Abstract
Providing safe fecal sludge (FS) sanitation has remained an important goal of global communities because of the high risks imposed on human health of the exposure to un-sanitized FS. This study used lactic acid fermentation as a pre-treatment technology to evaluate the sanitization effect of lactic acid bacteria (LAB) on FS. A combination of fermented rice flour and brown sugar was used as the medium to prepare LAB, and fecal coliforms were used as the indicator organisms. The addition of a LAB suspension grown in fermented rice flour and brown sugar to FS was studied to evaluate the survival of fecal coliforms. The pH decreased during ongoing lactic acid fermentation after the addition of the LAB suspension. The results revealed that fecal coliforms in reactors containing 1:1 and 2:1 w/w of FS and LAB suspension decreased to half of the initial concentration within seven days of the treatment process in comparison with that of the control reactor. Viable plate counts of 0.6 × 108, 0.9 × 108, and 2.4 × 108 CFU/100 mL were recorded from reactors 1:1, 2:1, and the control, respectively. The total elimination of the fecal coliforms below the detection limit (<3 log 10 CFU/100 mL) was observed in both reactors after 15–17 days, whereas the number of fecal coliforms remained at 2.3 × 108 CFU/100 mL in the control reactor. The fecal coliforms were eliminated because of the acidification caused by the LAB during the incubation time. The final pH in the treatment reactors 1:1 and 2:1 was 3.7 and 3.9. While the final pH in the control reactor was 7.91. The results revealed that the bacterial pathogens in FS can be completely eliminated through a low-cost technique and a simple lactic acid fermentation process.
Highlights
Recent works aim to improve the sustainability of fecal sludge (FS) management for resource recovery (Andreev et al, 2018; Bracken et al, 2005; World Health Organization (WHO) & (UNICEF), 2014)
The pH in the control remained within 7.53e7.91 throughout the experiment. These results suggested that two main factors influenced the sanitizing time and the efficiency of the lactic acid fermentation of FS, which include the combination of rice flour and brown sugar and the rapid drop of pH
This study demonstrated for the first time that the combination of fermented rice flour and brown sugar could be applied for the quick treatment of FS to reduce its pathogens and odor content before further treatment for soil amendment
Summary
Recent works aim to improve the sustainability of fecal sludge (FS) management for resource recovery (Andreev et al, 2018; Bracken et al, 2005; World Health Organization (WHO) & (UNICEF), 2014). Human feces could increase the soil fertility to achieve sustainable agriculture (Kimetu et al, 2004). The high concentrations of pathogens and several harmful organisms that are found in feces can contaminate the soil and crops (al-Ghazali & al-Azawi, 1990; Bracken et al, 2005; Jiang et al, 2002). Fresh human feces contains high amounts of pathogens, such as fecal coliforms, Helminth eggs, Escherichia coli, Salmonella spp, fecal streptococcus, and other bacteria, all of which are harmful to humans (Gold et al, 2017; Langergraber and Muellegger, 2005; Yemaneh, 2015). The direct use of FS in agriculture results in unhygienic conditions (Dold and Holland, 2011; Forbis-Stokes et al, 2016; Langergraber and Muellegger, 2005)
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