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| 2. |
- Schönning, Caroline, et al.
(författare)
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Microbial risk assessment of local handling and reuse of human faeces
- 2007
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Ingår i: Journal of Water and Health. - : I W A Publishing. - 1477-8920 .- 1996-7829. ; 5:1, s. 117-128
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Tidskriftsartikel (refereegranskat)abstract
- Dry urine-diverting toilets may be used in order to collect excreta for the utilisation of nutrients. A quantitative microbial risk assessment was conducted in order to evaluate the risks of transmission of infectious disease related to the local use of faeces as a fertiliser. The human exposures evaluated included accidental ingestion of small amounts of faeces, or a mixture of faeces and soil, while emptying the storage container and applying the material in the garden, during recreational stays to the garden, and during gardening. A range of pathogens representing various groups of microorganisms was considered. Results showed that 12-months' storage before use was sufficient for the inactivation of most pathogens to acceptable levels. When working or spending time in the garden the annual risk of infection by Ascaris was still slightly above 10-4 in these scenarios, although the incidence rate for Ascaris is very low in the population in question. Measures to further reduce the hygienic risks include longer storage, or treatment, of the faeces. The results can easily be extended to other regions with different incidence rates.
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| 3. |
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| 4. |
- Westrell, Therese, et al.
(författare)
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Drinking water consumption patterns in Sweden
- 2006
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Ingår i: Journal of Water and Health. - 1477-8920. ; 4:4, s. 511-522
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Tidskriftsartikel (refereegranskat)abstract
- Estimates on drinking water consumption are necessary in risk assessments on microbial hazardsin drinking water. Large differences in consumption habits between countries have beenreported. In order to establish estimates for the Swedish population, water consumption datafrom a waterborne outbreak investigation (157 people), a small water consumption study(75 people) and a large study on health and environmental factors (10,957 people) were analysed.A lognormal distribution for the daily direct/cold water intake in litres with m¼20.299 ands ¼ 0.570 was fitted to the quantitative data, representing the general population. The averagedaily consumption of tap water as plain drinking water and as heated tap water, e.g. in coffeeand tea, was 0.86 ^ 0.48 l and 0.94 ^ 0.69 l, respectively. Women consumed more cold tap waterthan did men, while men appeared to have a higher consumption of heated tap water. Cold tapwater intake was highest in the oldest age group, ($70 years). The consumption of bottled waterwas very low (mean 0.06 l/d) when compared to other countries.
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| 5. |
- Westrell, Therese, et al.
(författare)
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Short- and long-term variations of norovirus concentrations in the Meuse river during a 2-year study period
- 2006
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Ingår i: Water Research. - : Elsevier BV. - 0043-1354. ; 40:14, s. 2613-2620
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Tidskriftsartikel (refereegranskat)abstract
- Faecally impacted surface waters used for drinking water production may encompass risk for norovirus infections. To be able to assess a possible health risk, noroviruses should be quantified and fluctuations identified. In 2001, norovirus concentrations in the river Meuse displayed a seasonal distribution with high peaks during wintertime as determined by RT-PCR on serially diluted RNA. An intensified day-by-day sampling scheme in the winter of 2002/2003 revealed that the winter peak consisted of several peaks of varying duration and magnitude, possibly due to contamination events in the catchment. The highest estimated concentration was 1700 PCR-detectable units per litre (95% CI 250–8000), which if coinciding with failing treatment could lead to significant numbers in drinking water. Adaptive dynamic filtering was shown to adequately predict subsequent sample concentrations. If valid, such analyses could prove to be useful as early warning systems in risk management of water sources.
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| 6. |
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| 7. |
- Åström, Johan, 1977, et al.
(författare)
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Evaluation of the microbial risk reduction due to selective closure of the raw water intake before drinking water treatment
- 2007
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Ingår i: Journal of Water and Health. - 1996-7829 .- 1477-8920. ; 5:1, s. 81-97
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Tidskriftsartikel (refereegranskat)abstract
- Short-term peaks in pathogen concentrations may increase the risks for waterborne diseases considerably. In this study the occurrence of indicator organisms and pathogens in the river Göta älv at the raw water intake to Göteborg was evaluated and related to risk for drinking water consumption. About half of the 24 pathogen samples, taken during event and non-event conditions, were positive for at least one of the following: Cryptosporidium, Giardia, norovirus, enterovirus, Campylobacter and E. coli O157. Positive pathogen detects were often associated with heavy rainfalls and viruses with a sewage emergency discharge. The annualised probability of infection from this type of event was calculated from pathogen concentrations in a QMRA model. Given that the water intake is not closed, the risk given present water treatment seems to be acceptable for Giardia; however, it is at a borderline for Cryptosporidium and insufficient for noro- and enteroviruses. Present results emphasise the need for an appropriate intake regulation with respect to high pathogen loads, as the risk increases with time of exposure to pathogen contaminants. Rather than a threshold level on E. coli, reports on upstream microbial discharges are valuable for quick pathogen indications.
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| 8. |
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| 9. |
- Åström, Johan, 1977, et al.
(författare)
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Identification and management of microbial contaminations in a surface drinking water source
- 2007
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Ingår i: Journal of Water and Health. - 1996-7829 .- 1477-8920. ; 5:1, s. 67-79
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Tidskriftsartikel (refereegranskat)abstract
- Microbial contamination of surface waters constitutes a health risk for drinking water consumers which may be lowered by closing the raw water intake. We have evaluated microbial discharge events reported in the river Göta älv, which is used for raw water supply to the city of Göteborg. Elevated levels of faecal indicator bacteria were observed during periods of closed raw water intake. High bacteria levels were, however, also occasionally detected during periods of open intake, probably as a result of microbial discharge far upstream in the river which may be difficult to predict and manage by closing the intake. Accumulated upstream precipitations, resulting in surface runoff and wastewater contaminations in the catchment, correlated positively with the levels of total coliforms, E. coli, intestinal enterococci and sulfite-reducing clostridia. Levels of faecal indicator organisms were negatively correlated to the water temperature due to enhanced survival at lower temperatures. Wastewater discharges from a municipality located just upstream of the water intake resulted in elevated E. coli concentrations downstream at the raw water intake for Göteborg. To improve the prediction of microbial contaminations within the river Göta älv, monitoring data on turbidity and upstream precipitation are of particular importance.
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| 10. |
- Åström, Johan, 1977, et al.
(författare)
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Variability analysis of pathogen and indicator loads from urban sewer systems along a river
- 2009
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 59:2, s. 203-212
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Tidskriftsartikel (refereegranskat)abstract
- The pathogen loads within surface waters originating from urban wastewater sources needs to be assessed to support drinking water risk estimations and optimal selection of risk reduction measures. Locally reported discharges from sewer systems (>100,000 persons connected) were used to simulate the potential microbial loads into the Gota alv river, Sweden. Using Monte Carlo simulations, the median and 95% percentile (i.e. worst case) of total microbial load from wastewater treatment plants, sewer network overflows and emergency discharges were assessed and presented for dry and wet weather conditions. Wastewater treatment plants with secondary treatment represented a major source of E. coli, norovirus, Giardia and Cryptosporidium. During wet weather, comparably high microbial loads were found for sewer overflows due to heavy rains. Substantial loads were also associated with an incident of the emergency discharge of untreated wastewater. Simulated river water concentrations of faecal indicators (E. coli, sulfite reducing clostridia, somatic coliphages) and pathogens (norovirus, Giardia, Cryptosporidium) were confirmed by river sampling data, suggesting that urban wastewater is the major microbial source for this river.
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