Mechanical properties of faecal sludge
Funded by: Bill & Melinda Gates Foundation
March 2012 – January 2014

Partner organisations: eThekwini Water and Sanitation

Project description
In 2012, the Pollution Research Group (PRG) was contracted by the Bill & Melinda Gates Foundation (BMGF) to carry out research to document the properties of faecal sludge from different types of on-site sanitation facilities. It is expected that this investigation into the characteristics of faecal sludge will support innovation and design of improved sanitation facilities and processes. The properties of sludge vary greatly between different locations and types of facilities, and however few data exist that can properly inform innovations in sanitation. 

This study consists of two phases: 
  1. the collection of faecal sludge samples from different sanitation facilities; and 
  2. to analyse these sludge samples to assess their chemical mechanical and physiological properties.
The project involves collecting and analysing faecal sludge samples from different types of on-site sanitation facilities: wet and dry household VIP latrines, household UD toilets, household unimproved pit latrines, community ablution block VIP latrines, and school VIP toilet blocks. Approximately 60 facilities have been selected from four locations in eThekwini, based on discussion with eThekwini Water and Sanitation (EWS) and subsequent agreement with local councillors and community members. In each area, only a small number of facilities (five or less) will be emptied. EWS provided GIS data, detailing the conditions of the pits, households density, geology and slope conditions, presence of boreholes and other data to inform sample selection and collection.

Samples of the collected faecal sludge are being analysed to assess the chemical, mechanical and physiological properties, including its chemical composition, density, water content, biodegradability, methane production potential, material-type fractionation, rheology and thermal properties. The most of the analyses are standard tests that are currently being conducted in the PRG laboratory. Several analytical tests will be carried out in an external laboratory, given that the necessary equipment is not available yet at the PRG laboratory. The scope of analysis has been expanded to analyses of parasites found in the existing sludge samples. Given the relatively high load of parasites found in the excreta of Durban residents, and it is important to assess the characteristics of parasites existing in the sludge, including the concentration per gram sample, and the physiological state. This analysis has important implications for how sludge should be handled, used or disposed of, and whether it is a viable option as fertilizer.

PRG and BMGF anticipate that the data generated from the Mechanical Properties of Faecal Sludge will support the design and sizing of mechanical pit-emptying devices, transportation and processing systems for the excavated sludge, and the design of future on-site sanitation facilities. This project will interface closely with other projects from the BMGF which address different aspects of on-site sanitation. In addition, eThekwini Water and Sanitation are active partners in the project, and the Water Research Commission of South Africa is funding parallel initiatives with the Pollution Research Group (PRG). It will extend the knowledge generated by staff and research students with the PRG. A sludge classification system will be derived, which will enable municipalities to describe the sludges in their area and to provide data for designers and operators to provide enhanced sanitation services. Analysis will be made of the implications of the data for the practical applications listed above, integrating with other projects being carried out by the Pollution Research Group.

Publications and reports
  • Velkushanova, K. 2013. Properties of faecal sludge from on-site sanitation facilities in Durban, South Africa. Presentation to the 3rd IWA Development Congress and Exhibition “Catalysing Urban Water Transitions.” 14-17 October, 2013. Nairobi, Kenya.
  • Zuma, L., Rajan, M.A., Velkushanova, K., and Buckley, C.A. 2013. Physico-Chemical Properties of Faecal Sludge from Dry and Wet Pit Latrines. Poster presented to the 3rd IWA Development Congress and Exhibition “Catalysing Urban Water Transitions.” 14-17 October, 2013. Nairobi, Kenya.