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.

Regression models for predicting the die-off rate of E. coli in solar water disinfection

“…Another factor that aids disinfection in turbid water is water temperature which is usually higher due to the capacity of suspended particles to trap radiant heat emitted by the sun as infrared (IR). Amirsoleimani & Brion (2021) reported a statistically significant difference between the temperatures of 0 and 30 NTU SODIS water exposed to the same conditions in which SODIS containers with 30 NTU water were found to be much hotter. Improved efficiency has been reported in SODIS treating moderately turbid water (38 NTU) when compared with SODIS efficiency treating water of low turbidities (,5 NTU) (Meera & Ahammed 2008).…”

“…Water turbidity is an extremely important consideration in the application of SODIS. Previous studies have largely shown that the disinfection effectiveness of SODIS decreases significantly with increasing water turbidity (McGuigan et al 1998;Gómez-Couso et al 2009;Amirsoleimani & Brion 2021). For example, increasing turbidity from 0 to 200 NTU was found to decrease the die-off rate of E. coli from 5 to 1 log (Amirsoleimani & Brion 2021).…”

“…Previous studies have largely shown that the disinfection effectiveness of SODIS decreases significantly with increasing water turbidity (McGuigan et al 1998;Gómez-Couso et al 2009;Amirsoleimani & Brion 2021). For example, increasing turbidity from 0 to 200 NTU was found to decrease the die-off rate of E. coli from 5 to 1 log (Amirsoleimani & Brion 2021). This is because the depth of light penetration is significantly reduced in highly turbid water which interferes with the SODIS processes (Marques et al 2013).…”

Insights into Solar Disinfection Enhancements for Drinking Water Treatment Applications

“…the same inactivation results were only achieved when the temperature reached 60 • C [73]. Amirsoleimani and Brion [74] stated that the inactivation of E. coli markedly decreased (from 5 to 1 log) with the increase of water turbidity from 0 to 200 NTU. The authors followed the same protocol and found that more than 4-log inactivation of two Gram-positive bacteria (Staphylococcus epidermidis and Staphylococcus aureus) was achieved.…”