Introduction

Every day the world's six billion people produce over a million tons of faeces and current waste management methods are not coping; either in terms of protecting human health or the environment. Particularly in some regions of the world, such as South Africa , where there is a shortage of water, which prohibits providing everyone with water borne sanitation. There is a lot of interest in dry sanitation as an alternative to conventional methods and a review of the subject indicates that it really does work.

What is Dry Sanitation?

Dry sanitation is defined as the disposal of human waste without the use of water as a carrier; it is also known as a waterless toilet. Often the end product is used as a fertilizer. In developed countries, dry sanitation toilets were initially designed for use in remote areas for practical and environmental reasons. However, increasing environmental awareness has led to some people using them as an alternative to conventional systems. In developing countries they can be a low cost, environmentally acceptable, hygienic option.

With dehydrating waterless toilets, the urine is diverted away and the faeces collected in a chamber. Lime, ash or soil can be added, or in our case the faeces is dried with the aid of solar radiation and evaporation. Another example is the double pit urine diversion toilet used in Durban Metro, which is based on a design that has been in use in Vietnam since 1954.

With composting toilets, the faeces are broken down by bacteria (and sometimes fungi). Other organic matter is sometimes added. Temperature, airflow and moisture content all to be carefully controlled to maintain aerobic conditions; this is key. Urine is sometimes diverted, but more often evaporated. Examples in South Africa are the Enviroloo and Ecosan models.

Environmental Aspects

Advantages of dry sanitation are:

• Vastly reduced water use
• Protection of the groundwater
• Financial saving on water reticulation infra-structure
• Recycling of biowaste

Disadvantages of dry sanitation are:

• The composting environment needs to be carefully controlled; it is slow below 20C
• Dehydration is dependent on ambient weather conditions

Public Health Aspects  

Advantages of waterless toilets include:

• Faeces inaccessible to animals (cf use of veldt)
• Faeces isolated from groundwater (cf pit latrines)
• Minimal concentration of pathogens in end product (cf water borne sanitation)

Disadvantages of waterless toilets include:

• End waste still has to be handled
• Ascaris eggs are likely to be present
• Faeces may only be partly decomposed
• Effort and care from user, especially in composting toilets

Pathogen survival in dry sanitation

Ascaris sum eggs can survive up to six months and salmonella for five months in desiccated faeces. The best ways to kill off pathogens is with the addition of –

1. Lime or ash for a high pH
2. Time away from the host. Salmonella dies off after about five months and Ascaris ova after about six.
3. Temperature. All pathogens and worm eggs (Ascaris specifically) die off quite rapidly if temperatures of over 50C can be reached. This is rarely achieved in composting toilets, but, as the temperature in the Solarsan housings are on average 15C higher than ambient temperature, this is easily achieved in most regions of South Africa .

Cultural and Social Acceptability  

Our own and others' experience has shown that a slow introduction is better, with good training of future users and community education. The education should not be limited to use of the dry sanitation system, but extend to all aspects of personal and environmental hygiene. Many studies (see WRC) have shown that the provision of toilets – waterless or otherwise - is a necessary, but not sufficient step to achieving improvements in public health.

It is good practice to install several different systems in the households of willing and influential people, who are prepared to take ownership. The rest of the community can observe and then make an informed choice. Imposition from above, however well motivated, can be counter productive.

All dry sanitation systems require secondary treatment of the faeces. This ranges from moving the toilet when full (pit latrines, double vault system), to spreading the semi-rotted faeces (composting toilets, double vault system), to burning the faeces (dehydrating toilets). Nobody likes handling their own or others' faeces and, in most cases, a profound attitude shift is needed for dry sanitation to work. Ideally we would be using the end product (especially urine) as a fertilizer, but for the moment, the challenge is to find acceptance for a system that is neither water borne, nor a pit latrine, nor the veldt.

Solarsan, as part of its package, offers, not only a holistic hygiene education programme, but a three year contract whereby we can service the waterless toilet systems and collect and dispose of the contents, when it is necessary to do so, thereby circumventing initial community conservatism.

Conclusion

Dry Sanitation toilets have a lot of potential. They have clear environmental, social, financial and public health advantages. Their main disadvantage is that in many waterless toilet systems there is often insufficient reduction in pathogens. A point rarely acknowledged in promotional literature (independent or otherwise). Comparatively little money has been spent on research into pathogen die-off in dry sanitation and more research is needed.

What information is available we have used to develop our dry sanitation system. Our primary concern is for public and environmental health and secondary concern for economy and ease of installation.