From Cape Town to Sao Paulo, many cities around the world are struggling to meet the water demands of growing populations. In 1960, 34 % of the world’s population lived in cities. That number is 54 % today; by 2050, cities are projected to hold closer to three-quarters1 of all people.
Rapid migration into urban areas and population growth within the areas themselves have strained resources like water and energy. Cities receive a finite amount of water from sources — like upstream watersheds and dams — that must be shared with agricultural and industrial sectors. There’s a growing need to make urban water supply resilient to droughts and other disruptive forces.
At the same time, cities are struggling to manage the waste produced by these growing populations. In China, for example, cities collectively generate over 40 million metric tons of sewage sludge — enough to fill six Great Pyramids of Giza annually2. But treating wastewater is expensive, and it can take time to build support for investments.
When local institutions can’t afford to properly manage wastewater, it’s often dumped directly on land or in nearby waterbodies. Eighty percent of the world’s wastewater is discharged back into nature without further treatment or reuse3, endangering public health and sanitation. And sludge — the solid byproduct of wastewater treatment — is often spread on land, or landfilled. Even where wastewater is treated, sludge is often ignored and wasted. Beyond nutrient pollution and the potential spreading of pathogens, disposing of wastewater and sludge without treatment releases methane, a powerful greenhouse gas, that furthers climate change.
Read the full article at Water Online.
1United Nations. 2014. Revision of World Urbanization Prospects. https://esa.un.org/unpd/wup/
2World Resources Institute. 2017. “Waste-to-Energy: A Comic Uncovering Waste’s Hidden Potential” http://www.wri.org/blog/2017/10/waste-energycomic-uncovering-wastes-hidden-potential
3UN-Water. 2015. Wastewater Management: A UN-Water Analytical Brief. http://www.unwater.org/publications/wastewater-management-un-wateranalytical-brief/