In Record Drought, Texas Frackers Firefighters And Farmers Compete For Water

Comma please. I had to wonder about a Texas Fracker Firefighter.

Is it possible for treated waste water to be used for fracking? Or for that mater, firefighting?

Possible, yes. There are additional fertilizer elements from this source also, as long as total disslved solids are not excessive, but it may require excessive hauling costs from the water treatment plant.

This is an example of the free enterprise system at work. Decades ago the auto industry used millions of gallons of potable water to filter air from their painting booths. When they were forced to, they found other ways to do the job, without all that water. The uses you mentioned, are not the same, they still require water, but it doesn't need to be potable. In the long run, the costs of a distribution pipeline for this 'free' water will be less than the ever increasing costs of potable water.