The global water and wastewater treatment market is expected to reach half a trillion dollars by the end of this decade, according to Statista. Much of it now involves harsh chemicals and uses a lot of energy, but companies like Xylem, Veolia and Boston-based startup Gradiant are trying to reduce both costs and energy while eliminating chemicals. “We take highly contaminated wastewater which contains solvents, which contains dissolved salt, which contains organics, and we eliminate the entire liquid waste,” said Prakash Govindan, co-founder and chief technology officer at Gradiant. Gradiant’s technology mimics how nature creates rain. Wastewater is heated and pumped into a humidifier and mixed with ambient air. As the two interact, they are heated into vapor, leaving the contaminants behind. Using a proprietary technology, the vapor is transferred to a column with cool clean water. When the two mix, the air cools and drops fresh water, like rain falls from a cloud. The process, according to Gradiant, cuts traditional costs in half.