Solar water disinfection in large-volume containers: from the laboratory to the field. A case study in Tigray, Ethiopia

The lack of safe drinking water affects communities in low-to-medium-income countries most. This barrier can be overcome by using sustainable point-of-use water treatments. Solar energy has been used to disinfect water for decades, and several efforts have been made to optimise the standard procedure of solar water disinfection (SODIS process). However, the Health Impact Assessment of implementing advanced technologies in the field is also a critical step in evaluating the success of the optimisation. This work reports a sustainable scaling-up of SODIS from standard 2 L bottles to 25 L transparent jerrycans (TJC) and a 12-month field implementation in four sites of Tigray in Ethiopia, where 80.5% of the population lives without reliable access to safe drinking water and whose initial baseline average rate of diarrhoeal disease in children under 5 years was 13.5%. The UVA dose required for 3-log reduction of E. coli was always lower than the minimum UVA daily dose received in Tigray (9411 ± 55 Wh/m 2 ). Results confirmed a similar decrease in cases of diarrhoea in children in the implementation (25 L PET TJC) and control (2 L PET bottles) groups, supporting the feasibility of increasing the volume of the SODIS water containers to produce safer drinking water with a sustainable and user-friendly process.