Pathogen Destruction in
Urine-Diversion Sanitation Systems
Report No 1439/1/06
This report forms part of the output of Water Research Commission
project number K5/1439 entitled “Strategy for the furtherance
of knowledge and good practice of ecological sanitation (ecosan)
technology in South Africa”. The aims of this research
project were as follows:
- To establish the
current “state of the art” in ecological sanitation
- To determine:
- the nature of
taking place in the vault of a urine-diversion (UD) toilet; and
- the relevant pathogen
destruction parameters in order to increase understanding of the health
aspects of UD toilet operation and maintenance (O&M), as well
as safety criteria for use of the processed excreta.
- To explore
appropriate practices for faeces collection and disposal, in order to
facilitate the abovementioned safe O&M of the toilets.
- To produce a
report describing the research conducted for the project, with
conclusions and recommendations for improving the future implementation
of UD sanitation projects.
The literature review of this study was published by the Water Research
Commission as Report no. TT246/05. The other outputs emanating from
this study are presented in four separate volumes.
The four volumes are:
SUMMARY OF THIS VOLUME
- Volume 1: 1439/1/06
– Pathogen destruction in UD sanitation systems (this volume)
- Volume 2: 1439/2/06 - Use
and acceptance of UD sanitation systems in South Africa
- Volume 3: 1439/3/06 - Use of
human excreta from UD toilets in food gardens: Agronomic and health
- Volume 4: TT275/06 -
Guidelines for the design, operation and maintenance of UD sanitation
This volume is presented in four chapters:
Chapter 1: Introduction
The background and content of the whole project is described, in order
that this volume can be put into context.
Chapter 2: Laboratory
investigation of certain characteristics of
pathogen destruction in human excreta
This section of the report covers the following study objectives:
While pasteurisation was seen to be the most effective treatment for
faeces in UD toilets, it is not regarded as a practical option for
households. Addition of NaOH proved to be the second most effective
treatment but is also regarded as impractical due to its cost and the
difficulty of obtaining the product in rural areas. Therefore, due to
its generally ubiquitous nature, widespread use around the world and
proven efficacy, wood ash is regarded as the best option as a bulking
agent, biocide and sanitiser in household UD toilets.
- determination of the environmental
factors affecting the survival of excreted pathogens in dehydrated
faeces and how application of NaOH, ash and pasteurisation reduces the
numbers of pathogens in these faeces; and
- determination of the biocidal effect of
urine in relation to storage temperature and pH.
Regarding urine, while there is a low risk for transmission of
infectious diseases from handling, this research has shown that it
should be stored for at least 50 days before use.
Chapter 3: Detailed field
investigation into pathogen destruction
processes taking place in urine-diversion toilet vaults
This investigation was aimed at determining the minimum vault storage
time for faecal material commensurate with safety for handling. In
essence, the research was intended to determine pathogen die-off rates
under different conditions of faecal storage. Parameters investigated
included storage time, effect of various lid materials on vault
temperature, effect of ventilation, and effect of various bulking
The main conclusions were, firstly, that neither ventilation of the
vault nor the type of construction material result in any meaningful
difference in vault temperatures or the rate of pathogen die-off.
However, the type of bulking agent plays a role in this regard, with
some noticeable differences in the rate of pathogen die-off exhibited
between the various admixtures. An ordinary soil additive was seen to
produce the best results (probably through competition from soil
microorganisms), while UV light on an open heap of faecal material also
had an impact.
It was suggested that, in order to promote safety, faecal material
should preferably not be handled for a period of 12 months. UD toilet
vaults should therefore be sized so that the material can be stored for
12 months from the date of the last addition to the pile to the time it
is removed from the vault.
Chapter 4: Conclusions
Apart from pasteurisation, which is regarded as an impractical option
for households, NaOH proved to be the most effective treatment for
reducing pathogen numbers in faecal material. However, it is unlikely
to be readily affordable by poor households, nor is it likely to be
easily available in rural areas. Wood ash is currently the most widely
used bulking/disinfecting agent and the most likely scenario is that
this will continue. Further research should be directed at establishing
the most effective faeces:ash ratio for reliable disinfection in the
shortest possible time.
Although there is a low risk for transmission of infectious diseases
from handling urine, it should be stored for at least 50 days before
use. This should be compared with Swedish recommendations
(Schönning 2001) that vary from shorter storage times (1
month) at 4°C where the urine can be used on crops that are
processed before use as fodder or food, to longer storage times (6
months) at 20°C where the urine can be used on all kinds of
crops, even those that are consumed raw by humans.
Proper sanitisation of urine and faeces from urine-diversion toilets
before handling or further use (e.g. in food gardens) were seen to be
important for the protection of human health.