Recycled wastewater is not only as safe to drink as conventional potable water, it may even be less toxic than many sources of water we already drink daily, Stanford University engineers have discovered.
“We expected that potable reuse waters would be cleaner, in some cases, than conventional drinking water due to the fact that much more extensive treatment is conducted for them,” says Stanford professor William Mitch, senior author of an Oct.
27 study in Nature Sustainability comparing conventional drinking water samples to potable reuse water. “But we were surprised that in some cases the quality of the reuse water — particularly the reverse-osmosis-treated waters — was comparable to groundwater, which is traditionally considered the highest quality water.”
The discovery is encouraging news for a thirsty public and utility corporations straining to meet demand as drinking water supplies become more rare.
Why recycling?
Around the United States, there are numerous operational potable reuse systems. Since the 1970s, the Orange County Water District has operated the largest water recycling facility in the world.
Both Aurora, Colorado, and Atlanta, Georgia, employ potable reuse water as a component of their drinking water sources. By 2035, Los Angeles intends to recycle all of its wastewater.
But the urgency to make recycling wastewater as routine as recycling an empty La Croix can has increased due to decades of drought.
Water utilities are frantically looking for dependable water supplies, especially in the western U.S., which is suffering from a severe drought.
Traditional water sources, such the Colorado River and runoff from the Sierra Nevada, are becoming less abundant. Instead, utilities are focusing on potable reuse as a dependable water source because it is already something they can easily control and own.
In addition to a reliable supply of water, there are other advantages. According to Mitch, a professor of civil and environmental engineering at Stanford Engineering and the Stanford Doerr School of Sustainability, “If you’re not importing water, it means there’s more water for ecosystems in northern California or Colorado.
Cleaning up recycled water is also known to cost a lot less and require less energy than extracting the salt out of seawater.
“You’re cleaning up the wastewater, and therefore you’re not discharging wastewater and potential contaminants to California’s beaches.
” Cleanup team The engineers discovered that following treatment, potable reuse water is cleaner than typical drinking water obtained from rivers that are in immaculate condition.
Most rivers have effluent being dumped into them from upstream with far less treatment than is done in
Traditional wastewater treatment facilities are just not set up for extensive cleaning. This results in a lot of organic pollutants, such chemicals from shampoos and pharmaceuticals, drifting down the river and right into a water treatment facility.
Regulators want for more thorough processing at potable reuse treatment facilities. They state that utilities must use reverse osmosis, ozonation, biofiltration, and other cleaning processes to eliminate additional contaminants once treatment systems have removed dangerous organisms like viruses and amoebas.
With reverse osmosis treatment, water is forced under high pressure through a tiny filter that removes even salt and chloride. Mitch and his colleagues found that the method cleans wastewater just as well as, if not better than, groundwater, the industry benchmark.
Even when reverse osmosis wasn’t applied, reuse waters were less toxic than the samples of conventional drinking waters sourced from rivers across the United States.
Policy solutions for overlooked contaminants The Environmental Protection Agency aims to protect people from toxic drinking water by regulating a slew of chemicals. But some of the stuff floating in our water has yet to be identified or categorized by scientists.
In order to suss out the toxicity of different sources of tap water, the researchers a pplied water from various sources to hamster ovary cells, because they act similarly to human cells.
Mitch and his colleagues looked at whether cells slowed or stopped growing, compared to untreated cells. “Ideally, we picked up the effects of chemicals specifically measured by the EPA, as well as those that aren’t,” Mitch says.
The engineers discovered the compounds regulated by the EPA accounted for less than 1% of the harm to the ovary cells.
“Even if we include all these other unregulated compounds that a lot of us in this field have been focusing on, that still accounted for only about 16% of the total,” Mitch says.
“It really says we’re not necessarily focusing on the right contaminants.”
The culprits may be associated with disinfection. No matter where your tap water comes from, it will carry residual disinfectant to prevent pathogens growing in the pipes.
Disinfectants like chlorine react with chemicals in the water and convert them to something else, and that may be what’s killing the hamster cells.
The EPA regulates disinfection byproducts, but not all. “Our study indicates that maybe the toxicity exerted by these byproducts regulated by the government may not be so important.”
Mitch says his team plans to further investigate whether other side effects from disinfecting water could be causing toxicity.
His team is looking specifically at larger byproducts formed when disinfectants mix with pesticides, proteins or other organic matter.
Disinfecting water is necessary: Without it, we’d die from cholera and other waterborne diseases. But Mitch notes that disinfection is a balancing act between killing pathogens and minimizing exposure to harmful byproducts.
“We can’t get to zero contaminants. That would be ridiculously expensive, and probably unwarranted from a health point of view,” he says.
Whatever you do, Mitch warned, don’t stock your fridge with bottles of water. That plastic taste in bottled water tells you compounds from the plastic have migrated into the water, he says.
“At the end of the day, yes, there’s stuff in everything, but the reuse water quality is as good as tap water, which is pretty darn good.”
Source : Stanford University
