Africa Water, Sanitation & Hygiene Nov - Dec Vol. 9 No.6 | Page 32

Sanitation

How Do Urine-diverting Dry Toilets Work?
(This is an abridged excerpt of an 11-page interview, with questions from Jake Ling and answers from Chris Canaday:
http://www.chekhovskalashnikov.com/human-waste-disposal/ … and it described the problems of wáter-based sanitation
in Part 1: The Problem, of which an excerpt was published previously in Africa Water Sanitation & Hygiene Magazine.)

How did this new design for sustainable human waste
disposal come into being?
In the 1950s, before the regrettable Vietnam War, a team
of Vietnamese doctors analyzed why so many people were
sick and how to control this. They found a great number
of people were collecting “night soil” in buckets that were
emptied in the morning directly in agricultural fields,
where people worked largely barefoot.
The doctors realized that 90% of the fertilizer is in the
urine that transmits no disease when dispersed in the soil,
while essentially all the health risk is packaged with only
10% of the fertilizer, in the faeces. The answer was to keep
the urine separate and set it free on the soil immediately,
while jailing up the faeces, until they are not faeces any
more.
Can you explain how the design for this human waste
disposal system works?
It is very simple and seeks
to follow the natural order
of things. The urine and
faeces are kept separate, to
b