Labor- und Feldevaluationen der Performance innovativer Methoden der Trinkwasserbehandlung und sicherer Lagerung in Gebieten mit niedrigem Einkommen
Evaluation effektiver und nachhaltiger Interventionen, Strategien und Programme zu sauberem Trinkwasser
Evaluation der Wirkung des verbesserten Zugangs zu sauberem Trinkwasser
EPFL Lausanne, Department of Environmental Engineering. Course: "Sanitary engineering in developing countries"
ETH Zürich, Department of Civil and Environmental Engineering. Course: "Water supply, sanitation and waste infrastructure and services in developing countries."
Auszeichnungen und Preise
Schweizerischer Nachhaltigkeitspreis prix eco.ch, März 2017 mit dem Projekt "Sauberes Trinkwasser für Schulen und Gemeinden in Uganda mit Schwerkraftgetriebener Membranfiltration"
Spezialpreis des Energy Globe Awards, Oktober 2004 mit dem Projekt "SODIS, Solare Trinkwasserdesinfektion"
Dubai Internationaler Award Best Practice Certificate, UN-Habitat 2002, mit dem Projekt “SODIS, Solare Trinkwasserdesinfektion”
Mitglied des Steering Kommitees der Schweizerischen Expertengruppe und Community of Practice im Wasser und Siedlungshygiene Sektor (AGUASAN)
Mitglied des Stiftungsrates der Solaqua Stiftung
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Assessment of low-cost, non-electrically powered chlorination devices for gravity-driven membrane water kiosks in eastern Uganda
Recontamination during transport and storage is a common challenge of water supply in low-income settings, especially if water is collected manually. Chlorination is a strategy to reduce recontamination. We assessed seven low-cost, non-electrically powered chlorination devices in gravity-driven membrane filtration (GDM) kiosks in eastern Uganda: one floater, two in-line dosers, three end-line dosers (tap-attached), and one manual dispenser. The evaluation criteria were dosing consistency, user-friendliness, ease of maintenance, local supply chain, and cost. Achieving an adequate chlorine dosage (∼2 mg/L at the tap and ≥ 0.2 mg/L after 24 h of storage in a container) was challenging. The T-chlorinator was the most promising option for GDM kiosks: it achieved correct dosage (CD, 1.5-2.5 mg/L) with a probability of 90 per cent, was easy to use and maintain, economical, and can be made from locally available materials. The other in-line option, the chlorine-dosing bucket (40 per cent CD) still needs design improvements. The end-line options AkvoTur (67 per cent CD) and AquatabsFlo® (57 per cent CD) are easy to install and operate at the tap, but can be easily damaged in the GDM set-up. The Venturi doser (52 per cent CD) did not perform satisfactorily with flow rates > 6 L/min. The chlorine dispenser (52 per cent CD) was robust and user-friendly, but can only be recommended if users comply with chlorinating the water themselves. Establishing a sustainable supply chain for chlorine products was challenging. Where solid chlorine tablets were locally rarely available, the costs of liquid chlorine options were high (27-162 per cent of the water price).
Dössegger, L.; Tournefier, A.; Germann, L.; Gärtner, N.; Huonder, T.; Etenu, C.; Wanyama, K.; Ouma, H.; Meierhofer, R. (2021) Assessment of low-cost, non-electrically powered chlorination devices for gravity-driven membrane water kiosks in eastern Uganda, Waterlines, 40(2), 92-106, doi:10.3362/1756-3488.20-00014, Institutional Repository
Keeping water from kiosks clean: strategies for reducing recontamination during transport and storage in Eastern Uganda
Drinking water is frequently recontaminated during transport and storage when water is poured into jerrycans. To address this issue, three strategies aiming at reducing these recontamination risks were implemented at water kiosks in Eastern Uganda. In all three strategies, water at the kiosks was chlorinated to a free residual chlorine (FRC) concentration of 2 mg/L at the tap of the kiosk. In addition, water was collected in different containers for drinking water transport: a) uncleaned jerrycans, b) cleaned jerrycans, and c) cleaned improved containers with a wide mouth and a spigot. Water quality in the containers was compared to that of a control group collecting unchlorinated water in uncleaned jerrycans. Water samples were collected at the tap of the kiosk, from the containers of 135 households after they were filled at the tap, and from the same containers in the households after 24 h of water storage. The samples were analysed for counts of E. coli, total coliforms, and FRC. Household interviews and structured observations were conducted to identify confounding variables and to assess the influence of water, sanitation, and hygiene infrastructure and practices on recontamination.
All three intervention strategies contributed to significantly lower E. coli recontamination levels after 24 h than in the control group (Median (Mdn) = 9 CFU/100 mL, Interquartile Range (IQR) = 25). Median E. coli counts and mean FRC consumption were higher in uncleaned jerrycans (Median = 1 CFU/100 mL, IQR = 6, ΔFRC = 1.8 mg/L) than in cleaned jerrycans (Median = 0 CFU/100 mL IQR = 2, ΔFRC = 1.6 mg/L) and the lowest in cleaned improved containers (Median = 0 CFU/100 mL, IQR = 0, ΔFRC = 1.2 mg/L). The FRC concentration at the tap of 2 mg/L was too low to protect water from E. coli recontamination in uncleaned jerrycans over 24 h. Cleaning the jerrycans was inconvenient due to their small openings, therefore, sand was used. The cleaning with sand reduced recontamination with E. coli but did not reduce the count of total coliforms. Improved containers with a larger opening allowed for cleaning with a brush and showed the lowest levels of recontamination for both E. coli and total coliforms. In addition to the intervention strategies, households receiving a higher number of WASH education visits within the previous year had lower recontamination levels of E. coli in stored water (OR = 0.54, p = .003).
Gärtner, N.; Germann, L.; Wanyama, K.; Ouma, H.; Meierhofer, R. (2021) Keeping water from kiosks clean: strategies for reducing recontamination during transport and storage in Eastern Uganda, Water Research X, 10, 100079 (8 pp.), doi:10.1016/j.wroa.2020.100079, Institutional Repository
Advancements in and integration of water, sanitation, and solid waste for low- and middle-income countries
The water, sanitation, and solid waste sectors are closely related and have many interactions between their respective service chains in low-and middle-income countries. Currently, these interactions mostly lead to cross-contamination, and opportunities for co-benefits are seldom realized. This review presents the key advancements within each of these three development sectors in the past two decades. We identify numerous similarities such as decentralization, resource recovery, community involved planning, and digitalization. Despite the potential for synergies and the opportunities to maximize positive interactions, there have been few attempts to break the existing sectoral silos in order to integrate these three service chains. We argue that, with the right enabling environment, an integrated approach to holistically planning and implementing water supply, sanitation, and solid waste management can create positive interactions resulting in co-benefits among complementary development goals.
Association of nutrition, water, sanitation and hygiene practices with children's nutritional status, intestinal parasitic infections and diarrhoea in rural Nepal: a cross-sectional study
Background: Providing universal access to safe water, sanitation and hygiene (WASH) in remote Nepal remains challenging. We investigated WASH conditions and their association with children's nutritional status, intestinal parasitic infections and diarrhoea. Methods: Data was collected through a cross-sectional survey of 1427 households, including questionnaires, observations, stool analysis, anthropometry, water quality measurements, and assessment of clinical signs of nutritional deficiencies. Results: We found 55.5% of children were undernourished, 63.9% had clinical signs of nutritional deficiencies, 51.1% had intestinal parasitic infections and 52.2% had diarrhoea. Multivariate mixed logistic regression analysis revealed a statistically significant negative association between undernutrition and socio-economic level, with adjusted odds ratios (AOR) of 0.70 (95%-CI = 0.43-1.11) and 0.43 (95%-CI = 0.25-0.75) for high and intermediate levels compared to the lowest level. Undernutrition was negatively associated with regular deworming of children (AOR = 0.44, 95% CI = 0.20-0.94), food supplements (AOR = 0.57, 95% CI = 0.38-0.84), household's own food production (AOR = 0.67, 95% CI = 0.46-0.97) and personal hygiene (AOR = 0.83, 95% CI = 0.51-1.35). Nutritional deficiency was negatively associated with handwashing after cleaning a baby’s bottom (AOR = 0.60, 95% CI = 0.40-0.92) and cleanliness of caregiver's hands (AOR = 0.61, 95% CI = 0.41-0.89) and positively associated with keeping animals inside the house overnight (AOR = 1.71, 95% CI = 1.17-2.51) and the presence of total coliforms in the drinking water source (AOR = 10.44, 95% CI = 1.61-67.4). Diarrhoea was positively associated with intermittent water supply (AOR = 2.72, 95% CI = 1.18-6.31) and the presence of a mud floor (AOR = 2.29, 95% CI = 1.20-4.37) and negatively associated with cleanliness of the toilet (AOR = 0.68, 95% CI = 0.47-0.98), and the cleanliness of children’s hands (AOR = 0.62, 95% CI = 0.40-0.96). Conclusions: Our study found, more than half of the survey children were in a critical health condition. Results suggest that child health improvements are dependent on multiple public health improvements, including providing better nutrition, promoting adequate hygiene behaviour, such as handwashing, keeping the latrines clean, keeping the household environment free from animal faeces and assuring a reliable supply of safe water.
Shrestha, A.; Six, J.; Dahal, D.; Marks, S.; Meierhofer, R. (2020) Association of nutrition, water, sanitation and hygiene practices with children's nutritional status, intestinal parasitic infections and diarrhoea in rural Nepal: a cross-sectional study, BMC Public Health, 20(1), 1241 (21 pp.), doi:10.1186/s12889-020-09302-3, Institutional Repository
Does activated silver reduce recontamination risks in the reservoirs of ceramic water filters?
Efforts to provide safe water are challenged by recontamination and regrowth of pathogens in treated water during storage. This study evaluated the potential of metallic silver with a chemically etched surface to reduce recontamination risks during water storage in ceramic water filters. Batch experiments were conducted in the laboratory with water storage buckets containing three configurations of varying amounts of silver. Field trials in a rural area in Kenya assessed the effect of the same configurations in the storage buckets of locally produced ceramic pot filters without colloidal silver coating. The tests revealed that the etched silver slightly reduced microbiological recontamination risks during water storage despite the low diffusion of silver ions (<5 µg Ag/L). The effect was strongly influenced by water chemistry parameters. A statistically significant difference in the removal of E. coli (Δ Log Removal Value (LRV) = 0.6) and total coliforms (Δ LRV = 1.7) was found between households using a filter with silver in the water reservoir and those using a filter without silver. Multivariate regression of water handling factors and hygiene practices on filter performance revealed that the presence of silver in the reservoir and cleaning the filter element with a brush were associated with a better filter performance.
Meierhofer, R.; Rubli, P.; Oremo, J.; Odhiambo, A. (2019) Does activated silver reduce recontamination risks in the reservoirs of ceramic water filters?, Water, 11(5), 1108 (11 pp.), doi:10.3390/w11051108, Institutional Repository
Influence of container cleanliness, container disinfection with chlorine, and container handling on recontamination of water collected from a water kiosk in a Kenyan slum
The study assessed whether using clean containers that had been disinfected with chlorine at a water kiosk in the Kangemi slum in Nairobi reduced recontamination of treated water during drinking transport and storage. At the same time, the impacts of container handling and hygiene conditions at the household level on water quality changes during storage were evaluated. Data were collected during interviews with 135 households using either new, clean Maji Safi containers (MSCs) that had been disinfected with chlorine or normal uncleaned jerrycans (NJCs). Bacteriological water quality and free chlorine levels in both types of containers were measured after container filling at the kiosk and in the same containers after 24 h storage in households. The use of MSCs significantly reduced the risk of recontaminating the treated water. After water filling at the kiosk, none of the MSCs contained Escherichia coli bacteria, and 2.8% were contaminated after 24 h storage. In contrast, 6.2% of NJCs were contaminated after filling, and 15.2% after 24 h storage. Multivariate logistic regression indicated that the use of a clean water container and sufficient chlorine and the frequency of cleaning the container in the household mitigated recontamination. We suggest further investigation of water container designs that facilitate cleaning.
Meierhofer, R.; Wietlisbach, B.; Matiko, C. (2019) Influence of container cleanliness, container disinfection with chlorine, and container handling on recontamination of water collected from a water kiosk in a Kenyan slum, Journal of Water and Health, 17(2), 308-317, doi:10.2166/wh.2019.282, Institutional Repository
From water source to tap of ceramic filters - factors that influence water quality between collection and consumption in rural households in Nepal
The study assessed changes in water quality between the water source and the tap of locally produced low cost ceramic water filters used by a community living in hygienically critical conditions in a remote mountainous area in Western Nepal. Data was collected from 42 rural households during two visits. The effectiveness of filter handling on its performance was assessed through microbiological analysis, structured household interviews and structured observations. Water quality decreased significantly when source water was filled into transport containers, while the use of the filters improved drinking water quality for about 40% of the households. Highly inadequate filter cleaning practices involving the use of contaminated raw water, hands (geo mean = 110 E. coli CFU/100 mL) and cleaning tools (geo mean = 80 E. coli CFU/100 mL) stained hygienic parts of the filter. The use of boiling water to disinfect the filters was significantly correlated with improved filter performance and should be further promoted. However, even disinfected filters achieved a very low average LRV for E. coli of 0.4 in the field and performed worse than during laboratory tests (LRV for E. coli of 1.5-2). Comprehensive training on adequate filter handling, as well as better filter products, are required to improve the impact of filter use.
Meierhofer, R.; Bänziger, C.; Deppeler, S.; Kunwar, B. M.; Bhatta, M. (2018) From water source to tap of ceramic filters - factors that influence water quality between collection and consumption in rural households in Nepal, International Journal of Environmental Research and Public Health, 15(11), 2439 (14 pp.), doi:10.3390/ijerph15112439, Institutional Repository
GDM-Wasserkioske. Sauberes Trinkwasser für die ländliche Bevölkerung Ugandas
In ländlichen Gegenden Ugandas werden die an der Eawag entwickelten Ultrafiltrationsanlagen
eingesetzt, um die Versorgung mit sauberem Trinkwasser sicherzustellen. Die Anlagen an den
Ufern des Lake Victoria können mit sehr geringem Aufwand und ohne externe Ressourcen betrieben
werden. Wasserqualitätsuntersuchungen haben gezeigt, dass die Anlagen zuverlässig
sauberes Wasser liefern. Mit dem Verkauf des Wassers wird ein Einkommen generiert, das den
täglichen Betrieb und Unterhalt der Anlagen sichert.
Peter, M.; Meierhofer, R. (2018) GDM-Wasserkioske. Sauberes Trinkwasser für die ländliche Bevölkerung Ugandas, Aqua & Gas, 98(5), 36-39, Institutional Repository
Membrane filtration reduces recontamination risk in chlorinated household water containers
The study was conducted in the catchment area of two Gravity Driven Membrane Filtration (GDM) water kiosks in Uganda. It assessed if the cleaning and disinfection of jerrycans with chlorine can reduce risks for regrowth and recontamination of treated water during storage in undisturbed containers, as well as at the household level. In addition, the impact of water handling, household hygiene and safe storage determinants on water quality was evaluated. Results indicate that the cleanliness of the water storage container has a critical impact on water quality changes during storage. Safe drinking water at the point of consumption after 24 hours of storage at the household level can be achieved with a combination of ultrafiltration and subsequent chlorination.
Evaluating novel gravity-driven membrane (GDM) water kiosks in schools
This paper presents results of the field evaluation of three gravity driven membrane (GDM) water kiosks purifying Victoria lake water in schools in Uganda. The study evaluated the technical performance of the systems and the feasibility of the operation and maintenance concepts over two years of operation, as well as the financial viability of the business model and management concept and overall system sustainability. The results show that GDM water kiosks are a simple technology capable of treating turbid surface water and can autonomously supply good quality water to schools and communities. They require little maintenance, are simple to operate and maintain, and with trained local O&M team support, they offer sustainability of operation in remote low-income areas. The business and management model evaluation has not yet been completed and is ongoing.
Peter-Varbanets, M.; Dreyer, K.; McFadden, N.; Ouma, H.; Wanyama, K.; Etenu, C.; Meierhofer, R. (2017) Evaluating novel gravity-driven membrane (GDM) water kiosks in schools, In: WEDC conference 40, 2735 (7 pp.), Institutional Repository
Solar disinfection of viruses in polyethylene terephthalate bottles
Solar disinfection (SODIS) of drinking water in polyethylene terephthalate (PET) bottles is a simple, efficient point-of-use technique for the inactivation of many bacterial pathogens. In contrast, the efficiency of SODIS against viruses is not well known. In this work, we studied the inactivation of bacteriophages (MS2 and fX174) and human viruses (echovirus 11 and adenovirus type 2) by SODIS. We conducted experiments in PET bottles exposed to (simulated) sunlight at different temperatures (15, 22, 26, and 40°C) and in water sources of diverse compositions and origins (India and Switzerland). Good inactivation of MS2 (>6- log inactivation after exposure to a total fluence of 1.34 kJ/cm2) was achieved in Swiss tap water at 22°C, while less-efficient inactivation was observed in Indian waters and for echovirus (1.5-log inactivation at the same fluence). The DNA viruses studied, fX174 and adenovirus, were resistant to SODIS, and the inactivation observed was equivalent to that occurring in the dark. High temperatures enhanced MS2 inactivation substantially; at 40°C, 3-log inactivation was achieved in Swiss tap water after exposure to a fluence of only 0.18 kJ/cm2. Overall, our findings demonstrate that SODIS may reduce the load of single-stranded RNA (ssRNA) viruses, such as echoviruses, particularly at high temperatures and in photoreactive matrices. In contrast, complementary measures may be needed to ensure efficient inactivation during SODIS of DNA viruses resistant to oxidation.
Carratalà, A.; Calado, A. D.; Mattle, M. J.; Meierhofer, R.; Luzi, S.; Kohn, T. (2016) Solar disinfection of viruses in polyethylene terephthalate bottles, Applied and Environmental Microbiology, 82(1), 279-288, doi:10.1128/AEM.02897-15, Institutional Repository
Do sales models influence the purchase and use of ceramic filters in rural areas of Kenya and Bolivia?
Demand for safe water, as well as access to adequate and affordable products for drinking water treatment, is key for household water treatment (HWT) in low-income countries. Critical barriers, particularly in rural areas, are the lack of adequate marketing and sales models and the challenge of setting up distribution channels that reach low-income customers, leading to the unavailability of HWT products. Trials with four different social marketing and sales models, involving local Q1 entrepreneurs, staff of an NGO, community health workers and members of community-based organizations, were conducted in Kenya and Bolivia to test which marketing and sales strategies, as well as which behavioural determinants, influence product purchase and water treatment practices in different local contexts. Selling filters through the water utility, a community-based enterprise, was a promising retail model in Kenya and in Bolivia. Most successful were sales done by a women’s group in Bolivia. We found that community education activities, independent of the stakeholder carrying out the activity, are an important element to create demand for water treatment products. Other factors influencing product purchase and practice are very context specific and include: the turbidity of water, risk perception, socio-economic status, social norms and emotional attributes.
Meierhofer, R.; Flückiger, A. C.; Gebauer, H. (2016) Do sales models influence the purchase and use of ceramic filters in rural areas of Kenya and Bolivia?, Journal of Water Supply: Research and Technology AQUA, 65(1), 87-102, doi:10.2166/aqua.2015.069, Institutional Repository
The challenge of producing and marketing colloidal silver water filters in Nepal
Background: Obtaining safe drinking water can be a challenge in Nepal. By training potters and setting up production sites for Colloidal Silver Filters, several non-governmental organizations have tried to provide local people with a low-cost option for household water treatment. Out of 19 trained entrepreneurs, only four are currently producing filters. The goal of this evaluation was to find out what conditions lead to the successful continuation of the production and the reasons for failure. Methods: The evaluation of the potters was based on a Qualitative Comparative Analysis and the conditions looked at were: "Production", "Collaboration", "Market" and "Potter". Results: Analysis showed that production problems and insufficient demand led to the termination of ceramic filter production and that both trouble-free production and high demand are necessary for a sustainable business.
Assessing the societal benefits of applied research and expert consulting in water science and technology
Applied research and expert consulting are conducted at research institutions and universities that are supported by public investment. This is often justified on the basis of anticipated societal benefits. Thus it is incumbent on the institutions that conduct these activities to develop a sound basis for the assessment of their benefits and to be able to communicate these to the public.
Hering, J. G.; Hoffmann, S.; Meierhofer, R.; Schmid, M.; Peter, A. J. (2012) Assessing the societal benefits of applied research and expert consulting in water science and technology, GAIA: Ecological Perspectives for Science and Society, 21(2), 95-101, doi:10.14512/gaia.21.2.6, Institutional Repository
Gravity-driven membrane disinfection for household drinking water treatment
Ultrafiltration (UF) has been proven to be very effective in the treatment of water for the removal of particles, colloids and microorganisms. However, household application of UF is limited due to membrane fouling which results in complex and maintenance-intensive UF systems. In gravity-driven membrane disinfection (GDMD) technology, a stable membrane flux of 4-10 L.h-1m-2 is observed during ultrafiltration without any backflushing, chemical cleaning or an external energy supply for over 24 months, while operated at relatively low pressures (40-65 cm of water column). This novel approach to operate UF systems at stable flux conditions can be considered an important breakthrough in membrane technology, as it allows development of a robust, maintenance-free, low-cost and user-friendly household water treatment system, which has a great potential for implementation.
Peter-Varbanets, M.; Johnston, R.; Meierhofer, R.; Kage, F.; Pronk, W. (2011) Gravity-driven membrane disinfection for household drinking water treatment, In: Shaw, R. (Eds.), The future of water, sanitation and hygiene in low-income countries - innovation, adaptation and engagement in a changing world. Proceedings of the 35th WEDC international conference, Loughborough University, Loughborough, UK, 6-, 1086 (8 pp.), Institutional Repository
Health gains from solar water disinfection (SODIS): evaluation of a water quality intervention in Yaoundé, Cameroon
In developing countries, the burden of diarrhoea is still enormous. One way to reduce transmission of pathogens is by water quality interventions. Solar water disinfection (SODIS) is a low-cost and simple method to improve drinking water quality on household level. This paper evaluates the implementation of SODIS in slum areas of Yaoundé, Cameroon. Promoters trained 2,911 households in the use of SODIS. Two surveys with randomly selected households were conducted before (N = 2,193) and after (N = 783) the intervention. Using a questionnaire, interviewers collected information on the health status of children under five, on liquid consumption, hygiene and other issues. Prior to the intervention, diarrhoea prevalence amounted to 34.3% among children. After the intervention, it remained stable in the control group (31.8%) but dropped to 22.8% in the intervention group. Households fully complying with the intervention exhibited even less diarrhoea prevalence (18.3%) and diarrhoea risk could be reduced by 42.5%. Multivariate analyses revealed that the intervention effects are also observed when other diarrhoea risk factors, such as hygiene and cleanliness of household surroundings, are considered. According to the data, adoption of the method was associated with marital status. Findings suggest health benefits from SODIS use. Further promotional activities in low-income settings are recommended.
Graf, J.; Togouet, S. Z.; Kemka, N.; Niyitegeka, D.; Meierhofer, R.; Pieboji, J. G. (2010) Health gains from solar water disinfection (SODIS): evaluation of a water quality intervention in Yaoundé, Cameroon, Journal of Water and Health, 8(4), 779-796, doi:10.2166/wh.2010.003, Institutional Repository
Factors supporting the sustained use of solar water disinfection - experiences from a global promotion and dissemination programme
Every year, 1.8 million people, mainly children under the age of five, die of diarrhoea. Point-of-use water treatment methods, such as solar water disinfection (SODIS), reveal a great potential to reduce the global diarrhoea burden. Comprehensive microbiological research demonstrated the effectiveness of SODIS to destroy diarrhoea-causing pathogens in contaminated drinking water. Since the year 2000, SODIS is being promoted in developing countries through information and awareness campaigns, training and advising of the public sector (government institutions), networking activities, as well as user training at the grassroot level. The method is currently used in 33 countries by more than 2 million people. Several project evaluations and health impact studies reveal that the diarrhoea incidence of SODIS users has dropped by 16–57%. One year after project implementation, 20–80%of the trained people used SODIS on a regular basis. This paper looks into factors influencing acceptance and sustained use of SODIS on grassroot level, i.e. local availability of bottles, repeated promotion and training programmes, motivation and commitment of promoters, educational level of users, social pressure, and institutional aspects.
Water disinfection and hygiene behaviour in an urban slum in Kenya: impact on childhood diarrhoea and influence of beliefs
In this research project, we studied factors that presumably affect the incidence of diarrhoea among young children in urban slums in developing countries: consumption of safe drinks, hygiene behaviour, cleanliness of household surroundings and the quality of raw water. Beliefs concerning the causes of diarrhoea were also related to health-improving behaviour, namely the application of the water-treatment method SODIS (solar water disinfection) and hygiene behaviour. We conducted a survey in a shanty town in Nairobi, Kenya. Field workers interviewed 500 households. Analysis with regression models revealed that two out of the four postulated factors were significant: children have a lower risk of contracting diarrhoea when they consume high percentages of safe drinks and live in households with good hygiene. As regards beliefs, we found that biomedical knowledge of children's diarrhoea as well as the perceived social norm for treating water was associated with the use of SODIS and good hygiene.
Graf, J.; Meierhofer, R.; Wegelin, M.; Mosler, H.-J. (2008) Water disinfection and hygiene behaviour in an urban slum in Kenya: impact on childhood diarrhoea and influence of beliefs, International Journal of Environmental Health Research, 18(5), 335-355, doi:10.1080/09603120801966050, Institutional Repository
Does the reuse of PET bottles during solar water disinfection pose a health risk due to the migration of plasticisers and other chemicals into the water?
Solar water disinfection (SODIS) is a simple, effective and inexpensive water treatment procedure suitable for application in developing countries. Microbially contaminated water is filled into transparent polyethylene terephthalate (PET) plastic bottles and exposed to full sunlight for at least 6 h. Solar radiation and elevated temperature destroy pathogenic germs efficiently. Recently, concerns have been raised insinuating a health risk by chemicals released from the bottle material polyethylene terephthalate (PET). Whereas the safety of PET for food packaging has been assessed in detail, similar investigations for PET bottles used under conditions of the SODIS treatment were lacking until now. In the present study, the transfer of organic substances from PET to water was investigated under SODIS conditions using used colourless transparent beverage bottles of different origin. The bottles were exposed to sunlight for 17 h at a geographical latitude of 47° N. In a general screening of SODIS treated water, only food flavour constituents of previous bottle contents could be identified above a detection limit of 1 μg/L. Quantitative determination of plasticisers di(2-ethylhexyl)adipate (DEHA) and di(2-ethylhexyl)phthalate (DEHP) revealed maximum concentrations of 0.046 and 0.71 μg/L, respectively, being in the same range as levels of these plasticisers reported in studies on commercial bottled water. Generally, only minor differences in plasticiser concentrations could be observed in different experimental setups. The most decisive factor was the country of origin of bottles, while the impact of storage conditions (sunlight exposure and temperature) was less distinct. Toxicological risk assessment of maximum concentrations revealed a minimum safety factor of 8.5 and a negligible carcinogenic risk of 2.8 × 10−7 for the more critical DEHP. This data demonstrate that the SODIS procedure is safe with respect to human exposure to DEHA and DEHP.
Schmid, P.; Kohler, M.; Meierhofer, R.; Luzi, S.; Wegelin, M. (2008) Does the reuse of PET bottles during solar water disinfection pose a health risk due to the migration of plasticisers and other chemicals into the water?, Water Research, 42(20), 5054-5060, doi:10.1016/j.watres.2008.09.025, Institutional Repository