Assessment of the 20L SODIS bucket household water treatment technology under field conditions in rural Malawi.

Steven Brockliss,Kondwani Luwe,Tracy Morse,Giuliana Ferrero

doi:10.1016/j.ijheh.2021.113913

Abstract

Two billion people worldwide consume unsafe drinking water. The problem is particularly pronounced in Sub-Saharan Africa, where more than a quarter of the population relies on unimproved surface water sources. Based on the principles of solar water disinfection (SODIS), a new household water treatment technology, the SODIS bucket, was developed to improve the microbial quality of water from these sources based on controlled tests in a laboratory setting. This study set out to evaluate the efficacy of the technology in a field setting, in rural communities in the Chikwawa District in southern Malawi. SODIS experiments were carried out in two different vessels (1-L PET bottles and 20-L polypropylene SODIS buckets), over three months using unprotected water sources normally used by community members. Vessels were exposed to direct sunlight for 8h per day in a village setting and were sampled at regular intervals to determine total coliforms, E. coli, turbidity, UV transmittance and UV dose. In these experiments, the SODIS bucket reached inactivation targets for E. coli (<1CFU/100mL) in two of seven experiments and for total coliforms in one of seven for total coliforms (<50CFU/100mL), despite having greater UV doses than were seen in the evaluation carried out under controlled conditions during the bucket's development. PET bottles reached inactivation targets for both E. coli and total coliforms in five of seven experiments. There was no single factor that could be identified as preventing adequate inactivation, but the role of organic matter, inconsistent nature of the water source, and vessel size, when coupled with organic matter, were identified as contributing factors. This study highlights the need for further prototyping to provide a suitable pre-treatment step for unprotected water sources, and the importance of field testing with real-life parameters to ensure new technologies are context appropriate.

Highlights

Access to safe drinking water is essential to human health
In Sub-Saharan Africa, this problem is pronounced, where 26% of the population is reliant on unimproved water sources (UNICEF and World Health Organisation (WHO), 2019), and inadequate Water Sanitation and Hy giene (WASH) has been attributed to 60% of all diarrhoeal deaths (Prüss-Ustün et al, 2019)
For both Polyethylene Terephthalate (PET) bottles and solar water disinfection (SODIS) buckets, samples were collected in triplicate with samples from PET bottles collected from three different vessels and for the SODIS buckets, the three samples were collected from the same vessel

Summary

Introduction

Access to safe drinking water is essential to human health. Unsafe drinking water is estimated to cause 485,000 diarrhoeal deaths annually through the transmission of infectious diseases, of which up to 90% are children (WHO, 2019, 2007). Even when diarrhoea does not result in death it has long-lasting effects; delaying growth and development by reducing the intake of calories and nutrients. This puts at risk the 144 million people who are dependent on unimproved surface water sources such as rivers, lakes, ponds, and canals globally (UNICEF and WHO, 2019). A large proportion of the popu lation does not have access to water which is safely managed as described in the United Nations Sustainable Development Goals

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