Sustainable sanitation is a sanitation system designed to meet certain criteria and to work well over the long-term. The Sustainable Sanitation Alliance (SuSanA) includes five features (or criteria) in its definition of "sustainable sanitation": Systems need to be economically and socially acceptable, technically and institutionally appropriate and protect the environment and natural resources.
The purpose of sustainable sanitation is the same as sanitation in general: to protect human health. However, "sustainable sanitation" attends to all process of the system. This includes methods of collecting, transporting, treating and disposing of waste. Reuse of waste is not essential to the definition.
The Joint Monitoring Programme for Water Supply and Sanitation (JMP) of the WHO (World Health Organisation) and UNICEF (United Nations Children's Fund) was responsible for monitoring progress towards the Millennium Development Goal for drinking water and sanitation. For reasons of simplicity—being able to monitor the sanitation situation with household surveys—the JMP had to find a simple differentiation between "improved" sanitation (toilets that count towards the MDG goals) and "unimproved" sanitation (toilets that do not count towards the MDG goals).
Unimproved sanitation facilities according to the JMP include:
In some circumstances "improved" sanitation facilities can be regarded as not sustainable, whereas in other circumstances "unimproved" sanitation facilities can be regarded as sustainable. This is because it depends on the sanitation system, of which the toilet is only one part. For example, a pit latrine with a slab can become unsustainable sanitation if it is polluting the groundwater or if the waste sludge that is removed from the pit latrine is dumped into the environment. A bucket toilet can become sustainable if the collection, treatment and reuse or disposal of waste is taken care of in a safe manner, for example with the urine-diverting dry toilets that SOIL is employing in Haiti.
Sustainable sanitation, defined with the five sustainability measures, may or may not have an focus on reuse of excreta, because the criterion of "protecting the natural resources" is only one of several that need to be aimed towards. In comparison, ecological sanitation (ecosan) has a strong focus on the reuse of waste.
The main objective of a sanitation system is to protect and promote human health by providing a clean environment and breaking the cycle of disease. In order to be sustainable a sanitation system has to be not only economically viable, socially acceptable, and technically and institutionally appropriate, but it should also protect the environment and the natural resources. According to the Sustainable Sanitation Alliance, when improving an existing and/or designing a new sanitation system, sustainability criteria related to the following aspects should be considered:
Health aspects include the risk of exposure to pathogens and hazardous substances that could affect public health at all points of the sanitation system from the toilet via the collection and treatment system to the point of reuse or disposal. The topic also covers aspects such as hygiene, nutrition and the improvement of livelihood achieved by the application of a certain sanitation system, as well as downstream effects.
Environment and natural resources aspects involve the required energy, water and other natural resources for construction, operation and maintenance of the system, as well as the potential emissions to the environment resulting from use. It also includes the degree of recycling and reuse of excreta practiced and the effects of these, for example reusing the wastewater, returning nutrients and organic material to agriculture, and the protecting of other non-renewable resources, for example through the production of renewable energy (e.g. biogas or fuel wood).
Technology and operation aspects incorporate the functionality and the ease with which the system can be constructed, operated and monitored using the available human resources (e.g. the local community, technical team of the local utility etc.). It also concerns the suitability to achieve an efficient substance flow management from a technical point of view. Furthermore, it evaluates the robustness of the system, its vulnerability towards disasters, and the flexibility and adaptability of its technical elements to the existing infrastructure, to demographic and socio-economic developments and climate change.
Financial and economic issues relate to the capacity of households and communities to pay for sanitation, including the construction, maintenance and depreciation of the system. Besides the evaluation of investment, operation and maintenance costs, the topic also takes into account the economic benefits that can be obtained in “productive” sanitation systems, including benefits from the production of the recyclables (soil conditioner, fertiliser, energy and reclaimed water), employment creation, increased productivity through improved health and the reduction of environmental and public health costs.
Socio-cultural and institutional aspects take into account the socio-cultural acceptance and appropriateness of the system, convenience, system perceptions, gender issues and impacts on human dignity, the contribution to subsistence economies and food security, and legal and institutional aspects.
Most sanitation systems have been designed with the five aspects in mind, but in practice they are failing far too often because some of the criteria are not met. Since there is no one-for-all sanitation solution which fulfils the sustainability criteria, evaluation will depend on the local framework and will have to take into consideration the existing environmental, technical, socio-cultural and economic conditions.
Some basic principles to be observed when planning and implementing a sustainable sanitation system were endorsed by the members of the Water Supply and Sanitation Collaborative Council (the “Bellagio Principles for Sustainable Sanitation”) during its 5th Global Forum in November 2000:
Some examples for improving present sanitation practices in the short-term, purely from a technology perspective, are listed below:
With respect to the other sustainability factors, key areas of attention the creation of an enabling environment, market development and capacity development.