RESUMEN
Water, sanitation, and hygiene provisions are essential during emergencies to prevent infectious disease outbreaks caused by improper human excreta management in settlements for people affected by natural disasters and conflicts. Human excreta disinfection is required when long-term containment in latrines is not feasible on-site. Alkali additives, including lime, are effective disinfectants for wastewater and faecal sludge containing large amounts of solid and dissolved organic matter. The aim of this study was to determine the minimum dose and contact time of alkali additives for treating virus-containing human excreta in emergency situations. We used literature data collected by searching Google Scholar and Web of Science. The date of the last search for each study was 31th May 2023. Only peer-reviewed articles that included disinfection practices in combination with quantitative data for the physicochemical data of a matrix and viral decay were selected for data extraction. Two reviewers independently collected data from each study. We extracted datasets from 14 studies that reported quantitative information about their disinfection tests, including viral decay over time, matrix types, and physicochemical properties. Three machine learning algorithms were applied to the collected dataset to determine the time required to achieve specified levels of virus inactivation under different environmental conditions. The best model was used to estimate the contact time to achieve a 3-log10 inactivation of RNA virus in wastewater and faeces. The most important variables for predicting the contact time were pH, temperature, and virus type. The estimated contact time for 3 log inactivation of RNA virus was <2 h at pH 12, which was achieved by adding 1.8 and 3.1% slaked lime to wastewater and faeces, respectively. The contact time decreased exponentially with the pH of the sludge and wastewater. In contrast, the pH of the sludge and wastewater increased linearly with the slaked lime dosage. Lime treatment is a promising measure where long-term containment in latrine is not feasible in densely populated areas, as 1 day is sufficient to inactivate viruses. The relationship we have identified between required contact time and lime dosage is useful for practitioners in determining appropriate treatment conditions of human waste.
Asunto(s)
Desinfectantes , Virus , Humanos , Aguas Residuales , Aguas del Alcantarillado/químicaRESUMEN
BACKGROUND: Fortification of rice with slaked lime is an acceptable and inexpensive way to combat calcium (Ca) deficiency. However, bioavailability of calcium after intake of slaked lime fortified rice is yet to be investigated. OBJECTIVE: To measure the fractional absorption of Ca (FAC) from slaked lime fortified cooked rice. DESIGN: We conducted an experimental study using stable isotopes of Ca to measure FAC during a single morning test meal containing rice fortified with slaked lime. Participants (n = 22) were given slaked lime fortified rice 3 times a day for 4 days. On the morning of the fifth day, the participants were served the same amount of rice as previous the 4 days at the breakfast test meal with an accurately measured amount of 44Ca stable isotope oral tracer followed by an intravenous injection of 42Ca. Urine was collected over the next 24 hours in 3 consecutive 8-hour pools. Fractional absorption of Ca was calculated from the measurement of the relative enrichment of the of each administered tracer 44Ca and 42Ca using inductively coupled plasma mass spectrometry. RESULTS: The mean Ca concentration in the test meal was 879.5 ± 152.9 µg/g with a coefficient of variance (CV) of 17.2%. Although Ca absorption efficiency decreases with higher calcium intake, the total amount of calcium absorbed from test meal using FAC = 0.391 calculated from the third 8-hour urine pool was 69.0 (CV of 15.6) mg. CONCLUSIONS: We showed that one-fifth of daily calcium recommendation for women of reproductive age could be met by ingesting â¼200 g cooked slake fortified rice.