LA’s Ivanhoe Reservoir contains millions of gallons of drinking water for LA residents. In the summer, however, problem presents itself: the water can potentially become contaminated with bromate (depending on daily outbound flow rates, one would presume), which is a natural reaction between solar light, chlorine (a treatment chemical) and naturally-occurring bromide.
Seeing how chlorine is a necessary treatment additive and the bromide is a natural element within the water, Ivanhoe officials got creative and decided to keep sunlight away from the water by dropping over 3 million black spheres (called bird balls) into the reservoir. This effectively created an opaque layer atop the water that serves as a solar shield, which eliminates the solar component of the reaction. Problem solved. Yay, right?
But allow me to think out loud for a second: Ivanhoe is preventing the formation of a carcinogen by interrupting the photochemical reaction that forms bromate, the threat in question. But is anyone thinking about the potential toxicity of millions of plastic balls leeching into the drinking water supply, especially millions of black balls that take the beating of the LA sun all summer? To me, this seems like you could be trading one problem for another.