Every water treatment company, mine included, has a basic selling example: a jar of dirty water sits next to a jar of clear water that has gone through the company’s cleaning process. It is the cost of entry for water treatment, but is does not tell the whole story. In some cases what appears to be clear water is actually not clean, and therein lies the challenge for the fracking industry. You may wonder, how clear does not always equate with clean – a fair question that requires a serious answer.
Fracking requires 4.5-8 million gallons of water per well and concerns have been raised about the depletion of underground aquifers. The current practice of treating the flowback portion of the frac water has been to treat it as garbage and simply discharge it into disposal wells to never be seen again or be part of the eco-system. This practice has not only been a source of concern for earthquakes but, more important, many have voiced the opinion that water reuse regulation must be enacted in order to preserve our aquifer resources for agriculture and commercial applications. I agree that the industry needs a complete water management program in order to preserve our water resources and protect our future.
To date, the largest barrier for water reuse has been the variable nature of the flowback water produced at each frac site. Drillers are harvesting many different types of hydrocarbons (tight gas, coal-bed methane, natural gas, crude oil) by drilling into a diverse array of subterranean formations. The water that flows back from these sites ranges from thick black to very light brown, including every shade in-between.
Thousands of wells dot the landscape of our country and each one represents millions of gallons of flowback and produced water that require treatment. The sheer volume of water places yet another obstacle on water treatment companies operating in the industry. Treatment systems need to have the ability to process high volumes of water in a timely manner to produce a supply that remains at least as cost-effective an alternative as fresh water.
Many water treatment processes have been devised for frac water treatment, but few, if any, have been able to successfully address the whole array of complexities, inhibiting the industry’s full-scale adoption of water reuse practices.
Approaches to Water Treatment
One treatment approach is to evaporate the flow back water, resulting in two streams, distilled water and reject water that include solids and salt. The problem is that evaporators are expensive to build and to operate. Additionally, believe it or not, distilled water is actually harmful to the environment because it is void of oxygen and minerals. It is also bad to reuse for fracking operations because the absence of salt creates osmotic imbalance that would cause the clay formation to swell, resulting in up to 40% lower well productivity.
Another form of water treatment is Reverse Osmosis (RO). Like evaporators, this too has high CapEx and OpEx. Moreover, RO is limited to treat water with salt content of no higher than 70,000 parts per million (ppm) and ideally not much higher than 35,000 ppm. But this often does not reflect the natural state of water 10,000 feet deep, which can contain as much as 200,000 ppm of salt. And, even if RO could treat 100% of the water, the absence of salt in the filtered water would make it less than ideal to reuse for fracking operations, and the high level of reject water would become more problematic to dispose of as it would contain a concentrated blend of pollutants and salt.
Yet another approach is a class of technologies based on oxidation: using ozone, hydrogen peroxide, ultra-sound and ultra-violet light. These procedures neutralize volatile organic compounds and some non-degradable petroleum constituents. After treatment the water might appear clear, but it is not “clean.” The presence of “bleached” suspended solids and gels would gum up the hairline thin fractures in the shale formation, resulting in substantially lower well productivity.
Noteworthy is the fact that none of these processes provide a comprehensive solution; they are each, in their own respect, a screwdriver, a paintbrush, and a hammer. What the industry requires is a complete toolbox. The solution that will make water reuse a reality in fracking operations is the one that will accommodate the variable nature of frac water, process high volumes in a cost-effective manner, and treat it to reuse requirements. What has been lacking are two important stages: Pre-Treatment and Primary Treatment.
An example of a solid Primary-Treatment category is a chemical treatment followed by a physical separation of the pollutants. One approach to physical separation includes settlement clarification. It works on the principal that suspended solids heavier than water will settle downward to the bottom of the clarifier. The problem with this technology is that the presence of even a trace amount of emulsified oil would tend to float the suspended solids or keep them in suspension.
A better solution, unseen in the frac water treatment arena prior to our entry, is the application of the Dissolved Air Flotation (DAF) process. Prior to treatment, frac water is analyzed for constituents of concern and appropriate chemistry is applied to precipitate the pollutants from the water. The actual separation takes place when thousands of tiny air bubbles attach themselves to the suspended solids and lift them to the surface of the water, where they are then removed with a skimmer. Processing 900 gallons per minute (31,000 barrels/day) the Ecologix patented Integrated Treatment System (ITS-900) platform turns high volumes of used frac water into not just clear, but clean, reusable water in a cost-effective manner.
While the regulations for frac water quality are still under development, having a flexible, effective solution in place will leave drillers and operators better prepared when standards emerge in the coming months and years.
This article was originally published in Environmental Leader. View the source here.