Vast, valuable amounts of energy, essential agricultural nutrients, and water could be recovered from the world’s fast-growing volume of municipal wastewater, says the United Nations University.
A newly-published study reveals a staggering 380 billion cubic meters (m3 = 1000 litres) of wastewater are produced worldwide each year — five times the volume of water passing over Niagara Falls annually. That much water would fill Africa’s Lake Victoria in just under seven years, Lake Ontario in just over four years, and Lake Geneva in less than three months.
And the volume of wastewater is increasing quickly, with a projected rise of roughly 24% by 2030, 51% by 2050. By the mid-2030s, wastewater worldwide will roughly equal the volume of water flowing each year through the St. Lawrence River.
Among major nutrients, 16.6 million metric tonnes of nitrogen are embedded in wastewater produced worldwide annually, together with 3 million metric tonnes of phosphorus and 6.3 million metric tonnes of potassium. Theoretically, full recovery of these nutrients from wastewater could offset 13.4% of global demand for them in agriculture.
Beyond the economic gains of recovering these nutrients are critical environmental benefits such as minimizing eutrophication — the phenomenon of excess nutrients in a body of water causing dense plant growth and aquatic animal deaths due to lack of oxygen.
The energy embedded in wastewater, meanwhile, could provide electricity to 158 million households — roughly the number of households in the USA and Mexico combined.
The CGIAR Research Program on Water, Land and Ecosystems (WLE) and the International Water Management Institute (IWMI) contributed its latest research findings to the report. WLE and its lead research centre IWMI have been leading the sector on development of business models, which include an understanding of the incentives and barriers affecting safe wastewater reuse.