Pathogen Destruction in Urine-Diversion Sanitation Systems

Pathogen Destruction in Urine-Diversion Sanitation Systems
Report No 1439/1/06
June 2006

EXECUTIVE SUMMARY

BACKGROUND

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 (ecosan).
To determine:
1. the nature of processes taking place in the vault of a urine-diversion (UD) toilet; and
2. 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.

REPORT STRUCTURE

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:

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 aspects.
Volume 4: TT275/06 - Guidelines for the design, operation and maintenance of UD sanitation systems.

SUMMARY OF THIS VOLUME

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:

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.

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.

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 agents.

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.