Lactic Acid Fermentation, Urea and Lime Addition: Promising Faecal Sludge Sanitizing Methods for Emergency Sanitation

Abstract

In this research, three faecal sludge sanitizing methods—lactic acid fermentation, urea treatment and lime treatment—were studied for application in emergency situations. These methods were investigated by undertaking small scale field trials with pit latrine sludge in Blantyre, Malawi. Hydrated lime was able to reduce the E. coli count in the sludge to below the detectable limit within 1 h applying a pH > 11 (using a dosage from 7% to 17% w/w, depending faecal sludge alkalinity), urea treatment required about 4 days using 2.5% wet weight urea addition, and lactic acid fermentation needed approximately 1 week after being dosed with 10% wet weight molasses (2 g (glucose/fructose)/kg) and 10% wet weight pre-culture (99.8% pasteurised whole milk and 0.02% fermented milk drink containing Lactobacillus casei Shirota). Based on Malawian prices, the cost of sanitizing 1 m3 of faecal sludge was estimated to be €32 for lactic acid fermentation, €20 for urea treatment and €12 for hydrated lime treatment.

Off-Site Lime Stabilisation as an Option to Treat Pit Latrine Faecal Sludge for Emergency and Existing On-Site Sanitation Systems

“…In line with other previous studies [10,12,21], lime stabilisation in this study was able to sanitise faecal sludge to below the detection limit of 10 4 CFU/100 mL during four replica small-scale field trials. During the upscaled field trial the WHO standard guideline of 1000 CFU/100 mL was achieved within 1 hour at pH 12.…”

Development of a Field Laboratory for Monitoring of Fecal-Sludge Treatment Plants

“…During the bacteriological analysis of sterilized soil spiked with E. coli, a significantly lower standard deviation was found than in similar research [36]. The difference in the bacteriological results between samplers, with a standard deviation of 0.4 log units, was found to be in range with results presented by the literature [5,37].…”

“…The impact of untreated fecal sludge released in the environment is quite dramatic and may result in algae blooms, pest problems, and overfertilization of fields. FS-treatment processes, decision-making tools for field use in humanitarian aid are currently being developed [2,4,5]. The importance of the regular monitoring of FS treatment plants is stressed in the literature [6,7].…”

“…Thus, it was deemed highly important to enable the field laboratory to monitor a broad spectrum of different processes. A list of field-applicable treatment processes (Table 1) was compiled out of different literature sources [5,[10][11][12]. Regarding these processes, a basic set of parameters for the field laboratory (Table 1) was established by a literature search [6,7,[12][13][14][15][16][17] before onset of the development.…”

Structured Approach for Comparison of Treatment Options for Nutrient-Recovery From Fecal Sludge

“…Step 3: Multi-Dimensional Sustainability Assessment Analysis of the interviews with local stakeholders revealed several sustainability criteria of importance for nutrient recycling from Composting* X X X X Strauss et al, 2003;Strande et al, 2014;Komakech et al, 2015 Vermicomposting* X X X X Strande et al, 2014;Komakech et al, 2015;Bhat et al, 2018 Fly larvae composting* X X X X Strande et al, 2014;Komakech et al, 2015 Anaerobic treatment X X X Diener et al, 2014;Strande et al, 2014 Lactic acid fermentation X X X X Anderson et al, 2015;Andreev, 2017;Odey et al, 2018 Productive wetland X X X Koottatep et al, 2005;Strande et al, 2014 Algae production X X Grobbelaar, 2004;Barbera et al, 2018 Aquaculture X X Strande et al, 2014 Microbial fuel cells X X Raheem et al, 2018;Lu et al, 2019;Palanisamy et al, 2019 Chemical Precipitation X X X Shiba and Ntuli, 2017;Chapeyama et al, 2018;Tarragó et al, 2018;Li et al, 2019 Stripping and capture X Harder et al, 2019…”