Susan Leal: Recycling wastewater one way to fight freshwater scarcity

Getting enough fresh water is an increasing challenge in many places, like Southern California. Leal said one solution is to recycle wastewater.

Getting enough fresh water is an increasing challenge in Southern California – both because of the growing population and climate change-induced weather events, like drought.

That’s according to Susan Leal. She’s an associate of the School of Engineering and Applied Science at Harvard University, and co-author of the book, Running Out of Water. She told EarthSky:

When we were researching solutions to improve access to freshwater, we looked for solutions that were proven, solutions that could be replicated around the globe.

Leal said one such solution is for more places to recycle wastewater. In the 1990s, Southern California’s Orange County was pumping in most of its freshwater from the northern part of the state – hundreds of miles away. Orange County water officials realized this wasn’t sustainable. Leal said:

What they decided to do was recycle their own wastewater. They took water from their sewer plants, and took it through a very intricate treatment system, so that the water they produced was pristine level, like distilled water. And then they put it back into their underground reservoirs.

When that water sprang up again, locally, it could be treated and used just like any other tap water, she said. That’s still happening today.

And it is proven to be a wonderful boon for the county – it is not in dire straits as some of its surrounding counties.

The same strategy is being used half a world away in Singapore, Leal said, which has a similar water scarcity issue, and an increasing population.

Leal talked more about freshwater access solutions for agriculture, which accounts for up to 70% of the world’s freshwater use. She said workable water solutions exist when it comes to agriculture, too – she discovered adjustments made to sprinkler systems on farms, for example, that cut down on a farm’s water use by as much as 20 percent.

We also looked at proven solutions around agriculture. They are available, whether it’s for growing cotton, or rice. It’s not only the crops you choose, but it is also how you grow them. And what we were able to determine is that they are very low cost – meaning these solutions can pay for themselves.

We’ve seen them work, for example, in Imperial County, also in Southern California. It was once a desert, and was flooded accidentally in the early 1900s, and it became one of the large agricultural valleys in the United States, and in the world. In fact, they say that half the winter vegetables in the U.S. come from this county. And what they found is with some fairly low-cost technology put in place, they could reduce the use of water, so they could easily grow the food with 10 percent less water. Which may not sound like much, but it could mean the difference between having food for three decades, instead of one.

We asked her what she meant when she said “low-cost technology.”

It might mean putting in certain types of drip irrigation. In the case of Nebraska, where they put in a certain type of sprinkler system, they used close to 20 percent less water than they would have originally. The supplies in their groundwater reservoirs was already diminishing.

Image Credit: Clearly Ambiguous

One of the most significant things she discovered in writing her book, Leal said, is that while good solutions exist for water challenges, they are not necessarily being implemented where they should be, sometimes because those solutions are cost-prohibitive.

She said this especially applies to wastewater treatment plants, which are having trouble keeping up with runoff into sewers from floods. She said flooding is on the rise because of global warming, which increases the frequency and fury of storms.

Storm surges overwhelm wastewater systems, so that the waste cannot be properly treated. And then it goes, without the proper treatment, into river, lakes, bays, and oceans, which of course can cause a public health problem, and definitely causes a problem with aquatic life.

She gave an example, explaining the challenges:

An example is if you were running a wastewater system in New York City, and you were having to process the wastewater coming out of Manhattan. With a storm surge, your systems could be overwhelmed. And you might have to build a bigger wastewater treatment system. These systems, especially for large cities, cost billions of dollars.

Rising sea level is another problem for wastewater treatment facilities, she said. If salt water gets into these facilities, it prevents them from working properly. Leal said:

For people that are running water utilities, whether it’s in the U.S. or in other parts of the world, it’s no longer an issue of “Is climate changing going to affect our water supply?” – it’s now to the point of: “What to do we have to do to adapt, to a climate that has been changing?”

Hear the 90 second EarthSky interview with Susan Leal on recycling wastewater as one solution to freshwater scarcity, (at top of page.)

Beth Lebwohl