Scott:

Drilling and produced water fluids have a host of suspended particles or dissolved minerals ranging from calcium, magnesium, salts, fine sands, and clays. Not to mention an entire host of petroleum liquids, paraffin, etc. Believe it or not most of the clays and suspended particles are easily removed with standard waste water floculants or bonding agents. Many of the suspended minerals can be dropped out of solution with standard chemicals such a chlorine, etc. As long as the salt content is low it can be removed with reverse osmosis.

The main issue is costs of treatment. Reverse osmosis can be the most expensive portion of the process which for all intents and purposes basically turns it into potable drinking water. There are "acceptable" levels of salts in fresh water however. Many of the fresh water wells in Arkansas will contain levels of salt, copper, or especially iron that do not greatly effect the potability of the water but might effect the taste. We have all been in a location with lots of iron in the water that makes your jaw clinch when you drink it.

In Arkansas where water is plentiful recycling water is not a big issue. In areas of the desert where water is all but a commodity the costs of treating water make good economic sense. Plus it is good for the environment. At some point Arkansas, Pennsylvania, and other shale regions will most likely begin to institute programs to incentivise recycling programs to make it more economic to recycle water in lieu of disposing of it.

There will unfortunately always be risks of storing or transporting liquids that are harmful. The best way to reduce the risk is to reduce the exposure due to handling.