Plastic spheres block sunlight—and cancer

A Dark Thought: (Blow it Up!)  Irfan Khan

If you make a mess, just cover it up. That’s the theory behind the Department of Water and Power’s latest project in Los Angeles, which aims to prevent the formation of a carcinogen in two drinking-water sources, the Ivanhoe [pictured] and Elysian reservoirs.

The unwanted chemical, bromate, forms when sunlight, chlorine and the naturally occurring mineral bromide intermingle. The city considered solutions, like a tarp or metal cover, but they were all too costly, labor-intensive or ugly. Then the ball idea, courtesy of LADWP biologist Brian White, floated to the top. The layer of three million black polyethylene balls prevents sunlight from completing the deadly cocktail. If it seems a bit temporary, it is—officials plan to retire the balls in five years, when a replacement underground reservoir near Griffith Park is finished.

16 Comments

These black balls prevent sunlight from reaching the water, yes... but how much heat will they absorb, and what effect will the increased water temp have on bacterial growth? I mean, this is southern California - and it is drinking water, right?

What are they going to do with the balls after they've been removed?

A black tar pit-esque layer of several tons of black, non-biodegradable balls is somehow not ugly?

Yes, that could solve the sunlight problem but doesn't plastic have chemicals that can kill us....

This is drinking water right?

-THE KID

no really where are they going to put the litle rubber balls once they are removed. how are we going to use them again. scientists should think about things like this before they dump rubber balls or do stupid things like that.
WHOO HOO

Plus, couldn't all the money from labor, and design and the production of the balls in the first place be used more efficiently somewhere else like in the recycling department maybe?

aw3se4, it's plastic not rubber
it's probably a special kind of plastic that doesn't degrade in the sunlight or heat..i'm not a specialist of plastic

So that's where the boo balls in second life came from!

Why cant they just use a tarp to cover them it would be less money and easier.

z

nybaseballm, have you ever seen a tarp on a backyard pool? Seen it after it rains? Now multiply that by an order of, oh, lets say 1000. I've spent plenty of time in San Dog. It's not overly wet but it does rain, not to mention that water would make it's way over the edge of a tarp and eventually drag it lower and lower.

ScottSEA, the fact that the balls are black will only heat the upper layer of water. The lack of penetration of light to the lower depths will allow it to remain cool, if not grow colder. There will certainly be an increased temperature differential but it will most likely not have a major impact on the overall temp of the body of water. On top of that, any bacterial growth can be and is already filtered out at the water treatment plants. There isn't a pump that pulls the water straight out of the reservoir and dumps it right into your tap. I do agree with you about the eventual future of the balls though. It's more of a re-direction of problems than a true "solution" but then again, I don't have a better answer for the problem so it's hard to knock it. Maybe they could make one SERIOUS carnival ball pit when they're done.

Why don't the convert their water treatment plant from injecting chlorine, to one of the newer ozone based plants?
If the problem is the interaction between chlorine, and the bromide compound, wouldn't this be a better alternative? They would also eliminate there dependency on chlorine.
Milwaukee converted their systems years ago, after they had a mishap with the chlorine, and ended up causing a crypto outbreak. The way I understand it is that Milwaukee tap water is some of the best in the country, and they are proud of it.

The article says the balls are made of polyethylene, which is recyclable. It is not harmful to your health. Go look in your kitchen, most of the plastic food containers will have a recycle symbol with a number 1 on the bottom, which means it's made of polyethylene. The bromine in the water will react with chlorine to most likely form either bromodichloromethane or dibromochloromethane before it forms bromate. These are less carcinogenic than bromate. Treating the water with ozone would immediately cause bromate to form, not to mention retrofitting their treatment plant would cost millions as well. The treated water could be filtered through granular activated carbon filters to remove these bromide species before distributing it to the public, but the municipality must have determined this retrofit option to be too expensive.

Hey look at plastic bottles... they aren't supposed to be harmful to humans and look at all the chemicals found in them that causes cancer and who knows what?

Use natural sources to clean or cover up the water... plants.

Plus its good for the environment.

-THE KID

ideally there should be a natural, or at least more practical sounding, solution, as some of you have said. but if you think about it more practicaly, this a very sensible and cunning solution to a potentialy dangerous, or at least very costly, problem in a city with an already outrageous budget at a time when our economy isn't very good. why retrofit the system? why not use cheap, recylable plastic balls when you're just going to switch to a new resevoir in a few years anyway? seems like a great idea to me.

Hey timias...
Ozone, chlorine dioxide, even hypochlorite have been observed to produce bromate form bromide ion. So converting to an ozone system is not a good idea to prevent bromate formation in this water.

The best solution is to have a covered reservoir for their finished water, like every other municipality in the country.

Thanks for the information about the ozone system being a worse problem. The article only mentioned chlorine, and bromide as a problem, hence asking about ozone.

Blinding Light64

from cairo, N.Y.

ye know the black balls pose a serious risk they cover the water right? that means if the terrorists wanted to the could poison the water without anyone knowing, until its to late, scary!


138 years of Popular Science at your fingertips.

Innovation Challenges



Popular Science+ For iPad

Each issue has been completely reimagined for your iPad. See our amazing new vision for magazines that goes far beyond the printed page



Download Our App

Stay up to date on the latest news of the future of science and technology from your iPhone or Android phone with full articles, images and offline viewing



Follow Us On Twitter

Featuring every article from the magazine and website, plus links from around the Web. Also see our PopSci DIY feed


February 2012: The Future of Fun

Science is reinventing play, from extreme sports to gamification to ridiculous roller coasters to the playgrounds of tomorrow, and this issue is chock full of fun. Also, on a less fun note: Did global warming destroy my hometown?


circ-top-header.gif
circ-cover.gif
bmxmag-ps