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LA is dumping millions of plastic balls into its reservoir to tackle the drought

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Re: LA is dumping millions of plastic balls into its reservoir to tackle the drought

#11

Post by erikb »

markyc wrote: post #9
tristanj wrote: post #3

They're not dumping plastic balls in order to tackle the drought, they're being dumped because the EPA mandated that all reservoirs be covered. Direct sunlight will cause bromide and chlorine in the water to mix into bromate, a known carcinogen, and the EPA wants to prevent buildup of this compound in the drinking water supply. Covering the reservoir with a tarp is too expensive (costing over $300 million) and plasti…

doesn't the plastic + sunlight + heat combination release dangerous chemicals in the water? also, why are they black, doesn't that attract more heat?

That's also what I was wondering. Touching something wet, being warmed by the sun, and all that, can't be good for the black plastic.

Re: LA is dumping millions of plastic balls into its reservoir to tackle the drought

#12

Post by cengizkrbck »

Bootvis wrote: post #8

What I don't understand is that they dumped black balls in the reservoir. If you want to keep the water cool to lessen evaporation wouldn't it make sense to use white or reflecting balls so the water stays slightly cooler? I would be glad to know why black balls are chosen.

black is best suitable color to deflect UV rays.

Re: LA is dumping millions of plastic balls into its reservoir to tackle the drought

#13

Post by DanBC »

tristanj wrote: post #3

They're not dumping plastic balls in order to tackle the drought, they're being dumped because the EPA mandated that all reservoirs be covered. Direct sunlight will cause bromide and chlorine in the water to mix into bromate, a known carcinogen, and the EPA wants to prevent buildup of this compound in the drinking water supply. Covering the reservoir with a tarp is too expensive (costing over $300 million) and plasti…

Was the article edited after you read it?

> And the primary reason for deploying the hollow balls is more to protect the quality of the water rather than to simply stop it evaporating. In the reservoir water, the naturally occurring bromide was mixing with sunlight and chlorine (added to disinfect drinking water) to create dangerous levels of the the carcinogen bromate. Shade balls should stop that harmful chemical reaction from happening at a large scale, and of course by deflecting the Sun's rays, they also keep more of the water in liquid form.

Re: LA is dumping millions of plastic balls into its reservoir to tackle the drought

#14

Post by girvo »

tristanj wrote: post #3

They're not dumping plastic balls in order to tackle the drought, they're being dumped because the EPA mandated that all reservoirs be covered. Direct sunlight will cause bromide and chlorine in the water to mix into bromate, a known carcinogen, and the EPA wants to prevent buildup of this compound in the drinking water supply. Covering the reservoir with a tarp is too expensive (costing over $300 million) and plasti…

The article says all of that:

> And the primary reason for deploying the hollow balls is more to protect the quality of the water rather than to simply stop it evaporating

Re: LA is dumping millions of plastic balls into its reservoir to tackle the drought

#15

Post by erikb »

cengizkrbck wrote: post #12
Bootvis wrote: post #8

What I don't understand is that they dumped black balls in the reservoir. If you want to keep the water cool to lessen evaporation wouldn't it make sense to use white or reflecting balls so the water stays slightly cooler? I would be glad to know why black balls are chosen.

black is best suitable color to deflect UV rays.

Now you just said the opposite of what intuition suggests without any evidence, or even argument. Please elaborate and don't just heat up the discussion!

Re: LA is dumping millions of plastic balls into its reservoir to tackle the drought

#16

Post by DanBC »

erikb wrote: post #15
cengizkrbck wrote: post #12

Earlier quoted context omitted.

black is best suitable color to deflect UV rays.

Now you just said the opposite of what intuition suggests without any evidence, or even argument. Please elaborate and don't just heat up the discussion!

Black is the best colour to absorb UV. You want the UV to not reach the water, so you want whatever is on top of the water to not allow UV past.

Re: LA is dumping millions of plastic balls into its reservoir to tackle the drought

#17

Post by throwaway_yy2Di »

Bootvis wrote: post #8

What I don't understand is that they dumped black balls in the reservoir. If you want to keep the water cool to lessen evaporation wouldn't it make sense to use white or reflecting balls so the water stays slightly cooler? I would be glad to know why black balls are chosen.

According to a chemist on /r/askscience, the plastics probably contain carbon black [0] as a UV protectant. So it might not be deliberate.

    (/u/Platypuskeeper) Although I have not seen a specification of what
    the balls are made of, what I know from polymer chemistry is that the
    black is quite likely from carbon black (essentially soot), which is
    used as an additive/filler in polymers (e.g. tire rubber) for multiple
    reasons but not least UV protection. Carbon black is one of the most
    (if not the most) effective UV-protective additives, precisely because
    it absorbs the UV and prevents it from penetrating deeply into the
    plastic. Plastic without some UV protective additive would degrade
    pretty quickly in the California sun, not least HDPE which has pretty
    bad UV resistance.
https://www.reddit.com/r/askscience/comments/3gpu6x/why_are_...

[0] https://en.wikipedia.org/wiki/Carbon_black

Re: LA is dumping millions of plastic balls into its reservoir to tackle the drought

#18

Post by desdiv »

DanBC wrote: post #13
tristanj wrote: post #3

They're not dumping plastic balls in order to tackle the drought, they're being dumped because the EPA mandated that all reservoirs be covered. Direct sunlight will cause bromide and chlorine in the water to mix into bromate, a known carcinogen, and the EPA wants to prevent buildup of this compound in the drinking water supply. Covering the reservoir with a tarp is too expensive (costing over $300 million) and plasti…

Was the article edited after you read it? > And the primary reason for deploying the hollow balls is more to protect the quality of the water rather than to simply stop it evaporating. In the reservoir water, the naturally occurring bromide was mixing with sunlight and chlorine (added to disinfect drinking water) to create dangerous levels of the the carcinogen bromate. Shade balls should stop that harmful chemical r…

Wouldn't it make more sense to add the chlorine after the water is drawn from the reservoir?

Doesn't that fix the bromate problem at the root?

Re: LA is dumping millions of plastic balls into its reservoir to tackle the drought

#19

Post by PhasmaFelis »

Bootvis wrote: post #8

What I don't understand is that they dumped black balls in the reservoir. If you want to keep the water cool to lessen evaporation wouldn't it make sense to use white or reflecting balls so the water stays slightly cooler? I would be glad to know why black balls are chosen.

Black absorbs more light (and, yes, heat), which means less light penetrates through it to heat the water directly. If you block one bright light with a sheet of thin white plastic, and another with a sheet of thin black plastic, you'll see a lot more light shining through the former. And do remember that the primary purpose is to block UV, not heat, so you want maximum light absorption even if it means greater heat transfer.

Chrome-mirrored balls would certainly be even better, but the whole reason they're using plastic balls is because they're dirt cheap. If you have enough money to fill your reservoir with disco balls, you'd be better off just building a gigantic awning.

Re: LA is dumping millions of plastic balls into its reservoir to tackle the drought

#20

Post by rtpg »

desdiv wrote: post #18
DanBC wrote: post #13

Earlier quoted context omitted.

Was the article edited after you read it? > And the primary reason for deploying the hollow balls is more to protect the quality of the water rather than to simply stop it evaporating. In the reservoir water, the naturally occurring bromide was mixing with sunlight and chlorine (added to disinfect drinking water) to create dangerous levels of the the carcinogen bromate. Shade balls should stop that harmful chemical r…

Wouldn't it make more sense to add the chlorine after the water is drawn from the reservoir? Doesn't that fix the bromate problem at the root?

Just a guess, but maybe chlorine needs a good amount of time to be effective, and the transit time from reservoir to tap might not be enough
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