Water Engineering and Development Centre
Series: WELL Studies in Water, Sanitation and Environmental Health Task 324
Dry sanitation is defined in this report as the on-site disposal of human urine and faeces without the use of water as a carrier. This definition includes many of the most popular options for low-cost sanitation including pit latrines, Ventilated Improved Pits, SanPlats, etc. There has always been an interest in the reuse of human waste as a fertiliser, and there has been much recent work on the development of composting and other processes to permit human waste reuse.
This report examines the practice of dry sanitation with reuse in Mexico, with a particular focus on health issues and the lessons to be learned from case studies and experience.
Dry sanitation systems designed for excreta reuse were visited in Ixtlico el Chico (Morelos State) and San Juan Amecac (Puebla State). In Ixtlico el Chico, the more recently constructed toilets seem to fare better than the earliest models. Some problems with urine separation seemed universal, including blocked separators, difficulties for children in use of the urine separation devices, and inadequate urine absorption into ground during heavy rainfall. In San Juan Amecac, residents seemed able to manage the toilets well, apparently in no small part due to the frequent visits of sanitation extension workers.
Conclusions arising from the study include:
Reuse of the contents of dry sanitation systems offers both advantages and risks. There has been much recent publicity about the ecological advantages of composting and dehydrating toilets. There has been less attention to the demands these systems place upon the population for their safe adoption, and the risks of disease transmission that will result from inappropriate use.
Safe adoption of dry sanitation with reuse is a slow process. This is the over-riding message from NGOs and governmental organisations involved in promotion of dry sanitation with reuse in Mexico.
The risk to health from a given sanitation facility depends not only upon its technology, but also upon the health status of the family using the toilet. This fact is often forgotten in a number of the studies establishing the 'safety' of a given technology by establishing the absence of parasite eggs.
A greater understanding of pathogen die-off during the ordinary use of these technologies is required. While this report reviews the available evidence, a great deal more is required, especially given the current impetus behind the movement for ecological sanitation.
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