K5/2137 - Characterisation of on-site sanitation materials and products
VIP latrines and pour-flush toilets

Funded by: Water Research Commission
April 2012 – March 2015

Project description
In an effort to develop sustainable procedures for processing sludge from over 40 000 VIP latrines, the eThekwini Water and Sanitation division and their technology partner PSS have developed a machine for dehydrating and pasteurising VIP sludge and converting the dehydrated sludge into pellets. Qualitative tests have shown that the pellets may be beneficial as a fertilizer, but scientific data to confirm these results are lacking. There is increasing interest across South Africa and elsewhere to replicate this LaDePa (latrine dehydration and pasteurisation) machine because of its innovative method. However, the machine’s ability to process different sludges from other municipalities is unknown, and the machine would need to be redesigned if it is to be mass-produced for broader application. 

The WRC has commissioned the PRG to establish scientific data on the effectiveness and benefits of the LaDePa plant. The research team will carry out a number of investigations into the chemical, mechanical and microbiological characteristics of the feed material and the resultant product. In addition, an initial assessment of the operational range of the machine will be undertaken to guide the installation of comprehensive set of monitoring instrumentation (funded by BMGF) that will enable the assessment of the key treatment conditions for different batches of sludge. Finally, the project will investigate the characteristics of materials in the treatment tanks of pour-flush toilets. 

This project draws upon resources from parallel projects of the LaDePa plant funded by the Bill & Melinda Gates Foundation and eThekwini Water and Sanitation division. The WRC’s contribution supports two chemical engineering master’s degree graduates who will produce the data needed to enable rational decision-making about up-scaling of the machine and pellet production. Potential uses of the data include Environmental Impact Assessments, discharges to air, land and water, and agricultural benefit. 

To date, the research team has produced several protocols regarding operation and material characterisation. A protocol has been drafted for drying the sludge from VIPs to determine the optimal conditions for drying and to determine thermal properties of the various types of sludges, as well as to assist in the characterisation of the end production. Additionally, a protocol for the characterisation of sludge that is processed in the LaDePa machine is being revised and expanded to include the development of standard operating procedures on chemical, physical, and biological aspects of the sludge. In addition to the protocols, the research team has begun its assessment of the operation of the pour-flush system, looking specifically at the lifespan of a leech pit, the mechanism of degradation (aerobic or anaerobic), rate of degradation of faecal matter, presence of pathogens and other microbiological risks, the impact of the pour-flush toilet on ground water quality, and determining the most suitable method for emptying the pits.