TREAT Water Act or the Transitioning Research to Ensure Appropriate Treatment of Water Act This bill requires the Department of Energy (DOE) to establish a demonstration program for on-site treatment of produced water (e.g., water used to drill oil or gas wells). In carrying out the program, DOE should prioritize (1) first-of-a-kind or new approaches to treating produced water stationed on site, and (2) technologies that can be used at natural gas or oil development sites to reduce other environmental harm either through emissions or other environmental impact.