Microbiological Evaluation of 5 L- and 20 L Transparent Polypropylene Buckets for Solar Water Disinfection (SODIS)

Background: Solar water disinfection (SODIS) is an appropriate technology for household
treatment of drinking water in low-to-middle-income communities, as it is effective, low cost and easy
to use. Nevertheless, uptake is low due partially to the burden of using small volume polyethylene
terephthalate bottles (1.5–2 L). A major challenge is to develop a low-cost transparent container for
disinfecting larger volumes of water. (2) Methods: This study examines the capability of transparent
polypropylene (PP) buckets of 5 L- and 20 L- volume as SODIS containers using three waterborne
pathogen indicators: Escherichia coli, MS2-phage and Cryptosporidium parvum. (3) Results: Similar
inactivation kinetics were observed under natural sunlight for the inactivation of all three organisms in
well water using 5 L- and 20 L-buckets compared to 1.5 L-polyethylene-terephthalate (PET) bottles. The
PP materials were exposed to natural and accelerated solar ageing (ISO-16474). UV transmission of the
20 L-buckets remained stable and with physical integrity even after the longest ageing periods (9 months
or 900 h of natural or artificial solar UV exposure, respectively). The 5 L-buckets were physically
degraded and lost significant UV-transmission, due to the thinner wall compared to the 20 L-bucket. (4)
Conclusion: This work demonstrates that the 20 L SODIS bucket technology produces excellent bacterial,
viral and protozoan inactivation and is obtained using a simple transparent polypropylene bucket
fabricated locally at very low cost ($2.90 USD per unit). The increased bucket volume of 20 L allows for
a ten-fold increase in treatment batch volume and can thus more easily provide for the drinking water
requirements of most households. The use of buckets in households across low to middle income
countries is an already accepted practice.