Q How do we purify dirty water?
— Molly Torinus
A Christy Remucal, professor of civil and environmental engineering at the University of Wisconsin-Madison:
What we use to purify water depends a lot on where the water’s coming from and what we want to do with it.
If we’re going to drink water, it needs to be very clean and very safe. There are lots of regulations that we have to meet.
Drinking water is treated using chemical and physical processes. An example of a chemical process would be adding a disinfectant, something like chlorine that would be used to kill pathogens. These are things like bacteria or viruses that, if you drink them, could make you sick.
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We also use more physical processes like filtration or sedimentation to remove particles, solid things that we don’t want in our water.
A wastewater treatment plant uses those same processes but also biological processes. We use bacteria or other kinds of microorganisms that are basically taking our waste, like what goes down our toilets, and using it as food. That’s how we get rid of the waste that we put in water.
Typically, we get our drinking water from groundwater — water deep under the ground or surface water like a lake or a reservoir. Those tend to be cleaner and what we like to use for drinking water.
But a lot of places like California are dealing with water scarcity. Many of those places are thinking about using treated wastewater for drinking.
Most of the time, this water is used for irrigating crops or things like golf courses or landscapes. But treated wastewater can be made very, very clean. Some places like Singapore actually use it for drinking water.
There are places in the U.S. and other places that are considering going this route as water becomes more of a scarce resource.