Green Daily

The first part of the Ivanhoe reservoir's problem was the bromides. Naturally occurring chemical compounds, bromides often show up in seawater and groundwater. In and of themselves, they aren't dangerous. The 10-acre, 58-million gallon Los Angeles reservoir had a noticeable amount of these compounds.

The next step was man-made. Ivanhoe, like many reservoirs, adds chlorine to its water in order to fight against bacteria. Again, this is not really a problem, as chlorine is an efficient and, by most accounts, safe chemical for water purification. What's more, chlorine and bromide can exist side by side, happily ignoring each other.

The trouble came when sunlight showed up. The combination of bromide, chlorine and sunlight produces bromates, which are carcinogens. Unfortunately, this happened in the reservoir, threatening the water and the 600,000 Angelenos who rely on it for their daily water supply.

Los Angeles' solution? The city deployed 400,000 little black plastic balls. The balls float on the surface of the water, blocking the sunlight, short-circuiting the dangerous chemical reaction and saving the people of Los Angeles. In the process, they make the reservoir look like a huge pot of caviar.

Is this a green solution? Maybe, maybe not; on the one hand, it uses a hell of a lot of plastic. On the other hand, it saves the city from having to employ costlier, more drastic options, including shipping in bottled water, which would be really carbon-negative. Regardless of its sustainability, though, Los Angeles' answer is certainly elegantly simple!