Why did Americans throw 96 million black plastic balls into the reservoir and fish them again?

2020-01-24 | Old porridge popular science Original |

For a long time, many people have envied the American people to drink cold water, and drink it when the tap is turned on. There is no need to boil water, which proves that the water is good.

Almost ten years ago, people in California, USA, felt that there was something wrong with the tap water they were drinking. What's wrong? Because the water was found to be poisonous!

California is a relatively special place with a developed economy, but there are many areas with drought and water shortage, and its water needs to be transferred from a long delta area after treatment. There is one thing in the treated water that cannot be removed.It's bromide.

Americans are used to drinking cold tap water

Bromide itself is not a problem. It is a completely safe mineral. It is very common in salt water. Because its molecules are very small, it is difficult to remove from the water. But the water plant needs to be chlorinated when disinfecting the water.This chlorine is added to the water to act as a catalyst, and when exposed to the sun, it will generate bromate, a carcinogenic substance. When I heard that I had been drinking toxic water for many years, Californians were not happy. The council discussed it.Later, a regulation was issued, requiring the water plant to remove the carcinogenic bromate. If it fails, all reservoirs will be covered and the sun is not allowed.

Add a cover to Silver Lake in California?

As mentioned earlier, the bromide in the reservoir water is difficult to remove. In order to sterilize the chlorine, it must be added. The only way is to cover all the reservoirs.

  • California's response

The water plant has a large reservoir area. It is actually a lake with an area of ​​1.85 million square meters. It is no small challenge from the perspective of money or technology to cover it completely, until a biologistBrian White thought of something like "bird balls." The bird ball is not a ball for birds but a bird-proof ball. It was originally used in a pool near the airport to cover the water.

Bird Ball

We know that the airport needs to keep some water for fire fighting. At these levels, it is stored in a huge open-air pond. Many birds will fly over to drink water and make their homes nearby. But the airport does not welcome birds, theyFlying around the airport is easy to crash into the plane, so the airport will throw some hollow plastic balls into the pond. The plastic balls densely cover the water surface, and the birds will not come again if they can’t drink water.This kind of plastic ball is called a bird ball.

Birds are a risk factor at the airport

The Los Angeles Water and Power Administration asked a company to customize this kind of plastic ball. It was obviously inappropriate to call it bird ball, so it gave a new name called "Shade balls", which is also called shadow ball.

The shadow ball is about 10 cm in diameter and is made of polyethylene plastic. Due to the addition of a large amount of carbon black, the whole body is black. The hollow inside of the ball is filled with some drinking water, so that it can float on the water, and the windIt can’t be blown away. As long as the lake is densely covered with shadow balls, it is equivalent to adding a cover to the reservoir, which seems to be a perfect plan.

Los Angeles Mayor and ball

  • Usefulness of Shadow Ball

You may wonder why this shadow ball is made black, white is more reflective than black! This is a good question.

We know that the reason why Californians pour the ball into the reservoir is to block the sun from reaching the lake. Among all the colors, only black is inaccessible to most light. You take a white plastic ball against the sunlight.Seeing it is illuminated, it means that the white ball leaks light, but the black ball does not. Another is that although the black ball absorbs heat in the sun, the water under it will not sink when heated, and the black ball will dissipate heat at night.fast.

Nearly 100 million black plastic balls fell into the reservoir

Because the shadow ball blocks the sunlight, it also reduces the evaporation of the lake water by 80~90%, which can save a lot of water a year. This is very important for the drought and water shortage of California. Most of its water is from far awayExtracted from the local area, the annual evaporation of the reservoir reached more than 2 meters, which is not a small expenditure.

Another side effect is that the growth of algae in the reservoir is inhibited due to lack of sunlight, because this is mainly for domestic water. Americans do not raise fish and do not need aquatic plants, so they have no ecological problems.

Plastic ball can reduce water evaporation

  • Oppositional voice

Just like the two sides of a coin, everything has two sides. Since the day when the California water plant started to throw plastic balls into the reservoir, the voice of opposition has never been cut off.

Someone has calculated that the investment in these balls does not save much money due to water saving, because the authorities say that the shadow balls can save 1.1 million tons of water every year, which seems a lot. But 1.1 million tons of water is only worth 2 million US dollars, The cost of 96 million balls is 34.5 million U.S. dollars, even if the maintenance costs are not included, it will take 17 years to pay back. Moreover, the actual life of these balls is only 10 years, and the safety risk increases if they expire.

Reservoir staff

Some people think that these plastic balls seem to save water, but in fact a lot of water has been consumed in the process of producing these balls. Take the 96 million plastic balls in the Ivanhoe Reservoir, these polyethylene ballsPlastics are produced from petroleum, and the process of manufacturing these balls requires at least 2.9 million tons of water. That is to say, regardless of the monetary cost, it will take two and a half years to "pay back" from the perspective of water consumption.No wonder the Los Angeles Weekly bluntly called it "a very stupid way to save water."

At the same time, some people pointed out that polyethylene plastics are not always safe, because the total amount is huge and the balls need to be soaked in water for ten years. Such a long period of sunlight, soaking and collision friction will accelerate the aging of plastics, and it willPlastic particles are released in the water, and in more serious cases, endocrine disrupting chemicals that interfere with the hormone system of animals and humans Yang 2011 and endocrine disruptors such as bisphenol A BPA are released.

Plastic balls are risky

  • Los Angeles is constantly fishing for balls

In the past few years, the Los Angeles Water Department first threw balls into the reservoir with great fanfare, and then picked up 9.4 million sunshade balls from the reservoir every year. The media said that three of the four large reservoirs have been emptied, and now there is only one reservoir left.There is a ball in it.

In order to comply with the regulation that the lake cannot be exposed to the sun, they plan to build underground water storage facilities on the one hand, and at the same time find a way to replace the shadow ball with an awning. This means that the previous attempt failed and more investment is needed.

The water is drained

  • Should we study Los Angeles?

First of all, we need to see the particularity of California's water resources. It is because the water contains excessive amounts of bromate and cannot be removed, so the reservoirs have to be "covered" in accordance with regulations. We have not heard that many other places in the United States alsoThe black plastic ball is thrown into the reservoir to save water.

From the perspective of saving water or money, dumping tens of millions of plastic balls into the reservoir is not a cost-effective investment. In fact, there are examples of building solar power stations using open water in many places.On the one hand, it can greatly reduce the evaporation of water, generate electricity, and allow birds to have a place to roost and drink water. Although building a water power station is not perfect, it is at least compared to throwing tens of millions of black plastic balls into the lakeIt's still much better.

What do you think?

Water surface photovoltaic power station serves multiple purposes

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