| 1. |
- Malm, Annika, 1970, et al.
(författare)
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Replacement predictions for drinking water networks through historical data
- 2012
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Ingår i: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 46:7, s. 2149-2158
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Tidskriftsartikel (refereegranskat)abstract
- Lifetime distribution functions and current network age data can be combined to provide an assessment of the future replacement needs for drinking water distribution networks. Reliable lifetime predictions are limited by a lack of understanding of deterioration processes for different pipe materials under varied conditions. An alternative approach is the use of real historical data for replacement over an extended time series. In this paper, future replacement needs are predicted through historical data representing more than one hundred years of drinking water pipe replacement in Gothenburg, Sweden. The verified data fits well with commonly used lifetime distribution curves. Predictions for the future are discussed in the context of path dependence theory.
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| 2. |
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| 3. |
- Wang, Hao, et al.
(författare)
-
Hepatitis E virus genotype 3 strains and a plethora of other viruses detected in raw and still in tap water.
- 2020
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Ingår i: Water research. - : Elsevier BV. - 1879-2448 .- 0043-1354. ; 168
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Tidskriftsartikel (refereegranskat)abstract
- In this study, next generation sequencing was used to explore the virome in 20L up to 10,000L water from different purification steps at two Swedish drinking water treatment plants (DWTPs), and in tap water. One DWTP used ultrafiltration (UF) with 20nm pores, the other UV light treatment after conventional treatment of the water. Viruses belonging to 26 different families were detected in raw water, in which 6-9 times more sequence reads were found for phages than for known environmental, plant or vertebrate viruses. The total number of viral reads was reduced more than 4-log10 after UF and 3-log10 over UV treatment. However, for some viruses the reduction was 3.5-log10 after UF, as for hepatitis E virus (HEV), which was also detected in tap water, with sequences similar to those in raw water and after treatment. This indicates that HEV had passed through the treatment and entered into the supply network. However, the viability of the viruses is unknown. In tap water 10-130 International Units of HEV RNA/mL were identified, which is a comparable low amount of virus. The risk of getting infected through consumption of tap water is probably negligible, but needs to be investigated. The HEV strains in the waters belonged to subtypes HEV3a and HEV3c/i, which is associated with unknown source of infection in humans infected in Sweden. None of these subtypes are common among pigs or wild boar, the major reservoirs for HEV, indicating that water may play a role in transmitting this virus. The results indicate that monitoring small fecal/oral transmitted viruses in DWTPs may be considered, especially during community outbreaks, to prevent potential transmission by tap water.
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| 4. |
- Wang, Hao, et al.
(författare)
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Variations among Viruses in Influent Water and Effluent Water at a Wastewater Plant over One Year as Assessed by Quantitative PCR and Metagenomics
- 2020
-
Ingår i: Applied and Environmental Microbiology. - 1098-5336 .- 0099-2240. ; 86:24, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- Influent wastewater and effluent wastewater at the Rya treatment plant in Gothenburg, Sweden, were continuously monitored for enteric viruses by quantitative PCR (qPCR) during 1 year. Viruses in effluent wastewater were also identified by next-generation sequencing (NGS) in samples collected during spring, early summer, and winter. Samples of incoming wastewater were collected every second week. Seasonal variations in viral concentrations in incoming wastewater were found for noroviruses GII, sapovirus, rotavirus, parechovirus, and astrovirus. Norovirus GI and GIV and Aichi virus were present in various amounts during most weeks throughout the year, while hepatitis A virus, enterovirus, and adenovirus were identified less frequently. Fluctuations in viral concentrations in incoming wastewater were related to the number of diagnosed patients. The viruses were also detected in treated wastewater, however, with a 3- to 6-log10 reduction in concentration. Seven different hepatitis E virus (HEV) strains were identified in the effluents. Five of these strains belonged to genotype 3 and have been isolated in Sweden from swine, wild boars, and humans and in drinking water. The other two strains were divergent and had not been identified previously. They were similar to strains infecting rats and humans. Surveillance of enteric viruses in wastewater is a tool for early detection and follow-up of gastroenteritis outbreaks in society and for the identification of new viruses that can cause infection in humans.
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| 5. |
- Bondelind, Mia, 1980, et al.
(författare)
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Benchmarkingmodell för dricksvattenförsörjning i Sverige
- 2012
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Ingår i: Proceedings för Åttonde Nordiska Dricksvattenkonferensen, Stockholm Sverige 2012. ; , s. 36-39
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Swedish Water & Wastewater Association has initiated a benchmarking project to assess the quality and quantity, safety and efficiency of drinking water systems in Sweden. An important part of the project is to develop a benchmarking model which provides a useful tool for the municipalities to evaluate the status of their drinking water systems in respect to a safe drinking water quality and quantity. The increased focus on a safe drinking water, in terms of microbiological contaminants, originates from recent outbreaks of waterborne diseases in Östersund and Skellefteå in Sweden. The derived benchmarking model presented in this paper evaluates the safety of the water by a few carefully selected parameters. The model will apply to both small and large drinking water systems and will provide a useful tool for comparison of drinking water systems within Sweden to encourage for a continued improvement of the systems. In addition, the model provides a straightforward and transparent tool for the municipalities to communicate the status of the drinking water systems to the public.
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| 6. |
- Bondelind, Mia, 1980, et al.
(författare)
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Storlek och dynamik i sedimentbunden föroreningstransport i Göta älv orsakad av fartygspassage – inledande metodik-studie
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Flera olika källor bidrar till föroreningar i älven där till exempel metaller släpps ut via industrier och organiska ämnen släpps ut med avlopps-, dag- och kylvatten. Olika verksamheter har funnits längs med Göta älv under en lång tid och på många ställen finns föroreningar som via grundvattnet lakas ur jorden eller som tillförs älven genom skred. I sedimenten i älven har organiska miljögifter (t.ex. TBT, PCB, PAH och dioxiner) och metaller så som kadmium, koppar, bly, kvicksilver och zink uppmätts. Den årliga sedimenttransporten i Göta älv har uppskattas till 130-170 000 ton. Den totala mängden sediment som eroderas av fartyg har uppskattas till 40 000 ton per år, men då har inte hänsyn tagit till att en del av detta material har resuspenderats. Partiklarna i vattnet är potentiella föroreningsbärare då många tungmetaller fäster på partiklar, och smittämnen som bakterier, virus och parasitära protozoer är partiklar vilka kan utgöra en hälsorisk för konsumenterna. Turbiditetsmätningar längs Göta älv har visat ökade turbiditetsvärden efter fartygspassager i älven, men det är framförallt den initiala, kortvariga toppen som uppmärksammats. För att finna lämpliga åtgärder när det gäller provtagningar som underlag för masstransport och konsekvenser för råvattenintag behövs kunskaper om hela förloppet i tid och i djupled.Denna inledande studie har syftat till att undersöka metodik för att beskriva storlek och dynamik för den av fartyg orsakade turbiditetsökningen och eventuella föroreningstransporten i Göta älv. Studien har genomförs genom analyser av föroreningsinnehåll i vattenprover, hydrodynamisk modellering med anpassning för fartygspassagernas påverkan och mätning av vattenhastighet i älven vid Lärjeholm. Den huvudsakliga hypotesen är att föroreningstransporten varierar i djupled och att dynamiken i föroreningspassagen som vissa fartygspassager orsakar bör beaktas. Detta skulle kunna ge bättre underlag för planering och utvärdering av provtagningar. Det kan också ge en möjlighet att minska föroreningsmängden i det råvatten som tas in vid Göteborg stads råvattenintag vid Lärjeholm genom att lägga intaget på lämpligt djup i förhållande till föroreningstransporten. Tänkbara åtgärder för att ta in mindre föroreningar i intaget är ändrat intagsdjup eller stängning vid vissa båtpassager.Resultaten från denna begränsade studie ska tolkas med försiktighet, men visar att den relativt kraftiga ökning av grumlighet och partikelbundna föroreningar som kan observeras i samband med fartygspassager på grund av sin korta varaktighet har liten betydelse jämfört med den ökning som kan kvarstå under åtskilliga timmar. Blyhalten kan till exempel dubbleras och en ökning kvarstå under mer än tre timmar. Föroreningshalter av t ex bly kan under den första timmen efter passagen öka med djupet för att under de följande timmarna vara mer jämnt fördelade i djupprofilen. De partiklar som resuspenderas vid fartygspassager tycks till stor del ha en så låg sedimentationshastighet att de under normal fartygstrafik inte hinner sedimentera innan nästa passage. Hydrodynamisk modellering kan vara ett kraftfullt verktyg för att prediktera flödesmönster, erosion och turbiditetsökning vid fartygspassager. Med en modell kan olika scenarier utvärderas och rekommendationer utfärdas utifrån resultaten. Mätning av turbulens, strömmar och turbiditet under och bakom fartygen bör genomföras för att undersöka om sedimentet resuspenderas i fartygets bana och sedan dispergera in till älvkanten. Undersökning bör genomföras om vissa partier i älven ger upphov till större mängd upprivet sediment som sedan transporteras ned förbi intaget. En möjlighet skulle kunna vara att minska resuspensionen genom att anpassa fartygens hastigheter efter storlek och last, samt om de går motströms eller medströms. Detta skulle ge ytterligare underlag för representativa stickprover efter fartygspassager för beräkning av masstransport med djup- och tidsberoende.
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| 7. |
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| 8. |
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| 9. |
- Heinicke, Gerald, 1973, et al.
(författare)
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Application of a QMRA model for surface water treatment to investigate a waterborne outbreak of calicivirus
- 2009
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Ingår i: American Water Works Association, Global Conference on Microbial Contaminants in Drinking Water 2009, 5-8 October, Singapore. ; , s. 7-
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The QMRA modelling tool developed by the Swedish Water & Wastewater Association was applied to investigate a probably waterborne outbreak of calicivirus that occurred in the municipality of Lilla Edet, Sweden, after a period with heavy rain. Of the inhabitants that receive water from the municipal water works, 32% reported gastroenteritis in the period investigated. For the QMRA study, the pathogen load in the raw water source was estimated by describing specific discharge events of wastewater upstream the intake of the municipal water works, including dilution and transport time in the river. Estimates of the concentration of norovirus in wastewater, the efficiency of treatment processes in the waterworks, exposure volumes and dose-response relationships were based on literature data that are included in the modelling tool. In a scenario analysis, the probability of infection related to the three discharge events was quantified. The QMRA model estimated probabilities of infection comparable to the proportion of people reported estimated to have fallen ill in the epidemiological study. Sources of uncertainty and potential for improvement were identified for the in-data and for the modelling tool.
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| 10. |
- Larsson, C., et al.
(författare)
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Epidemiology and estimated costs of a large waterborne outbreak of norovirus infection in Sweden
- 2014
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Ingår i: Epidemiology and Infection. - : Cambridge University Press (CUP). - 1469-4409 .- 0950-2688. ; 142:3, s. 592-600
-
Tidskriftsartikel (refereegranskat)abstract
- A large outbreak of norovirus (NoV) gastroenteritis caused by contaminated municipal drinking water occurred in Lilla Edet, Sweden, 2008. Epidemiological investigations performed using a questionnaire survey showed an association between consumption of municipal drinking water and illness (odds ratio 4 center dot 73, 95% confidence interval 3 center dot 53-6 center dot 32), and a strong correlation between the risk of being sick and the number of glasses of municipal water consumed. Diverse NoV strains were detected in stool samples from patients, NoV genotype I strains predominating. Although NoVs were not detected in water samples, coliphages were identified as a marker of viral contamination. About 2400 (18 center dot 5%) of the 13000 inhabitants in Lilla Edet became ill. Costs associated with the outbreak were collected via a questionnaire survey given to organizations and municipalities involved in or affected by the outbreak. Total costs including sick leave, were estimated to be similar to 8700000 Swedish kronor (similar to euro0 center dot 87 million).
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| 11. |
- Lindhe, Andreas, 1981, et al.
(författare)
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Cost-effectiveness analysis of risk-reduction measures to reach water safety targets
- 2011
-
Ingår i: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 45:1, s. 241-253
-
Tidskriftsartikel (refereegranskat)abstract
- Identifying the most suitable risk-reduction measures in drinking water systems requires a thorough analysis of possible alternatives. In addition to the effects on the risk level, also the economic aspects of the risk-reduction alternatives are commonly considered important. Drinking water supplies are complex systems and to avoid sub-optimisation of risk-reduction measures, the entire system from source to tap needs to be considered. There is a lack of methods for quantification of water supply risk reduction in an economic context for entire drinking water systems. The aim of this paper is to present a novel approach for risk assessment in combination with economic analysis to evaluate risk-reduction measures based on a source-to-tap approach. The approach combines a probabilistic and dynamic fault tree method with cost-effectiveness analysis (CEA). The developed approach comprises the following main parts: (1) quantification of risk reduction of alternatives using a probabilistic fault tree model of the entire system; (2) combination of the modelling results with CEA; and (3) evaluation of the alternatives with respect to the risk reduction, the probability of not reaching water safety targets and the cost-effectiveness. The fault tree method and CEA enable comparison of risk-reduction measures in the same quantitative unit and consider costs and uncertainties. The approach provides a structured and thorough analysis of risk-reduction measures that facilitates transparency and long-term planning of drinking water systems in order to avoid sub-optimisation of available resources for risk reduction.
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| 12. |
- Lindhe, Andreas, 1981, et al.
(författare)
-
Fault tree analysis for integrated and probabilistic risk analysis of drinking water systems
- 2009
-
Ingår i: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 43:6, s. 1641-1653
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Tidskriftsartikel (refereegranskat)abstract
- Drinking water systems are vulnerable and subject to a wide range of risks. To avoid sub-optimisation of risk-reduction options, risk analyses need to include the entire drinking water system, from source to tap. Such an integrated approach demands tools that are able to model interactions between different events. Fault tree analysis is a risk estimation tool with the ability to model interactions between events. Using fault tree analysis on an integrated level, a probabilistic risk analysis of a large drinking water system in Sweden was carried out. The primary aims of the study were: (1) to develop a method for integrated and probabilistic risk analysis of entire drinking water systems; and (2) to evaluate the applicability of Customer Minutes Lost (CML) as a measure of risk. The analysis included situations where no water is delivered to the consumer (quantity failure) and situations where water is delivered but does not comply with water quality standards (quality failure). Hard data as well as expert judgements were used to estimate probabilities of events and uncertainties in the estimates. The calculations were performed using Monte Carlo simulations. CML is shown to be a useful measure of risks associated with drinking water systems. The method presented provides information on risk levels, probabilities of failure, failure rates and downtimes of the system. This information is available for the entire system as well as its different sub-systems. Furthermore, the method enables comparison of the results with performance targets and acceptable levels of risk. The method thus facilitates integrated risk analysis and consequently helps decision-makers to minimise sub-optimisation of risk-reduction options.
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| 13. |
- Lindhe, Andreas, 1981, et al.
(författare)
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Integrated risk analysis from source to tap: Case study Göteborg
- 2008
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Ingår i: The 6th Nordic Drinking Water Conference, Oslo, Norway, 9-11 June, 2008. - 9788241402937 ; , s. 231-241
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- To achieve an efficient risk management of a drinking-water system the entire system has to be considered, from source to tap. An important part of risk management is to identify hazards and estimate risks, i.e. to conduct risk analyses. In order to provide a relevant basis for evaluating risks and efficiently prioritising risk reduction options, a risk analysis needs to properly consider interaction between different parts and components of the system. This is especially important in complex systems. Logic tree models have the capability of properly reflect system functionality as well as facilitating quantification of risk levels. A fault-tree model was therefore constructed for an integrated and probabilistic risk analysis of the drinking-water system in Göteborg, Sweden. The main (top) event studied in the analysis was supply failure, which included quantity and quality failures. Quantity failure occurs when no water is delivered to the consumer and quality failure when water is delivered, but unfit for human consumption according to existing water-quality standards. Hard data and expert judgements were used for estimating probabilities of events, consequences and uncertainties of estimates. Monte Carlo simulations were used for the calculations in order to facilitate uncertainty analysis of risk levels. The risk analysis provided information on the probability of failure, rate of failure and mean down time of the system. The number of people affected was also included in the fault tree and risk levels were expressed as Costumer Minutes Lost. The primary aims of this paper were to apply a fault-tree method, for integrated and probabilistic risk analysis of drinking-water systems, on the system in Göteborg and show how the results can be used. The results showed, for example, that the raw water part contributes most to the total risk level and that the distribution part includes frequent failures that most often have a short duration and affect a small number of people. The method was found to facilitate a quantitative and integrated risk analysis of the drinking-water system and the results provide information not only on risk levels, but also on the dynamic behaviour of the system. In addition, the method is capable of relevant handling interaction of system components. Furthermore, it provides transparency and facilitates for formal updating when new information becomes available. Hence, it is concluded that the method provides useful information for discussing and evaluating risks as well as possible risk reduction options.
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| 14. |
- Lindhe, Andreas, 1981, et al.
(författare)
-
Quantitative risk assessment of water supply systems from source to tap
- 2009
-
Ingår i: TECHNEAU: Safe Drinking Water from Source to Tap. - 1843392755
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In the 3rd edition of the Guidelines for Drinking-water Quality, the World Health Organisation concludes that an integrated management of risks in source waters, treatment systems and distribution networks is the most efficient way to guarantee safe drinking water to consumers. The integrated approach is fundamental to avoid sub-optimisation of risk-reduction efforts. This paper presents an application of an integrated and quantitative risk model for comparing risk-reduction alternatives to support decisions for reaching specified water safety targets. A fault tree approach is used for structuring the risk analysis and for estimating the risk, expressed as Costumer Minutes Lost (CML). Input information is a combination of hard data and expert judgements. Uncertainties in input information are considerable and modelled by a Bayesian statistical approach. The Göteborg drinking water system is used to exemplify model application. Quantitative safety targets have been confirmed at the political level as a basis for long-term planning of investments and reinvestments. Four different risk-reduction alternatives concerning additional raw water supplies and increased treatment capacity were compared. A combination of increased treatment capacity and additional raw water sources was shown to provide the greatest risk reduction. The paper describes how a structured and thorough analysis of risk-reduction options can facilitate transparency and long-term planning of drinking water systems.
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| 15. |
- Malm, Annika, 1970, et al.
(författare)
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Förnyelseplanering av vatten- och avloppsförsörjningsnät i 18 svenska kommuner
- 2009
-
Ingår i: The 11th Nordic Wastewater Conference, 10-12 November 2009, Odense, Denmark.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The water and wastewater pipe net management is of considerable interest. The management influences risk for distribution interruption, health disruptions and environmental safe sewer discharge. There are also huge values involved. The renewal of the pipe networks is the major question, each municipality has to handle. There is a lot of knowledge among the water administrations in the municipalities; however the knowledge is often in the mind of the employees. Water engineers in 18 Swedish municipalities of various categories have been interviewed. Most municipalities are in short of a systematic renewal planning, such as risk analysis or cost calculated goals. The interviewed municipalities felt that there renewal rate should be higher, but they have no structural instrument to show the reasons. Priorities were done as “worst first”, and the selection of “worst” were built on experience. There is a need of structure in order to assist the municipalities to rely on their work, and to express to politicians and others the future rehabilitation needs.
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| 16. |
- Malm, Annika, 1970, et al.
(författare)
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The association of drinking water treatment and distribution network disturbances with Health Call Centre contacts for gastrointestinal illness symptoms
- 2013
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Ingår i: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 47:13, s. 4474-4484
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Tidskriftsartikel (refereegranskat)abstract
- There are relatively few studies on the association between disturbances in drinking waterservices and symptoms of gastrointestinal (GI) illness. Health Call Centres data concerningGI illness may be a useful source of information. This study investigates if there is anincreased frequency of contacts with the Health Call Centre (HCC) concerning gastrointestinal symptoms at times when there is a risk of impaired water quality due to disturbances at water works or the distribution network. The study was conducted inGothenburg, a Swedish city with 0.5 million inhabitants with a surface water source ofdrinking water and two water works. All HCC contacts due to GI symptoms (diarrhoea,vomiting or abdominal pain) were recorded for a three-year period, including also sex, age,and geocoded location of residence. The number of contacts with the HCC in the affectedgeographical areas were recorded during eight periods of disturbances in the water works(e.g. short stops of chlorine dosing), six periods of large disturbances in the distributionnetwork (e.g. pumping station failure or pipe breaks with major consequences), and 818pipe break and leak repairs over a three-year period. For each period of disturbance theobserved number of calls was compared with the number of calls during a control periodwithout disturbances in the same geographical area. In total about 55, 000 calls to the HCCdue to GI symptoms were recorded over the three-year period, 35 per 1000 inhabitants andyear, but much higher (>200) for children
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| 17. |
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| 18. |
- Moona, Nashita, 1985, et al.
(författare)
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Partial renewal of granular activated carbon filters for improved drinking water treatment
- 2018
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Ingår i: Environmental Science: Water Research and Technology. - : Royal Society of Chemistry (RSC). - 2053-1419 .- 2053-1400. ; 4:4, s. 529-538
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Tidskriftsartikel (refereegranskat)abstract
- There is a trend of increasing natural organic matter (NOM) in raw drinking waters of Nordic countries due to climate change. Seasonal deterioration in NOM quality imparts challenges for delivering a consistently high drinking water quality. In this study, a simple and cost-effective operational strategy was investigated that improved short-term NOM removal in a full-scale treatment plant. Three granular activated carbon (GAC) media biofilters were modified by replacing a small fraction of saturated filter media with new media. Relative to replacing the entire biofilter media, this approach required lower capital cost and shorter downtime and maintained conditions for biological filter functioning. NOM removal efficiencies were compared in modified versus unmodified (reference) filters using online UV absorbance, and offline fluorescence and dissolved organic carbon measurements. The modified biofilters showed improved organic matter removal lasting for at least four weeks. Partial replenishment of GAC in full-scale biofilters may be a useful and sustainable operational strategy for coping with temporarily high NOM loads in raw waters that might otherwise cause water quality problems.
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| 19. |
- Moona, Nashita, 1985, et al.
(författare)
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Partial replenishment of biological activated carbon filters to improve natural organic matter removal
- 2018
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Ingår i: Proceedings of IWA World Water Congress & Exhibition 2018.
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Konferensbidrag (refereegranskat)abstract
- Natural organic matter (NOM) in surface waters negatively impacts drinking water treatment and is a precursor of harmful disinfection by-products (DBPs). Granular activate carbon (GAC) filters are integral components of many drinking water treatment plants (WTPs) due to the ability to remove NOM and organic micro pollutants from raw waters. However, GAC filters lose adsorption capacity and convert to biologically activated carbon (BAC) filter relatively quickly. This paper reports on a full-scale BAC filter modification strategy to enhance short-term NOM removal. This is achieved by adding a small amount of fresh GAC to BAC filters which increases adsorption while maintaining biological degradation of organics by the microbes attached to the BAC. This strategy was implemented at two treatment plants in Sweden. Modified filters showed better removal of humic-like and protein-like NOM fractions than reference filters that did not receive fresh GAC, indicating improved functioning of both adsorption and biological treatment. The result shows that both biodegradation and adsorption mechanism improved within the filters.
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| 20. |
- Moona, Nashita, 1985, et al.
(författare)
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Temperature-dependent mechanisms of DOM removal by biological activated carbon filters
- 2019
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Ingår i: Environmental Science: Water Research and Technology. - : Royal Society of Chemistry (RSC). - 2053-1419 .- 2053-1400. ; 5:12, s. 2232-2241
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Tidskriftsartikel (refereegranskat)abstract
- Seasonal variability in the removal of dissolved organic matter (DOM) by drinking water biological activated carbon (BAC) filters is often attributed to temperature changes. However, it can be rather difficult to directly relate temperature to treatment efficiency at full scale due to seasonal variations in other influential parameters like DOM concentration and character, and microbial activity. Furthermore, processes in BAC filters include adsorption, desorption and biodegradation within biofilms while each respond differently to temperature. This study aimed to decouple these processes by studying the removal of various DOM fractions from coagulated and settled drinking water when in contact with aged (>3 years) BAC filter material at different water temperatures. DOM removal was measured as changes in dissolved organic carbon (DOC), ultraviolet absorbance at 254 nm (UV254) and fluorescence. Under the particular experimental conditions there was little evidence of biological removal; instead, removal of DOM fractions emitting at longer wavelengths ("humic-like", >430 nm) was consistent with chemisorption, removal of DOM emitting at intermediate wavelengths ("humic-like", 390-420 nm) was consistent with physisorption, and multiple mechanisms were indicated for "protein-like" (<380 nm) DOM. Non-biological mechanisms of DOM removal by aged BAC filters are often assumed to be unimportant; however, these results suggest they are important for some DOM fractions, especially during periods of reduced microbial activity.
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| 21. |
- Persson, Frank, 1970, et al.
(författare)
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Mikrobiologiska barriärer i vattenrening
- 2005
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The objective was to investigate the microbial barrier function of the most common process combination applied to Swedish surface waters – coagulation / flocculation followed by settling and rapid filtration. The effect of operational conditions was studied, as well as alternative and add-on processes, such as biological pre-filtration of raw water without ozonation, ultrafiltration (UF) and nanofiltration (NF). Analytical parameters included the removal of natural organic matter (NOM) and regrowth potential. The work was carried out in close cooperation between engineers and microbiologists. The barrier function of chemical treatment was investigated in pilot-scale by challenge tests and a novel method for following raw water particles, based on the detection of algae by flow cytometry. Results indicate that chemical treatment represents a robust yet mediocre barrier. The measured barrier function for added viruses was around 99.99 %, but considerably lower for particles in the size range of protozoan parasites (~99 %) and in bacteria size (~90 %). The measured reduction in numbers of indicator bacteria added in high concentrations was however higher. Considering the sparse information on the microbial quality and variability of Swedish surface water, the barrier function at many waterworks appears insufficient over chemical treatment alone, and therefore requires additional processes and/or disinfection to reliably eliminate the risk of waterborne disease. Processes were investigated that increase microbial barrier function. Chemical treatment was complemented with UF with a nominal pore diameter close to virus size. Alternatively, chemical treatment may be replaced by NF with high removal of NOM. Since the feasibility of membranes processes is limited by fouling, different pre-treatment options were compared. The UF and NF pilot plants achieved very high removal efficiencies for particles in the size ranges of protozoan parasites and bacteria, as well as two surrogate viruses (bacteriophages) with different surface properties. Both NF and postchemical treatment UF were subject to irreversible fouling that could not be solved by chemical cleaning. Compared to conventional pre-treatment with rapid filters, biological pre-filtration significantly amended fouling problems in the NF pilot plant. Bulk NOM was reduced to a minor degree in the biofilters (~10 %), while higher removals of the biodegradable fractions (~20–30 %) and biofilm formation potential (80–90 %) were experienced. Biological pre-filtration was furthermore evaluated as a way to stabilize the feed water quality to chemical treatment. Particle removal became less dependent on filter function, which increased the robustness of the process. Batch tests revealed potential savings of coagulant with pre-filtration, due to lower organic and particle load. Natural odour substances (geosmin and MIB), almost unaffected by conventional treatment, were reliably removed in the pre-filters. For further details in English, see the scientific publications on the project.
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| 22. |
- Rosen, Lars, 1962, et al.
(författare)
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Comparing Raw Water Options to Reach Water Safety Targets Using an Integrated Fault Tree Model
- 2008
-
Ingår i: International Water Association Conference, Water Safety Plans: Global Experiences and Future Trends, Lisbon, Portugal, 12-14 May, 2008.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In the 3rd edition of the Guidelines for Drinking-water Quality, the World Health Organization (WHO) concludes that an integrated management of risks in source waters, treatment systems and distribution networks is the most effective way to guarantee safe drinking water to consumers. The integrated approach is fundamental to avoid sub-optimisation of risk reduction efforts. This paper presents an application of an integrated and quantitative risk model for comparing risk-reduction alternatives to support decisions for reaching specified water safety targets. A fault tree approach is used for structuring the risk analysis and for estimating the risk, expressed as Costumer Minutes Lost. Input information is a combination of hard data and expert judgements. Uncertainties in input information are considerable and modelled by a Bayesian statistical approach. The Göteborg drinking water system is used to exemplify model application. Quantitative safety targets have been confirmed at the political level as a basis for long-term planning of investments and reinvestments. Four different risk reduction alternatives were compared and increased treatment capacity in combination with additional raw water supply was shown to provide the greatest risk reduction. The paper describes how a structured and thorough analysis of risk reduction options can facilitate transparency and long-term planning of drinking water systems.
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| 23. |
- Rosen, Lars, 1962, et al.
(författare)
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Comparing risk-reduction measures to reach water safety targets using an integrated fault tree model
- 2010
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Ingår i: Water Science and Technology: Water Supply. - : IWA Publishing. - 1606-9749. ; 10:3, s. 428-436
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Tidskriftsartikel (refereegranskat)abstract
- In the third edition of the Guidelines for Drinking-water Quality, the World Health Organization concludes that an integrated management of risks in source waters, treatment systems and distribution networks is the most effective way to guarantee safe drinking water to consumers. The integrated approach is fundamental to avoid sub-optimisation of risk-reduction measures. This paper presents an application of an integrated and quantitative risk model for comparing risk-reduction measures to support decisions for reaching specified water safety targets. A fault tree approach is used for structuring the risk analysis and for estimating the risk, expressed as Customer Minutes Lost (CML). Input information is a combination of hard data and expert judgements. Uncertainties in input information are considerable and modelled by a Bayesianstatistical approach. A drinking water system in Sweden is used to exemplify model application. Quantitative safety targets have been confirmed at the political level as a basis for long-term planning of investments and reinvestments. One target defines an acceptable risk level of 144 annual CML for the average consumer. For the current system structure an estimated risk of 612CML was obtained. Four risk-reduction alternatives were compared and they reduce the risk to between 50 and 81 CML, i.e. below the acceptable level. The paper describes how a structuredand thorough analysis of risk-reduction measures can facilitate transparency and long-term planning of drinking water systems.
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| 24. |
- Saguti, Fredy, et al.
(författare)
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The UV Dose Used for Disinfection of Drinking Water in Sweden Inadequately Inactivates Enteric Virus with Double-Stranded Genomes
- 2022
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Ingår i: International Journal of Environmental Research and Public Health. - : MDPI AG. - 1660-4601 .- 1661-7827. ; 19:14
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Tidskriftsartikel (refereegranskat)abstract
- Irradiation with ultraviolet light (UV) at 254 nm is effective in inactivating a wide range of human pathogens. In Sweden, a UV dose of 400 J/m(2) is often used for the treatment of drinking water. To investigate its effect on virus inactivation, enteric viruses with different genomic organizations were irradiated with three UV doses (400, 600, and 1000 J/m(2)), after which their viability on cell cultures was examined. Adenovirus type 2 (double-stranded DNA), simian rotavirus 11 (double-stranded RNA), and echovirus 30 (single-stranded RNA) were suspended in tap water and pumped into a laboratory-scale Aquada 1 UV reactor. Echovirus 30 was reduced by 3.6-log(10) by a UV dose of 400 J/m(2). Simian rotavirus 11 and adenovirus type 2 were more UV resistant with only 1-log(10) reduction at 400 J/m(2) and needed 600 J/m(2) for 2.9-log(10) and 3.1-log(10) reductions, respectively. There was no significant increase in the reduction of viral viability at higher UV doses, which may indicate the presence of UV-resistant viruses. These results show that higher UV doses than those usually used in Swedish drinking water treatment plants should be considered in combination with other barriers to disinfect the water when there is a risk of fecal contamination of the water.
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| 25. |
- Sokolova, Ekaterina, 1986, et al.
(författare)
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Decay of Bacteroidales Genetic Markers in Relation to Traditional Fecal Indicators for Water Quality Modeling of Drinking Water Sources
- 2012
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 46:2, s. 892-900
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Tidskriftsartikel (refereegranskat)abstract
- The implementation of microbial fecal source tracking (MST) methods in drinking water management is limited by the lack of knowledge on the transport and decay of host-specific genetic markers in water sources. To address these limitations, the decay and transport of human (BacH) and ruminant (BacR) fecal Bacteroidales 16S rRNA genetic markers in a drinking water source (Lake Radasjon in Sweden) were simulated using a microbiological model coupled to a three-dimensional hydrodynamic model. The microbiological model was calibrated using data from outdoor microcosm trials performed in March, August, and November 2010 to determine the decay of BacH and BacR markers in relation to traditional fecal indicators. The microcosm trials indicated that the persistence of BacH and BacR in the microcosms was not significantly different from the persistence of traditional fecal indicators. The modeling of BacH and BacR transport within the lake illustrated that the highest levels of genetic markers at the raw water intakes were associated with human fecal sources (onsite sewers and emergency sewer overflow). This novel modeling approach improves the interpretation of MST data, especially when fecal pollution from the same host group is released into the water source from different sites in the catchment.
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| 26. |
- Sokolova, Ekaterina, 1986, et al.
(författare)
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Estimation of pathogen concentrations in a drinking water source using hydrodynamic modelling and microbial source tracking
- 2012
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Ingår i: Journal of Water and Health. - : IWA Publishing. - 1477-8920 .- 1996-7829. ; 10:3, s. 358-370
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Tidskriftsartikel (refereegranskat)abstract
- The faecal contamination of drinking water sources can lead to waterborne disease outbreaks. To estimate a potential risk for waterborne infections caused by faecal contamination of drinking water sources, knowledge of the pathogen concentrations in raw water is required. We suggest a novel approach to estimate pathogen concentrations in a drinking water source by using microbial source tracking data and fate and transport modelling. First, the pathogen (norovirus, Cryptosporidium, Escherichia coli O157/H7) concentrations in faecal contamination sources around the drinking water source Lake Rådasjön in Sweden were estimated for endemic and epidemic conditions using measured concentrations of faecal indicators (E. coli and Bacteroidales genetic markers). Afterwards, the fate and transport of pathogens within the lake were simulated using a three-dimensional coupled hydrodynamic and microbiological model. This approach provided information on the contribution from different contamination sources to the pathogen concentrations at the water intake of a drinking water treatment plant. This approach addresses the limitations of monitoring and provides data for quantitative microbial risk assessment(QMRA) and risk management in the context of faecal contamination of surface drinking water sources.
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| 27. |
- Sokolova, Ekaterina, 1986, et al.
(författare)
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Hydrodynamic modelling and forecasting of microbial water quality in a drinking water source
- 2014
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Ingår i: Aqua. - : IWA Publishing. - 0003-7214. ; 63:3, s. 189-199
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Tidskriftsartikel (refereegranskat)abstract
- Faecal contamination often enters drinking water sources through emergency discharges, which occur as a result of technical malfunctions or a hydraulic overload of the sewer system during periods of heavy rain. In October–November 2012, several emergency discharges entered Lake Rådasjön – a drinking water source for Gothenburg, Sweden. To describe and forecast the influence of these emergency discharges on the microbial water quality, the spread of Escherichia coli (E. coli) within the lake was simulated using a three-dimensional hydrodynamic model. The model was run for a period of four months using the observed data, and for a period of 9 days using meteorological forecast data. The modelling results showed how much every contamination source contributed to the total E. coli concentrations at the water intakes. The agreement between the modelling results and the measured concentrations was satisfactory. The results of this study led to the decision to use the lake for drinking water production. This study demonstrated that the proposed modelling approach can be used to provide short-term forecasts of the microbial water quality in drinking water sources.
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| 28. |
- Sokolova, Ekaterina, 1986, et al.
(författare)
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Hydrodynamic Modelling of Microbial Water Quality in a Drinking Water Source
- 2013
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Ingår i: Urban Environment. Proceedings of the 11th Urban Environment Symposium (UES), held in Karlsruhe, Germany, 16-19 September 2012. - Dordrecht : Springer Netherlands. - 9789400777552 ; , s. 517-526
-
Konferensbidrag (refereegranskat)abstract
- The presence of faecal contamination in drinking water sources can cause waterborne disease outbreaks. The aim of this article was to study the influence of wastewater discharges from a wastewater treatment plant on microbial water quality in a drinking water source—the river Göta älv in Sweden. To fulfil this aim, the fate and transport of the faecal indicators E. coli and somatic coliphages in the river Göta älv were simulated using a three-dimensional hydrodynamic model. The validation of the hydrodynamic model confirmed a good model performance: the correlation coefficient was 0.99; the absolute mean difference between the simulated and measured water surface elevation was 0.03 m, which is 11.1 % of the standard deviation of the measured data. The modelling results revealed that during overflow events at the wastewater treatment plant, discharges of untreated wastewater contributed more to the concentrations of faecal indicators at the water intake than discharges of treated wastewater. The hydrodynamic modelling of microbial water quality proved to be a useful tool to estimate the contribution of different sources to the total contamination of raw water used for drinking water supply and, therefore, to provide decision-support information for preventive and mitigative risk-reduction measures.
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| 29. |
- Sokolova, Ekaterina, 1986, et al.
(författare)
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Hydrodynamic modelling of the microbial water quality in a drinking water source as input for risk reduction management
- 2013
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 497, s. 15-23
-
Tidskriftsartikel (refereegranskat)abstract
- To mitigate the faecal contamination of drinking water sources and, consequently, to prevent waterborne disease outbreaks, an estimation of the contribution from different sources to the total faecal contamination at the raw water intake of a drinking water treatment plant is needed. The aim of this article was to estimate how much different sources contributed to the faecal contamination at the water intake in a drinking water source, Lake Rådasjön in Sweden. For this purpose, the fate and transport of faecal indicator Escherichia coli within Lake Rådasjön were simulated by a three-dimensional hydrodynamic model. The calibrated hydrodynamic model described the measured data on vertical temperature distribution in the lake well (the Pearson correlation coefficient was 0.99). The data on the E. coli load from the identified contamination sources were gathered and the fate and transport of E. coli released from these sources within the lake were simulated using the developed hydrodynamic model, taking the decay of the E. coli into account. The obtained modelling results were compared to the observed E. coli concentrations at the water intake. The results illustrated that the sources that contributed the most to the faecal contamination at the water intake in Lake Rådasjön were the discharges from the on-site sewers and the main inflow to the lake – the river Mölndalsån. Based on the modelling results recommendations for water producers were formulated. The study demonstrated that this modelling approach is a useful tool for estimating the contribution from different sources to the faecal contamination at the water intake of a drinking water treatment plant and provided decision-support information for the reduction of risks posed to the drinking water source.
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| 30. |
- Sokolova, Ekaterina, 1986, et al.
(författare)
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Water quality modelling, monitoring and microbial source tracking for microbial risk assessment of a drinking water source
- 2012
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Ingår i: Åttonde Nordiska Dricksvattenkonferensen, Svenskt Vatten, NordIWA, Stockholm, 18-20 juni 2012. ; , s. 94-98
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- To prevent waterborne disease outbreaks, mitigation of faecal contamination of drinking water sources and sufficient treatment of water at the drinking water treatment plant (DWTP) are required. The aim of this study was to combine and apply several tools to investigate the raw water quality and determine the risk for waterborne infections in a drinking water source for the cities of Mölndal and Gothenburg in Sweden, Lake Rådasjön. To identify the major contamination sources around the lake and their contribution to the faecal contamination at the water intakes of DWTPs, monitoring of faecal indicators and pathogens was combined with microbial source tracking and water quality modelling. The microbial source tracking was performed to determine the human or ruminant origin of faecal contamination using host-specific Bacteroidales genetic markers. The decay of these genetic markers in relation to the decay of traditional faecal indicators in water environment was investigated in outdoor microcosm trials performed in different seasons. Using measured concentrations of Bacteroidales genetic markers the pathogen (norovirus and Cryptosporidium) concentrations in faecal contamination sources around the lake were estimated for endemic and epidemic conditions. Afterwards, the fate and transport of faecal indicators and pathogens within the lake were simulated using a three-dimensional coupled hydrodynamic and microbiological model, which was calibrated based on the decay data from the microcosm trials. Based on the obtained results a microbial risk assessment of a conventional DWTP was conducted using two different approaches – optimal disinfection practices (ODP) and quantitative microbial risk assessment (QMRA). The results showed that the on-site sewers were the source that contributed the most to the pathogen concentrations at the water intakes under both endemic and epidemic conditions. The results from both the ODP and QMRA risk assessments indicated that the barrier efficiency against Cryptosporidium and possibly viruses may be too low at a conventional DWTP. This study demonstrated how different approaches and tools can be applied to evaluate the risks for waterborne infections and prioritise mitigation measures related to faecal contamination of surface drinking water sources.
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| 31. |
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| 32. |
- Tornevi, Andreas, et al.
(författare)
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Precipitation Effects on Microbial Pollution in a River: Lag Structures and Seasonal Effect Modification
- 2014
-
Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203 .- 1932-6203. ; 9:5
-
Tidskriftsartikel (refereegranskat)abstract
- Background: The river Gota Alv is a source of freshwater for 0.7 million swedes. The river is subject to contamination from sewer systems discharge and runoff from agricultural lands. Climate models projects an increase in precipitation and heavy rainfall in this region. This study aimed to determine how daily rainfall causes variation in indicators of pathogen loads, to increase knowledge of variations in river water quality and discuss implications for risk management. Methods: Data covering 7 years of daily monitoring of river water turbidity and concentrations of E. coli, Clostridium and coliforms were obtained, and their short-term variations in relation with precipitation were analyzed with time series regression and non-linear distributed lag models. We studied how precipitation effects varied with season and compared different weather stations for predictive ability. Results: Generally, the lowest raw water quality occurs 2 days after rainfall, with poor raw water quality continuing for several more days. A rainfall event of >15 mm/24-h (local 95 percentile) was associated with a three-fold higher concentration of E. coli and 30% higher turbidity levels (lag 2). Rainfall was associated with exponential increases in concentrations of indicator bacteria while the effect on turbidity attenuated with very heavy rainfall. Clear associations were also observed between consecutive days of wet weather and decreased water quality. The precipitation effect on increased levels of indicator bacteria was significant in all seasons. Conclusions: Rainfall elevates microbial risks year-round in this river and freshwater source and acts as the main driver of varying water quality. Heavy rainfall appears to be a better predictor of fecal pollution than water turbidity. An increase of wet weather and extreme events with climate change will lower river water quality even more, indicating greater challenges for drinking water producers, and suggesting better control of sources of pollution.
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| 33. |
- Vinas, Victor, 1988, et al.
(författare)
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Cross-connections in drinking water distribution networks: Quantitative microbial risk assessment in combination with fault tree analysis and hydraulic modelling
- 2022
-
Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 831
-
Tidskriftsartikel (refereegranskat)abstract
- Deficiencies in drinking water distribution networks, such as cross-connections, may lead to contamination of the drinking water and pose a serious health risk to consumers. Cross-connections and backflows are considered among the most severe public health risks in distribution networks. The aim of this paper was to provide a framework for estimating the risk of infection from cross-connection and backflow events. Campylobacter, norovirus, and Cryptosporidium were chosen as reference pathogens for this study. The theoretical framework was constructed based on the fault tree analysis methodology. National aggregated cross-connection incident data was used to calculate the probability of a contamination event occurring in Swedish networks. Three risk cases were evaluated: endemic, elevated, and extreme. Quantitative microbial risk assessment (QMRA) was used to assess daily risk of infection for average national estimates. The framework was also evaluated using local data from the Gothenburg network. The daily risk of infection from cross-connection and backflow events in Swedish networks was generally above an acceptable target level of 10−6 for all reference pathogens and modelled cases; the exception was for the Gothenburg system where the risk was lower than 10−7. An outbreak case study was used to validate the framework results. For the outbreak case study, contaminant transport in the network was simulated using hydraulic modelling (EPANET), and risk estimates were calculated using QMRA. The outbreak simulation predicted between 97 and 148 symptomatic infections, while the epidemiological survey conducted during the outbreak reported 179 cases of illness. The fault tree analysis framework was successfully validated using an outbreak case study, though it was shown on the example of Gothenburg that local data is still needed for well-performing systems. The framework can help inform microbial risk assessments for drinking water suppliers, especially ones with limited resources and expertise in this area.
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| 34. |
- 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
-
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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| 35. |
- Åström, Johan, 1977, et al.
(författare)
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Kvantitativ mikrobiell källspårning med Bacteroidales qPCR för bedömning och åtgärder av patogenrisker i en ytvattentäkt
- 2010
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Ingår i: Den 7. Nordiske Drikkevandskonference, 7.-9. juni 2010, DGI-byen, Köpenhamn, Danmark. - 8790455983
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Flera viktiga vattenburna patogener i Norden kan smitta mellan djur och människor, exempelvis parasiten Cryptosporidium. Det finns flera skäl för dricksvattenproducenter att inkludera mikrobiologisk källspårning i kartläggningen av sina råvattentäkter, och EU:s ramdirektiv för vatten tar upp principen om att åtgärda vid föroreningskällan och att förorenaren betalar. Vi har använt kvantitativ PCR (qPCR) för att detektera genetiska markörer av ordningen Bacteroidales från människor och idisslare i vattenprov från Rådasjön, en dricksvattentäkt för mer än 500 000 invånare i Västsverige. Den humana markören återfanns på alla provpunkter omkring sjön och vid råvattenintaget på 16 m djup, generellt i högre halter än E. coli, vilken bekräftar en tydlig avloppspåverkan. Idisslarmarkören återfanns mer sporadiskt, med högst halter invid en strandbetesmark där ungdjur vistats under sommarhalvåret. Resultat från provtagningar vid regnhändelser i en bäck nära råvattenintaget bekräftade human förorening från uppströms liggande enskilda avlopp, medan idisslarmarkören på motsvarande sätt återfanns vid regnhändelser vid strandbetesmark. Den fekala kontamineringen vid råvattenintagen till följd av olika riskhändelser vid Rådasjön (sannolikhet) har sammanvägts med litteraturangiven potential hos olika genotyper av Cryptosporidium att orsaka infektion (konsekvens) i en riskmatris. Sammanvägningen visar att avloppsrelaterade riskhändelser vid denna sjö står för en avsevärt större risk för kryptosporidieinfektion än idisslarrelaterade riskhändelser. Resultaten visar att qPCR-detektion av genetiska markörer kan kasta nytt ljus över ursprunget till fekal förorening i ytvattentäkter, men bör kombineras med en bedömning av riskhändelser i det aktuella området.
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| 36. |
- 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
-
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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| 37. |
- Åström, Johan, 1977, et al.
(författare)
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Variability analysis of pathogen and indicator loads from urban wastewater systems along a river for drinking water risk estimations
- 2007
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Ingår i: Abstract, WaterMicro 2007. 14th International Symposium on Health-Related Water Microbiology. ; Extended abstract:P1036, s. 2-
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- BACKGROUND AND OBJECTIVESPathogens in source waters represent a health risk for drinking water consumers that may result in waterborne diseases, if not sufficiently removed within water treatment plants. According to the water safety plans in the WHO Drinking Water Guidelines (3rd ed.), identification and comparison of drinking water hazards within the catchment is of significant importance to accomplish effective risk management. In comparison to baseline concentrations significantly higher levels have been documented after heavy rainfalls (Kistemann et al. 2002; Signor et al. 2005) and a large number of waterborne outbreaks documented have been preceded by periods of heavy rainfalls (Rose et al. 2000; Curriero et al. 2001). Heavy rainfalls with wastewater discharges, in combination with treatment failures, resulted in the largest waterborne outbreak in Sweden in 1988. In this paper we have assessed the spatial and temporal distribution of wastewater discharges from urban areas along the river Göta älv used for drinking water supply to about 700 000 people including the city of Göteborg. The objectives were to assess the pathogen loads and variability by simulations of wastewater discharges from the urban sewage systems. The simulations have been compared with measured concentrations of pathogens and faecal indicator bacteria in the river.METHODSMicrobial point sources in municipal sewage systems along the river Göta älv, upstream the raw water intake to the city of Göteborg, were identified and quantified in relation to time and magnitude. Data on discharges of treated wastewater from wastewater treatment plants (WWTPs), as well as untreated wastewater from combined sewer overflows (CSOs) and sanitary sewer overflows (SSOs), were collected, including onsite monitoring and urban wastewater modelling results. Literature data on the concentrations as well as the reduction of indicator bacteria (E. coli and spores of clostridia), Campylobacter, noroviruses, Giardia and Cryptosporidium within sewage systems were used. Through Monte Carlo simulations the daily microbial loads to the river were calculated using pathogen concentrations and discharge information from the wastewater systems for each single discharge point. Microbial loads were calculated for baseline conditions and for rain event conditions, based on a half year data period. Baseline conditions were defined as dry weather periods with discharges predominantly of treated wastewater. Rain event conditions were separately described for two wet weather periods, including discharges from CSOs and SSOs. Assuming a total mixing of wastewater pathogens discharged into the river, the downstream microbial concentration was approximated and compared to sampling data on indicator and pathogens from the river Göta älv for the same data period.RESULTSThe discharge volumes of treated wastewater varied highly between WWTPs along the river as a function of persons connected and the portion of stormwater within the system. CSOs as well as SSOs activated during wet weather periods increased the discharge volumes from the urban sewer systems. Daily loads simulated for the indicator bacteria as well as the pathogens were presented in figures, showing the contributions for the separate municipalities along the river. In general, the pathogen loads during baseline conditions were defined by the flow and the number of persons connected to each system, while the pathogen loads during rain conditions were additionally set by the degree of combined and sanitary sewer overflows. Downstream positive detections of norovirus were made during a wet weather period with multiple discharges of combined and sanitary sewer overflows registered along the river, confirming the simulated results. Overall, the river concentrations approximated by these simulations, were in the same range for the faecal indicator bacteria as compared to sampling data for the same period, but higher for the Campylobacter and slightly lower for norovirus, Giardia and Cryptosporidium. CONCLUSIONS AND SIGNIFICANCE OF THE WORK In this study, local flow and volume registrations were used to theoretically assess the pathogen load along a river used as a source for drinking water production. The range of pathogen loads from the urban areas, as well as the differences between dry and wet weather conditions, illustrates the potential variability of source water pathogen concentrations. This information may be used for assumptions on pathogen concentration, such as within quantitative microbial risk assessments. Present simulation results also suggest a first prioritization for reduction of microbial loads within urban wastewater systems along this river, such as the need for local additional wastewater treatment steps in order to bring down the spread of pathogens. This investigation is also a starting point to further investigate presently unquantified microbial sources, such as unregistered CSOs, SSOs and animal contaminations, as well as the microbial effects from sedimentation, die-off and the downstream microbial transport mechanisms in the river.
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| 38. |
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