Drinking treated sewage water may not be your cup of tea, but it may be the clean safe water solution for the future--and you are probably doing it already anyway.
The National Research Council (NRC) says that advances in treatment technology for municipal wastewater means water often flows out of treatment plants as clean as what many of us drink today. "With recent advances in technology and treatment design, potable reuse can reduce the concentrations of chemical and microbial contaminants to levels comparable to or lower than those present in many drinking water supplies," reports the Council, a Congressionally chartered scientific advisory body of the nation’s leading researchers, in a new study. "Municipal wastewater reuse offers the potential to significantly increase the nation’s total available water resources."
Every day, about 12 billion gallons of municipal wastewater--about 37% of the total discharge--is released into an ocean or coastal estuary. Reusing this water would increase the U.S. water supply by 6%, and constitute 27% of the public supply. As water supplies tighten, this enormous source of water may prove too valuable to ignore, even if many instinctively recoil from the idea of drinking what once flowed down your sink, or toilet.
Yet, for one thing, we already use plenty of former "municipal" (read: sewage) water for applications like watering lawns and industrial cooling. We also drink plenty of water from sources that contains wastewater discharged by communities upstream. "This practice is not officially acknowledged as potable reuse," says the Council, but "a large fraction [of some cities’ drinking water] originated as wastewater effluent from upstream communities, especially under low-flow conditions." In other words, you’re already drinking the toilet water of the people up the river from you. In other other words, shit flows downstream. So, we’re already effectively just one step away from officially reusing the water for drinking before diluting in rivers, lakes, or aquifers and sending it downstream.
Today, the Council says only about 1% of the U.S. water supply is "reused" wastewater; just a fraction of that is ever used directly for drinking. But continuously improving filtration techniques can eliminate almost all pathogens and trace organic chemicals. In two areas studied by the NRC where drinking water was drawn from wastewater, the risk from 24 selected chemical contaminants did not exceed that from existing water supplies.
But the approach is not risk-free. Rather, the NRC argues, the goal should be a very low and appropriate risk rather than idealized purity, which does not exist in our drinking water system today anyways. It suggests obtaining a better, quantified understanding of the risk uncertainties about how different reuse systems could work, and putting fail-safes against treatment breakdowns.
For now, the "risk from potable reuse does not appear to be any higher, and may be orders of magnitude lower, than currently experienced in at least some current (and approved) drinking water treatment systems."
With technology getting better all the time, it won’t be long before former wastewater is pouring crystal clear from your tap, if it isn’t already.