State data shows the amount of hydraulic fracturing wastewater pumped underground in Ohio increased by more than 15 percent last year.
The increase comes as drilling for shale in the process known as fracking has slowed nationwide.
A Columbus Dispatch analysis of Ohio Department of Natural Resources numbers shows Ohio took in nearly 29 million barrels of fracking wastewater in 2015.
That figure is about 4 million more barrels than in 2014.
Injection wells pump wastewater from oil and gas drilling deep inside the earth. Some such wells in Ohio have been linked to earthquakes.
Ohio typically takes more fracking wastewater from outside Ohio than within, but the latest figures show about 55 percent of the wastewater ending up in state injection wells came from Ohio.
