Recycled wastewater is not only safe to drink - it may even be cleaner than many traditional sources of drinking water, according to a study from Stanford University.
The research shows treated wastewater can be more dependable and less toxic than many common tapwater sources, including rivers and groundwater. The study compared conventional drinking water samples to wastewater purified as a drinking water - also known as direct potable reuse water. It concluded that after treatment, recycled wastewater is cleaner than conventional drinking water sourced from rivers.
"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.”
In order to evaluate the toxicity of different sources of tapwater, the researchers applied water from various sources to hamster ovary cells, which are similar to human cells, and looked at whether the cells slowed or stopped growing, compared to untreated cells.
“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,” said Stanford professor William Mitch, senior author of the study, which has been published in Nature Sustainability.
“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.”
Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30% of all readily available freshwater in the world is groundwater. Typically, groundwater is cleaner and easier and cheaper to treat than surface water, because it tends to be less polluted as the soil on top acts as a filter.
Although desalination is often touted as the alternative way to produce drinking water in the face of dwindling supplies, this study makes the case that recycled wastewater may not only be cleaner, but could also have a less detrimental impact on the environment - as treating recycled wastewater requires significantly less energy than extracting the salt from seawater.
As drinking water sources become more scarce, this discovery is promising news.