With millions of gallons of fresh water going into each hydraulic fracturing well, it’s no wonder that hundreds of thousands of gallons can come back out. This isn’t fresh water anymore, but rather a rich combination of fracturing fluids, cutting sands, chips of broken rock, and much more. Anywhere from 30% to 80% of the water that goes into the fracturing well can return to the surface within the first 90 days of operation alone. Known as produced water or flowback water, this liquid requires special handling and disposal. Treating the water onsite is one of the best ways to reduce the costs associated with it because it’s often possible to improve the quality enough to reuse it for future hydraulic fracturing. If reuse is not needed, or not possible, treatment can result in water clean enough to spread across open ground without risking environmental damage. Learn about the challenges and benefits of treating produced water with frac pits and ponds.
What’s in Produced Water from Hydraulic Fracturing?
Since hydraulic fracturing goes far deeper than traditional oil and gas drilling, it also taps into ancient deposits of brine that may have extreme salt levels. Thanks to the fracturing process that gives this technique its name, processed water also tends to be full of tiny bits of broken rock that contribute to a high level of total dissolved solids (TDS). Suspended solids are also an issue due to the use of rounded fracturing sand. Regardless of the precise hydrocarbons being claimed, the produced water will contain a mixture of dispersed oil and grease that is reactive and hard on many liner materials. Many produced water flows are surprisingly high in bacteria and organic compounds as well, depending on what the water travels through as it exits the ground. Heavy metals and radionuclides are some of the most concerning components that are generally dissolved into the fluid as it travels through the tightly packed rock formations. Finally, all the chemicals added to the fracking fluid are still mixed into the produced water, including corrosion inhibitors to protect equipment and emulsion breakers to keep oil easier to cleanup.
The Value of Water Recycling for Fracking
Produced water varies in content during the various stages of hydraulic fracturing. The first flows will be rich in oil and grease due to it rising to the top of the newly fractured area. Later flows will be mostly water and likely close to clean enough for immediate reuse. Unfortunately, the demand for more fresh water supplies is highest in the beginning when produced water is least likely to work for this use. Thorough and rapid treatment systems can turn even the earliest flows of produced water into recycled water to keep a fracturing operation going without new deliveries of water. Treating later flows, that won’t be used by the same wells, can still help supply a nearby operation rather than requiring it to truck in water from hundreds of miles away.
Treatment Options
There are dozens of wastewater treatment techniques that can work well on produced water from fracking. As the exact viscosity and chemical composition of the water changes over the course of the operation, it may be necessary to change or adjust the water treatments being used. The goal of discharge, disposal, or reuse also affects which treatments are the best choice. Some of the most popular treatments for produced water today include:
- De-sanding; which is the first stage of almost all fracking water treatments unless sand wasn’t used
- Adsorption; where powdered or liquid minerals and carbon are added to remove heavy metals while losing very little moisture
- Capacitive Deionization; a technique of creating deionized water to attract particles out and clean up dissolved solids
- Cyclonic and Centrifugal removal methods; which are used for both de-oiling and de-sanding steps early in the process
- Forward and Reverse Osmosis, which work on salts, dissolved minerals, and even difficult to remove organic compounds
- Freeze and Thaw Evaporation, a process to concentrate chemicals while separating out pure water for reuse
- Oxidation with classic liquid or gas treatments like chlorine and oxygen, which causes the rapid breakdown of organic and some inorganic compounds
- Microfiltration and ultrafiltration, two treatments primarily targeted suspended and dissolved solids that can’t be removed with settling and flocculation alone.
All of these treatment options require frac ponds or pits, with durable liners, that won’t break down from exposure to the chemicals and physical stresses. For example, Freeze and Thaw Evaporation requires a lined pad exposed to freezing temperatures and subjected to constant abrasion from the formation of ice. Lining these kinds of pits and ponds can be challenging even with the best materials. If you need expert advice on getting started with an advanced produced water treatment option, reach out to us at BTL Liners.
Controlling Fouling
Fouling, in a produced water treatment system, refers to the growth of all sorts of microbes that can interfere with the process. From bacterial colonies to algae, there are dozens of types of microbes that are attracted to the nutrient rich environment of the produced water pit. No amount of salt content or heavy metals can completely stop all microbes from flourishing since many species have adapted specifically to these kinds of difficult conditions. While aerobic bacteria are sometimes used in the treatment of produced water mixtures high in organic compounds, anaerobic bacteria and microbes are more likely to cause problems than assist in water treatment. Warm conditions and high nutrient levels can trigger issues with fouling in as little as one week. Fouled produced water creates new contamination risks and odor issues, not to mention the potential for damage to the treatment equipment. Aeration, circulating the water, and using biocides are the three best ways to prevent fouling in produced water pits. Circulation and aeration can cause leaks if the water movement disturbs the bottom of an unlined pond. Line the pit or pond so that water currents aren’t an issue.
Treating produced water may require extra care when designing frac pits, but it’s well worth the opportunity to reclaim and reuse the liquids. BTL Liners fabricates liners that are made from RPE to help them handle the most demanding water treatment processes, including those commonly used for produced water reclamation.
