Reusing Wastewater for Crops Could Reduce Water Scarcity, If We Can Stomach It.

Recycling wastewater for agricultural use could reduce food production’s freshwater consumption, but overcoming the “yuck” factor could prove tricky.

  • Some compounds in partially treated wastewater are actually nutritious for soils, replacing or diminishing the need for fertilizers.

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What happens to water after washing your hands or flushing the toilet? Worldwide, over 80 percent of wastewater is released untreated into the environment. Cleaning that water and recycling it for use in agriculture could cut down on pollution of lakes and streams and slow the rate at which food production depletes freshwater. And the nutrients in partially treated wastewater can nourish plants, diminishing the need for fertilizers.

A new paper in Agricultural Water Management by researchers at the University of Alicante in Spain analyzed 125 studies for themes related to the acceptance and use of recycled wastewater for irrigation in agriculture. It found that while the public is concerned about health risks, farmers also consider the long-term effects of the wastewater on the quality and health of their soil, which can vary. And beyond practical considerations of risks and benefits, recycling wastewater has an inherent “yuck factor” to be overcome.

Eating a green bed of lettuce grown with recycled wastewater might trigger concern or even disgust — a response known as the “yuck factor.”

Unsurprisingly, the researchers found that the yuck factor is less of an issue for farmers during times of drought or when the quality of the recycled wastewater is high. Economics can overcome the yuck factor, too. In the Thessaly region of Greece, 57.9 percent of farmers responded that they would pay for reclaimed water if it cost half the price of freshwater. Only 8.4 percent would pay for recycled water if it cost only a little less than freshwater.

Consumers, on the other hand, appear more likely to accept the use of wastewater to irrigate crops if they trust the institutions managing the water and if they understand the treatment process, environmental benefits, and issues of water scarcity. One strategy to build trust in wastewater treatment, the researchers say, is to build and run small-scale demonstrations before implementing full-scale water reuse programs so the public can see the quality of the water themselves. Because seeing is believing.

Recycled water is treated to different extents depending on its future use. For example, recycled water entering the drinking water supply is treated more than recycled water used for irrigation.

When adequately treated for a given use, recycled water is safe. But, about 10 percent of irrigated land globally uses untreated or partially treated wastewater, according to a paper cited in the review.

That presents clear risks for human health and for the environment. Pathogens can be transported in undertreated wastewater, as can metals, pharmaceuticals, and endocrine-disrupting chemicals. Disease organisms can move from reused water to food. Metals and salts from the water can build up in soil, changing soil properties such as pH and affecting plant growth.

But other compounds in the water are actually nutritious for soils, replacing or diminishing the need for fertilizers. One study highlighted by the researchers found that in Hyderabad, India, farmers believed the partially treated wastewater contained nutrients that were beneficial to their crops. However, growers also changed which crops they grew because of increasing soil salinity.

Some places are finding success. In Israel, most treated wastewater is recycled and accounts for 40 percent of the water used for irrigation. A 2012 report found that California reused 13 percent of its municipal wastewater, with 37 percent of that going to agriculture. In the dust of the state’s recent drought, cities like Los Angeles are looking to move beyond reuse in agriculture to bring recycled wastewater back to the tap.

The World Health Organization and the United Nations issued recommendations for safe reuse of water in 1973 and 1987, respectively. Those guidelines, along with others from the European Union, the United States, and elsewhere, have informed development of wastewater reuse regulations around the world. But some cities and countries have limited ability to reliably uphold water treatment regulations.

Moving forward, “the main challenge in using wastewater for irrigation is to shift from informal, unplanned uses of untreated or partially treated wastewater to planned safe uses,” according to a 2017 United Nations report. As this paper points out, education is an important part of that picture.

“As citizens become more familiar with the technology and general understanding of the associated benefits of increasing water reuse,” it concludes, “officials, planners, and managers may come up against less opposition to additional applications and achieve greater water savings through the widespread implementation of water reuse programs” — a move that could prove crucial to meeting the needs of an increasingly thirsty world.

Becky Mackelprang is a plant biologist and science communicator.

This article is republished from Ensia under a Creative Commons license. Read the original article.

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4 comments / Join the Discussion

    As noted by others, biosolids from WWTP are being spread on farm land without proper, even adequate treatment. There is a documentary out now called “Biosludged” that is quite terrible to watch. This is a shame, because propoerly treated wastewater, CAN be made completely clean… it just costs more. We are doing it in agriculture, where we are held to very high standards because we dont have any political pull.

    Industrial sludge rife with toxic chemicals is spread on mid-west corn and soy fields … under an “organic” designation.
    No one’s thinking about the health implications, either way. Because our governments are all hand-in-glove with the industries that produce, purvey and use the contaminants.
    Grow a garden at home. Compost your vegies and coffee grounds.
    I recently bought “organic” compost containing residue of a pesticide excreted in ruminant feces. I had, luckily, used it only on a small patch of my garden. That was 7 years ago, and peas still won’t grow there. But finally some weeds do. I suppose that means things are looking up.
    Several market and nursery growers had to scrape off 18″ of soil, and purchase soil to try to grow a second crop in. Two I heard of personally (and I’m not connected with either industry) were forced out of business by using the stuff.

    Given the lack of treatment of biosolids from wastewater treatment before it is spread on agricultural land, I have strong doubt that wastewater would be sufficiently treated before agricultural use. The imperative seems to be low cost, not limiting contamination.

    Hi Becky, My Norwegian cousin whom taught Environmental Science subjects in the University there, informed me that melting Glacier Ice represents fresh water, and should float in the “top layer of Ocean water”,which of course has a high level of salt, and is therefore heavier, than glacier water! It would seem that if this is true- that the top layer could be siphoned off, and easily desalinated, if necessary? That in turn should allow many Coastal Cities Worldwide to choose that water for both drinking and if needed for Agricultural use, vs. using reconstituted Wastewater!

    I have also been informed by a Water Tech here, (working for our local Utility Co.) that the chemicals (think bleach) used in treating Wastewater here-produces a known carcinogen, & if that is correct, represents another reason to consider Glacier melt water, if it can be recaptured?

    I’ve been a Water Conservationist for 30+ years now and at a soon to be 75 yrs., have mostly been shocked (here in Colorado) at how poorly our Waterways have been treated. Still, I have managed to bring about some improvements- even working alone for many years, and going against the “powers that be”, charged with protecting our waters and waterways.

    Imagine if many Worldwide (everyday Citizens & Scientists) will help with ideas and various actions, and be open-minded enough to understand, that we may in fact be able to make a big difference, while protecting the health of many of the World’s Citizens, while providing them with much needed water which can be consumed without a risk to their health?

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