A QUANTITATIVE APPROACH TO PREDICT ... - SuSanA

Since faecal sludge is of great concern when it comes to ecosan because it is known to
contain more pathogens as compared to urine, it is important to elaborate how these
pathogens are killed to ensure safety. Some of the pathogens contained in faeces are
bacteria, viruses, protozoa and helminths. They only affect public health when they get
into the field or water bodies, or get to a person directly when the person does not wash
the hand properly after visiting the toilet or drink water or eat food contaminated with
them. 34 It was mentioned that faeces can be treated by composting and drying for
fertilizer. These processes ensure increment in storage time, temperature, dryness, pH,
ultraviolet radiation, and competing natural soil organisms which makes the survival of
the pathogens impossible. 35 Most pathogens survive below temperatures of 5°C (degree
Celsius) and die very quickly at high temperatures like above 40°C. 36 Due to that, as
temperatures increases during composting and drying, most of them are killed.
Considering the pH, it is argued that highly alkaline conditions renders the pathogens
inactive and so this happens as alkaline is added during the process. In terms of
ultraviolet radiations, it has been also observed that the presence of solar radiation
reduce the survival time of the pathogens in the soil or on crops. When it comes to
competing natural organisms, the presence of other organisms affecting each other by
predation, release of antagonistic substances and competition for nutrients reduce the
life-span of the pathogens. The pathogens are adapted to living in the gut of human
beings and are therefore not able to compete well with organisms in the general
environment. Moreover, these pathogens entering the environment are anaerobic and are
easily overcome by the aerobic environment they find themselves. 37
There are four broad categories of ecosan projects and these are rural upgrading, periurban
(suburbs) and urban upgrading, new urban development and non-residential
project. 38 The rural upgrading is a classical ecosan project where farming households in
rural areas get support to establish the ecosan systems and then the households
themselves handle the processing and use of the fertilizer (mainly excreta) in their
farms. The peri-urban and urban project takes place in cities and towns where existing
sanitation systems are converted into ecosan systems. In such cases, because of the
34 Strauss, Martin et al, 2003, p.3
35 Winblad, Uno and Simpson-Hébert, Mayling, 2004, p.12
36 Ibid
37 Ibid
38 Werner, Christine, et al 2003, pp. 21-23
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