What is source-based sanitation?

Revolution in Sanitation: From Urban Cleanliness to Circular Economy

During the 20th century, four main missions shaped our understanding and approach to sanitation: collecting, transporting, treating, and discharging wastewater. These missions helped achieve several essential objectives.

The first mission, collection, allowed for the capture of wastewater at its source, thus preventing its accumulation in the streets and public spaces, which drastically reduced the spread of waterborne diseases. Transport, the second mission, involved the development of sophisticated infrastructures, such as pipe networks, to convey this water to treatment plants. This process was crucial in keeping wastewater away from inhabited areas, thereby ensuring a healthier and safer environment for populations. Treatment, the third mission, was a true technological and scientific feat. Thanks to the invention of advanced purification techniques, wastewater could be stripped of its contaminants, reducing its impact on nature. Finally, the fourth mission, discharge, involved returning this treated water to the natural environment, with minimal impact on aquatic ecosystems.

These initiatives allowed for the achievement of objectives such as the sanitation of cities. The success of these interventions has been so significant that today, we take the cleanliness of our urban environments for granted. Moreover, they have played a decisive role in protecting water bodies, ensuring a good ecological state of rivers, lakes, and oceans.

However, a reflection is necessary. By treating wastewater solely as waste, we have often neglected its potential as valuable resources. Indeed, wastewater contains nutrients, energy, and water which, if correctly recovered and reused, can significantly contribute to environmental sustainability. Today, the challenge is to rethink our approach to integrate these resources into a circular economy so that sanitation is not only a matter of public health but also a pillar for a sustainable future.

Towards a Circular Economy: Redefining Wastewater as Tomorrow’s Resources

When discussing the resources contained in wastewater, the first idea that comes to mind is their potential reuse, notably as irrigation water for urban green spaces. Moreover, wastewater is full of essential nutrients, such as nitrogen, phosphorus, and potassium, which are the pillars of soil fertility. In modern agriculture, these elements are often supplied by chemical fertilizers, which departs from the natural cycle of organic matter and can lead to environmental problems such as waterway pollution. By recovering these nutrients from wastewater, we have the opportunity to reintegrate these elements into the natural cycle, thus promoting more sustainable and environmentally friendly agriculture.

In a world where overall efficiency and the circular economy are gaining importance, it becomes logical and necessary to integrate the valorization of wastewater into the traditional missions of sanitation. This means not only treating wastewater to make it harmless but also transforming it into beneficial resources for our society. This transition requires investments in new technologies and paradigm shifts in our resource management approach.

In other words, it is time to “close the loop.” This involves rethinking our economic and ecological model to become more circular. Instead of seeing wastewater as an end, we must consider it a beginning – a new source of raw materials that can be reintroduced into the economic cycle. This will not only reduce our ecological footprint but also create new economic opportunities and ensure more resilient management of our natural resources.

Source Sanitation: Towards an Ecological and Decentralized Revolution

Over the past three decades, collective sanitation has made enormous progress. Thanks to techniques such as composting and biogas production, it is now possible to recover nutrients and energy contained in the organic matter of wastewater. However, these methods remain marginal and collective sanitation presents certain limitations, particularly in terms of capacity. In this context, decentralized sanitation seems to be a promising alternative. Indeed, it could avoid the exorbitant costs associated with updating current equipment necessary to accompany urban expansion.

To succeed in this transition, it is essential to rethink our basic paradigms. This means favoring decentralized sanitation and seeking to valorize resources before proceeding with their treatment. This approach is at the heart of what is called “source sanitation.” Historically, pioneers like Friedensreich Hundertwasser, an avant-garde architect of the 70s, integrated innovative concepts such as composting toilets in their buildings. His vision, both jubilant and audacious, already fully aligns with the spirit of circularity that animates us today.