Data centers are springing up around the world to handle the torrent of information from the expanding web of devices ingrained in people’s lives and the economy. Managing that digital information gusher is big business. It also comes with hidden environmental costs.

For years, companies that operate data centers have faced scrutiny for the huge amounts of electricity they use storing and moving digital information like emails and videos. Now, the U.S. public is beginning to take notice of the water many facilities require to keep from overheating. Like cooling systems in large office buildings, water often is evaporated in data center cooling towers, leaving behind salty wastewater known as blowdown that has to be treated by local utilities.