke
, observed only in the dead‐end filtration, both systems removed phages similarly. It is concluded that short‐distance river bank filtration, alone, does not meet WHO requirements for drinking water. However, the concomitant reduction of suspended solids renders the filtered water amenable to further treatment steps.
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