Bacterial community structure transformed after thermophilically composting human waste in Haiti

Abstract

Recycling human waste for beneficial use has been practiced for millennia. Aerobic (thermophilic) composting of sewage sludge has been shown to reduce populations of opportunistically pathogenic bacteria and to inactivate both Ascaris eggs and culturable Escherichia coli in raw waste, but there is still a question about the fate of most fecal bacteria when raw material is composted directly. This study undertook a comprehensive microbial community analysis of composting material at various stages collected over 6 months at two composting facilities in Haiti. The fecal microbiota signal was monitored using a high-density DNA microarray (PhyloChip). Thermophilic composting altered the bacterial community structure of the starting material. Typical fecal bacteria classified in the following groups were present in at least half the starting material samples, yet were reduced below detection in finished compost: Prevotella and Erysipelotrichaceae (100% reduction of initial presence), Ruminococcaceae (98–99%), Lachnospiraceae (83–94%, primarily unclassified taxa remained), Escherichia and Shigella (100%). Opportunistic pathogens were reduced below the level of detection in the final product with the exception of Clostridium tetani, which could have survived in a spore state or been reintroduced late in the outdoor maturation process. Conversely, thermotolerant or thermophilic Actinomycetes and Firmicutes (e.g., Thermobifida, Bacillus, Geobacillus) typically found in compost increased substantially during the thermophilic stage. This community DNA-based assessment of the fate of human fecal microbiota during thermophilic composting will help optimize this process as a sanitation solution in areas where infrastructure and resources are limited.

Greenhouse gas fluxes from human waste management pathways in Haiti

“…Currently, 32% of the global population rely on sanitation services that are considered less than basic needs, and only 39% of the global population has access to safely managed sanitation services that considers the full life cycle of this organic waste stream (WHO/ UNICEF, 2017). EcoSan via the thermophilic composting of solid organic waste has been shown to be effective at eliminating pathogenic microorganisms (Piceno et al, 2017) and Ascaris, a parasitic nematode that causes intestinal disease (Berendes et al, 2015). It is also thought to be a cost-effective alternative to sewered systems or waste stabilization ponds, particularly in areas of the world where financial resources and infrastructure are limited (WWC, 2018).…”

Biological and thermochemical conversion of human solid waste to soil amendments

“…Sanergy HSW compost and thermochemically-processed HSW used in our research was fully sterilized. Nevertheless, other studies have described difficulties in sterilizing HSW through thermophilic composting (Niwagaba et al, 2009, Lemunier et al, 2005, Piceno et al, 2017). Lemunier et al (2005) observed Salmonella serovar Enteritidis colonies in mature, thermophilically-composted HSW after 12 weeks.…”

Realizing the Circular Economy for Sanitation: Assessing Enabling Conditions and Barriers to the Commercialization of Human Excreta Derived Fertilizer in Haiti and Kenya

“…The buckets are emptied into large composting bins; the walls are made up of pallets filled with carbon-rich material like straw to allow for air to flow through and provide sufficient aeration in the bin. The treatment process has previously been described in Berendes et al [23] and Piceno et al [24]. The bin is sealed when full and left untouched for 2-3 months depending on the temperature and pathogen concentration evolution in the compost bins.…”