Most fracking wastewater in the United States is injected deep underground, and an increasing amount is recycled for subsequent drilling or sent to advanced water treatment facilities. However, a handful of states still allow the wastewater to be used for watering cattle, sprayed onto roads for dust control or sent to municipal water-treatment plants not equipped to handle the chemicals involved.
Abstract and study here: Annual Review of Environment and Resources
All bad ideas, according to the authors of this survey, who work at Stanford, Duke University, MIT, Ohio State University, Newcastle University, Los Alamos National Laboratory and the National Oceanic and Atmospheric Administration. One study they cite found that the agricultural use of fracking wastewater killed more than half of nearby trees within two years.