At the surface of the drinking water reservoir Ivanhoe Reservoir in Los Angeles in 2015 they released millions of black plastic balls. Youtuber Derek Muller (spoon of Veritasium) went to the reservoir to discover their purpose.
The problem of toxic carcinogenic compounds
The first thoughts are aimed at reducing water evaporation, but the main goal in this case is different: 96 million plastic balls prevents the formation of toxic carcinogenic compounds.
In this case, the source of the problem was bromide, a chemical that occurs naturally in salty seawater. Bromide itself is not harmful to humans, but if some of the salt water enters the tank and is subsequently treated with ozone along with the rest of the drinking water, bromate (a salt of bromic acid containing the bromate anion) can be formed.
The company that supplies water and electricity to Los Angeles has been monitoring bromate levels. Measurements have shown that the amount of this carcinogenic substance continues to increase for some reason. Experts subsequently discovered that when bromide and chlorine interact with sunlight, even more bromate is formedthan when bromide and chlorine act on ozone.
Black balls on the surface
Then came an unusual idea, which at the time was called “bird balls”. These were black balls commonly used at airports to prevent birds from landing in nearby waters. In addition, they are also very effective at blocking light. “They fixed the bromate problem right away,” Marty Adams — head of the city’s utility that focuses on the generation and distribution of electricity and water supply — told Muller.
Shade balls don’t have to be just black, they are produced in a number of sizes, from different materials and actually don’t even have to be balls – all according to the purpose they are supposed to fulfill.
The balls are made to last up to ten years. After releasing them into the tank cleaning equipment can use less chlorine to fight algae growth, which thrive in bright sunlight. Although water evaporation was not originally intended, the fact that the balls keep the water below them significantly cooler is another benefit.
“For all these reasons, the balls reduce evaporation by 80 to 90 percent,” explains Muller. “That’s quite significant in the dry conditions that prevail in the area around Los Angeles.”
Balls with a diameter of 10 centimeters are made of high-density polyethylene (HDPE) with an admixture of carbon black. This material is less dense than water and floats on the surface of the tank even if it breaks down.
2023-10-07 10:46:39
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