Transcript ITCHON 2010 Use of Dehydrated Faeces

Use of Dehydrated Faeces
Gina S. Itchon, Xavier University
Use of Dehydrates Faeces
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Use of Dehydrates Faeces
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Contents
1. Concept
2. How it can optimize SSWM
3. Applicability
4. Advantages and disadvantages
5. References
Use of Dehydrates Faeces
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1. Concept of the Use of Dehydrated Faeces in
Agriculture
In a dehydration toilet, the excreta inside the processing vault are
dried with the help of sun, natural evaporation and ventilation.
After dehydration, faeces will reduce in volume by about 75%.
Primary motivation for dehydrating the faeces is that dried faeces act
as a hostile environment for pathogens and help to reduce the amount
of pathogens in the faeces significantly over time.
However, dry faeces may still contain pathogens. Oocysts, for example,
can survive extreme environmental conditions and re-grow under
favourable conditions.
Secondary treatment (composting, vermicomposting) of dehydrated
faeces should always be considered (if possible) as an additional barrier
to inactivate pathogens (and here most importantly Ascaris).
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1. How it can optimise SSWM
Dry storage of the faeces recycles more organic matter and Nitrogen to
the soil, but the organic matter is less stable. Dried faecal matter is a
complete Phosphorus and Potassium fertiliser, which also contributes
considerable amounts of Nitrogen.
While the total amount of nutrients excreted with faeces is lower
than with urine, the concentration of nutrients, and especially P and
K, is high in faeces. P is particularly valuable for the plant in its
early development and important for good root development.
Faeces contain organic matter, which increases the water-holding
and ion-buffering capacity of the soil, serves as food for the
microorganisms and is important for improving soil structure.
Use of Dehydrates Faeces
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3. Applicability
The handling and use of dried faeces may not be acceptable to some.
However, because the dried faeces should be dry, crumbly, and odour
free, the use of dehydrated faeces may be more acceptable than that
of manure or sludge.
Dried faeces are not as well treated or as useful as a soil amendment
as composted faeces. However, they contain significant amounts of
phosphorus, important in the early stage of plant growth and are useful
for replenishing poor soils and for boosting the carbon content and thus
the water-holding properties of soil with low-risk of pathogen
transmission.
Faeces should be incorporated into the soil and covered by a soil upper
layer.
Also the fertilisation of vegetables eaten raw should be avoided.
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4. Advantages and Disadvantages
Advantages:
Disadvantages:
• Periodical incorporation can
improve the structure and
water-holding capacity of soil
•Labour intensive
• Simple technique for all users
• Low cost
• Low
risk
of
pathogen
transmission (when fully dried
and properly handled)
• May
encourage
income
generation (tree planting and
fruit production)
•Requires that faeces are kept
strictly dry
•Pathogens may exist in a
dormant stage (oocysts) which
may
become
infectious
if
moisture is added
•Can only partly replace fertiliser
(N,P,K)
(TILLEY et al. 2008)
(TILLEY et al. 2008)
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5. References
•
TILLEY, E., LÜTHI, C., MOREL, A., ZURBRÜGG, C., SCHERTENLEIB, R. (2008): Compendium of Sanitation Systems
and Technologies. Switzerland: Swiss Federal Institute of Aquatic Science (EAWAG) & Water Supply and Sanitation
Collaborative Council (WSSCC)
•
WHO (2006): Guidelines for the Safe Use Wastewater, Excreta and Greywater, Volume 4: Excreta and Greywater
Use in Agriculture. Geneva: World Health Organisation
•
ECOSANRES. (2008): Guidelines on the Use of Urine and Faeces in Crop Production. (EcoSanRes Factsheets, No. 6)
Stockholm, Sweden: Stockholm Environment Institute (SEI)
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