Fate of faecal pathogen indicators during faecal sludge composting with different bulking agents in tropical climate

M Manga; M A Camargo-Valero; C Anthonj; B E Evans

doi:10.1016/j.ijheh.2020.113670

Fate of faecal pathogen indicators during faecal sludge composting with different bulking agents in tropical climate

Int J Hyg Environ Health. 2021 Mar:232:113670. doi: 10.1016/j.ijheh.2020.113670. Epub 2020 Dec 9.

Authors

M Manga¹, M A Camargo-Valero², C Anthonj³, B E Evans⁴

Affiliations

¹ The Water Institute at UNC, Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, 4114 McGavran Hall, Campus Box # 7431, NC 27599, Chapel Hill, NC, USA; BioResource Systems Research Group, School of Civil Engineering, University of Leeds, Leeds, LS2 9JT, UK; Department of Construction Economics and Management, College of Engineering, Design, Art and Technology (CEDAT), Makerere University, P.O. Box 7062, Kampala, Uganda. Electronic address: musamanga@cedat.mak.ac.ug.
² BioResource Systems Research Group, School of Civil Engineering, University of Leeds, Leeds, LS2 9JT, UK; Departamento de Ingeniería Química, Universidad Nacional de Colombia, Campus La Nubia, Manizales, Colombia.
³ The Water Institute at UNC, Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, 4114 McGavran Hall, Campus Box # 7431, NC 27599, Chapel Hill, NC, USA; Institute for Hygiene and Public Health, Medical Faculty, University of Bonn, GeoHealth Centre, Bonn, Germany.
⁴ BioResource Systems Research Group, School of Civil Engineering, University of Leeds, Leeds, LS2 9JT, UK.

PMID: 33310349
DOI: 10.1016/j.ijheh.2020.113670

Abstract

In recent years, composting has increasingly been promoted as a reliable method for sanitizing Faecal Sludge (FS) from onsite sanitation systems, particularly where there are opportunities to use the recovered nutrients in agriculture. However, there remain gaps in our understanding of the fate of infectious faecal pathogens during composting, particularly in tropical climates. This study investigated the influence of different locally available bulking agents on the inactivation efficiency of composting by tracking the fate of four key indicator organisms (E. coli, Salmonella spp., Enterococci spp., and viable helminth eggs). Dewatered FS was mixed with different bulking agents - i.e. Sawdust (SD), Coffee husks (CH) and Brewery waste (BW). Compost piles of FS:SD, FS:CH, and FS:BW in a volumetric ratio of 1:2 were set-up in duplicate (3 m³ each), composted on a pilot scale and monitored weekly for the survival of pathogen indicators for a period of 15 weeks. The study findings suggest that the different bulking agents have a statistically significant (p < 0.05) effect on the temperature evolution and survival of pathogen indicators in compost. CH was the most suitable bulking agent for composting with FS as piles containing CH exhibited higher pathogen inactivation efficiency and shorter inactivation periods of 6 weeks compared to 8 weeks for SD and BW piles. Time-temperature was the most important factor responsible for pathogen inactivation. However, other mechanisms such as indigenous microbial and toxic by-products such as NH₄₊-N also played an important role in the inactivation of pathogens. The results suggest that co-composting of FS with a sawdust, coffee husk or brewery waste for 8 weeks with thermophilic temperatures of about 48-60 °C sustained in the composting piles for more than 38 days, using 7 days turning frequency, is sufficient to ensure complete sanitization of FS before reuse in agriculture.

Keywords: Bulking agents; Composting; Faecal pathogen indicators; Faecal sludge treatment; Helminth eggs; Wastewater reuse.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Composting*
Escherichia coli
Feces
Sewage
Soil
Temperature
Tropical Climate

Substances

Sewage
Soil