Safe Drinking Water at Home: Evidence from a randomised trial in Uganda

The intervention consists of the random distribution of three different water treatment methods over the selected treatment population and training in its correct use. The treatments are an improved cook stove to boil water, ceramic filtration and membrane filtration. Since behavioural nudges are proven effective to increase uptake of POU water treatment (Luoto et al., 2014), each cook stove and drinking water filter is accompanied by a leaflet with instructions on the use and maintenance needs. The cook stoves and drinking water filters are distributed to the dwellings of the selected households by the researchers and members of HEWASA, with the help of local guides of the Village Health Teams (VHTs). Members of HEWASA provide individual training at the dwelling of the responsible household members in use and maintenance of the assigned water treatment method.

2023-04-20

2023-05-15

1. Drinking water quality
2. Diarrhoeal disease
3. Uptake
4. Household savings

1. The participating households will be asked to identify the main drinking water container in the dwelling and a water sample will be taken from the designated water container. To assess the microbiological improvements in drinking water quality, household water samples will be analysed in the lab on the presence of total thermotolerant coliforms (TTC), and in particular the bacterium E.coli. The assessment will be performed using the membrane filtration technique on membrane lauryl sulphate medium. The unit of measurement is Colony Forming Units (CFU). A second aspect of water analysis is turbidity, i.e. a measure for the presence of particles in the drinking water. The unit of analysis is Nephelometric Turbidity Units (NTU). The values of TTC, E.coli and turbidity will both be reported in levels (CFU/NTU) and in logarithmic value reductions (LVR).

2. Diarrheal disease will be measured by recording cases among children below five years of age. A diarrhoea case is defined according to the WHO-definition as “three or more loose stools passed within 24 hours, or more frequently than is normal for the individual''. The primary outcomes of diarrheal disease will focus both on incidence and longitudinal prevalence. The method is therefore twofold. First, the female household head will be surveyed on diarrhoea cases in the previous seven days among children below five years of age at each follow-up wave. Second, each household will be provided with a diary to indicate whether a child experienced diarrhoea on a daily basis. These diaries will be collected by the VHTs every two weeks before or after religious meetings. The outcome of interest ‘diarrhoea’ will be obscure to the target population, as the relevant symptom diarrhoea will be added to a list of other symptoms such as fever and cough both for the survey and the diary method (see also Performance and expectancy biases, p.14). The incidence outcomes will be reported binary by addressing whether a child had diarrhoea in the previous seven days. The longitudinal prevalence will be reported as a continuous variable indicating the number of days with diarrhoea between the survey waves and over the full 18-month period.

3. At each household visit the enumerators observe whether the water storage container or filter contains treated drinking water, a possible objective indicator of cook stove or filter use (Rosa et al., 2014). Furthermore, the self-reported use of the cook stove and the drinking water filter will be surveyed. The respondent responsible for the cook stove or the filter will be asked when water treatment was last applied. If the treatment method is no longer being used or has broken down (irreversibly clogged, damaged etc.), the time it went out of service will be recorded and the filter or cook stove will be replaced by a new one. The objective and subjective use of the filter will both be expressed binary, respectively based on the presence of (treated) water and the reported use in the previous day (or today).

4. To address financial savings due to water filtration or energy efficient boiling, all respondents will be surveyed on the household expenses for charcoal, firewood or other fuels used for the treatment of drinking water or cooking in the previous seven days. Since households could receive charcoal, firewood or other fuels from relatives, they will also be questioned on the amount of each consumed in the previous seven days. Additionally, 40 households receiving the cook stove will be closely monitored during one week at each follow-up to weigh the exact amount of wood fuel used for boiling. The total monetary value will be both expressed in the local currency Ugandan Shilling and converted to US Dollar. If a household collects firewood for free from the surrounding bushes, the time spent to collect firewood in the previous seven days will be estimated by multiplying the number of roundtrips with the average timespan needed to collect firewood. The time saved will be expressed in hours.

1. Drinking water quality
2. Diarrhoeal disease
3. Uptake
4. Household savings

1. Apart from the primary outcomes TTC, E.coli and turbidity for drinking water quality at home, secondary outcomes are considered. First, households will be asked about their primary water source. These choices could change due to seasonal availability of water, but also because of the intervention. For instance, receiving a water filter could induce households to fetch water at more turbid sources closer to the home. We survey whether there is a qualitative change in the nature of the source (well, borehole etc.). Next, we analyse a water sample of each indicated source on the same characteristics as outlined above to determine potential changes in source water quality over the course of the intervention. Second, we analyse the consumption of porridge by the households in the last seven days. Porridge is a slightly alcoholic homebrew drink composed from maize, cassava and/or yeast flower mixed with water. It is often brewed as a substitute for water, in the absence of a potable water source.
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3. As a secondary outcome, the respondent will be asked whether a household member drank unfiltered or non-boiled water in the previous day. If this is the case, the respondent will be asked whether another method was used or whether the water was left untreated. Reasons addressed by the responsible household member will be recorded. This measure of adherence to treated water also will be reported binary, and separately for children below five, children above five and adults. All reasons addressed for not drinking treated water will be listed and thematically ordered.

4. As secondary outcomes, the indirect savings in resources and time due to lower health care expenses and less absent days at school or work because of diarrhoea will be recorded. The respondent will be surveyed about medical expenditures and the absence of children and adults due to diarrhoea in the previous seven days. The first will be reported in monetary terms as outlined above, while the latter will be reported in number of days.

Experimental evidence to answer the four research questions will be obtained by a four-arm randomised controlled trial over an 18-month period. The trial will include three treatment groups that each receive either a cook stove for energy efficient boiling, the ceramic filter or a membrane filter, and one control group that continues business as usual. The RCT design allows to identify and compare the long run causal impacts of the three treatments on uptake, microbiological water quality, diarrheal disease among young children and household time and money savings. Data will be obtained by a baseline survey and four follow-up surveys, accompanied by drinking water quality analysis at point of source and point of use. The treatment will be phased-in, i.e. all households in the control group will receive a water filter at the end of the experiment.

Not available

The randomization is done per strata, which is in this study the two districts of interest. All eligible households in the two districts are randomly assigned to the four trial arms (boiling, ceramic filter, membrane filter and business as usual) with an assignment rate of 25% in each arm. The study arms are non-overlapping arms. The randomization is done by means of the random number generator in Stata 17.

Randomisation is done at household level. This is individual randomisation for the outcomes drinking water quality, uptake and household savings. This is group level randomisation for the outcome diarrhoeal disease, since a household often counts multiple children below five years.

No

The households can be considered as clusters for the outcome diarrheal disease (for reasons outlined above).
600 households are involved in this study.

600 households and approximately 1200 children.

The four treatment arms all contain 150 households and approximately 300 children.

600 households evenly divided over four treatment arms account for a small to medium standardised minimal detectable effect size of 0.36 in TTC. An 18 pp difference in the number of samples containing TTC between the membrane filter and the ceramic filters can be detected. 600 households with two children under-five evenly divided over four treatment arms account for a small to medium standardised minimal detectable effect size of 0.26 in diarrheal disease. A 9 pp difference in the number of children below five years experiencing diarrhoea in the last week between the membrane filter and the ceramic filter can be detected. The estimated effect sizes are rather conservative as they already account for 5% non-compliance in the treatment group and 10% attrition. Moreover, these calculations do not consider the increased power stemming from the multiple rounds of post-treatment data collection, as suggested by McKenzie (2012).