Why would a city cover one of its biggest reservoirs with millions of black plastic spheres? In Los Angeles, the answer was not publicity. In practical terms, the city was trying to stop sunlight from changing treated water after it had already left the plant.<\/p>\n\n\n\n
LADWP finished deploying nearly 96 million shade balls across the 175 acre Los Angeles Reservoir in 2015, saying the cover would protect water quality, slow evaporation, and curb algae growth before that water reached homes and businesses.<\/p>\n\n\n\n
The chemistry was the real headache. LADWP says sunlight hitting bromide rich, chlorinated water can help create bromate<\/a>, a regulated drinking water contaminant. <\/p>\n\n\n\n The EPA lists bromate with a maximum contaminant level of 0.010 milligrams per liter and a health goal of zero because of cancer risk concerns. That helps explain why this was not just a drought story. It was also part of Los Angeles\u2019 effort to comply with federal and state rules for uncovered treated water reservoirs.<\/p>\n\n\n\n The idea itself came from “bird balls” used elsewhere to keep birds off ponds. LADWP adapted it for drinking water. The spheres are made of high density polyethylene<\/a>, about 4 inches wide (roughly 10 centimeters), and the ones used at the Los Angeles Reservoir are partially filled with drinking water so strong winds do not push them aside. <\/p>\n\n\n\n Their black color comes from carbon black, which LADWP says helps block light and makes the plastic more resistant to sun damage. The utility also says the material is food grade and certified for drinking water contact by NSF.<\/p>\n\n\n\nAlso Read: It looks like just another camping gadget, but this small wind turbine could be the solution many people have been looking for to charge their cell phones, laptops, or external batteries<\/a><\/h4>\n<\/div>\n<\/div><\/div>\n<\/div>\n\n\n\n
How the balls actually work<\/h2>\n\n\n\n