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May 2, 2010 8:31 PM   Subscribe

How do municipal water treatment facilities ensure that water is safe?

Considering the current Boston problem with water, what steps do municipal public works departments determine the quality of water? How is public water treated? Bacteria and algae aside, how do they remove chemical contaminants from water? And what happens to waste water if it can't be decontaminated?
posted by at the crossroads to Grab Bag (13 answers total)
This is a job for Wiki, isn't it?
posted by Some1 at 8:35 PM on May 2, 2010

Response by poster: Yeah, I guess my question is a little too broad for AskMe, but timely. Thanks for pointing me to Wiki. Are there any other online resources that explain how water is treated?
posted by at the crossroads at 8:41 PM on May 2, 2010

your local wastewater treatment plant probably does tours. i know the one in fayetteville, ar was fascinating.
posted by nadawi at 8:43 PM on May 2, 2010

Totally seconding nadawi. There's a pretty big difference between large cities and smaller towns, though.

During my visit to the local treatment plant when I was in college in a small town in Iowa, I kinda regret asking the tourdude, "What was the oddest thing that you've seen come through this system?"

There's a (in retrospect not) surprising amount of basic microbiology involved - both in testing (bacterial titres, phage titres) and how to use microorganisms to treat the wastewater and render it safe to release back into the ecosystem.

To answer your last question... they just flush it into the environment and hope that it just dilutes out. Yeah. It sucks. Thats why we have loads of intersex fish. At least* they're high on stimulants and anti-depressants.

posted by porpoise at 9:36 PM on May 2, 2010

Ah, my daughter's favorite show when she was much younger covered this. This is only one of many ways, but it is a common one.
posted by barc0001 at 10:14 PM on May 2, 2010

how do they remove chemical contaminants from water?

In a lot of cases it's prohibitively difficult, so they try to start with water that doesn't have anything like that in it. That's why so many cities bring their water in from such a great distance.

New Orleans is one of the few cities which cannot do that. Wells won't work there (they'd turn salty) and there's no clean water to bring in, so they have to use the Mississippi. My memory from when I visited was that it was the worst tap water I'd ever encountered, anywhere I'd ever traveled, because there was so much junk dissolved in the source (the river) which pretty much couldn't be taken out.

In SoCal they've been experimenting with reprocessing sewage to create drinking water. San Diego in particular has been pushing this idea.

But one of the big problems with that is hormones. Many women take birth control pills, which often contain estrogen analogs. A bit of that comes out in their urine, goes into and through the reprocessing plant, and ends up in the resulting drinking water in very small quantities.

If women drink that, it isn't a problem. But if men drink that, for months or years, eventually the hormones will affect them, in ways we men don't like to think about. The quantities are really very small, but when it comes to those kinds of hormones it doesn't take much. I haven't heard that anyone has figured out how to solve this problem yet.
posted by Chocolate Pickle at 11:25 PM on May 2, 2010

Here's a previous answer I gave about how waste water here in Savannah is treated. While this water is probably safe to drink, it's not used for such, just sold to golf ranges for water.

The actual drinking water in Savannah comes from two sources, well water and surface water (lakes, rivers). The well water isn't treated much, doesn't need to be, just a few chemicals to kill bacteeria. The surface water is treated more heavily and run through filters to get rid of particles.
posted by Brandon Blatcher at 4:04 AM on May 3, 2010

Please note that the OP's question has to do with drinking water, not wastewater.
posted by megatherium at 4:18 AM on May 3, 2010

Here in Singapore, we're drinking something that's been branded "NEWater." It's waste water that is first filtered, then purified by reverse osmosis, and finally disinfected with UV. This recyled sewage makes up a relatively small part of the Singapore water supply (less than 10% -- the rest comes from resevoirs, desalination plants, and pipes from neighboring Malaysia), but it is claimed to be cleaner than other water sources.
posted by blue mustard at 5:12 AM on May 3, 2010

Water is tested often at water treatment plants before it hits the mains but it isn't a constant process. Generally if all steps in the process remain constant then there is little change. Sure it depends on the source whether it is a lake or river or reservoir. Rivers vary more than lakes especially at different times of the year. Then there is the possibility of contaminants in the mains outside of the treatment plant.

There are strict levels made at the federal level for water quality but most water treatment plants set their own higher levels. There are also many types of treatment which vary from plant to plant. The thing to remember is that there always will be contaminants unless you actually distill the water (very expensive). The theory and regulations behind water treatment is that most contaminants don't have to be removed - they merely have to present in minute quantities.
posted by JJ86 at 6:07 AM on May 3, 2010

Mod note: few comments removed - can we stick to facts and answers please? thank you.
posted by jessamyn (staff) at 6:13 AM on May 3, 2010

Your water utility may send you a pamphlet on this with your water bill; we get a water quality report quarterly with results from the water testing for various contaminants and other stuff (with short details of how the tests are conducted and where to get more information), and we get a yearly summary of treatment methods, sources, etc.
posted by Eyebrows McGee at 6:51 AM on May 3, 2010

When I worked for a small water utility they treated the water with bleach - once a month someone would drive to the local grocery store and buy a case of Clorox laundry bleach to fill the machine that added the bleach at the pumping station. Our water was pumped up from wells as opposed to surface rivers, etc so it was going in to the system clean and the only real risk of contamination was from backflow or a broken pipe. It always struck me as funny that it was just regular laundry bleach. What would happen if someone goofed and bought scented?
posted by ChrisHartley at 9:29 AM on May 3, 2010

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