Department Water Resources and Drinking Water

Mitigation of geogenic groundwater contamination

Water Resource Quality (WRQ) was an integrated project running from 2006-2012 at Eawag that aimed to develop a generally applicable framework for the mitigation of geogenic contamination in groundwater used for drinking, in particular concerning arsenic and fluoride. We combined natural and social scientific expertise for the solution of a health problem that affects 100s of millions of people worldwide. The mitigation framework developed by the WRQ team from Eawag can help decision makers and water resource managers to identify contaminated regions and to provide feasible options to help reduce the effects of contamination.

Geogenic Contamination

Geogenic contamination refers to naturally occurring elevated concentrations of certain elements in groundwater (such as arsenic, fluoride, uranium or selenium) which have a negative health effect on humans consuming this water. Geogenic contamination of groundwater might be a result of geochemical characteristics of the aquifer material - eg. high concentrations of the contaminant in the rock matrix, dissolving during water-rock interaction, or occur due to environmental conditions such as an arid climate or reducing conditions in the aquifer which facilitate the contaminant to occur in a more mobile state.

The most wide-spread geogenic contaminants are arsenic and fluoride, affecting the health of hundreds of millions of people worldwide.

Fluoride

Fluoride is the 13th most abundant element in the earth’s crust (625 mg/kg) and exists in trace amounts in almost all groundwaters across the world. According to estimations from UNESCO, more than 200 million people worldwide rely on drinking water with fluoride concentrations exceeding the present WHO guideline of 1.5 mg/L. Fluorosis, associated with elevated fluoride concentrations in drinking water has been reported in a range of countries.

While low fluoride intake may prevent dental caries, excess intake causes different types of fluorosis; primarily dental and skeletal fluorosis. White line striations on the teeth followed by brown patches and, in severe cases, brittling of the enamel are common symptoms of dental fluorosis. This is not only a health problem but also has psychological and social impacts, as people are ashamed and possibly ostracised due to their bad teeth. Skeletal fluorosis first causes pain in different joints, then limits joint movement, leading to stiffness and skeletal crippling. Besides dental and skeletal fluorosis, other manifestations such as nervousness, depression and muscle weakness have been reported in connection with high fluoride intake.

More information

Where does fluoride groundwater contamination occur?

What are the effects of fluoride on human health?

International Society for Fluoride Research

WHO: Fluoride in Drinking Water
 

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OLYMPUS DIGITAL CAMERA

Arsenic

The WHO guideline value for arsenic in drinking water has been set to 10 µg/L, though in several countries higher values are used (e.g. 50 µg/L in China).

High arsenic concentrations in groundwater have been found to be responsible for health problems summarized under the term arsenicosis, which develop over a period of several years. Symptoms of arsenicosis range from skin disorders (melanosis, keratosis) to cardiovascular diseases, cancer and the impairment of the neurodevelopment of children. Since there is no cure for arsenicosis to date, the provision of safe water for the prevention of this disease is the vital mitigation approach.

More information

Where does arsenic groundwater contamination occur?

What are the effects of arsenic on human health?

WHO: Arsenic in Drinking Water
 

Team

WRQ was an inter-disciplinary project and the development of the framework relied on the integration of expertise from a range of fields. An understanding of the physical system, together with socio-economic and behavioural factors at different scales were necessary. Scientists from three Eawag departments were involved:

The project team therefore comprised geochemical specialists, modelers and social scientists and relied on the cooperation with valuable global partners. It was initiated and led by Dr. Annette Johnson, who passed away in November 2015. One of her special areas was the handling of geogenic trace substances in ground water and drinking water (click for further information on Annette Johnsons research).
 

WRQ team at Eawag

Dr. Michael Berg Head of Department Tel. +41 58 765 5078 Send Mail
  • GIS modelling and arsenic removal
  • WRQ project management
Dr. Stephan Hug Tel. +41 58 765 5454 Send Mail
  • Arsenic removal
  • Deep well evaluation
Dr. Joel Podgorski Tel. +41 58 765 5760 Send Mail
  • GIS modelling and arsenic removal
  • Development of online GIS modelling tools
Ruth Scheidegger Tel. +41 58 765 5502 Send Mail
  • Material flow analysis
  • Uptake of fluoride through food and water
  • Institutional and socio-economic research

Former team members

Dr. Annette Johnson

WRQ project manager
Fluoride removal and GIS modelling

Dr. Chris Zurbrügg

WRQ project management

Dr. Christoph Lüthi

Institutional settings and enabling environments

Dr. Hansi Mosler

Psychological acceptance and promotion studies

Anja Bretzler

WRQ managing assistant
Fluoride removal filters

Dr. Luis Rodriguez-Lado

Post-doctoral researcher
Development of online GIS modelling tools

Dr. Hanspeter Bader

Material flow analysis

Jennifer Inauen

 

Alexandra Huber

 

Lars Osterwalder

 

Dr. Heiko Gebauer

 

Dr. Richard Johnston

 

Dr. Manouchehr Amini

 

Dr. Lenny Winkel

 

Dr. Robert Tobias

 

Dr. Nasreen Khan

 

Yama Tomonaga

 

Kim Müller

 

Thomas Rosenberg

 

Partners

The WRQ team maintains partnerships with research institutions and NGOs in a range of countries where problems occur due to geogenic contamination of drinking water.

Ethiopia

Addis Ababa University, Ethiopia

In 2009 Eawag and Addis Ababa University (AAU) launched a three-year research project funded by the Swiss National Science Foundation and the Swiss Agency for Development and Cooperation (SNF-SDC) with the title “Optimization and Acceptance of Fluoride Removal Options in Rural Ethiopia”.

The WRQ fluoride removal team is working together with Dr. Feleke Zewge from AAU's Chemistry Department and Head of the Fluorosis Mitigation Office on the development and testing of different filter materials based on aluminium oxide or calcium phosphate for the removal of fluoride from drinking water.

The institutional support for the implementation of fluoride mitigation strategies is being investigated in cooperation with Prof. Yacob Arsano from the Department of Political Science and International Relations.

 

Non-Government Organisations (NGOs)

Field trials of bone char-based filters on a household as well as community scale are being undertaken in rural communities in the Rift Valley in cooperation with the Oromo Self-Help Organisation (OSHO) and Swiss Interchurch Aid (HEKS). OSHO offers vital assistance in the implementation, distribution and monitoring of filters and in the realisation of household surveys on filter use and acceptance. We are grateful to HEKS for their financial support

Bangladesh

Extensive work on arsenic mitigation in Bangladesh would not be possible without the cooperation with a range of local partners:

1) Dr. Kazi Matin Ahmed, professor in the University of Dhaka's Geology Department, is a global expert on arsenic contamination of groundwater. We work together in assessing the quality of groundwater in  different geological units, not only in terms of arsenic but other chemical parameters including iron, manganese, and salinity. By identifying strata which yield favorable water for all chemical parameters, new water sources can be installed which truly provide safe drinking water.


2) UNICEF Bangladesh has been one of the leading agencies responding to the arsenic threat facing Bangladesh. Our team of environmental psychologists is fielding surveys with support from UNICEF to identify the driving psychological factors which cause people to adopt (or to not adopt) new arsenic-safe sources of drinking water. Results will inform an ongoing revision of UNICEF's arsenic communication strategy. Our team members also coordinate with UNICEF Bangladesh on interpretation of nation-wide drinking water quality surveys.

3)  SONO Technology Research (STR), LTD, Kushtia, Bangladesh and Prof. Abul Hussam of George Mason University (GMU) in Fairfax, Virginia, USA, have developed the award-winning SONO arsenic removal filter. In collaboration with STI and Prof. Abul Hussam, Eawag scientists have carried out research to test the long-term performance of the filters and help to better understand the physical and chemical processes in the different filter sections.

4) Dhaka Community Hospital

Kenya

Catholic Diocese of Nakuru

 

In spring 2006, Eawag and the Catholic Diocese of Nakuru (CDN) launched a joint collaboration with the main objectives:

  • to further develop and optimize a low-cost defluoridation method known as contact precipitation
  • to investigate the removal processes for bone char defluoridation and contact precipitation
  • to foster implementation and dissemination of apatite-based defluoridation treatment

The Water Programme of the Catholic Diocese of Nakuru (CDN) was created in 1985. Today the Programme employs approximately 60 people and operates in several areas within Eastern Africa. Major activities are: drilling of deep wells, construction of water schemes and rainwater harvesting.

While working on the different water projects it became apparent that high levels of fluoride in the raw water lead to negative health impacts, commonly known as fluorosis. In 1998, a new section called CDN Water Quality (CDN WQ) was initiated as part of the Water Programme that took over the challenge to find a way to reduce fluoride levels in the water for safe human consumption.

CDN WQ comprises four working groups dealing with the production of bone char and calcium phosphate pellets, filter implementation, water quality testing and awareness creation. Up to date, more than 50 community and 1,000 household filters for fluoride removal have been implemented by CDN WQ in different parts of Kenya.

For further information, please contact info@cdnwaterquality.co.ke

China

Since September 2009, researchers from the Research Center for Eco-Environmental Sciences in Beijing and from the China Medical University in Shenyang are our partners in the REMARC project (Risk Maps of Arsenic Contamination in Groundwaters of China). Their valuable contribution to the project made it possible to dispose of a database of 2,369 sampling points covering the provinces of Inner Mongolia, Gansu, Shanxi, Heilongjiang and Ningxia that will be used to build the risk models.

 

Mr. Guifan Sun
(Prof., MD)
Arsenic and Fluoride Research Centre, School of Public Health, China Medical University.
No. 92 Bei Er Road, Heping District, Shenyang, PR China, Postal Code: 110001
Telephone: +86-24-2326-1744
Fax: +86-24-2326-1744
E-mail: sungf@mail.cmu.edu.cn

Prof Dr. Jianbo Shi
(Researcher, PhD)
State Key Laboratory of Environmental Chemistry and Ecotoxicology
Research Center for Eco-Environmental Sciences.
Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, China.
Telephone: +86-10-6284 9334
E-mail: jbshi@rcees.ac.cn

Ms. Quanmei Zheng,
(Prof., MD)
Department of Geochemical Diseases, School of Public Health, China Medical University.
No. 92 Bei Er Road, Heping District, ShenyanChina Medical University.
No. 92 Bei Er Road, Heping District, Shenyang, PR China, Postal Code: 110001
Telephone: +86-24-2326-1744
Fax: +86-24-2326-1744
E-mail: qmzheng@mail.cmu.edu.cn

Ms. Shuhua Xi
(Prof. PhD.)
Department of Geochemical Diseases, School of Public Health, China Medical University.
No. 92 Bei Er Road, Heping District, Shenyang China Medical University.
No. 92 Bei Er Road, Heping District, Shenyang, PR China, Postal Code: 110001
Telephone: +86-24-2326-1744
Fax: +86-24-2326-1744
E-mail: shxi@mail.cmu.edu.cn

Qiang Zhang
(PhD student)
Arsenic and Fluoride Research Centre, School of Public Health, China Medical University.
No. 92 Bei Er Road, Heping District, Shenyang, PR China, Postal Code: 110001
Telephone: +86-24-2326-1744
Fax: +86-24-2326-1744
E-mail: z2008@gmail.com

Iran

Isfahan University of Technology (IUT)

 

Eawag has long standing working relations with the College of Agriculture of Isfahan University of Technology (IUT) in Iran. In the past we have collaborated in many projects, including:

  • Cation exchange capacity of arid soils [1]
  • Mapping risk of cadmium and lead [2]
  • Modelling cadmium variability [3]
  • Modelling runoff and erosion using SWAT [4]
  • Estimation of field capacity and wilting point for arid soils of central Iran from basic soil physical and chemical properties [5]
  • Spatial and temporal variations of nitrate concentration in the groundwaters of Isfahan province, central Iran
  • Temporal and spatial variability of soil moisture in Iran
  • Assessment of regional water endowments, water constraints to food production, and implications for virtual water trade in Iran
  • Hydrologic and water quality modeling of Zayandehrud Watershed
  • Transport of cadmium, zinc, copper, and lead in a sewage sludge amended calcareous soil
  • Estimating soil shear strength, saturated hydraulic conductivity and infiltration using pedotransfer function and artificial neural network


[1] Amini, M., K. C. Abbaspour, H. Khademi, N. Fathianpour, M. Afyuni, and R. Schulin. 2005. Neural Network Models to predict Cation Exchange Capacity in Arid Regions of Iran. European Journal of Soil Science. 56 (4): 551-559.

[2] Amini, M. Afyuni, H. Khademi, K. C. Abbaspour, R. Schulin. 2005. Mapping risk of cadmium and lead contamination to human health in soils of Central Iran. Science of Total Environment 347:54-77.

[3] Amini, M., M. Afyuni, H. Khademi, K. C. Abbaspour. 2005. Variability of Available Cadmium in Relation to Soil Properties and Landuse in Arid region of Central Iran. Water Air and Soil Pollution, 162:205-218.

[4] Rostamian, R., S. F. Mousavi, M. Heidarpour, M. Afyuni and K. C. Abbaspour. 2007. Application of SWAT Model for Estimating Runoff and Sediment in a Mountainous Watershed in Central Iran. The fourth International SWAT conference, Delft, Netherland.

[5] Nourbakhsh, F. M. Afyuni, K.C. Abbaspour, and R. Schulin. 2005. Estimation of field capacity and wilting point from basic soil physical and chemical properties. Arid Land Research and Management. 19:81-85.

Our research partners at IUT have agreed to collaborate with the WRQ project for a more detail and comprehensive study of F in Iran. The IUT collaborators include:

Prof. Majid Afyuni Environmental Soil Physics
Prof. Seyed Farhad Mousavi Groundwater Resources
Prof. Hossein Khademi Soil Minerology and Genesis
Dr. Ahmad Khatoonabadi
Social Science
Dr. Amir Khoshgoftar Soil Chemist

Vietnam

Hanoi University of Science: Centre of Environmental Technology and Sustainable Development

 

A long-term education and research partnership has been established between the Swiss Federal Institute of Aquatic Science and Technology (Eawag) and the Hanoi University of Science. Capacity building is accomplished by applied research projects in environmental chemistry and environmental engineering, as well as in pilot-scale and scaling-up studies for enhancing drinking water quality. Senior Vietnamese researchers and graduated students are educated in project planning and performing research including a strong emphasis on analytical quality control and elaborate data interpretation.

Arsenic contamination of groundwater and drinking water in Vietnam was discovered in 1998 within this capacity building program [1]. This finding has led to manifold studies, such as

  • research on arsenic removal options [2]
  • investigating the levels and state of human arsenic exposure [3]
  • development of a low-cost biosensor for arsenic analysis [4]
  • elucidation of geochemical mechanism(s) leading to arsenic contamination of groundwater [5]
  • blanket groundwater surveys of the Red River Delta (Northern Vietnam) and the Mekong Delta (Cambodia and Southern Vietnam) [3, 6]


[1] “Arsenic Contamination of Groundwater and Drinking Water in Vietnam: A Human Health Threat.” Berg M. et al. 2001, Environ. Sci. Technol. 35, 2621–2626.

[2] “Arsenic Removal from Groundwater by Household Sand Filters: Comparative Field Study, Model Calculations, and Health Benefits.” Berg M. et al. 2006, Environ. Sci. Technol. 40, 5567–73.

[3] “Magnitude of arsenic pollution in the Mekong and Red River Deltas – Cambodia and Vietnam.” Berg M. et al. 2007, Sci. Total Environ. 372, 413–425.

[4] “Bacterial Bioassay for Rapid and Accurate Analysis of Arsenic in Highly Variable Groundwater Samples.” Trang et al. 2005, Environ. Sci. Technol. 39, 7625–30.

[5] “Hydrological and Sedimentary Controls Leading to Arsenic Contamination of Groundwater in the Hanoi Area, Vietnam.” Berg M. et al. submitted.

[6] “Arsenic and Manganese Contamination of Drinking Water Resources in Cambodia: Coincidence of Risk Areas with Low Relief Topography.” Buschmann et al 2007, Environ. Sci. Technol. 41, 2146–2152.

 

Publications

Water Quality

Statistical modeling of global geogenic arsenic contamination in groundwater

Contamination of groundwaters with geogenic arsenic poses a major health risk to millions of people. Although the main geochemical mechanisms of arsenic mobilization are well understood, the worldwide scale of affected regions is still unknown. In this study we used a large database of measured arsenic concentration in groundwaters (around 20,000 data points) from around the world as well as digital maps of physical characteristics such as soil, geology, climate, and elevation to model probability maps of global arsenic contamination. A novel rule-based statistical procedure was used to combine the physical data and expert knowledge to delineate two process regions for arsenic mobilization: “reducing” and “high-pH/oxidizing”. Arsenic concentrations were modeled in each region using regression analysis and adaptive neuro-fuzzy inferencing followed by Latin hypercube sampling for uncertainty propagation to produce probability maps. The derived global arsenic models could benefit from more accurate geologic information and aquifer chemical/physical information. Using some proxy surface information, however, the models explained 77% of arsenic variation in reducing regions and 68% of arsenic variation in high-pH/oxidizing regions. The probability maps based on the above models correspond well with the known contaminated regions around the world and delineate new untested areas that have a high probability of arsenic contamination. Notable among these regions are South East and North West of China in Asia, Central Australia, New Zealand, Northern Afghanistan, and Northern Mali and Zambia in Africa.
Amini, M.; Abbaspour, K. C.; Berg, M.; Winkel, L.; Hug, S. J.; Hoehn, E.; Yang, H.; Johnson, C. A. (2008) Statistical modeling of global geogenic arsenic contamination in groundwater, Environmental Science and Technology, 42(10), 3669-3675, doi:10.1021/es702859e, Institutional Repository

Statistical modeling of global geogenic fluoride contamination in groundwaters

The use of groundwater with high fluoride concentrations poses a health threat to millions of people around the world. This study aims at providing a global overview of potentially fluoride-rich groundwaters by modeling fluoride concentration. A large database of worldwide fluoride concentrations as well as available information on related environmental factors such as soil properties, geological settings, and climatic and topographical information on a global scale have all been used in the model. The modeling approach combines geochemical knowledge with statistical methods to devise a rule-based statistical procedure, which divides the world into 8 different “process regions”. For each region a separate predictive model was constructed. The end result is a global probability map of fluoride concentration in the groundwater. Comparisons of the modeled and measured data indicate that 60−70% of the fluoride variation could be explained by the models in six process regions, while in two process regions only 30% of the variation in the measured data was explained. Furthermore, the global probability map corresponded well with fluorotic areas described in the international literature. Although the probability map should not replace fluoride testing, it can give a first indication of possible contamination and thus may support the planning process of new drinking water projects.
Amini, M.; Mueller, K.; Abbaspour, K. C.; Rosenberg, T.; Afyuni, M.; Møller, K. N.; Sarr, M.; Johnson, C. A. (2008) Statistical modeling of global geogenic fluoride contamination in groundwaters, Environmental Science and Technology, 42(10), 3662-3668, doi:10.1021/es071958y, Institutional Repository

Predicting groundwater arsenic contamination in Southeast Asia from surface parameters

Arsenic contamination of groundwater resources threatens the health of millions of people worldwide, particularly in the densely populated river deltas of Southeast Asia. Although many arsenic-affected areas have been identified in recent years, a systematic evaluation of vulnerable areas remains to be carried out. Here we present maps pinpointing areas at risk of groundwater arsenic concentrations exceeding 10 g l-1. These maps were produced by combining geological and surface soil parameters in a logistic regression model, calibrated with 1,756 aggregated and geo-referenced groundwater data points from the Bengal, Red River and Mekong deltas. We show that Holocene deltaic and organic-rich surface sediments are key indicators for arsenic risk areas and that the combination of surface parameters is a successful approach to predict groundwater arsenic contamination. Predictions are in good agreement with the known spatial distribution of arsenic contamination, and further indicate elevated risks in Sumatra and Myanmar, where no groundwater studies exist.
Winkel, L.; Berg, M.; Amini, M.; Hug, S. J.; Johnson, C. A. (2008) Predicting groundwater arsenic contamination in Southeast Asia from surface parameters, Nature Geoscience, 1, 536-542, doi:10.1038/ngeo254, Institutional Repository

Hydrogeological survey assessing arsenic and other groundwater contaminants in the lowlands of Sumatra, Indonesia

Groundwater conditions in the lowlands of Sumatra, where peat swamps are the dominant landscape, were investigated. Based on topography, soil and geological surface properties, this large area (about 100,000 km2) is vulnerable to groundwater As enrichment under reducing aquifer conditions. The reconnaissance groundwater survey was conducted in the province of South Sumatra, covering both presumed low- and high-risk areas of As enrichment. Five distinct types of groundwater were recognized, reflecting a variety of geological sources and chemical conditions which are understood to be typical for the whole east coast of Sumatra. Groundwater collected from tubewells in the youngest (Holocene) swamp deposits had elevated As concentrations (>10 μg L−1) with a maximum of 65 μg L−1. Other elements exceeding the WHO drinking water guideline values include B, Mn, and Se. In contrast to large deltas of continental South and SE Asia, significantly lower sediment loads are transported by the rivers of Sumatra. The organic-rich Holocene sediments are hence relatively thin. Tubewells tapping the oldest geological formations of the study area (middle Miocene to Pliocene) have a broad range of redox conditions reflecting variations in aquifer geochemistry. This group is generally characterized by alkaline pH conditions and high contents of Na, B, Se, and Sr. Oxic groundwaters were found in regions elevated above 20 m a.s.l. and are characterized by low concentrations of dissolved solids and acidic pH values (average 5.1). To date, groundwater data for the increasingly populated island of Sumatra are non-existent in the international literature and this study thus provides a basis for future in-depth groundwater studies. The complete georeferenced database of groundwater analysis is provided as supplementary material.
Winkel, L.; Berg, M.; Stengel, C.; Rosenberg, T. (2008) Hydrogeological survey assessing arsenic and other groundwater contaminants in the lowlands of Sumatra, Indonesia, Applied Geochemistry, 23(11), 3019-3028, doi:10.1016/j.apgeochem.2008.06.021, Institutional Repository
Berg, M.; Amini, M.; Hug, S. J.; Johnson, C. A.; Winkel, L. (2010) Delineating areas of groundwater arsenic contamination from surface parameters and geology at depth, In: Jean, J.-S.; Bundschuh, J.; Bhattacharya, P. (Eds.), Arsenic in geosphere and human diseases. As-2010. Proceedings of the 3rd international congress on arsenic in the environment, 79-81, Institutional Repository
Rodríguez-Lado, L.; Amini, M.; Johnson, C. A.; Berg, M.; Sun, G.; Zhang, Q.; Shi, J.; Zhang, K. (2010) Potential arsenic hazard risk in groundwater in China, In: Jean, J.-S.; Bundschuh, J.; Bhattacharya, P. (Eds.), Arsenic in geosphere and human diseases. As-2010. Proceedings of the 3rd international congress on arsenic in the environment, 154-155, Institutional Repository

Contamination of drinking water resources in the Mekong delta floodplains: arsenic and other trace metals pose serious health risks to population

This study presents a transnational groundwater survey of the 62,000 km2 Mekong delta floodplain (Southern Vietnam and bordering Cambodia) and assesses human health risks associated with elevated concentrations of dissolved toxic elements. The lower Mekong delta generally features saline groundwater. However, where groundwater salinity is <1 g L− 1 Total Dissolved Solids (TDS), the rural population started exploiting shallow groundwater as drinking water in replacement of microbially contaminated surface water. In groundwater used as drinking water, arsenic concentrations ranged from 0.1–1340 µg L− 1, with 37% of the studied wells exceeding the WHO guidelines of 10 µg L− 1 arsenic. In addition, 50% exceeded the manganese WHO guideline of 0.4 mg L− 1, with concentrations being particularly high in Vietnam (range 1.0–34 mg L− 1). Other elements of (minor) concern are Ba, Cd, Ni, Se, Pb and U. Our measurements imply that groundwater contamination is of geogenic origin and caused by natural anoxic conditions in the aquifers. Chronic arsenic poisoning is the most serious health risk for the ~2 million people drinking this groundwater without treatment, followed by malfunction in children's development through excessive manganese uptake. Government agencies, water specialists and scientists must get aware of the serious situation. Mitigation measures are urgently needed to protect the unaware people from such health problems.
Buschmann, J.; Berg, M.; Stengel, C.; Winkel, L.; Sampson, M. L.; Trang, P. T. K.; Hung Viet, P. (2008) Contamination of drinking water resources in the Mekong delta floodplains: arsenic and other trace metals pose serious health risks to population, Environment International, 34(6), 756-764, doi:10.1016/j.envint.2007.12.025, Institutional Repository

Modelling arsenic hazard in Cambodia: a geostatistical approach using ancillary data

The As concentration in shallow groundwater in Cambodia was estimated using 1329 georeferenced water samples collected during the period 1999–2004 from wells between 16–100 m depth. Arsenic concentrations were estimated using block regression-kriging on the log transformed As measurements. Auxiliary raster maps (DEM-parameters, remote sensing images and geology) were converted to 16 principal components that were used to explain the distribution of As over the study area. The regression-kriging model was validated using an external set of 276 samples, and the results were compared to those obtained by ordinary block kriging. The regression analysis revealed that there is a good correlation between topographic environmental variables and the content of As in groundwater. This result is broadly consistent with the findings of previous studies and is not unexpected given models of microbial mediated As mobilization in recent low lying sediments. Kândal, Prey Vêng and Kâmpóng Cham are the provinces with the highest potential As hazard, indicating the requirement for development and implementation of policy control measures. The regression-kriging model explained 48% of the variability in the validation set. However, the model does not show good results for the prediction of high As concentration. This points to the existence of local environmental factors, not captured by this model, that highly influence the mobilization of As in groundwater. Even if the results of the validation of regression-kriging and ordinary kriging are similar, the regression kriging approach provides a more realistic description of the distribution of As since it also captures the large-scale variation of As in the study area.
Rodríguez Lado, L.; Polya, D.; Winkel, L.; Berg, M.; Hegan, A. (2008) Modelling arsenic hazard in Cambodia: a geostatistical approach using ancillary data, Applied Geochemistry, 23(11), 3010-3018, doi:10.1016/j.apgeochem.2008.06.028, Institutional Repository

Hydrological and sedimentary controls leading to arsenic contamination of groundwater in the Hanoi area, Vietnam: the impact of iron-arsenic ratios, peat, river bank deposits, and excessive groundwater abstraction

Groundwater contamination by arsenic in Vietnam poses a serious health threat to millions of people. In the larger Hanoi area, elevated arsenic levels are present in both, the Holocene and Pleistocene aquifers. Family-based tubewells predominantly tap the Holocene aquifer, while the Hanoi water works extract more than 600,000 m3/day of groundwater from the Pleistocene aquifer. Detailed groundwater and sediment investigations were conducted at three locations exhibiting distinct geochemical conditions, i.e., i) high levels of dissolved arsenic (av. 121 µg/L) at the river bank, ii) low levels of dissolved arsenic (av. 21 µg/L) at the river bank and, iii) medium levels of dissolved arsenic (60 µg/L) in an area of buried peat and excessive groundwater abstraction. Seasonal fluctuations in water chemistry were studied over a time span of 14 months.
Sediment-bound arsenic (1.3–22 µg/g) is in a natural range. Arsenic correlates with iron (r2>0.8) with variation related to grain size. Sediment leaching experiments showed that arsenic can readily be mobilized at each of the three locations. Low levels of arsenic in groundwater (<10 µg/L) generally exhibit manganese reducing conditions, whereas elevated levels are caused by reductive dissolution under iron- and sulphate reducing conditions. Average arsenic concentrations in groundwater are twofold higher at the river bank than in the peat area. The lower levels of arsenic contamination in the peat area are likely controlled by the high abundance of iron present in both the aqueous and sediment phases. With median molar Fe/As ratios of 350 in water and 8700 in the sediments of the peat area, reduced iron possibly forms new mineral phases that resorb (or sequester) previously released arsenic to the sediment. Despite similar redox conditions, resorption is much less significant at the river bank (Fe/As(aq)=68, Fe/As(s)=4700), and hence, arsenic concentrations in groundwater reach considerably higher levels.
Drawdown of Holocene water to the Pleistocene aquifer in the peat area, caused by the pumping for the Hanoi water works, clearly promotes reducing conditions in Pleistocene groundwater. This demonstrates that excessive abstraction of water from deep wells, i.e., wells tapping water below the arsenic burdened depth, can cause a downward shift of iron-reducing conditions and concurrently mobilize arsenic along the way.
Vertical migration of reduced groundwater may also impact aquifers under natural hydrological conditions. Seepage of DOC-enriched groundwater derived from degradation of organic matter in the clayey sediments at the river bank was observed to enhance (and maintain) iron-reducing conditions in the aquifer where organic matter is scarce. Once the aquifer becomes reduced, arsenic is released from the aquifer solid-hosts but additionally derives from the arsenic-enriched groundwater seeping from the clay into the aquifer. This behaviour is an important mechanism for arsenic contamination in aquifers that might not necessarily contain enough organic matter in their sediments to induce reducing conditions independently.
Berg, M.; Trang, P. T. K.; Stengel, C.; Buschmann, J.; Hung Viet, P.; Van Dan, N.; Giger, W.; Stüben, D. (2008) Hydrological and sedimentary controls leading to arsenic contamination of groundwater in the Hanoi area, Vietnam: the impact of iron-arsenic ratios, peat, river bank deposits, and excessive groundwater abstraction, Chemical Geology, 249(1–2), 91-112, doi:10.1016/j.chemgeo.2007.12.007, Institutional Repository

Impact of sulfate reduction on the scale of arsenic contamination in groundwater of the Mekong, Bengal and Red River deltas

Arsenic-enriched groundwater has been a pressing human health issue for more than a decade, with tens of millions of people worldwide being at risk of chronic As poisoning through the consumption of As-burdened groundwater. To elucidate the importance of dissolved S on the scale of As concentrations, the composition of groundwater samples from 926 locations spanning over the floodplains of three severely arsenic affected regions in Asia (Bengal-, Mekong-, Red River deltas), were assessed. A binary mixing model based on Cl− or B as conservative tracers implies that two types of water may be regarded as end-members with respect to groundwater composition in these deltas, namely surface derived water (approximated by river water) and saline water identical to residual sea water. Six redox zones were distinguished by comparing the model-calculated concentrations with the measured values. Only one zone (denoted methanogenic) had very high average As concentrations and they were significantly higher than in the other zones – for all three regions, regardless of applying Cl− or B as a tracer in the model. Average As concentrations ± standard error in the methanogenic zone were 182 ± 23 μg L−1 (n = 50%), 41 ± 6 μg L−1 (n = 43%), and 61 ± 20 μg L−1 (n = 24%) in the Mekong, Red River and Bengal delta, respectively. Arsenic levels were significantly lower in the SO4-reducing and the Fe-reducing zones, where averages were 23 ± 7 μg L−1 (n = 27%, zone I), 14 ± 3 μg L−1 (n = 48%, zone S) and 26 ± 9 μg L−1 (n = 64%, zone S). These results suggest that a sufficient supply of inhibits the release of As to groundwater and that reduction may be as important as Fe reduction in controlling the enrichment of As in groundwater.
Buschmann, J.; Berg, M. (2009) Impact of sulfate reduction on the scale of arsenic contamination in groundwater of the Mekong, Bengal and Red River deltas, Applied Geochemistry, 24(7), 1278-1286, doi:10.1016/j.apgeochem.2009.04.002, Institutional Repository

Water Resources / Water Availability

Application of a SWAT model for estimating runoff and sediment in two mountainous basins in central Iran

The Soil and Water Assessment Tool (SWAT) was used to model runoff and sediment in the Beheshtabad (3860 km2) and Vanak (3198 km2) watersheds in the northern Karun catchment in central Iran. Model calibration and uncertainty analysis were performed with sequential uncertainty fitting (SUFI-2), which is one of the programs interfaced with SWAT, in the package SWAT-CUP (SWAT Calibration Uncertainty Programs). Two measures were used to assess the goodness of calibration and uncertainty analysis: (a) the percentage of data bracketed by the 95% prediction uncertainty (95PPU) (P factor), and (b) the ratio of average thickness of the 95PPU band to the standard deviation of the corresponding measured variable (D factor). Ideally, the P factor should tend towards 1 with a D factor close to zero. These measures together indicate the strength of the calibration-uncertainty analysis. Runoff and sediment data from four hydrometric stations in each basin were used for calibration and validation. The P factor for Beheshtabad stations ranged from 0.31 to 0.86, while those for Vanak stations were between 0.71 and 0.80. The D factor for Beheshtabad ranged from 0.3 to 1.1, and for Vanak it was 0.77–1.16. These measures indicate a fair model calibration and accounting of uncertainties. The predicted runoff values were quite similar to those for discharge.
Rostamian, R.; Jaleh, A.; Afyuni, M.; Mousavi, S. F.; Heidarpour, M.; Jalalian, A.; Abbaspour, K. C. (2008) Application of a SWAT model for estimating runoff and sediment in two mountainous basins in central Iran, Hydrological Sciences Journal, 53(5), 977-988, doi:10.1623/hysj.53.5.977, Institutional Repository

Modeling blue and green water availability in Africa

Despite the general awareness that in Africa many people and large areas are suffering from insufficient water supply, spatially and temporally detailed information on freshwater availability and water scarcity is so far rather limited. By applying a semidistributed hydrological model SWAT (Soil and Water Assessment Tool), the freshwater components blue water flow (i.e., water yield plus deep aquifer recharge), green water flow (i.e., actual evapotranspiration), and green water storage (i.e., soil water) were estimated at a subbasin level with monthly resolution for the whole of Africa. Using the program SUFI-2 (Sequential Uncertainty Fitting Algorithm), the model was calibrated and validated at 207 discharge stations, and prediction uncertainties were quantified. The presented model and its results could be used in various advanced studies on climate change, water and food security, and virtual water trade, among others. The model results are generally good albeit with large prediction uncertainties in some cases. These uncertainties, however, disclose the actual knowledge about the modeled processes. The effect of considering these model-based uncertainties in advanced studies is shown for the computation of water scarcity indicators.
Schuol, J.; Abbaspour, K. C.; Yang, H.; Srinivasan, R.; Zehnder, A. J. B. (2008) Modeling blue and green water availability in Africa, Water Resources Research, 44(7), 1-18, doi:10.1029/2007WR006609, Institutional Repository

Comparing uncertainty analysis techniques for a SWAT application to the Chaohe Basin in China

Distributed watershed models are increasingly being used to support decisions about alternative management strategies in the areas of land use change, climate change, water allocation, and pollution control. For this reason it is important that these models pass through a careful calibration and uncertainty analysis. To fulfil this demand, in recent years, scientists have come up with various uncertainty analysis techniques for watershed models. To determine the differences and similarities of these techniques we compared five uncertainty analysis procedures: Generalized Likelihood Uncertainty Estimation (GLUE), Parameter Solution (ParaSol), Sequential Uncertainty FItting algorithm (SUFI-2), and a Bayesian framework implemented using Markov chain Monte Carlo (MCMC) and Importance Sampling (IS) techniques. As these techniques are different in their philosophies and leave the user some freedom in formulating the generalized likelihood measure, objective function, or likelihood function, a literal comparison between these techniques is not possible. As there is a small spectrum of different applications in hydrology for the first three techniques, we made this choice according to their typical use in hydrology. For Bayesian inference, we used a recently developed likelihood function that does not obviously violate the statistical assumptions, namely a continuous-time autoregressive error model. We implemented all these techniques for the soil and water assessment tool (SWAT) and applied them to the Chaohe Basin in China. We compared the results with respect to the posterior parameter distributions, performances of their best estimates, prediction uncertainty, conceptual bases, computational efficiency, and difficulty of implementation. The comparison results for these categories are listed and the advantages and disadvantages are analyzed. From the point of view of the authors, if computationally feasible, Bayesian-based approaches are most recommendable because of their solid conceptual basis, but construction and test of the likelihood function requires critical attention.
Yang, J.; Reichert, P.; Abbaspour, K. C.; Xia, J.; Yang, H. (2008) Comparing uncertainty analysis techniques for a SWAT application to the Chaohe Basin in China, Journal of Hydrology, 358(1–2), 1-23, doi:10.1016/j.jhydrol.2008.05.012, Institutional Repository

Assessing the impact of climate change on water resources in Iran

As water resources become further stressed due to increasing levels of societal demand, understanding the effect of climate change on various components of the water cycle is of strategic importance in management of this essential resource. In this study, we used a hydrologic model of Iran to study the impact of future climate on the country's water resources. The hydrologic model was created using the Soil and Water Assessment Tool (SWAT) model and calibrated for the period from 1980 to 2002 using daily river discharges and annual wheat yield data at a subbasin level. Future climate scenarios for periods of 2010–2040 and 2070–2100 were generated from the Canadian Global Coupled Model (CGCM 3.1) for scenarios A1B, B1, and A2, which were downscaled for 37 climate stations across the country. The hydrologic model was then applied to these periods to analyze the effect of future climate on precipitation, blue water, green water, and yield of wheat across the country. For future scenarios we found that in general, wet regions of the country will receive more rainfall while dry regions will receive less. Analysis of daily rainfall intensities indicated more frequent and larger-intensity floods in the wet regions and more prolonged droughts in the dry regions. When aggregated to provincial levels, the differences in the predictions due to the three future scenarios were smaller than the uncertainty in the hydrologic model. However, at the subbasin level the three climate scenarios produced quite different results in the dry regions of the country, although the results in the wet regions were more or less similar.
Abbaspour, K. C.; Faramarzi, M.; Ghasemi, S. S.; Yang, H. (2009) Assessing the impact of climate change on water resources in Iran, Water Resources Research, 45(10), 1-16, doi:10.1029/2008WR007615, Institutional Repository

Food and Water Uptake

Substance flow analysis: a case study of fluoride exposure through food and beverages in young children living in Ethiopia

Context: Dental and skeletal fluorosis is endemic in the Ethiopian Rift Valley. Children are especially vulnerable to excessive fluoride intake because their permanent teeth are still being formed. Strategies to reduce the total fluoride intake by children are thus warranted.
Case presentation: By combining the results of field studies in Ethiopia, the relevant pathways for fluoride intake have been identified in 28 children 2–5 years of age living in two villages on the Wonji Shoa Sugar Estate in the Ethiopian Rift Valley. The focus of the present study was to simulate the fluoride intake of the children using the methods of material flow analysis (MFA) and substance flow analysis.
Discussion: With a model based on MFA, we quantified the potential reduction in total fluoride intake given different scenarios—for example, by reducing the fluoride intake from drinking water and cooking water. The results show clearly that only by removing fluoride completely from both drinking and cooking water does the probability of remaining below the daily tolerable upper intake level exceed 50%. Both prepared food and food ingredients must be taken into consideration when assessing the total fluoride intake by children living in high-fluoride areas.
Relevance: This knowledge will help health personnel, the government, and the food authorities to give scientifically based advice on strategies for reducing the total fluoride intake by children living in high-fluoride areas in the Ethiopian Rift Valley.
Malde, M. K.; Scheidegger, R.; Julshamn, K.; Bader, H.-P. (2011) Substance flow analysis: a case study of fluoride exposure through food and beverages in young children living in Ethiopia, Environmental Health Perspectives, 119(4), 579-584, doi:10.1289/ehp.1002365, Institutional Repository

Spatial distribution and temporal variability of arsenic in irrigated rice fields in Bangladesh. 1. irrigation water

Around 38% of the area of Bangladesh is irrigated with groundwater to grow dry season crops, most importantly boro rice. Due to high As concentrations in many groundwaters, over 1000 tons of As are thus transferred to arable soils each year, creating a potential risk for future food production. We studied the reactions and changing speciation of As, Fe, P, and other elements in initially anoxic water during and after irrigation and the resulting spatial distribution of As input to paddy soils near Sreenagar (Munshiganj), 30 km south of Dhaka, in January and April 2005 and February 2006. The irrigation water had a constant concentration of 397 ± 7 μg L-1 As (∼84% As III), 11 ± 0.1 mg L-1 Fe, and 2 ± 0.1 mg L-1 P. During the fast flow along the longest irrigation channel (152 m) As, Fe, and P speciation changed, but total concentrations did not decrease significantly, indicating that As input to fields was independent of the length of the irrigation channels. In contrast, during slow water flow across the fields, As, Fe, and P concentrations decreased strongly with increasing distance from the water inlet, due to formation and settling of As- and P-bearing Fe aggregates and by adsorption to soil minerals. Total As concentrations in field water were ∼3 times higher close to the inlet than in the opposite field corner shortly after irrigation, and decreased to below 35 μg L-1 over the next 72 h. The laterally heterogeneous transfer of As, Fe, and P from irrigation water to soil has important consequences for their distribution in irrigated fields and needs to be considered in sampling and in assessing the dynamics and mass balances of As fluxes among irrigation water, soil, and floodwater.
Roberts, L. C.; Hug, S. J.; Dittmar, J.; Voegelin, A.; Saha, G. C.; Ali, M. A.; Badruzzaman, A. B. M.; Kretzschmar, R. (2007) Spatial distribution and temporal variability of arsenic in irrigated rice fields in Bangladesh. 1. irrigation water, Environmental Science and Technology, 41(17), 5960-5966, doi:10.1021/es070298u, Institutional Repository

Spatial distribution and temporal variability of arsenic in irrigated rice fields in Bangladesh. 2. Paddy soil

Arsenic-rich groundwater from shallow tube wells is widely used for the irrigation of boro rice in Bangladesh and West Bengal. In the long term this may lead to the accumulation of As in paddy soils and potentially have adverse effects on rice yield and quality. In the companion article in this issue, we have shown that As input into paddy fields with irrigation water is laterally heterogeneous. To assess the potential for As accumulation in soil, we investigated the lateral and vertical distribution of As in rice field soils near Sreenagar (Munshiganj, Bangladesh) and its changes over a 1 year cycle of irrigation and monsoon flooding. At the study site, 18 paddy fields are irrigated with water from a shallow tube well containing 397 ± 7 μg L-1 As. The analysis of soil samples collected before irrigation in December 2004 showed that soil As concentrations in paddy fields did not depend on the length of the irrigation channel between well and field inlet. Within individual fields, however, soil As contents decreased with increasing distance to the water inlet, leading to highly variable topsoil As contents (11-35 mg kg-1,0-10 cm). Soil As contents after irrigation (May 2005) showed that most As input occurred close to the water inlet and that most As was retained in the top few centimeters of soil. After monsoon flooding (December 2005), topsoil As contents were again close to levels measured before irrigation. Thus, As input during irrigation was at least partly counteracted by As mobilization during monsoon flooding. However, the persisting lateral As distribution suggests net arsenic accumulation over the past 15 years. More pronounced As accumulation may occur in regions with several rice crops per year, less intense monsoon flooding, or different irrigation schemes. The high lateral and vertical heterogeneity of soil As contents must be taken into account in future studies related to As accumulation in paddy soils and potential As transfer into rice.
Dittmar, J.; Voegelin, A.; Roberts, L. C.; Hug, S. J.; Saha, G. C.; Ali, M. A.; Badruzzaman, A. B. M.; Kretzschmar, R. (2007) Spatial distribution and temporal variability of arsenic in irrigated rice fields in Bangladesh. 2. Paddy soil, Environmental Science and Technology, 41(17), 5967-5972, doi:10.1021/es0702972, Institutional Repository

Arsenic release from paddy soils during monsoon flooding

Bangladesh relies heavily on groundwater for the irrigation of dry-season rice. However, the groundwater used for irrigation often contains high concentrations of arsenic, potentially jeopardizing the future of rice production in the country. In seasonally flooded fields, topsoil arsenic concentrations decrease during the monsoon season, suggesting that flooding attenuates arsenic accumulation in the soils. Here we examine the chemistry of soil porewater and floodwater during the monsoon season in rice paddies in Munshiganj, Bangladesh, to assess whether flooding releases significant quantities of arsenic from the soils. We estimate that between 51 and 250 mg m−2 of soil arsenic is released into floodwater during the monsoon season. This corresponds to a loss of 13–62% of the arsenic added to soils through irrigation each year. The arsenic was distributed throughout the entire floodwater column by vertical mixing and was laterally removed when the floodwater receded. We conclude that monsoon floodwater removes a large amount of the arsenic added to paddy soils through irrigation, and suggest that non-flooded soils are particularly at risk of arsenic accumulation.
Roberts, L. C.; Hug, S. J.; Dittmar, J.; Voegelin, A.; Kretzschmar, R.; Wehrli, B.; Cirpka, O. A.; Saha, G. C.; Ali, M. A.; Badruzzaman, A. B. M. (2010) Arsenic release from paddy soils during monsoon flooding, Nature Geoscience, 3(1), 53-59, doi:10.1038/ngeo723, Institutional Repository

Dittmar, J., Voegelin, A., Roberts, L. C., Hug, S. J. Saha, G. C., Ali, M. A., Badruzzaman, A. B. M., Kretzschmar, R. (2007) Spatial Distribution and Temporal Variability of Arsenic in Irrigated Rice Fields in Bangladesh. 2. Paddy Soil. Environmental Science & Technology 41(17), 5967-5972

Technologies

Avoiding high concentrations of arsenic, manganese and salinity in deep tubewells in Munshiganj District, Bangladesh

Over 85% of shallow tubewells (STWs) in the district of Mushiganj, Bangladesh, are affected by As concentrations above 50 μg/L. Deep tubewells (DTWs) are among the preferred mitigation options for reducing exposure to As. Around the town of Sreenagar (30 km South of Dhaka) water samples were collected from existing STWs and DTWs, monitoring wells (5–210 m depth) and newly installed DTWs. Analysis of water samples from 2005 to 2010 indentified three types of groundwater currently used for drinking: (1) Shallow water from 20 to 100 m deep dark-grey sediments with high As-concentrations (100–1000 μg/L), intermediate-high Fe (2–11 mg/L), intermediate Mn (0.2–1 mg/L) relatively low EC (400–900 μS/cm) dominated by Ca–Mg–. (2) Water from 140 to 180 m deep light-grey sediments with low As (<10 μg/L), intermediate Mn (0.2–1.0 mg/L), intermediate Fe (1–5 mg/L), low total organic C, N and , and intermediate EC (1200–1800 μS/cm) dominated by Ca–Mg––Na–Cl. (3) Deep water from 190 to 240 m deep brown sediments with low As (<10 μg/L), high Mn (2–5 mg/L), low Fe (<3 mg/L), and high EC (2000–3000 μS/cm) dominated by Ca–Mg–Na–Cl with high Ca and Cl concentrations. Drillers have traditionally used the transition from grey to brown sediments as an indicator for the depth from which safe drinking water can be obtained. However, in most of the tubewells in the studied area of over 190 m depth, Mn exceeds the WHO-limit of 0.4 mg Mn/L by a factor 2–5 and the water tastes noticeably saline. Based on the depth-resolved water compositions and a small survey of DTWs in a 2.5 × 2.5 km2 area, a depth range of 150–180 m with light-grey sediments is recommended for the construction of new DTWs. Pumping tests have shown that the deeper aquifer is largely separated from the upper aquifer, such that small volume water abstraction for drinking with hand pumps can be deemed safe as long as wells are periodically tested. DTWs are an excellent option for avoiding high As concentrations. However, before installing larger numbers of new DTWs, monitoring wells should be installed to determine the optimal depth for water withdrawal in each area.
Hug, S. J.; Gaertner, D.; Roberts, L. C.; Schirmer, M.; Ruettimann, T.; Rosenberg, T. M.; Badruzzaman, A. B. M.; Ali, M. A. (2011) Avoiding high concentrations of arsenic, manganese and salinity in deep tubewells in Munshiganj District, Bangladesh, Applied Geochemistry, 26(7), 1077-1085, doi:10.1016/j.apgeochem.2011.03.012, Institutional Repository
Hug, S. J.; Leupin, O. X.; Berg, M. (2008) Bangladesh and Vietnam: different groundwater compositions require different approaches to arsenic mitigation, Environmental Science and Technology, 42(17), 6318-6323, doi:10.1021/es7028284, Institutional Repository

pH dependence of fenton reagent generation and As(III) oxidation and removal by corrosion of zero valent iron in aerated water

Corrosion of zerovalent iron (ZVI) in oxygen-containing water produces reactive intermediates that can oxidize various organic and inorganic compounds. We investigated the kinetics and mechanism of Fenton reagent generation and As(III) oxidation and removal by ZVI (0.1m2/g) from pH 3-11 in aerated water. Observed half-lives for the oxidation of initially 500 μg/L As(III) by 150 mg Fe(0)/L were 26-80 min at pH 3-9. At pH 11, no As(III) oxidation was observed during the first two hours. Dissolved Fe(II) reached 325, 140, and 6 μM at pH 3, 5, and 7. H2O2 concentrations peaked within 10 min at 1.2, 0.4, and <0.1 μM at pH 3, 5, and 7, and then decreased to undetectable levels. Addition of 2,2′-bipyridine (1-3 mM), prevented Fe(II) oxidation by O2 and H2O2 and inhibited As(III) oxidation. 2-propanol (14 mM), scavenging OH-radicals, quenched the As(III) oxidation at pH 3, but had almost no effect at pH 5 and 7. Experimental data and kinetic modeling suggest that As(III) was oxidized mainly in solution by the Fenton reaction and removed by sorption on newly formed hydrous ferric oxides. OH-radials are the main oxidant for As(III) at low pH, whereas a more selective oxidant oxidizes As(III) at circumneutral pH.
Katsoyiannis, I. A.; Ruettimann, T.; Hug, S. J. (2008) pH dependence of fenton reagent generation and As(III) oxidation and removal by corrosion of zero valent iron in aerated water, Environmental Science and Technology, 42(19), 7424-7430, doi:10.1021/es800649p, Institutional Repository

Arsenic removal from groundwaters containing iron, ammonium, manganese and phosphate: a case study from a treatment unit in northern Greece

The city of Malgara in the municipality of Aksios, in northern Greece, relies on local groundwater for the municipal water supply. The groundwater has pH 7.9 and contains elevated concentrations of arsenic (20 µg/L), phosphate (550 µg/L), manganese (235 µg/L) and ammonium (1.2 mg/L), whereas the iron concentration (165 µg/L) is relatively low. Arsenic, manganese and ammonium exceed the parametric values, according to the EC directive 98/83. This directive has been adopted as national law since the beginning of 2003 and a groundwater treatment plant is in operation since the beginning of 2005. The treatment plant consists of aeration, up-flow filtration for the biological oxidation of ammonium, manganese and arsenic, followed by coagulation with FeClSO4 at a concentration of 2.3 mg Fe/L, and final down-flow filtration for the removal of arsenic and the additional iron. In a final stage, the water is disinfected with NaOCl before the distribution to the consumers. During aeration, Fe(II) is oxidized and some phosphate is sorbed on the formed iron oxides but remains in suspension until it is removed during the subsequent biological filtration stage. Mn(II) is oxidized by biological oxidation and the produced insoluble manganese oxides are removed by filtration. NH4+ is biologically oxidized and removed from the water via nitrification and formation of nitrates. As(III) is oxidized but not removed during the biological filtration stage. Arsenic is removed to below 10 µg/L during the subsequent coagulation and filtration treatment stage. Similarly, the final concentrations of Fe(tot), Mn(tot) and NH4+ are below the EC parametric values of 200, 50 and 500 µg/L respectively.
Katsoyiannis, I. A.; Zikoudi, A.; Hug, S. (2008) Arsenic removal from groundwaters containing iron, ammonium, manganese and phosphate: a case study from a treatment unit in northern Greece, Desalination, 224(1–3), 330-339, doi:10.1016/j.desal.2007.06.014, Institutional Repository

Effect of phosphate, silicate, and Ca on the morphology, structure and elemental composition of Fe(III)-precipitates formed in aerated Fe(II) and As(III) containing water

We investigated Fe(III)-precipitates formed from Fe(II) oxidation in water at pH 7 as a function of dissolved Fe(II), As(III), phosphate, and silicate in the absence and presence of Ca. We used transmission electron microscopy (TEM), including selected area electron diffraction (SAED) and energy dispersive X-ray spectroscopy (EDX) to characterize the morphology, structure and elemental composition of the precipitates. Results from our companion X-ray absorption spectroscopy (XAS) study suggested that the oxidation of Fe(II) leads to the sequential formation of distinct polymeric units in the following order: Fe(III)–phosphate oligomers in the presence of phosphate, silicate-rich hydrous ferric oxide (HFO-Si) at high Si/Fe (>0.5) or 2-line ferrihydrite (2L-Fh) at lower Si/Fe (0.1–0.5), and lepidocrocite (Lp) in the absence of phosphate at low Si/Fe (<0.1). Results from this study show that the size of the polymeric units increased along the same sequence and that the aggregation of these polymeric units resulted in spherical particles with characteristic surface textures changing from smooth to coarse. The diameter of the spherical particles increased from 15 to 380 nm as the molar ratio (P + Si + As)/Fe(II) in the starting solution decreased and larger spherical particles precipitated from Ca-containing than from Ca-free solutions. These trends suggested that the size of the spherical particles was controlled by the charge of the polymeric units. Spherical particles coagulated into flocs whose size was larger in the presence than in the absence of Ca. Further observations pointed to the importance of Fe(II) oxidation and polymerization versus polymer aggregation and floc formation kinetics in controlling the spatial arrangement of the different polymeric units within Fe(III)-precipitates. The resulting structural and compositional heterogeneity of short-range-ordered Fe(III)-precipitates likely affects their colloidal stability and their chemical reactivity and needs to be considered when addressing the fate of co-transformed trace elements such as arsenic.
Kaegi, R.; Voegelin, A.; Folini, D.; Hug, S. (2010) Effect of phosphate, silicate, and Ca on the morphology, structure and elemental composition of Fe(III)-precipitates formed in aerated Fe(II) and As(III) containing water, Geochimica et Cosmochimica Acta, 74(20), 5798-5816, doi:10.1016/j.gca.2010.07.017, Institutional Repository

Solar oxidation and removal of arsenic at circumneutral pH in iron containing waters

An estimated 30-50 million people in Bangladesh consume groundwater with arsenic contents far above accepted limits. A better understanding of arsenic redox kinetics and simple water treatment procedures are urgently needed. We have studied thermal and photochemical As(III) oxidation in the laboratory, on a time scale of hours, in water containing 500 μg/L As(III), 0.06-5 mg/L Fe(II,III), and 4-6 mM bicarbonate at pH 6.5-8.0. As(V) was measured colorimetrically, and As(III) and As(tot) were measured by As(III)/As(tot)-specific hydride-generation AAS. Dissolved oxygen and micromolar hydrogenperoxide did not oxidize As(III) on a time scale of hours. As(III) was partly oxidized in the dark by addition of Fe(II) to aerated water, presumably by reactive intermediates formed in the reduction of oxygen by Fe(II). In solutions containing 0.06-5 mg/L Fe(II,III), over 90% of As(III) could be oxidized photochemically within 2-3 h by illumination with 90 W/m2 UV-A light. Citrate, by forming Fe(III)citrate complexes that are photolyzed with high quantum yields, strongly accelerated As(III) oxidation. The photoproduct of citrate (3-oxoglutaric acid) induced rapid flocculation and precipitation of Fe(III). In laboratory tests, 80-90% of total arsenic was removed after addition of 50 μM citrate or 100-200 μL (4-8 drops) of lemon juice/L, illumination for 2-3 h, and precipitation. The same procedure was able to remove 45-78% of total arsenic in first field trials in Bangladesh.
Hug, S. J.; Canonica, L.; Wegelin, M.; Gechter, D.; von Gunten, U. (2001) Solar oxidation and removal of arsenic at circumneutral pH in iron containing waters, Environmental Science and Technology, 35(10), 2114-2121, doi:10.1021/es001551s, Institutional Repository

An adapted water treatment option in Bangladesh: solar oxidation and removal of arsenic (SORAS)

An estimated one-third of Bangladesh's population of 130 million is exposed to arsenic from consumption of ground water with arsenic concentrations above the currently accepted limit of 50 ppb. Until all wells are tested and arsenic-free water is available, most people will continue to depend on water with unknown arsenic concentrations and are at high risk of chronic arsenic poisoning. Several adapted arsenic removal technologies are now available and are briefly reviewed. Typically, arsenic is oxidized and partly precipitated in a first unit, followed by adsorption in a second unit acting as a filter column. Many of these technologies are convenient and efficient and should be applied as quickly as possible. However, the construction and maintenance of removal units require technical skills, special materials and often chemicals. Clogging of the filters and growth of pathogens remain unresolved issues and partly delay the large-scale introduction of units using filter columns. Another option, Solar Oxidation and Removal of Arsenic (SORAS), is a very simple water treatment method that involves the addition of 4-8 drops of lemon juice per liter of water, followed by exposure to sunlight for several hours in UVA-transparent containers such as PET bottles. After sedimentation of the precipitates, the water is decanted and/or filtered. SORAS can be applied in waters in which clearly visible brown iron (hydr)oxide precipitates are formed, which is the case with iron concentrations above 8 mg/L. Under this condition, SORAS is able to remove 75-90% of the arsenic. Although SORAS might not be as convenient as filtering methods and does not always reach the limit of 50 ppb, it is applicable immediately at no cost and bacteriological risk. Waters with high iron content also have the highest probability of elevated arsenic concentrations, such that SORAS could immediately lead to a four-fold reduction of the arsenic intake in a large fraction of the population until better methods are available.
Hug, S. J. (2001) An adapted water treatment option in Bangladesh: solar oxidation and removal of arsenic (SORAS), Environmental Sciences: International Journal on Environmental Physiology and Toxicology, 8(5), 467-479, Institutional Repository

Arsenic removal with iron(II) and iron(III) in waters with high silicate and phosphate concentrations

Arsenic removal by passive treatment, in which naturally present Fe(II) is oxidized by aeration and the forming iron-(III) (hydr)oxides precipitate with adsorbed arsenic, is the simplest conceivable water treatment option. However, competing anions and low iron concentrations often require additional iron. Application of Fe(II) instead of the usually applied Fe(III) is shown to be advantageous, as oxidation of Fe(II) by dissolved oxygen causes partial oxidation of As(III) and iron(III) (hydr)oxides formed from Fe(II) have higher sorption capacities. In simulated groundwater (8.2 mM HCO3-, 2.5 mM Ca2+, 1.6 mM Mg2+, 30 mg/L Si, 3 mg/ L P, 500 ppb As(III), or As(V), pH 7.0 ± 0.1), addition of Fe(II) clearly leads to better As removal than Fe(III). Multiple additions of Fe(II) further improved the removal of As(III). A competitive coprecipitation model that considers As(III) oxidation explains the observed results and allows the estimation of arsenic removal under different conditions. Lowering 500 μg/L As(III) to below 50 μg/L As(tot) in filtered water required >80 mg/L Fe(III), 50-55 mg/L Fe(II) in one single addition, and 20-25 mg/L in multiple additions. With As(V), 10-12 mg/L Fe(II) and 15-18 mg/L Fe(III) was required. In the absence of Si and P, removal efficiencies for Fe(II) and Fe(III) were similar: 30-40 mg/L was required for As(III), and 2.0-2.5 mg/L was required for As(V). In a field study with 22 tubewells in Bangladesh, passive treatment efficiently removed phosphate, but iron contents were generally too low for efficient arsenic removal.
Roberts, L. C.; Hug, S. J.; Ruettimann, T.; Billah, M. M.; Khan, A. W.; Rahman, M. T. (2004) Arsenic removal with iron(II) and iron(III) in waters with high silicate and phosphate concentrations, Environmental Science and Technology, 38(1), 307-315, doi:10.1021/es0343205, Institutional Repository

Arsenic removal from groundwater by household sand filters: comparative field study, model calculations, and health benefits

Arsenic removal efficiencies of 43 household sand filters were studied in rural areas of the Red River Delta in Vietnam. Simultaneously, raw groundwater from the same households and additional 31 tubewells was sampled to investigate arsenic coprecipitation with hydrous ferric iron from solution, i.e., without contact to sand surfaces. From the groundwaters containing 10-382 μg/L As, 99%, 90%, and 71%, respectively. The concentration of dissolved iron in groundwater was the decisive factor for the removal of arsenic. Residual arsenic levels below 50 Ag/L were achieved by 90% of the studied sand filters, and 40% were even below 10 Ag/L. Fe/As ratios of >= 50 or >= 250 were required to ensure arsenic removal to levels below 50 or 10 Ag/L, respectively. Phosphate concentrations > 2.5 mg P/L slightly hampered the sand filter and coprecipitation efficiencies. Interestingly, the overall arsenic elimination was higher than predicted from model calculations based on sorption constants determined from coprecipitation experiments with artificial groundwater. This observation is assumed to result from As(III) oxidation involving Mn, microorganisms, and possibly dissolved organic matter present in the natural groundwaters. Clear evidence of lowered arsenic burden for people consuming sand-filtered water is demonstrated from hair analyses. The investigated sand filters proved to operate fast and robust for a broad range of groundwater composition and are thus also a viable option for mitigation in other arsenic affected regions. An estimation conducted for Bangladesh indicates that a median residual level of 25 Ag/L arsenic could be reached in 84% of the polluted groundwater. The easily observable removal of iron from the pumped water makes the effect of a sand filter immediately recognizable even to people who are not aware of the arsenic problem.
Berg, M.; Luzi, S.; Trang, P. T. K.; Viet, P. H.; Giger, W.; Stüben, D. (2006) Arsenic removal from groundwater by household sand filters: comparative field study, model calculations, and health benefits, Environmental Science and Technology, 40(17), 5567-5573, doi:10.1021/es060144z, Institutional Repository

Behavioural Change

Evidence-based tailoring of behavior-change campaigns: increasing fluoride-free water consumption in rural Ethiopia with persuasion

Two hundred million people worldwide are at risk of developing dental and skeletal fluorosis due to excessive fluoride uptake from their water. Since medical treatment of the disease is difficult and mostly ineffective, preventing fluoride uptake is crucial. In the Ethiopian Rift Valley, a fluoride-removal community filter was installed. Despite having access to a fluoride filter, the community used the filter sparingly. During a baseline assessment, 173 face-to-face interviews were conducted to identify psychological factors that influence fluoride-free water consumption. Based on the results, two behavior-change campaigns were implemented: a traditional information intervention targeting perceived vulnerability, and an evidence-based persuasion intervention regarding perceived costs. The interventions were tailored to household characteristics. The campaigns were evaluated with a survey and analyzed in terms of their effectiveness in changing behavior and targeted psychological factors. While the intervention targeting perceived vulnerability showed no desirable effects, cost persuasion decreased the perceived costs and increased the consumption of fluoride-free water. This showed that altering subjective perceptions can change behavior even without changing objective circumstances. Moreover, interventions are more effective if they are based on evidence and tailored to specific households.
Huber, A. C.; Tobias, R.; Mosler, H.-J. (2014) Evidence-based tailoring of behavior-change campaigns: increasing fluoride-free water consumption in rural Ethiopia with persuasion, Applied Psychology: Health and Well-Being, 6(1), 96-118, doi:10.1111/aphw.12018, Institutional Repository

Predicting water consumption habits for seven arsenic-safe water options in Bangladesh

Background: In Bangladesh, 20 million people are at the risk of developing arsenicosis because of excessive arsenic intake. Despite increased awareness, many of the implemented arsenic-safe water options are not being sufficiently used by the population. This study investigated the role of social-cognitive factors in explaining the habitual use of arsenic-safe water options.
Methods: Eight hundred seventy-two randomly selected households in six arsenic-affected districts of rural Bangladesh, which had access to an arsenic-safe water option, were interviewed using structured face-to-face interviews in November 2009. Habitual use of arsenic-safe water options, severity, vulnerability, affective and instrumental attitudes, injunctive and descriptive norms, self-efficacy, and coping planning were measured. The data were analyzed using multiple linear regressions.
Results. Linear regression revealed that self-efficacy (B = 0.42, SE = .03, p < .001), the instrumental attitude towards the safe water option (B = 0.24, SE = .04, p < .001), the affective attitude towards contaminated tube wells (B = −0.04, SE = .02, p = .024), vulnerability (B = −0.20, SE = .02, p < .001), as well as injunctive (B = 0.08, SE = 0.04, p = .049) and descriptive norms (B = 0.34, SE = .03, p < .001) primarily explained the habitual use of arsenic-safe water options (R2 = 0.688). This model proved highly generalizable to all seven arsenic-safe water options investigated, even though habitual use of single options were predicted on the basis of parameters estimated without these options.
Conclusions. This general model for the habitual use of arsenic-safe water options may prove useful to predict other water consumption habits. Behavior-change interventions are derived from the model to promote the habitual use of arsenic-safe water options.
Inauen, J.; Tobias, R.; Molser, H.-J. (2013) Predicting water consumption habits for seven arsenic-safe water options in Bangladesh, BMC Public Health, 13, 417 (10 pp.), doi:10.1186/1471-2458-13-417, Institutional Repository

Does the implementation of hardware need software? A longitudinal study on fluoride-removal filter use in Ethiopia

Evidence suggests that the effectiveness of technology designed to provide safe and healthy water is dependent on the degree of its use. In addition to providing safe water "hardware" (i.e., new infrastructure or equipment) to populations at risk, it might be necessary to also provide suitable "software" programs (behavior change strategies) to support use. A longitudinal survey was conducted in rural Ethiopia following the distribution of fluoride-removal household filters. Three intervention groups were evaluated. Group 1 only received the hardware, i.e., the fluoride-removal filter. Groups 2 and 3 also received software in the form of two evidence-based psychological interventions: a planning and social prompts intervention and an educational workshop with pledging. Group 2 received both software interventions, and Group 3 only received the educational workshop. The effects of the hardware and software on behavior and thus filter use were analyzed along with specific psychological factors. The results showed that the provision of the hardware alone (the fluoride-removal filter) was not enough to ensure sufficient use of the equipment. The addition of a software component in the form of psychological interventions increased filter use up to 80%. An increase in filter use was measured following each intervention resulting in the health-risk being minimized. We conclude that it is necessary that the implementation of hardware of this nature is accompanied by evidence-based intervention software.
Sonego, I. L.; Huber, A. C.; Mosler, H.-J. (2013) Does the implementation of hardware need software? A longitudinal study on fluoride-removal filter use in Ethiopia, Environmental Science and Technology, 47(22), 12661-12668, doi:10.1021/es402787s, Institutional Repository

Determining behavioral factors for interventions to increase safe water consumption: a cross-sectional field study in rural Ethiopia

In developing countries, the lack of safe water options leads to many health risks. In the Ethiopian Rift Valley, most water sources are contaminated with an excess of fluoride. The consumption of fluoride-contaminated water leads to dental and skeletal fluorosis. The article presents an approach to designing community interventions based on evidence from quantitative data. After installing a community filter, a baseline study was conducted in 211 households to survey the acceptance and usage of the filter. To identify important psychological factors that lead to health behavior change, the Risk, Attitude, Norm, Ability, Self-regulation (RANAS) model was taken into account. Descriptive statistics were calculated for behavioral determinants, and their influence on consumption was analyzed with a linear regression. For every behavioral factor, an intervention potential (IP) was calculated. It was found that perceived distance, factual knowledge, commitment, and taste strongly influenced participants' consumption behavior and therefore should be tackled for interventions.
Huber, A. C.; Mosler, H.-J. (2013) Determining behavioral factors for interventions to increase safe water consumption: a cross-sectional field study in rural Ethiopia, International Journal of Environmental Health Research, 23(2), 96-107, doi:10.1080/09603123.2012.699032, Institutional Repository

Determinants of exclusive consumption of fluoride-free water: a cross-sectional household study in rural Ethiopia

Aim. The occurrence of high fluoride concentrations in the ground- and surface water all over the world leads to the risk of developing dental and skeletal fluorosis. In Ethiopia, 8 million people depend on water sources with excessive fluoride. In four project areas in the Ethiopian Rift Valley, fluoride removal household filters based on bone char media have been implemented. This study examines possible predictors of consuming filtered water derived from various behavior change theories.
Subject and methods. In a complete cross-sectional survey, 160 filter users were interviewed through structured face-to-face interviews. A logistic regression was carried out to reveal factors predicting consumption of filtered water.
Results. The results show that the consumption of fluoride-free water is mainly related to people's pride in offering filtered water to guests (status norm) and the feeling of being able to produce enough water with the filter (perceived behavioral control). Moreover, the study showed that the more filter users like the taste of filtered water and the more expensive they perceive the filter media, the more likely users will exclusively consume filtered water (attitudinal beliefs). Furthermore, perceiving the act of filling as a matter of habit (perceived habit) enhances filtered water consumption.
Conclusion. Based on the results, possible intervention strategies to change the influential psychological factors and, hence, increase the consumption of treated water can be designed.
Huber, A. C.; Bhend, S.; Mosler, H.-J. (2012) Determinants of exclusive consumption of fluoride-free water: a cross-sectional household study in rural Ethiopia, Journal of Public Health (Berlin, Heidelberg), 20(3), 269-278, doi:10.1007/s10389-011-0445-z, Institutional Repository

Sustainable use of arsenic-removing sand filters in Vietnam: psychological and social factors

Elevated arsenic concentrations in drinking water pose a health threat to millions of people. Although point-of-use sand filters provide an effective technical solution for mitigating arsenic exposure, the actual reduction in health risk also depends on psychological factors that influence behaviors related to this device. For example, acquiring a sand filter must be preferred to competing options for investing effort and money and, once installed, the users must regularly maintain the filters. These key behaviors of sustainable use are related to psychological factors, such as problem awareness, benefits and costs, social and affective influences, and the perception of practical difficulties. This study investigated the sustainable use of arsenic-removing sand filters in Vietnam. Based on questionnaire surveys, data were gathered in 319 rural households and analyzed with regression models. Psychological factors explained significant variance in the investigated key behaviors. Significant factors included perceived improvements in water healthiness and taste, monetary costs, social norms, and affective influences. In questions with open answers, interviewees mentioned various practical problems, particularly those related to the inflexibility of the device and the effort of changing the sand. Interestingly, many interviewees operate the sand filters for removing iron from the water but are unaware of problems with arsenic.
Tobias, R.; Berg, M. (2011) Sustainable use of arsenic-removing sand filters in Vietnam: psychological and social factors, Environmental Science and Technology, 45(8), 3260-3267, doi:10.1021/es102076x, Institutional Repository

Personal, social, and situational factors influencing the consumption of drinking water from arsenic-safe deep tubewells in Bangladesh

Naturally occurring arsenic in groundwater in Bangladesh poses a well-known public health threat. The aim of the present study is to investigate fostering and hindering factors of people's use of deep tubewells that provide arsenic-safe drinking water, derived from the Protection Motivation Theory and the Theory of Planned Behavior. Structured personal interviews were conducted with 222 households in rural Sreenagar, Bangladesh. Multiple linear regressions were carried out to identify the most influential personal, social, and situational behavior determinants. Data revealed that social factors explained greater variance in the consumption of drinking water from deep tubewells than did situational and personal factors. In an overall regression, social factors played the biggest role. In particular, social norms seem to strongly influence deep tubewell use. But also self-efficacy and the perceived taste of shallow tubewell water proved influential. Concurrently considering other important factors, such as the most mentioned response cost (i.e., time needed to collect deep tubewell water), we propose a socially viable procedure for installing deep tubewells for the extended consumption of arsenic-safe drinking water by the Bangladeshi population.
Mosler, H.-J.; Blöchliger, O. R.; Inauen, J. (2010) Personal, social, and situational factors influencing the consumption of drinking water from arsenic-safe deep tubewells in Bangladesh, Journal of Environmental Management, 91(6), 1316-1323, doi:10.1016/j.jenvman.2010.02.012, Institutional Repository

Persuasion factors influencing the decision to use sustainable household water treatment

Solar water disinfection (SODIS) is a sustainable water treatment method. With the help of the sun and plastic bottles, water is treated and illnesses prevented. This paper aims to identify the factors influencing SODIS uptake, that is, why someone may become a SODIS user. This uptake decision can be influenced by persuasion. From behaviour theory, variables are recognised which have been proven to influence intention and behaviour and simultaneously can be influenced by persuasion. A total of (n = 878) structured interviews were conducted in a field study in Zimbabwe. Linear and binary logistic regressions showed that several of the initially proposed persuasion variables have significant influence. Persuasion factors have a stronger influence on the uptake of SODIS use and on intention to use SODIS in the future than on the amount of SODIS water consumed. Ideas are presented for using the effective variables in future SODIS campaigns and campaigns in other fields.
Kraemer, S. M.; Mosler, H.-J. (2010) Persuasion factors influencing the decision to use sustainable household water treatment, International Journal of Environmental Health Research, 20(1), 61-79, doi:10.1080/09603120903398301, Institutional Repository

Promotion of solar water disinfection: comparing the effectiveness of different strategies in a longitudinal field study in Bolivia

Solar water disinfection (SODIS) is a simple method designed to treat microbiologically contaminated drinking water at the household level. This study focused on the effective promotion of the SODIS method using various strategies. In a longitudinal field study, we compared 2 interpersonal strategies (promoters and opinion leaders) and a centralized strategy (health fair) with a control group. Indicators of effectiveness were SODIS knowledge, SODIS adoption rate, and potential reach. The results suggest that use of promoters is the most successful strategy in terms of reaching people and changing their behavior toward SODIS use. The opinion leaders - although less effective - show some potential to stimulate communication among people about SODIS. Only the health fair did not have a big impact on behavior. Further discussion includes the costs of the various promotional activities, limitations, and recommendations for future projects.
Tamas, A.; Tobias, R.; Mosler, H.-J. (2009) Promotion of solar water disinfection: comparing the effectiveness of different strategies in a longitudinal field study in Bolivia, Health Communication, 24(8), 711-722, doi:10.1080/10410230903264022, Institutional Repository

Water disinfection and hygiene behaviour in an urban slum in Kenya: impact on childhood diarrhoea and influence of beliefs

Diarrhoea is one of the major causes of childhood death in developing countries. In this research project, we studied factors that presumably affect the incidence of diarrhoea among young children in urban slums: 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 Kibera, a huge shantytown in Nairobi, Kenya. Field workers interviewed a random sample of 500 households. Analysis with regression models revealed that two out of the four postulated factors (mentioned above) 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 behaviour. As regards beliefs, we found that biomedical knowledge of children’s diarrhoea as well as the perceived social norm for treating water are associated with the use of SODIS and good hygiene behaviour. These findings underline the importance of water treatment at household level and safe hygiene practices for protecting the health of young children growing up in urban slum settlements. Our data suggest that these measures are more important for diarrhoea prevention than efforts focussing on cleaning up neighbourhoods.
Graf, J. (2007) Water disinfection and hygiene behaviour in an urban slum in Kenya: impact on childhood diarrhoea and influence of beliefs, 44 p, Institutional Repository

Factors affecting the diffusion of solar water disinfection: a field study in Bolivia

This study examines a broad array of theory-based factors derived from diffusion research that affect the current and intended use of solar water disinfection (SODIS), a simple, low-cost technology for treating drinking water at the household level. The perceived attributes of an innovation, the nature of the social system in which it is diffused, the extent of change agents' promotional efforts in diffusing it, and the nature of the communication channels used were operationalized by 16 variables. The aim of the study is to determine the influence of each factor and its predictive power. Eight areas in Bolivia were visited, and 644 families were interviewed on the basis of a structured questionnaire. Simultaneous multiple regression analysis showed that 9 of the 16 factors derived from diffusion research contributed significantly to predicting the current use of SODIS. The implications of the findings for customizing future SODIS diffusion activities are outlined.
Heri, S.; Mosler, H.-J. (2008) Factors affecting the diffusion of solar water disinfection: a field study in Bolivia, Health Education and Behavior, 35(4), 541-560, doi:10.1177/1090198108321248, Institutional Repository

Differences in influence patterns between groups predicting the adoption of a solar disinfection technology for drinking water in Bolivia

The lack of safe drinking water is one of the major problems faced by developing countries. The consequences of contaminated water are diseases such as diarrhea, one of the main causes of infant mortality. Because of its simplicity, solar water-disinfection technology provides a good way of treating water at the household level. Despite its obvious advantages and considerable promotional activities, this innovation has had rather a slow uptake. We conducted a field survey in which 644 households in Bolivia were interviewed in order to gain insights on motivations that resulted in adopting the technology. The aim was to examine possible differences in the predictors for adopting this technology during the diffusion process using the theory of innovation diffusion. Our findings indicate that early adoption was predicted by increased involvement in the topic of drinking water and that adoption in the middle of the diffusion process was predicted by increased involvement by opinion leaders and by recognition of a majority who supported the technology. Finally, late adoption was predicted by recognition that a majority had already adopted. Suggestions for future promotional strategies are outlined.
Moser, S.; Mosler, H.-J. (2008) Differences in influence patterns between groups predicting the adoption of a solar disinfection technology for drinking water in Bolivia, Social Science and Medicine, 67(4), 497-504, doi:10.1016/j.socscimed.2008.04.002, Institutional Repository

Attitudinal and relational factors predicting the use of solar water disinfection: a field study in Nicaragua

Solar water disinfection (SODIS) is an uncomplicated and cheap technology providing individuals with safe drinking water by exposing water-filled plastic bottles to sunlight for 6 hours to kill waterborne pathogens. Two communities were visited, and 81 families (40 SODIS users and 41 nonusers) were interviewed. The relationship between several factors and the intention to use SODIS in the future and actual use were tested. The results showed that intention to use and actual use are mainly related to an overall positive attitude, intention to use is related to the use of SODIS by neighbors, and actual use is related to knowledge about SODIS; SODIS users reported a significantly lower incidence in diarrhea than SODIS nonusers. These results suggest that promotion activities should aim at creating a positive attitude, for example, by choosing a promoter that is able to inspire confidence in the new technology.
Altherr, A.-M.; Mosler, H.-J.; Tobias, R.; Butera, F. (2008) Attitudinal and relational factors predicting the use of solar water disinfection: a field study in Nicaragua, Health Education and Behavior, 35(2), 1-14, doi:10.1177/1090198106288251, Institutional Repository

Institutional Analysis

Household's willingness to pay for arsenic safe drinking water in Bangladesh

This study examines willingness to pay (WTP) in Bangladesh for arsenic (As) safe drinking water across different As-risk zones, applying a double bound discrete choice value elicitation approach. The study aims to provide a robust estimate of the benefits of As safe drinking water supply, which is compared to the results from a similar study published almost 10 years ago using a single bound estimation procedure. Tests show that the double bound valuation design does not suffer from anchoring or incentive incompatibility effects. Health risk awareness levels are high and households are willing to pay on average about 5 percent of their disposable average annual household income for As safe drinking water. Important factors influencing WTP include the bid amount to construct communal deep tubewell for As safe water supply, the risk zone where respondents live, household income, water consumption, awareness of water source contamination, whether household members are affected by As contamination, and whether they already take mitigation measures.
Khan, N. I.; Brouwer, R.; Yang, H. (2014) Household's willingness to pay for arsenic safe drinking water in Bangladesh, Journal of Environmental Management, 143, 151-161, doi:10.1016/j.jenvman.2014.04.018, Institutional Repository

Arsenic mitigation in Bangladesh: an analysis of institutional stakeholders' opinions

While Bangladesh made significant achievements in safe water coverage via installation of shallow tubewells (STWs) nationwide, this success was shattered by the discovery of arsenic (As) in the STWs. The extent and severity of As groundwater contamination throughout Bangladesh and its detrimental effects on human health are well known and demand long-term sustainable mitigation. It is an immensely complex and expensive task to bring tens of millions of arsenic exposed people under safe water coverage. While various mitigation measures have been undertaken by various organizations, most have not achieved their expected outcomes due to technical, spatial and socio-economic challenges. Better understanding of these challenges by institutional stakeholders is crucial for sustainable arsenic mitigation in Bangladesh. In this study, institutional stakeholders' opinions on various aspects of As mitigation were elicited to identify their preferences for and reservations of specific mitigation measures. The current status of As mitigation activities and the factors influencing the success of As mitigation were also explored. Institutional weakness, lack of accountability and a latency period were the major factors hindering sustainable As mitigation. The results also suggested that the stakeholders' understanding of the As problem and their preferences for the different mitigation measures have a significant impact on the effectiveness of As mitigation. Mitigation of As contamination is a complex issue that requires a coordinated effort from various levels of stakeholders. The concept of "paying for water", which is currently potentially unknown in the rural areas of Bangladesh, also needs to be developed as this will create a stronger sense of user ownership of As safe water and thus better water management.
Khan, N. I.; Yang, H. (2014) Arsenic mitigation in Bangladesh: an analysis of institutional stakeholders' opinions, Science of the Total Environment, 488, 493-504, doi:10.1016/j.scitotenv.2013.11.007, Institutional Repository

The socio-economics of arsenic removal

Nearly an eighth of the population in Bangladesh relies on arsenic-contaminated drinking water. Arsenic-removal filters could help to reduce exposure, but their price is high for the poor and their maintenance is cumbersome.
Johnston, R. B.; Hanchett, S.; Hoque Khan, M. (2010) The socio-economics of arsenic removal, Nature Geoscience, 3, 2-3, doi:10.1038/ngeo735, Institutional Repository