H.R. 9861, the TREAT Water Act, directs the Secretary of Energy to establish a demonstration program focused on treating produced water at oil and natural gas drilling sites. Produced water is the water that comes out as a byproduct when drilling and fracturing oil or gas wells, and this bill aims to develop and test new approaches for treating it on-site rather than elsewhere. The program will prioritize innovative, first-of-a-kind technologies and methods that not only treat the produced water but also reduce other environmental harm at drilling operations. The Secretary of Energy must consult with other relevant federal agencies, including the Department of the Interior and the Environmental Protection Agency, in setting up and running the program. The bill amends the Energy Act of 2020 but does not specify funding amounts or implementation timelines in the provided text.