Nav: Home

Vast amounts of valuable energy, nutrients, water lost in world's fast-rising wastewater streams

February 03, 2020

Vast amounts of valuable energy, agricultural nutrients, and water could potentially be recovered from the world's fast-rising volume of municipal wastewater, according to a new study by UN University's Canadian-based Institute for Water, Environment and Health (UNU-INWEH).

Today, some 380 billion cubic meters (m3 = 1000 litres) of wastewater are produced annually worldwide - 5 times the amount of water passing over Niagara Falls annually - enough to fill Africa's Lake Victoria in roughly seven years, Lake Ontario in four, and Lake Geneva in less than three months.

Furthermore, the paper says, wastewater volumes are increasing quickly, with a projected rise of roughly 24% by 2030, 51% by 2050.

Today, the volume of wastewater roughly equals the annual discharge from the Ganges River in India. By the mid-2030s, it will roughly equal the annual volume flowing through the St. Lawrence River, which drains North America's five Great Lakes.

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 agricultural demand for them.

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 study's estimates and projections are based on theoretical amounts of water, nutrients, and energy that exist in the reported municipal wastewater produced worldwide annually.

The authors underline that information on wastewater volumes -- generated, available, and reused - is scattered, infrequently monitored and reported, or unavailable in many countries. They also acknowledge the limitations of current resource recovery opportunities.

Nonetheless, says lead author Manzoor Qadir, Assistant Director of UNU-INWEH, in Hamilton, Canada: "This study offers important insights into the global and regional potential of wastewater as a source of water, nutrients, and energy. Wastewater resource recovery will need to overcome a range of constraints to achieve a high rate of return but success would significantly advance progress against the Sustainable Development Goals and others, including adaptation to climate change, 'net-zero' energy processes, and a green, circular economy."

Among many findings:
  • The energy value in 380 billion m3 of wastewater is estimated to be 53.2 billion m3 methane - enough to provide electricity for up to 158 million households, or 474 million to 632 million people, assuming an average of three to four persons per household. Given the foreseen wastewater increases, that number rises to 196 million households in 2030, and 239 million households in 2050.

  • In agriculture, the volume of water potentially recoverable from wastewater could irrigate up to 31 million hectares - equal to almost 20% of the farmland in the European Union (assuming two crops and a maximum 12,000 m3 of water per hectare per year). "The reclaimed water can be used to irrigate new areas or replace valuable freshwater where crops are already irrigated."

  • World wastewater production is expected to reach 470 billion m3 by 2030, the year by which the SDGs are supposed to be met - a 24% increase from today. And by 2050, it will reach 574 billion m3, a 51% increase.

  • Asia is the largest wastewater producer with an estimated 159 billion cubic meters, representing 42% of urban wastewater generated globally, with expectations of that proportion rising to 44% by 2030

  • Other regions producing large volumes of wastewater: North America (67 billion m3) and Europe (68 billion cubic meters) - virtually equal volumes despite Europe's higher urban population (547 million vs. North America's 295 million. The difference is explained by per capita generation of wastewater: Europe 124 cubic meters; North America 231 cubic meters). By contrast, Sub-Saharan Africa produces 46 cubic meters of wastewater per capita - about half of the global average (95 cubic meters), reflecting limited water supply and poorly-managed wastewater collection systems in most urban settings.

  • Full recovery from wastewater could, theoretically, offset 14.4% of global demand for nitrogen as a fertilizer nutrient; phosphorus 6.8% and potassium 18.6%. Based on current levels of nitrogen, phosphorus, and potash use in agriculture worldwide (estimated at 193 million metric tonnes in 2017), the study says about 13.4% of the global fertilizer nutrient demand could be supplemented by full nutrient recovery from wastewater.

  • The nutrients in wastewater could theoretically generate revenue of $13.6 billion globally: $9.0 billion from the recovery of nitrogen, $2.3 billion from phosphorus, and $2.3 billion from potassium.
The paper cites prior research showing that human urine is responsible for 80% of the nitrogen and 50% of phosphorus entering municipal wastewater treatment plants. "Removing these nutrients in time would not only be environmentally beneficial," the paper says, "resulting in less eutrophication, it would reduce the cost of wastewater treatment while supporting closed-loop processes."

Current wastewater nutrient recovery technologies have made significant progress. In the case of phosphorous, recovery rates range from 25% to 90%.

The paper points out that maximizing economically the potential use of thermal energy in wastewater swings on several basic requirements, including a minimum flow rate of 15 litres per second, short distances between heat source and sink, and high-performance heat pumps.

Says Vladimir Smakhtin, Director of UNU-INWEH, a global leader in research related to unconventional water sources: "Municipal wastewater was and often still is seen as filth. However, attitudes are changing with the growing recognition that enormous potential economic returns and other environmental benefits are available as we improve the recovery of the water, nutrients and energy from wastewater streams."

Co-authors comments

"Safely managed wastewater is the key to water-related sustainable development at a time when the world is embarking on achieving SDGs, particularly SDG 6.3, which calls on us to half the proportion of untreated wastewater and substantially increase recycling and safe reuse globally by 2030."

Praem Mehta, UNU-INWEH / McMaster University, Hamilton, Canada

"This data can be used to develop national action plans aiming at water resources management, pollution control measures, nutrient and fertilizer access, and energy recovery and energy production systems."

Younggy Kim, McMaster University, Hamilton, Canada

"It is important to note that many innovations are available and are being refined to bridge the gap between current resource recovery levels and resource recovery potential."

Blanca Jiménez Cisneros, UNESCO and the National Autonomous University of Mexico

"For countries to progress, there is a need to invest in a supportive regulatory and financial environment towards a green economy, and to leverage private capital for resource recovery-related business models that are financially feasible and increase cost recovery from municipal wastewater."

Pay Drechsel, International Water Management Institute, Sri Lanka

"There is a need to facilitate and expedite implementation of resource recovery innovations particularly in low- and middle-income countries where most municipal wastewater still goes into the environment untreated. This concerns mainly the growing small and medium-size towns where agricultural land is still in proximity but also urban agricultural areas around larger cities."

Amit Pramanik, Water Research Foundation, Alexandria, VA, USA

"The SDG challenge is on, and step-wise approaches are needed which should involve both the public and emerging private sectors which often struggle with inadequate regulatory frameworks, limited finance, and the lack of capacity to develop or evaluate bankable business plans about resource recovery and reuse. As the demands for freshwater are ever-growing and scarce water resources are increasingly stressed, ignoring the opportunities leading to safely managed wastewater is nothing less than unthinkable in the context of a circular economy."

Oluwabusola Olaniyan, Winnipeg Water and Waste Department, Canada.
-end-
Funding: Global Affairs Canada / Government of Canada

UNU-INWEH

The UNU Institute for Water, Environment and Health is a member of the United Nations University family of organizations. It is the UN Think Tank on Water created by the UNU Governing Council in 1996. Its mission is to help resolve pressing water challenges of concern to the UN, its Member States and their people, through knowledge-based synthesis of existing bodies of scientific discovery; cutting edge targeted research that identifies emerging policy issues; application of on-the-ground scalable solutions based on credible research; and relevant and targeted public outreach.

Related research, unconventional water sources:

Rising levels of toxic brine as desalination plants meet growing water needs

Click here: http://bit.ly/2HcOSyM

UNU-INWEH is supported by the Government of Canada through Global Affairs Canada and hosted by McMaster University.

UN University Institute for Water, Environment and Health

Related Nitrogen Articles:

Reducing reliance on nitrogen fertilizers with biological nitrogen fixation
Crop yields have increased substantially over the past decades, occurring alongside the increasing use of nitrogen fertilizer.
Flushing nitrogen from seawater-based toilets
With about half the world's population living close to the coast, using seawater to flush toilets could be possible with a salt-tolerant bacterium.
We must wake up to devastating impact of nitrogen, say scientists
More than 150 top international scientists are calling on the world to take urgent action on nitrogen pollution, to tackle the widespread harm it is causing to humans, wildlife and the planet.
How nitrogen-fixing bacteria sense iron
New research reveals how nitrogen-fixing bacteria sense iron - an essential but deadly micronutrient.
Corals take control of nitrogen recycling
Corals use sugar from their symbiotic algal partners to control them by recycling nitrogen from their own ammonium waste.
Foraging for nitrogen
As sessile organisms, plants rely on their ability to adapt the development and growth of their roots in response to changing nutrient conditions.
Inert nitrogen forced to react with itself
Direct coupling of two molecules of nitrogen: chemists from Würzburg and Frankfurt have achieved what was thought to be impossible.
Researchers discover new nitrogen source in Arctic
Scientists have revealed that the partnership between an alga and bacteria is making the essential element nitrogen newly available in the Arctic Ocean.
Scientists reveal impacts of anthropogenic nitrogen discharge on nitrogen transport in global rivers
Scientists found that riverine dissolved inorganic nitrogen in the USA has increased primarily due to the use of nitrogen fertilizers.
Nitrogen gets in the fast lane for chemical synthesis
A new one-step method discovered by synthetic organic chemists at Rice University allows nitrogen atoms to be added to precursor compounds used in the design and manufacture of drugs, pesticides, fertilizers and other products.
More Nitrogen News and Nitrogen Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Climate Mindset
In the past few months, human beings have come together to fight a global threat. This hour, TED speakers explore how our response can be the catalyst to fight another global crisis: climate change. Guests include political strategist Tom Rivett-Carnac, diplomat Christiana Figueres, climate justice activist Xiye Bastida, and writer, illustrator, and artist Oliver Jeffers.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Speedy Beet
There are few musical moments more well-worn than the first four notes of Beethoven's Fifth Symphony. But in this short, we find out that Beethoven might have made a last-ditch effort to keep his music from ever feeling familiar, to keep pushing his listeners to a kind of psychological limit. Big thanks to our Brooklyn Philharmonic musicians: Deborah Buck and Suzy Perelman on violin, Arash Amini on cello, and Ah Ling Neu on viola. And check out The First Four Notes, Matthew Guerrieri's book on Beethoven's Fifth. Support Radiolab today at Radiolab.org/donate.