You need to design a treatment plant for flowback water from Marcellus Shale dri

Question

You need to design a treatment plant for flowback water from Marcellus Shale drilling. The well produces 1 MGD. The water coming out of the plant contains 150 ppm ultimate BOD with a pH = 7.2. 11. The first step is to raise the pH of the water to precipitate some of the salts. You are going to mix the flowback water with another stream containing water at a pH of 13 in a CSTR with a volume = 0.5 MG. If you want the combined stream to have a pH of 10, calculate the flowrate of the incoming stream. Assume the OH- “decays” (reacts) at a rate of 10 hr-1

Explanation / Answer

Hydraulic fracturing involves water — both at the forward-facing end with fracking fluid, the water-based chemical cocktail that is vaccinated into the shale, and at the back end where there is flowback water and produced water.

Flowback water (which literally “flows back” during the fracking process) is a mixture of fracking fluid and formation water (i.e., water rich in brine from the targeted shale gas-rich rock). Once the chemistry of the water approaching out of the well resembles the rock formation rather than the fracking fluid, it is known as formed water and can continue to flow as long as a well is in operation. (“Natural Gas, Hydrofracking and Safety: The Three Faces of Fracking Water.”)

Fracking wastewater can contain huge amounts of saline (salts), toxic metals, and radioactivity. And so the gas businesses have a problem

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