One of the biggest objections to hydraulic fracturing centers around the fact that huge amounts of water are needed for the process. In fact, each well requires 60,000 to 100,000 barrels of water; it is the base fluid and biggest component of hydraulic fracturing. The problem is that agricultural, industrial and domestic users are vying for the same fresh water that producers need. Additionally, the flow-back and produced water coming out of the wells is contaminated so it cannot be simply returned to lakes and streams or aquifers and must be sent to disposal wells unless it is properly treated.
While they are both produced as a result of hydraulic fracturing, flow-back and produced water are quite different. Flow-back is a water-based solution that flows back to the surface during and after the completion of hydraulic fracturing. This fluid can contain clays, chemical additives, dissolved metal ions and total dissolved solids (TDS) and has a murky appearance from high levels of suspended particles. Most of the flow-back occurs in the first seven to 10 days of fracturing, but it can continue to flow for weeks and can be up to 20 to 40% of the volume that is initially injected into the well. Contrast this with produced water, which is naturally occurring water found in shale formations. It flows to the surface throughout the entire lifespan of the well and has high levels of TDS. It also leaches out minerals from the shale and contains dissolved hydrocarbons such as methane, ethane and propane along with naturally occurring radioactive materials (NORM) such as radium isotopes.