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FEATURE STORYMarch 18, 2022

Water Challenges Inspire Innovation and a Circular Economy, From Senegal to India and Ecuador

A group of women collecting water under a tree in an arid field, in the region of Saint Louis, Senegal.

A group of women collect water in the region of Saint Louis, Senegal.

Photo: Vincent Tremeau / The World Bank


  • Like many cities impacted by population growth and climate change, Dakar, Senegal, could face a future without enough water for all.
  • To build water security, Dakar is turning wastewater and sanitation byproducts into assets with the help of the private sector.
  • Guayaquil, Ecuador and Chennai, India, are among a growing number of cities adopting more sustainable practices to create a virtuous cycle of water use and reuse.

Nestled on the Cap-Vert peninsula along Senegal’s Atlantic coast, Dakar is one of Africa’s most beautiful and vibrant cities. But like many cities impacted by rapid population growth and a changing climate, Dakar could face a future without enough water for all. A new World Bank report warns that Senegal urgently needs to prioritize water security or face serious constraints on economic growth, with Greater Dakar particularly at risk.

These findings do not come as a surprise – Dakar has been hit by water stress and shortages for the past decade. In response, the city has shown it is prepared to be innovative. With the help of partners and an operating model that delegates urban water supply and sanitation to the private sector, Dakar is working to keep up with growth. It recently began moving to a more holistic way of managing and reusing its water and sanitation resources while encouraging water demand management through the reduction of water losses. Treated wastewater now irrigates some of the country’s most productive farmlands on the outskirts of the city. Byproducts of the sanitation system are being repurposed as fertilizer for farmers’ fields, and biogas is powering a wastewater treatment plant, saving resources and money.

Dakar recently began moving to a more holistic way of managing and reusing its water and sanitation resources while encouraging water demand management through the reduction of water losses.

Like Dakar, a growing number of cities in developing countries are adopting more sustainable practices that create a virtuous cycle of use and reuse. Such practices are the building blocks of a circular economy in which water, energy and other resources are managed sustainably, waste and pollution are reduced, and the environment is preserved. With climate change already exacerbating pre-existing water issues in cities, a new initiative at the World Bank Water Global Practice is supporting countries to adopt circular economy practices and build resilience for the water sector.

Guayaquil, Ecuador, for example, is tackling a decades-long sewage pollution problem in its rivers and estuaries by focusing on all the elements of safe sanitation – from improving infrastructure and the sewerage network, to ensuring the poor have coverage and customers can effectively connect to the network. Water quality is monitored upstream of the city, and river basin planning is used to better understand water quality stressors. Two new plants will treat wastewater and transform biogas from sewage sludge digestion into enough electricity to meet 35-40% of the plants’ needs.

Chennai, India responded to the need for more water amid rapid industrial and population growth by becoming more circular and resilient. It mandated rainwater harvesting and became the first city in India to reuse 10% of collected wastewater, with plans to achieve a reuse rate of 75%. As part of this effort, the Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB) sells treated wastewater to industrial users and with the additional revenues, it can cover all operating and maintenance costs. CMWSSB is the only utility in the country with two large-scale desalination plants. The utility is also recovering energy from wastewater in more than half of its wastewater treatment plants and is preparing to sell most of the biosolids created by the process as manure for agricultural land.

Landscape in Dakar, Senegal

View of the city of Dakar, Senegal. 

Photo: Sarah Farhat / The World Bank

Senegal Becoming a Center of Expertise on Water and Waste Reuse

Senegal began laying the groundwork for a circular economy two decades ago. Policies and regulations anticipated the need for better use and reuse of water and waste. Today, Dakar’s sanitation and stormwater utility, Office National de l’Assainissement du Sénégal (ONAS), is turning wastewater and sanitation byproducts into assets with the help of the private sector. Senegal’s innovative approach has made it a center of expertise, with representatives of some 15 countries visiting Dakar to learn from the utility’s experience.

The Dakar utility began piloting new strategies to deal with shortfalls in water supply affecting customers and the region’s horticulturalists and farmers. To ease water shortages for horticulturalists, the utility began to sell treated wastewater to nearby farmers and later extended the system to irrigate the crops of hundreds of market gardeners near its Cambérène wastewater treatment plant. The facility plans to increase its capacity for wastewater treatment from 19,000 cubic meters per day to 92,000 cubic meters per day.

"The various forms of recovery of the treated water from the treatment process of the Cambérène wastewater treatment plant, which we have so far experimented with, have finally proved to us the inestimable value of this by-product,” said ONAS Managing Director Ababacar Mbaye. “Indeed, in addition to being a precious raw material, purified water is a real alternative resource to water pressure and is a boon for the revival of agricultural development, public works, watering of green spaces, among others".

To promote efficiency and reduce operational costs, the Cambérène wastewater plant also began recovering the biogas generated in the wastewater treatment process. The biogas is used to generate heat and power in an onsite cogeneration system to power the facility, resulting in a 28% savings in energy use.  

The utility is selling dried and stabilized fecal sludge as fertilizer to farmers and flower growers. The fecal sludge is processed by the wastewater treatment plant run by ONAS and a fecal sludge treatment plant run by a private company, with both plants located at the Cambérène complex. The proximity and collaboration between the two plants ensure they can have economies of scale and are also close to the places where their products can be reused efficiently.

Such forward thinking will be critical in the years ahead as Senegal innovates to address its water challenges.


The World Bank
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