Achieving ecological sanitation solutions requires a change in how people think about and act according to human excreta. Human excreta are made out of two basic components, urine and faeces. Each has very different properties, they are produced in different quantities, and they require different care in processing.

Urine contains nearly 80% of the total nitrogen found in excreta and about two-thirds of the excreted phosphorus and potassium.

Each person urinates annually about 4 kg of nitrogen, 0.4 kg of phosphorus, and nearly 1 kg of potassium. So, urine is a pure nutrient solution, which contains very low levels of heavy metals and normally also of pathogenic organisms.

Source: http://www.stockholmvatten.se/pdf_arkiv/english/urinsep_eng.pdf

Recycling these nutrients from wastewater as fertilizer reduces the need of industrially produced fertilizer and also reduces discharges of nutrient-rich water from treatment plants into watercourses. Returning these nutrients to soils may restore soil fertility more than reliance on commercial fertilisers. To do this in a most appropriate way is to separate the urine from faeces. The urine separation technology is comparatively simple and has been adequately tested. While the faeces go through a process of de-composition and clarification, the urine can be applied to the soil as soon as the fermentation process is concluded.

Urine-separating toilets differ from ordinary toilets in that they have two bowls, a front bowl for urine and a rear bowl for faeces and toilet paper. From here the urine passes through a separate pipe system, which should not contain any metal parts, to a holding tank, that is connected to one or more households. The holding tanks can be of fibreglass plastic, as used as standard products in other construction works.

From there the urine is collected and removed for further storage by the farmer, who uses the urine as fertilizer. A good solution for storage seems to be the so called "balloon tanks" made out of rubber, which are airtight, require little construction work, are reasonably priced and minimize nitrogen losses during storage. They also, due to their black surface and the high solar radiation can raise the temperature of the urine mixture and thus the pathogen elimination.

Source: http://www.stockholmvatten.se/
pdf_arkiv/english/
urinsep_eng.pdf

Urine in itself presents virtually no risk of infection. But it can be contaminated by pathogens present in faeces. Infection risks in connection with urine separation can be minimized, by taking certain security measures.

Source: http://www.stockholmvatten.se/
pdf_arkiv/english/urinsep_eng.pdf

Storage eliminates or reduces the number of pathogens in the urine. If the recommendations concerning application techniques are followed, urine can be used for all crops if it has been stored at not less than 20°C for at least six months and for all crops except food crops that are to be consumed raw if storage takes place at not less than 4°C for at least six months. In the case of food crops that are consumed raw, it is recommended, as a safety barrier, that a withholding period of one month should be observed between fertilization and harvesting and that the urine be incorporated into the soil. Nevertheless, it is recommended to hold new examinations on the subject, because due to the high bio-activity in Brazil storage time might as well be considerably below the six month margin.

The total amount of urine to be collected in Sitio Joaninha can be estimated with 495 m3/a. As the storage period is not longer then 6 month, storage capacity has to be 247,5 m3, which is half of this amount. The storage capacity should be divided through the 4 farming zones with 2 storage tanks each. Thus, each tank should have a capacity of 32 m3.

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