Optimization of lactic acid fermentation for pathogen inactivation in fecal sludge

Emmanuel Alepu Odey,Zifu Li,Xiaoqin Zhou,Yichang Yan

doi:10.1016/j.ecoenv.2018.03.075

Emmanuel Alepu Odey, Zifu Li + Show 2 more

Open Access

https://doi.org/10.1016/j.ecoenv.2018.03.075

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Abstract

The efficiency of lactic acid fermentation (LAF) as a pretreatment for human feces was investigated in laboratory-scale experiments that lasted for 3 weeks. The sanitization effect of LAF on fecal sludge (FS) was conducted in triplicate. This study used three materials, namely, lactobacillus of lactic acid bacteria, fermented cassava flour, and fermented rice flour, which were known to enhance the production of lactic acid. Each material was mixed in three different reactors at equal ratio with raw FS (i.e., 1:1 v/w, w/w, and w/w). The pH decline rate, lactic acid production rate, and fecal coliform suppression degree were monitored over the period of the treatment process as parameters to evaluate the efficiency of various LAF for pathogen inactivation in FS. Results showed that only fermented rice flour was able to completely inactivate the indicator organism (fecal coliform) at the end of fermentation. Final plate counts of 8.6 × 108 CFU/100 mL, 2.4 × 108 CFU/100 mL, and zero (0) were achieved from lactobacillus, fermented cassava flour, and fermented rice flour treatment processes, respectively. The final pH from the reactors that contained lactobacillus and FS, cassava flour and FS, and fermented rice flour and FS were 5.5, 8, and 3.9, respectively. This study revealed that not all LAF materials can effectively suppress pathogens in FS. The results serve as the foundation in developing an effective, cheap, and easy to use LAF on FS pretreatment for pathogen inactivation.

Highlights

Adequate facilities for the safe treatment or disposal of fecal sludge (FS) should be established globally
To determine the lactic acid content and production efficiency of lactic acid fermentation (LAF) from fermented materials and their fermentation efficiency when applied in LAF of FS, the community composition and dynamics of LAB associated with lactobacillus, cassava flour, and rice flour fermentation were investigated by using a culture-dependent approach
The results showed that Lactobacillus Sp., which was a strain from fermented rice flour, produced high lactic acid content compared to cassava flour and lactobacillus

Summary

Introduction

Adequate facilities for the safe treatment or disposal of fecal sludge (FS) should be established globally. A study revealed that about 1800 children die every day due to diseases associated with inadequate hygiene, lack of sanitation, and contaminated water (UNICEF, 2013) To address these issues, the millennium development goal (MDG) target aimed to reduce the 2.5 billion people without adequate sanitation in half by 2015. In the past few years, dry and low water sanitation has gained worldwide attention with the concept that FS can be directly processed at the point of recovery or collected and transported to the point of treatment (Mackie Jensen et al, 2008; Verbyla et al, 2016; Yemaneh et al, 2012) Several products, such as fertilizers, biofuels, water, biogas and compost, can be recovered after treatment (Bracken and Ysunza, 2005; Jepsen et al, 1997; World Health Organization (WHO) (WHO) and (UNICEF), 2014)

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