Ecological Sanitation systems have been recently developed to help ameliorate the problems of pollution, excess usage of water and wastage of nutrients, which were characterising the historical ‘drop and store’ and the ‘flush and discharge’ systems. Despite the added advantages of ecological sanitation systems, the systems have inherent problems in their design and operation, among which is the performance of the ventilation system as far as accelerating drying of faecal matter is concerned. The objective of the study was to develop a modified system that would accelerate drying. Accelerating drying would be useful in shortening the retention period required before faecal matter can be rendered safe for handling, resulting in smaller units and reduced overall costs. Field visits were made to the South Western Towns Water and Sanitation Project area, specifically Kabale and Kisoro. Other Ecosan and similar kind of toilets were visited in Mbarara and around Kampala. A total of 25 sites were visited and 20 people interviewed. Data was collected by use of checklists and questionnaires and from the Meteorological Department. The data was analysed and basing on the results, an appropriate design to accelerate drying was produced, costed and design drawings produced. From the analysis of the data, the Ecosan systems were found to be employing natural ventilation, but often with a number of loopholes hence they were not effective. Inadequacies included small vent pipe diameters, improper and weak materials, inadequate height above the roof, e.t.c. After all considerations, it was found that a minimum vent pipe diameter of 150mm is required for efficient ventilation. In addition much better results are obtained when a rotary vent turbine is incorporated to further increase the rate of extraction of water evaporated from the vaults. Another method of increasing the rate of drying in the vaults was the use of one-way glass for the vault covers and Insulating the walls to allow in as much direct sunlight as possible and at the same time reduce on the amount of heat lost through the vaults walls. These conditions are very important, if accelerated drying is to be realised.

Bibliographic information

Ntabadde, M.K. (2004). Design of a dry toilet ventilation system to accelerate drying Final year project report Makerere University, Faculty of Technology Department of civil engineering, Makerere, Uganda

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