After the initiative of farmers to reduce by 25% the consumption of water, in California the ultimate weapon against the drought of black balls. Specifically, the mayor of Los Angeles, Eric Garcetti writes on facebook:
“Los Angeles has just completed a project to protect the water reserve distributing the shade balls on its surface, keeping it clean and safe”
The solution was developed by the Department of Water and Power and the object in question is the Ivanhoe Reservoir (this reservoir will be replaced in the future by an underground cistern). The problems to be faced were mainly two:
- Every year, because of the great heat, evaporate about 300 million gallons of water.
- The bromide ion, naturally present in water and chlorine dioxide, added as a disinfectant, in the presence of sunlight react and form the ion bromate, BrO3-, which is a carcinogen.
Ninety-six million shade balls, this is the number of balls placed in the tank by 11 billion liters of water in the city of Los Angeles. The balls made of polyethylene are BPA-Free (ie free from Bisphenol A, compound essential for the synthesis of plastics and suspected to be harmful to humans).
Each ball has a diameter of about 10 cm and is made of high density polyethylene, a thermoplastic polymer that is derived from petroleum suitable for not spoiling the contact with water. According to the filmmakers, these balls should last about 10 years and do not emit chemicals into the air. They are black because in them contain charcoal to help absorb the sun’s UV rays. Doing so will prevent water to evaporate under high temperatures and also will also reduce the uncontrolled growth of algae and bacteria and the triggering of chemical reactions between bromide ion and chlorine dioxide.
The cost of the transaction is $ 34.5 million, which translates into about 36 cents per ball, and allowed to cover an area of 175 acres (710,000 m²) which is home to 3.3 billion gallons of water. Those responsible for this ecological solution have chosen to opt for the balls having regard to the size of the surface to be covered: the quote for the realization of a simple protective sheet was 300 million dollars, an expense unattainable which would mean, inter alia, the need to split into two parts the reservoir.
It is not the first time that the balls are used to preserve watersheds. Besides, who will pass in front of large reservoirs of drinking water will see a show given by all those dots blacks that seem to invade the precious liquid, but rather care for them.