Thursday, July 05, 2012

shit works

South Africa’s pit latrines are filling up faster than their expected design life. The solution? Safely using human waste as fertiliser.

“Only one third of municipalities have a budget to maintain on-site sanitation. If pits fill up, all the hard work that was done to address the sanitation backlog will be wasted. Why not use faecal sludge (FS) to address the growing problem of food insecurity by planting fruit trees? Or use the sludge to cultivate trees for fuel or paper production?” asked WRC researcher David Still. The result was the formation of the project titled “What happens when pit latrines get full.”

“It is clear that in our country the use of vacuum tankers is not always a solution because of access problems, and also because of the foreign objects found in pit latrines,” he said.

Human excreta or FS have valuable nutrients such as Nitrogen, Phosphates and Potassium and the average person excretes enough of this per year to sufficiently fertilise 300 to 400 square metres of crops. However, using FS as a fertiliser can be hazardous because of the pathogens it contains, especially if it is used for surface spreading and where edible crops are cultivated. There is also a risk that the FS could contaminate groundwater.

“We looked at the possibility of harnessing the nutrient value of the sludge whilst containing the hazard posed by the pathogens until they died off,” said Still.

By burying the FS in pits and planting on top of it, pathogens were contained and eventually died off. In order to test for the presence of FS pathogens, the researchers searched for the eggs of the large roundworm, a hardy parasite. If the eggs were found, it meant that the FS still contained pathogens and was harmful. “Analysis of sludge extracted at periodic intervals indicated that no roundworms could be found after a period of 30 months after burial in the ground,” Still said.

Communities can grow fuel wood trees or fruit trees according to their requirements. Plant growth and fruit development are greatly improved with the application of the sludges. The technology has enormous potential. Making sanitation work also raises such exciting possibilities for smart management of our resources,” Bhagwan said.

Providing sanitation is not just about building more toilets. It is also about managing sanitation smartly.

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