Sustainable Sanitation

Present conventional forms of wastewater management and sanitation fall either under the category of conventional waterborne or dry (pit) systems. In both cases, the design is based on the premise that excreta are waste, and that this waste should be disposed of. It is also assumed that the environment can safely assimilate this waste. These assumptions lead to linear flows of resources and wastes and often cause severe environmental pollution (see also water pollution). The technological developments that were once designed to solve the sanitation problem have become part of the problem, not the answer to it (ESREY 2000).

Conventional centralised systems

On-site systems

In pit systems, which are abundant in many parts of the world, the toilet does form a barrier between human beings and excreta. Yet, this barrier is incomplete. Pit latrines are mostly designed to retain solids and infiltrate liquids. When liquids infiltrate, nutrients, and worse, pathogens also infiltrate. If there are large settlements, or if the toilets are built too close to water sources, this can lead to a severe pollution of ground and surface waters, as shown above. Consequences are a high prevalence of waterborne diseases.

Also conventional waterborne systems have their drawbacks. One of the largest is probably that they are linear “end-of-pipe” systems, which are constructed on the assumption that a treatment will take place at the end of the pipe. Yet, worldwide, more than 90% of the wastewater does not receive any treatment at all (CORCORAN et al. 2010), thus polluting an even larger amount of water. There are several other important drawbacks of centralised water-based sewerage (see also water pollution). Some of the most important are: 

• Mixing different wastewater streams: In centralised systems, wastewater from a range of different sources (domestic, industrial, street runoff) gets mixed, thus creating a wastewater with properties that are hard to handle for any treatment plant — even high tech ones. The range of different harmful substances (heavy metals, chemical and medical residues etc.) contained in such wastewater makes it also difficult to recycle it.

• Water use: Centralised sewage systems use a large amount of water; not only for flushing the toilet, but there also has to be a certain minimum water flow to ensure that the gravity operated sewers work. Water is getting an ever more scarce resource. According to the 2006 Human Development Report, “the scarcity at the heart of the global water crisis is rooted in power, poverty and inequality, not in physical availability” (UNDP 2006). In other words: there would be enough water for everyone, if it would be used wisely. Using water to flush toilets is definitely not the most sensible solution.

• Energy consumption: Many centralised conventional sewage treatment plants are effective, but very expensive and plant usually highly energy intensive, which again adds to cost, and also makes them susceptible to failure.

• Health risks: Wastewater, which is not treated and discharged into other surface water bodies, is a severe health risk to the people downstream using this water. “Unmanaged wastewater is a vector of disease, causing child mortality and reduced labour productivity, but receives a disproportionately low and often poorly targeted share of development aid and investment in developing countries. At least 1.8 million children under five years die every year due to water related disease, or one every 20 seconds (CORCORAN et al. 2010)” (see also health and hygiene issues).

• Social acceptance: Many approaches to improve sanitary circumstances are well meant, but were largely planned top-down. Often, this can result in a non-acceptance of a system, leading to the fact that the sanitation systems are not well maintained, and do not function properly (see also socio-economic aspects).

• Closing the loop: Yet, the largest drawbacks of centralised sewer system as they are used today is that they – in most cases – do not favour recycling of resources and thus closing the loop: Water (often groundwater) enters the water distribution system, and is essentially discharged into surface water, leading to groundwater depletion. And nutrients, which essentially come from the soil, are discharged into waterways, leading to soil depletion on the one hand and eutrophication on the other hand.

Sustainable sanitation aims at overcoming these drawbacks. It is not a certain technology, but an approach with certain underlying principles. There are a number of technologies (see for instance sanitation systems) that can be used to make sanitation and wastewater management more sustainable. The term “sustainable sanitation” in principle denominates the same as ecological sanitation, though the latter has a stronger focus on source separation.

The first and foremost principle is probably the one to recognise that excreta and wastewater are not a waste, but a valuable resource that can be reused and recycled. This is actually — to speak in a simplified way — the very basis of sustainability: to use resources wisely and without impairing the possibilities of future generations to meet their own needs.

Sustainable sanitation can be defined more precisely (adapted from SUSANA 2008):

The main objective of any 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 do this, and additionally be economically viable, socially acceptable, and technically and institutionally appropriate, and it should also protect the environment and the natural resources. This implies the following criteria:

• Health and hygiene: The sanitation system must put an effective barrier between its user and the environment, and must prevent exposure 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 and downstream populations — hence it also includes hygiene behaviour (see also health and hygiene issues).

• Environment and natural resources: In order to be sustainable, the sanitation system must protect and respect the natural environment and resources. Wherever possible, the resources contained in excreta and wastewater (energy, nutrients, water) are recycled, thereby protecting other resources (e.g. by replacing fossil fuels through biogas). Should use little energy, water or other resources (e.g. for construction, operation and maintenance), and should produce as little harmful emissions to the environment as possible (both liquid, solid and gaseous) (see recharge and reuse).

• Technology and operation: A sustainable sanitation system utilises a technology and a mode of operation that are well adapted to local circumstances. This includes the system’s functionality and the ease with which the entire system including the collection, transport, treatment and reuse and/or final disposal can be constructed, operated and monitored by the local community and/or the technical teams of the local utilities. Furthermore, the robustness of the system, its vulnerability towards power cuts, water shortages, floods, etc. and the flexibility and adaptability of its technical elements to the existing infrastructure and to demographic and socio-economic developments are important aspects to be evaluated (see implementation tools).

• Financial and economic issues: The cost of a sanitation system must relate to the financial capacity of households, communities or institutions and includes not only the costs for construction, but also arising costs for operation, maintenance and necessary reinvestments of the system. Besides the evaluation of these direct costs also direct benefits e.g. from recycled products (soil conditioner, fertiliser, energy and reclaimed water) and external costs and benefits have to be taken into account. Such external costs are e.g. environmental pollution and health hazards, while benefits include increased agricultural productivity and subsistence economy, employment creation, improved health and reduced environmental risks (see financing).

• Socio-cultural and institutional aspects: A sanitation system only lasts and can be sustainable if it is appropriate and accepted by the community. Again, this includes the whole sanitation system — i.e. not only toilets, but also maintenance and operation and the recharge and reuse system adopted. A sustainable sanitation system must hence be socially acceptable, convenient, respect gender issues and impacts on human dignity, consider impacts on food security. In regards to institution aspects, it must be in compliance with the legal framework and must make for stable and efficient institutional settings (see also sociocultural issues).

Most sanitation systems have been designed with these aspects in mind, but in practice they are failing far too often because some of the criteria are not met. In fact, there is probably no system that is absolutely sustainable. The concept of sustainability is more of a direction rather than a stage to reach. Nevertheless, it is crucial, that sanitation systems are evaluated carefully with regard to all dimensions of sustainability. Since there is no one-for-all sanitation solution, which fulfils the sustainability criteria in different circumstances to the same extent, this system evaluation will depend on the local framework and has to take into consideration existing environmental, technical, socio-cultural and economic conditions.

Taking into consideration the entire range of sustainability criteria, it is important to observe some basic principles when planning and implementing a sanitation system. These were already developed some years ago by a group of experts and were endorsed by the members of the Water Supply and Sanitation Collaborative Council as the “Bellagio Principles for Sustainable Sanitation” during its 5th Global Forum in November 2000 (EAWAG/SANDEC & WSSCC 2000):

1. Human dignity, quality of life and environmental security at household level should be at the centre of any sanitation approach (see also sociocultural issues).
2. In line with good governance principles, decision-making should involve participation of all stakeholders, especially the consumers and providers of services (see also creating an enabling environment).
3. Waste should be considered a resource, and its management should be holistic and form part of integrated water resources, nutrient flow and waste management processes (see also IWRM).
4. The domain in which environmental sanitation problems are resolved should be kept to the minimum practicable size (household, neighbourhood, community, town, district, catchments, and city) (see also community led urban environmental sanitation).

To summarise, sustainable sanitation is a simple approach: the most basic principle is that it considers wastewater and excreta not as a waste, but as a resource, that sanitation has to be socially acceptable and should be as economically viable as possible. There is no “one-fits-all” approach, much rather, the most adequate solution has to be found from case to case, considering climatic conditions, water availability, agricultural practices, socio-cultural preferences, affordability, safety, and technical prerequisites — just to name a few.