Department Sanitation, Water and Solid Waste for Development

Solar disinfection (SODIS) is a simple drinking water treatment method that improves microbiological water quality where other means are unavailable. It makes use of the deleterious effect of solar irradiation on pathogenic microbes and viruses. A positive impact on health has been documented in several epidemiological studies. However, the molecular mechanisms damaging cells during this simple treatment are not yet fully understood. Here we show that protein damage is crucial in the process of inactivation by sunlight. Protein damages in UVA-irradiated Escherichia coli cells have been evaluated by an immunoblot method for carbonylated proteins and an aggregation assay based on semi-quantitative proteomics. A wide spectrum of structural and enzymatic proteins within the cell is affected by carbonylation and aggregation. Vital cellular functions like the transcription and translation apparatus, transport systems, amino acid synthesis and degradation, respiration, ATP synthesis, glycolysis, the TCA cycle, chaperone functions and catalase are targeted by UVA irradiation. The protein damage pattern caused by SODIS strongly resembles the pattern caused by reactive oxygen stress. Hence, sunlight probably accelerates cellular senescence and leads to the inactivation and finally death of UVA-irradiated cells.

Solar disinfection (SODIS) is used as an effective and inexpensive tool to improve the microbiological quality of drinking water in developing countries where no other means are available. Solar UVA light is the agent that inactivates bacteria during the treatment. Damage to bacterial membranes plays a crucial role in the inactivation process. This study showed that even slightly irradiated cells (after less than 1 h of simulated sunlight) were strongly affected in their ability to maintain essential parts of their energy metabolism, in particular of the respiratory chain (activities of NADH oxidase, succinate oxidase and lactate oxidase were measured). The cells' potential to generate ATP was also strongly inhibited. Many essential enzymes of carbon metabolism (glucose-6-phosphate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, lactate dehydrogenase and malate dehydrogenase) and defence against oxidative stress (catalases and glutathione-disulfide reductase) were reduced in their activity during SODIS. The work suggests that damage to membrane enzymes is a likely cause of membrane dysfunction (loss of membrane potential and increased membrane permeability) during UVA irradiation. In this study, the first targets on the way to cell death were found to be the respiratory chain and F₁F₀ ATPase.

Pathogenic enteric bacteria are a major cause of drinking water related morbidity and mortality in developing countries. Solar disinfection (SODIS) is an effective means to fight this problem. In the present study, SODIS of two important enteric pathogens, Shigella flexneri and Salmonella typhimurium, was investigated with a variety of viability indicators including cellular ATP levels, efflux pump activity, glucose uptake ability, and polarization and integrity of the cytoplasmic membrane. The respiratory chain of enteric bacteria was identified to be a likely target of sunlight and UVA irradiation. Furthermore, during dark storage after irradiation, the physiological state of the bacterial cells continued to deteriorate even in the absence of irradiation: apparently the cells were unable to repair damage. This strongly suggests that for S. typhimurium and Sh. flexneri, a relatively small light dose is enough to irreversibly damage the cells and that storage of bottles after irradiation does not allow regrowth of inactivated bacterial cells. In addition, we show that light dose reciprocity is an important issue when using simulated sunlight. At high irradiation intensities (>700 W m^–2) light dose reciprocity failed and resulted in an overestimation of the effect, whereas reciprocity applied well around natural sunlight intensity (<400 W m^–2).

The effectiveness of solar disinfection (SODIS), a low-cost household water treatment method for developing countries, was investigated with flow cytometry and viability stains for the enteric bacterium Escherichia coli. A better understanding of the process of injury or death of E. coli during SODIS could be gained by investigating six different cellular functions, namely: efflux pump activity (Syto 9 plus ethidium bromide), membrane potential [bis-(1,3-dibutylbarbituric acid)trimethine oxonol; DiBAC₄(3)], membrane integrity (LIVE/DEAD BacLight), glucose uptake activity (2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxy-D-glucose; 2-NBDG), total ATP concentration (BacTiter-Glo) and culturability (pour-plate method). These variables were measured in E. coli K-12 MG1655 cells that were exposed to either sunlight or artificial UVA light. The inactivation pattern of cellular functions was very similar for both light sources. A UVA light dose (fluence) of <500 kJ m^-2 was enough to lower the proton motive force, such that efflux pump activity and ATP synthesis decreased significantly. The loss of membrane potential, glucose uptake activity and culturability of > 80% of the cells was observed at a fluence of ∼ 1500 kJ m^-2, and the cytoplasmic membrane of bacterial cells became permeable at a fluence of > 2500 kJ m^-2, Culturable counts of stressed bacteria after anaerobic incubation of sodium pyruvate-supplemented tryptic soy agar closely correlated with the loss of membrane potential. The results strongly suggest that cells exposed to > 1500 kJ m^-2 solar UVA (corresponding to 530 W m^-2 global sunlight intensity for 6 h) were no longer able to repair the damage and recover. Our study confirms the lethal effect of SODIS with cultivation-independent methods and gives a detailed picture of the 'agony' of E. coli when it is stressed with sunlight.

Aims: To determine the efficacy of solar disinfection (SODIS) for enteric pathogens and to test applicability of the reciprocity law.
Methods and Results: Resistance to sunlight at 37°C based on F₉₉ values was in the following order: Salmonella Typhimurium > Escherichia coli > Shigella flexneri > Vibrio cholerae. While F₉₀ values of Salm. Typhimurium and E. coli were similar, F₉₉ values differed by 60% due to different inactivation curve shapes. Efficacy seemed not to be dependent on fluence rate for E. coli stationary cells. Sensitivity to mild heat was observed above a temperature of 45°C for E. coli, Salm. Typhimurium and Sh. flexneri, while V. cholerae was already susceptible above 40°C.
Conclusions: Salmonella Typhimurium was the most resistant and V. cholerae the least resistant enteric strain. The reciprocity law is applicable for stationary E. coli cells irradiated with sunlight or artificial sunlight.
Significance and Impact of the Study: Escherichia coli might not be the appropriate indicator bacterium to test the efficacy of SODIS on enteric bacteria and the physiological response to SODIS might be different among enteric bacteria. The applicability of the reciprocity law indicates that fluence rate plays a secondary role in SODIS efficacy. Stating inactivation efficacy with T₉₀ or F₉₀ values without showing original data is inadequate for SODIS studies.

Knowledge about the sensitivity of the test organism is essential for the evaluation of any disinfection method. In this work we show that sensitivity of Escherichia coli MG1655 to three physical stresses (mild heat, UVA light, and sunlight) that are relevant in the disinfection of drinking water with solar radiation is determined by the specific growth rate of the culture. Batch- and chemostat-cultivated cells from cultures with similar specific growth rates showed similar stress sensitivities. Generally, fast-growing cells were more sensitive to the stresses than slow-growing cells. For example, slow-growing chemostat-cultivated cells (D = 0.08 h^–1) and stationary-phase bacteria from batch culture that were exposed to mild heat had very similar T₉₀ (time until 90% of the population is inactivated) values (T_{90, chemostat} = 2.66 h; T_{90, batch} = 2.62 h), whereas T₉₀ for cells growing at a µ of 0.9 h^–1 was 0.2 h. Wepresent evidence that the stress sensitivity of E. coli is correlated with the intracellular level of the alternative sigma factor RpoS. This is also supported by the fact that E. coli rpoS mutant cells were more stress sensitive than the parent strain by factors of 4.9 (mild heat), 5.3 (UVA light), and 4.1 (sunlight). Furthermore, modeling of inactivation curves with GInaFiT revealed that the shape of inactivation curves changed depending on the specific growth rate. Inactivation curves of cells from fast-growing cultures (µ = 1.0 h^–1) that were irradiated with UVA light showed a tailing effect, while for slow-growing cultures (µ = 0.3 h^–1), inactivation curves with shoulders were obtained. Our findings emphasize the need for accurate reporting of specific growth rates and detailed culture conditions in disinfection studies to allow comparison of data from different studies and laboratories and sound interpretation of the data obtained.

SODIS is a solar water disinfection process which works by exposing untreated water to the sun in plastic bottles. Field experiments were carried out in Cochabamba, Bolivia, to obtain standard UV-A (320–405 nm) dose values required to inactivate non-spore forming bacteria, spores of Bacillus subtilis, and wild type coliphages. inactivation kinetics for non-spore forming bacteria are similar under SODIS conditions, exhibiting dose values ranging between 15 and 30 Wh m^–2 for 1 log₁₀ (90%) inactivation, 45 to 90 Wh m^–2 for 3 log₁₀ (99.9%), and 90 to 180 Wh m^–2 for 6 log₁₀ (99.9999%) inactivation. Pseudomonas aeruginosa was found to be the most resistant and Salmonella typhi, the most sensitive of the non-sporulating organisms studied here. Phages and spores serve as model organisms for viruses and parasite cysts. A UV-A dose of 85 to 210 wh m^–2 accumulated during one to two days was enough to inactivate 1 log₁₀ (90%) of these strong biological structures. The process of SODIS depended mainly on the radiation dose [Wh m^–2] an organism was exposed to. An irradiation intensity exceeding some 12 Wm^–2 did not increase the inactivation constant. A synergistic effect of water temperatures below 50 °C was not observed. Data plotting from various experiments on a single graph proved to be a reliable alternative method for analysis. inactivation rates determined by this method were revealed to be within the same range as individual analysis.

Last year's publication of Rob Reed's article 'Sunshine and fresh air: a practical approach to combating water disease' provoked sustained reader interest in what seems such a simple solution to a major problem. Here we can publish the results of extensive field and lab tests.

This article comprises the work of several research teams which analysed the effectiveness of solar water disinfection (SODIS) in various laboratory and field investigations carried out at different test sites over the last five years. SODIS was applied as batch and continuous flow process (SODIS reactor). The process is most effective with a water temperature of at least 50 °C. Transparent plastic bags allow a 3-log reduction (99.9%) of faecal coliforms and Vibrio cholerae through heating and radiation at an UV-A dose of 54 Wh/m² over a period of 140 min. The SODIS reactor produces around 100 L of drinking water per square metre of solar collector and day.

The exposure of water to sunlight radiation improves the microbiological quality of water. This treatment process called solar water disinfection could be used at household level to treat small quantities of water for drinking purposes. The bactericidal effect of UV-A and violet light and their combined effects assumed as hypothesis by earlier research could be verified by the laboratory tests carried out at EAWAG. A 3-log reduction of E. coli requires a fluence close to 2,000 kJ/m² or 555 W·h/m² (dose of solar radiation integrated in the 350-450 nm wavelength range), which correspond to ~5 h of mid-latitude midday summer sunshine. The same dose inactivates also the bacteriophage f2 and a rotavirus to a similar order of magnitude, whereas a picornavirus (encephalomyocarditis virus) was observed to be twice as resistant. Water temperatures with a threshold of ~50 °C considerably increase the inactivation rate of bacteria induced by solar radiation whereas the inactivation rate of viruses steadily increases with temperatures in the range of 20-50 °C. The recorded synergetic effects of solar radiation and thermal water treatment favour a combined use of these two water-treatment processes.

Solar water disinfection (SODIS) is a simple, effective and inexpensive water treatment procedure suitable for application in developing countries. Microbially contaminated water is filled into transparent polyethylene terephthalate (PET) plastic bottles and exposed to full sunlight for at least 6 h. Solar radiation and elevated temperature destroy pathogenic germs efficiently. Recently, concerns have been raised insinuating a health risk by chemicals released from the bottle material polyethylene terephthalate (PET). Whereas the safety of PET for food packaging has been assessed in detail, similar investigations for PET bottles used under conditions of the SODIS treatment were lacking until now. In the present study, the transfer of organic substances from PET to water was investigated under SODIS conditions using used colourless transparent beverage bottles of different origin. The bottles were exposed to sunlight for 17 h at a geographical latitude of 47° N. In a general screening of SODIS treated water, only food flavour constituents of previous bottle contents could be identified above a detection limit of 1 μg/L. Quantitative determination of plasticisers di(2-ethylhexyl)adipate (DEHA) and di(2-ethylhexyl)phthalate (DEHP) revealed maximum concentrations of 0.046 and 0.71 μg/L, respectively, being in the same range as levels of these plasticisers reported in studies on commercial bottled water. Generally, only minor differences in plasticiser concentrations could be observed in different experimental setups. The most decisive factor was the country of origin of bottles, while the impact of storage conditions (sunlight exposure and temperature) was less distinct. Toxicological risk assessment of maximum concentrations revealed a minimum safety factor of 8.5 and a negligible carcinogenic risk of 2.8 × 10⁻⁷ for the more critical DEHP. This data demonstrate that the SODIS procedure is safe with respect to human exposure to DEHA and DEHP.

A simple water treatment process called SODIS (solar water disinfection) consists of filling polluted water in PET bottles that are exposed to sunlight for 5-6 hours. However, sunlight does not only destroy disease-causing microorganisms found in the water but also transforms the plastic material into photoproducts. Laboratory and field tests revealed that these photoproducts are generated at the outer surface of the bottles. No indication for migration of possible photoproducts or additives from PET bottles into water was observed with the applied analytical methods.

In developing countries, the burden of diarrhoea is still enormous. One way to reduce transmission of pathogens is by water quality interventions. Solar water disinfection (SODIS) is a low-cost and simple method to improve drinking water quality on household level. This paper evaluates the implementation of SODIS in slum areas of Yaoundé, Cameroon. Promoters trained 2,911 households in the use of SODIS. Two surveys with randomly selected households were conducted before (N = 2,193) and after (N = 783) the intervention. Using a questionnaire, interviewers collected information on the health status of children under five, on liquid consumption, hygiene and other issues. Prior to the intervention, diarrhoea prevalence amounted to 34.3% among children. After the intervention, it remained stable in the control group (31.8%) but dropped to 22.8% in the intervention group. Households fully complying with the intervention exhibited even less diarrhoea prevalence (18.3%) and diarrhoea risk could be reduced by 42.5%. Multivariate analyses revealed that the intervention effects are also observed when other diarrhoea risk factors, such as hygiene and cleanliness of household surroundings, are considered. According to the data, adoption of the method was associated with marital status. Findings suggest health benefits from SODIS use. Further promotional activities in low-income settings are recommended.

In this research project, we studied factors that presumably affect the incidence of diarrhoea among young children in urban slums in developing countries: consumption of safe drinks, hygiene behaviour, cleanliness of household surroundings and the quality of raw water. Beliefs concerning the causes of diarrhoea were also related to health-improving behaviour, namely the application of the water-treatment method SODIS (solar water disinfection) and hygiene behaviour. We conducted a survey in a shanty town in Nairobi, Kenya. Field workers interviewed 500 households. Analysis with regression models revealed that two out of the four postulated factors were significant: children have a lower risk of contracting diarrhoea when they consume high percentages of safe drinks and live in households with good hygiene. As regards beliefs, we found that biomedical knowledge of children's diarrhoea as well as the perceived social norm for treating water was associated with the use of SODIS and good hygiene.

The positive health effects in the Ng’ombe slum in Lusaka can be attributed to the consumption of safe water. A health impact survey reveals that irregular and regular SODIS use reduces diarrhoea incidence among children below five by 59.4 and 54.0 %, respectively compared to the control group. Users with a high consumption of treated water also exhibit improved hygiene behaviour. Trained households, which did not apply SODIS, more often used other household water treatment methods and had 12.7 % less diarrhoea than untrained households.

Applied research and expert consulting are conducted at research institutions and universities that are supported by public investment. This is often justified on the basis of anticipated societal benefits. Thus it is incumbent on the institutions that conduct these activities to develop a sound basis for the assessment of their benefits and to be able to communicate these to the public.

Sandec’s commitment to household water treatment projects has a long-standing tradition, especially the widely promoted solar water disinfection (SODIS) method. But what are the long-term benefits several years after project conclusion? A three-country comparison reveals that Household Water Treatment and Safe Storage (HWTS) use is quite widespread; yet, consumption of untreated water still persists.

Every year, 1.8 million people, mainly children under the age of five, die of diarrhoea. Point-of-use water treatment methods, such as solar water disinfection (SODIS), reveal a great potential to reduce the global diarrhoea burden. Comprehensive microbiological research demonstrated the effectiveness of SODIS to destroy diarrhoea-causing pathogens in contaminated drinking water. Since the year 2000, SODIS is being promoted in developing countries through information and awareness campaigns, training and advising of the public sector (government institutions), networking activities, as well as user training at the grassroot level. The method is currently used in 33 countries by more than 2 million people. Several project evaluations and health impact studies reveal that the diarrhoea incidence of SODIS users has dropped by 16–57%. One year after project implementation, 20–80%of the trained people used SODIS on a regular basis. This paper looks into factors influencing acceptance and sustained use of SODIS on grassroot level, i.e. local availability of bottles, repeated promotion and training programmes, motivation and commitment of promoters, educational level of users, social pressure, and institutional aspects.

Objectives: To use a psychological theory of behavioural change to measure and interpret the effectiveness of different promotional strategies for achieving long-term usage of a household water treatment and safe storage (HWTS) system in peri-urban Zimbabwe.
Study design: Solar disinfection (SODIS) was introduced into five peri-urban communities near Harare, Zimbabwe. Six different interventions were developed and were applied in four communities in different combinations, with the fifth remaining as a control area where no interventions were implemented.
Methods: Throughout the 26 months of the study nine longitudinal panel surveys were conducted in which SODIS usage was estimated using three separate metrics: reported, calculated, and observed. A total of 1551 people were interviewed.
Results: The three indicators of SODIS usage broadly agreed with one another. By any measure, the most effective intervention was household visits by trained promoters in combination with persuasion. Households which received household visits maintained SODIS usage rates of 65% or more, even six months after the cessation of all promotional activities. Households receiving other interventions were significantly less effective. Interventions like prompts or public commitment after the application of household visits were effective at maintaining good practices once these were established.
Conclusions: Household promotion in combination with persuasion appears more effective than other approaches, especially when followed with interventions targeting the maintenance of the new behaviour. With this intervention it is possible that around 65% of the households continue to use solar water disinfection (SODIS) more than two years after the initial promotion, and six months after the end of all interventions

Household water treatment (HWT) has the potential to reduce waterborne diseases in developing countries. In this article, factors from social–psychological theories are analyzed in order to design effective interventions that promote HWT. Two treatment behaviors—solar disinfection (SODIS) and boiling—are compared with untreated-water consumption using data from a SODIS campaign in Bolivia. The main drivers of intention are affective beliefs, health beliefs related to untreated water, and descriptive norms. Behavior is primarily influenced by the habit related to each water type. Strong interrelations between beliefs and the habit related to one water type and the intention or consumption related to the others exist. Future campaigns should not only promote the target health behavior, but also investigate predictors of the health-risk behavior in order to prevent it.

Solar water disinfection (SODIS) is a sustainable method of water treatment. Despite the simplicity and many advantages of SODIS, past behaviour change campaigns have seen limited success. This study aims to compare intervention strategies in their efficiency in changing behaviour and to analyse which behavioural factors are differentially affected. The following factors were analysed in this study: intention, subjective norm, behavioural control, beliefs, habits, frequency of talking, knowledge and tension. The promotion strategies used in this intervention study were promoters, a pass-on task, prompts, public commitment and disseminating knowledge with inducing tension. Inhabitants of high-density areas near Harare, Zimbabwe, were interviewed at different points in time. High SODIS consumption was achieved when the promoter intervention was followed by a memory-aiding technique such as prompts or public commitment. Consequently, this combined-intervention strategy increased all behavioural factors and kept them at a high level. A continued pass-on task alone did not change behaviour and had decreasing effects on several behavioural factors. When the pass-on task was combined with disseminating knowledge with inducing tension, high SODIS water consumption was also reached, but several behavioural factors stayed at a low level. More effective intervention strategies are identified and discussed.

Solar Water Disinfection (SODIS) is a simple method designed to treat microbiologically contaminated drinking water at household level. This article characterizes relapse behavior in comparison with continued SODIS use after a 7-month nonpromotion period. In addition, different subtypes among relapsers and continuers were assumed to diverge mainly in their intention to use SODIS and their degree of cognition intensity. Data were taken from a longitudinal SODIS promotion study. Cluster analyses were applied to find subtypes among 166 relapsers and 123 continuers. Overall relapsers have lower values for all psychological variables compared to overall continuers. A low-value and a high-value relapser subtype as well as a low-value and a high-value continuer subtype were found. Low-value relapsers differ from high-value relapsers in one central belief (taste), in affective connotation, social norms, and dissonance. Interestingly, high-value relapsers have values almost as high as low-value continuers, differing only in their degree of habit. Only high-value continuers seem to be stable and did not show a decrease in critical habit variables over time. The different subtypes are placed along the behavior change process, and possible interventions for each type are highlighted.

Solar water disinfection (SODIS) is a sustainable household water treatment technique that could prevent millions of deaths caused by diarrhoea. The behaviour change process necessary to move from drinking raw water to drinking SODIS is analysed with the Transtheoretical Model of Change (TTM). User groups and psychological factors that differentiate between types of users are identified. Results of a 1.5 year longitudinal study in Zimbabwe reveal distinguishing factors between groups, from which it can be deduced that they drive the development of user groups. Implications are drawn for campaigns with the aim of bringing all user types to a regular use.

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.

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.

The potential for reducing diarrhoea morbidity and improving the health status of children in developing countries using solar water disinfection (SODIS) has been demonstrated in past research. A baseline survey was conducted to explore the feasibility and necessity of introducing SODIS in peri-urban communities of Zimbabwe. The survey sought to establish drinking water quality in these areas and to determine the health and hygiene beliefs as well as practices related to water handling in the household. Microbiological water quality tests and personal interviews were carried out in Epworth township and Hopley farm, two peri-urban areas near the capital of Zimbabwe, Harare. These two areas are among the poorest settlements around Harare with 80% of inhabitants being informal settlers. Community meetings were held to introduce solar water disinfection prior to the survey. This was followed by administration of questionnaires, which aimed to investigate whether the community had ever heard about SODIS, whether they were practicing it, other means that were being used to treat drinking water as well as health and hygiene beliefs and practices. It was found out that most households cannot afford basic water treatment like boiling as firewood is expensive. People generally reported that the water was not palatable due to objectionable odour and taste. Microbiological water quality tests proved that drinking water was contaminated in both areas, which makes the water unsafe for drinking and shows the necessity of treatment. Although the majority of people interviewed had not heard of SODIS prior to the interview, attitudes towards its introduction were very positive and the intention to do SODIS in the future was high. Amongst the ones who had heard about SODIS before the study, usage was high. Plastic PET bottles, which were used for the SODIS experiments are currently unavailable and this has been identified as a potential hindrance to the successful implementation of SODIS.

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.

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.

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.