Abstract
The use in agriculture of excreta from urine-diversion toilets can be an alternative solution to the lack of sanitation and high costs of mineral fertilizers inherent to developing countries. The objective of this study was to evaluate the hygienic quality of urine used as fertilizer through an ecological sanitation system in Ouagadougou peri-urban areas. Chemical and microbiological analyses were performed in urine samples taken before and after thirty (30) days of storage in jerry cans exposed to sunlight. The concentrations of 7.0 g/l; 3.5 and 9.6 g/l of ammonia nitrogen for mean, minimum and maximum respectively, are obtained in unstored urine samples. These concentrations did not practically vary with the storage. On average, values of other chemical parameters analyzed in stored urine were as follows: pH, 8.8; phosphorus (P), 0.3 g/l; potassium (K), 1.9 g/l; total dissolved solids (TDS), 21.0 g/l; cadmium (Cd), 154.3 μg/l; copper (Cu), 5.2 μg/l; lead (Pb), 15.2 μg/l; chromium (Cr), 6.1 μg/l; nickel (Ni), 154.0 μg/l. Escherichia coli, staphylococci, enterococci, Salmonella and spores of Clostridium perfringens were detected in unstored urine samples, with 26% of fecal contamination rate. The time of storage (30 days) under sunlight was enough for almost all bacteria removal in urine samples. Although the fertilizing value of urine was confirmed, it would be important to take account of the best practices on applying in soils, because of the high TDS contents. Also, the risk linked to micropollutants in urine-based fertilizers could be negligible in view of low quantities. The results obtained in this study prove that after 30 days of exposure to sunlight urine collected via eco-toilet becomes bacteriologically sanitized, and can therefore be used to fertilize soils. However, it is necessary to demonstrate the inactivation of other groups of enteric microorganisms in human urine during storage.
Highlights
To date, about 2.5 billion individuals in the world have no access to adequate sanitation facilities [1]
The results of pH, total dissolved solids (TDS), ammonia nitrogen, phosphorus and potassium obtained are shown in the Table 1
It is well known that the main proportion of the nitrogen in urine is excreted as urea, which is transformed into ammonia in the collection tank and which increases the pH to 8.8 - 9.0 [4]
Summary
About 2.5 billion individuals in the world have no access to adequate sanitation facilities [1]. The resort to eco-toilets in developing countries constitutes an alternative to the lack of sanitation and high costs of mineral fertilizers. Urine-diversion toilet is the most widespread ecological sanitation equipment in the world [3]. Its nutrient contribution is important that mineral fertilizers [5] [6]. Micropollutants such as heavy metals, hormones, pharmaceutical residues and pathogens can be excreted in urine [4] [7]. For the ecological sanitation system used in this study, the adopted urine treatment consists in storage in tanks, exposure to sun for days [9]. Arid soils are most affected by salinization [3] [15]
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