Understanding the sludge accumulation in VIPs, UDS and other onsite sanitation systems, and strategies to manage desludging in the future when pits are full

Funded by: Water Research Commission
April 2007 – March 2010

Partner organisations: Partners in Development, eThekwini Water and Sanitation

Project description
In 2007, the Pollution Research Group joined Partners In Development in an investigation into sludge accumulation in VIPs and possible strategies to manage desludging when pits become full. The research set out to establish how many VIPs will require some form of intervention to sustain its use in the future. The study also evaluated more affordable and easier ways of desludging VIPs when they are full. Through a review of the extant knowledge, interviews with experts in the field, and field investigations of VIPs and other onsite sanitation systems, the study aimed to determine sludge build-up in sanitation systems over their life span and to develop new technologies, strategies and processes to manage desludging and its safe disposal. 

The study was proposed in an effort to develop critical knowledge and strategies regarding maintenance and rehabilitation of VIPs for local water authorities and municipalities to properly address the sanitation backlog in South Africa. In 2007, the sanitation backlog in SA was estimated at approximately 2 million households, costing R10 billion (2006 rands) and anticipated to take at least seven years to complete. Given that most municipalities have thousands of full or nearly full VIPs that will need to be emptied before the government’s plan is in full effect. This project was intended to develop practical and cost-effective strategies for emptying VIPs and managing faecal waste matter, and ensure that sanitation practitioners in South Africa become aware of innovative ways of dealing with faecal sludge which will prove more sustainable in the long term. 

Pollution Research Group was involved in conducting field investigations to determine sludge build up in on-site sanitation systems in the eThekwini Municipality; conducting trials of the effects of different chemical additives in the degradation of sludge in different sanitation conditions (dry/wet; VIP/UDDT); and developing an empirical model to predict sludge accumulation rate estimates. The research team designed and tested several prototypes to improve pit emptying including a pit screw auger, a gobbler, a NanoVac which uses piston pumps, an eVac that uses a vane pump, and a pressure vessel that can either collect sludge or pump air or water into a pit to aid in sludge removal. While each prototype proved effective under specific conditions the eVac demonstrated potential usage in multiple field conditions. 

Publications and reports

  • WRC Knowledge Hub – Tackling the Challenges of Full Pits (Vol. 1, 2 & 3) 
  • Montessuit, Charlotte. 2010. Laboratory Protocols for testing of the efficacy of commercial pit latrines additives and water as additive. Internship Final Report.