Water, sanitation and hygiene-related diseases are responsible for 7% of all deaths and 8% of all disability adjusted live years (DALYs), as well as the loss of 320 million days of productivity in developing countries. Though laboratory and field trials have shown that household water treatment (HWT) technologies can quickly improve the microbiological quality of drinking water, questions remain about the effectiveness of these technologies under real-world conditions. Furthermore, the value that rural communities attach to HWT is unknown, and it is not clear why, in spite of the fact that rural African households need household water treatment (HWT) most, they are the least likely to use them. The primary objective of this multi-level study was to assess the post-implementation effectiveness of selected HWT technologies in the Nyanza and Western Provinces of Kenya. The study was carried out in the rainy season between March and May, 2011 using a mixed method approach. Evidence was collected in order to build a case of evidence of HWT effectiveness or ineffectiveness in a post-implementation context. A quasi-experimental design was used first to conduct a Knowledge, Attitudes and Practices (KAP) survey in 474 households in ten intervention and five control villages (Chapter 3). The survey assessed the context in which household water treatment was being used in the study villages to provide real-world information for assessing the effectiveness of the technologies. An interviewer-administered questionnaire elicited information about the water, sanitation and hygiene-related KAP of the study communities. A household water treatment (HWT) survey (Chapter 4) was carried out in the same study households and villages as the KAP study, using a semi-structured questionnaire to gather HWT adoption, compliance and sustained use-related information to provide insight into the perceived value the study households attach to HWT technologies, and their likelihood of adoption of and compliance with these technologies. The drinking water quality of 171 (one quarter of those surveyed during KAP) randomly selected households was determined and tracked from source to the point of use (Chapter 5). This provided insights into HWT effectiveness by highlighting the need for HWT (as indicated by source water quality) and the effect of the study households’ KAP on drinking water quality (as indicated by the stored water quality). Physico-chemical and microbiological water quality of the nineteen improved and unimproved sources used by the study households was determined, according to the World Health Organisation guidelines. The microbiological quality of 291 water samples in six intervention and five control villages was determined from source to the point-of-use (POU) using the WHO and Sphere Drinking Water Quality Guidelines. An observational study design was then used to assess the post-implementation effectiveness of the technologies used in 37 households in five intervention villages (Chapter 6). Three assessments were carried out to determine the changes in the microbiological quality of 107 drinking water samples before treatment (from collection container) and after treatment (from storage container) by the households. The criteria used to assess the performance of the technologies were microbial efficacy, robustness and performance in relation to sector standards. A Quantitative Microbial Risk Assessment (QMRA) was then carried out in the HWT effectiveness study households to assess the technologies’ ability to reduce the users’ exposure to and probability of infection with water-borne pathogens (Chapter 7). The KAP survey showed that the intervention and control communities did not differ significantly in 18 out of 20 socio-economic variables that could potentially be influenced by the structured manner of introducing HWT into the intervention villages. The majority of the intervention group (IG) and the control group (CG) were poor or very poor on the basis of household assets they owned. The predominant level of education for almost two-thirds of the IG and CG respondents was primary school (completed and non-completed). Though very few were unemployed in IG (8.07%) and CG (14.29%), the two groups of respondents were predominantly engaged in subsistence farming — a low income occupation. With regard to practices, both groups had inadequate access to water and sanitation with only one in two of the households in both IG and CG using improved water sources as their main drinking water source in the non-rainy season. One in ten households in both study groups possessed an improved sanitation facility, though the CG was significantly more likely to practice open defecation than the IG. The self-reported use of soap in both study groups was mainly for bathing and not for handwashing after faecal contact with adult or child faeces. Despite the study groups' knowledge about diarrhoea, both groups showed a disconnection between their knowledge about routes of contamination and barriers to contamination. The most frequent reason for not treating water was the perceived safety of rain water in both the IG and CG. / The HWT adoption survey revealed poor storage and water-handling practices in both IG and CG, and that very few respondents knew how to use the HWT technologies correctly: The IG and CG were similar in perceived value attached to household water treatment. All HWT technologies had a lower likelihood of adoption compared to the likelihood of compliance indicators in both IG and CG. The users’ perceptions about efficacy, time taken and ease of use of the HWT technologies lowered the perceived value attached to the technologies. The assessment of the drinking water quality used by the study communities indicated that the improved sources had a lower geometric mean E. coli and total coliform count than the unimproved sources. Both categories of sources were of poor microbiological quality and both exceeded the Sphere Project (2004) and the WHO (2008) guidelines for total coliforms and E. Coli respectively The study communities’ predominant drinking water sources, surface water and rainwater were faecally contaminated (geometric mean E. coli load of 388.1±30.45 and 38.9±22.35 cfu/100 ml respectively) and needed effective HWT. The improved sources were significantly more likely than the unimproved sources to have a higher proportion of samples that complied with the WHO drinking water guidelines at source, highlighting the importance of providing improved water sources. The lowest levels of faecal contamination were observed between the collection and storage points which coincided with the stage at which HWT is normally applied, suggesting an HWT effect on the water quality. All water sources had nitrate and turbidity levels that exceeded the WHO stipulated guidelines, while some of the improved and unimproved sources had higher than permissible levels of lead, manganese and aluminium. The water source category and the mouth type of the storage container were predictive of the stored water quality. The active treater households had a higher percentage of samples that complied with WHO water quality guidelines for E. coli than inactive treater households in both improved and unimproved source categories. In inactive treater households, 65% of storage container water samples from the improved sources complied with the WHO guidelines in comparison to 72% of the stored water samples in the active treater households. However the differences were not statistically significant. The HWT technologies did not attain sector standards of effective performance: in descending order, the mean log10 reduction in E. coli concentrations after treatment of water from unimproved sources was PUR (log₁₀ 2.0), ceramic filters (log₁₀ 1.57), Aquatab (log₁₀ 1.06) and Waterguard (log₁₀ 0.44). The mean log10 reduction in E. coli after treatment of water from improved sources was Aquatab (log₁₀ 2.3), Waterguard (log₁₀ 1.43), PUR (log₁₀ 0.94) and ceramic filters (log₁₀ 0.16). The HWT technologies reduced the user’s daily exposure to water-borne pathogens from both unimproved and improved drinking water sources. The mean difference in exposure after treatment of water from unimproved sources was ceramic filter (log₁₀ 2.1), Aquatab (log₁₀ 1.9), PUR (log₁₀ 1.5) and Waterguard (log₁₀ 0.9), in descending order. The mean probability of infection with water-borne pathogens (using E.coli as indicator) after consumption of treated water from both improved and unimproved sources was reduced in users of all the HWT technologies. The difference in reduction between technologies was not statistically significant. The study concluded that despite the apparent need for HWT, the study households’ inadequate knowledge, poor attitudes and unhygienic practices make it unlikely that they will use the technologies effectively to reduce microbial concentrations to the standards stipulated by accepted drinking water quality guidelines. The structured method of HWT promotion in the intervention villages had not resulted in more hygienic water and sanitation KAP in the IG compared to the CG, or significant differences in likelihood of adoption and compliance with the assessed HWT technologies. Despite attaching a high perceived value to HWT, insufficient knowledge about how to use the HWT technologies and user concerns about factors such as ease of use, accessibility and time to use will impact negatively on adoption and compliance with HWT, notwithstanding their efficacy during field trials. Even though external support had been withdrawn, the assessed HWT technologies were able improve the quality of household drinking water and reduce the exposure and risk of water-borne infections. However, the improvement in water quality and reduction in risk did not attain sector guidelines, highlighting the need to address the attitudes, practices and design criteria identified in this study which limit the adoption, compliance and effective use of these technologies. These findings have implications for HWT interventions, emphasising the need for practice-based behavioural support alongside technical support.