New developments on semi-mechanical pit emptying devices


Water for people’s Sanitation as a business program’s research and development arm, the Kampala Sani-Hub Project began collaboration with the Water Research Council (WRC) in South Africa, under the Sanitation Research Fund for Africa (SRFA), to better understand the process of developing new sanitation technologies which meet the needs of the market. The project is based in Kampala, Uganda, where, amongst other technologies, the primary focus is on the development of low cost semi-mechanical pit emptying devices such as the Rammer and Nibbler and a decentralized faecal sludge treatment plant. The research on the Rammer and Nibbler was conducted at the Kampala Sanihub led by two Researchers, Sam Malinga and Herbert Atayo who are both Engineers. This research was undertaken to develop better devices that could pump thick sludge, cleaner, go deeper and are affordable to entrepreneurs wishing to start a pit emptying business. Slump cone tests were carried out to determine the consistency of wetness and fluidity of a synthetic sludge which would be used to estimated shear strength of synthetic sludge. Shear strength of 100pa, 500pa, and 2kpa were selected to determine the pumping limit of existing pumps. Synthetic sludge comprising of 85% top soil and 15% kaolin clay were prepared for pump testing for respective shear strength calculated.

Pump testing was performed on the Gulper, Rammer, and Nibbler. The parameters evaluated include; time taken to prime, insertion and removal from the pit, and output within 30 seconds. The results showed that the Rammer was capable of pumping sludge of up to 500pa shear strength with a greater discharge than other devices. The design improvements were carried out on both the Rammer and Nibbler. For the Rammer, the donkey tail was incorporated, both the fixed strut and internal rising bar were made modular to allow the device to enter deeper into a pit, and inner fixed cylinder bend was reduced to 25° to limit flow restrictions. The Nibbler design improvements were made on the chain, delivery, discs, and smooth chain movement. The technologies were demonstrated to the operators and desktop survey was carried out to gain feedback on these devices. This report also contains further recommendations to be Field testingmade to the devices.