Imagine you’ve got a very fine sieve, and you’re trying to push muddy water through it with your bare hands. That’s hard work. Reverse osmosis uses pressure to force water through a super-tight membrane that catches pretty much everything—lead, chlorine, even microscopic nasties.
But here’s the kicker: the membrane gets clogged with all that bad stuff. To keep the filter clean and functional, the system uses a little stream of water to constantly wash the membrane’s surface. That “washing” water is the wastewater.
So, the water you’d normally call “waste” is actually the water that carried away the dirt. It’s not dirty in a scary way; it’s just a bit more concentrated with minerals and whatnot. It’s the leftover rinse water from your super-efficient car wash, not a toxic spill.
How Much Are We Really Talking About?
Here’s where the panic usually sets in. Most home RO systems have a ratio of about 3 to 1 (waste to clean water) for every gallon of filtered water you get. Some newer efficient models get down to 1 to 1. So, to fill your reusable water bottle (about 20 ounces), the system might use 60 ounces of incoming water total.
That sounds like a lot until you compare it to your daily routine. A standard shower uses about 2 gallons per minute. A five-minute shower is 10 gallons. Your ten-minute shower is 20 gallons. Suddenly, the three gallons of “waste” you produced today for your drinking and coffee water feels like a tiny drop in the proverbial bucket.
Chromatography Wastewater Analysis at Greg Booth blog
We’re talking about pennies per day on your water bill. It’s less than the water you accidentally run while brushing your teeth or waiting for the shower to get hot. It’s the water you might spill when your cat decides the kitchen floor needs a bath.
