Solar disinfection of turbid hygiene waters in Lexington, KY, USA

Abstract

Solar disinfection (SODIS) could be a key to providing a clean, hygiene water for birthing uses, but the recommended climate zone is limited, the microbial indicators are related to gastrointestinal illness and not wound infections. SODIS feasibility was investigated to remove Escherichia coli from turbid water at temperatures less than 50 °C in Lexington, KY. Increasing turbidity from 0 to 200 NTU decreased E. coli inactivation from 5 to 1 log. With the same experimental protocol, more than 4-log inactivation of Staphylococcus aureus and Staphylococcus epidermidis (common human-skin microorganisms related to serious post-partum infections of both mother and child) was achieved at different turbidity levels with a maximum, in-bottle temperature of 49.2 °C after 5.5 h. The thermal inactivation of the bacterial indicators was assessed without UV radiation and turbidity in water at 37 and 47 °C. Skin bacteria were inactivated completely after 9.5 h at 47 °C, but only 58% removal happened for thermo-tolerant E. coli. These results suggest that SODIS application may be expanded geographically to treat water for hygiene purposes. However, as E. coli is also capable of causing wound infections, UV with thermal inactivation may be required to produce safe hygiene water by SODIS outside of recommended latitudes. HIGHLIGHTS Solar disinfection (SODIS) was applied for the first time to remove Staphylococcus aureus from water to provide safe hygiene water for birthing.; Human skin bacteria are more susceptible to thermal inactivation than gastrointestinal bacteria.; SODIS protocols need to be updated to evaluate process indicators bacteria for hygiene purposes.; Consideration of solar disinfection for treating contaminated water for hygiene purposes could have a significant positive impact on saving the lives of women in labour and those of their newborns and decreasing the number of postpartum infections.;

Keywords

• hygiene
• solar disinfection
• staphylococcus aureus
• thermal resistance
• turbidity
• water