Natural gas production is an all-time high. Over the past decade, the dramatic growth of shale gas, made possible by hydraulic fracturing or fracking, has led to generation of huge volumes of wastewater known as brine or produced water.
Hydraulic Fracturing
Hydraulic fracturing or fracking is a process of pumping shallow, hard oiled, chemicalized wastewater, at extreme underground level, at a very high pressure to crack open pores within a shale rock formation to extract the oil and natural gas. Fracking consumes an enormous amount of water. The water used for fracking is a mixture of water, sand, and chemicals. The sand stays put in the cracks, which creates pathway for oil and gas to travel.
Fracking Water Treatment System
The process comprises multiple steps and several different chemicals. The chemicals change depends on the company doing the fracking and the characteristics of the formation.
When the pressure is released from fracking, some of the fluid that is pumped flow back to the surface. Natural occurring water (produced water) also flow in addition to this flow-back water. A short while later natural gas and oil flow. With time, the amount of pumped water flowing back decreases and the produced water flow increases. Typically, a frack uses 3-5 million gallons of water, out of which, about one-third of the water pumped will return to the surface.
There is no way to predict the water quality with all the variables and it changes rather quickly for the first two weeks of flow. Post two weeks, the water flow is majorly produced water, which is regulated different to that of frack water.
Environmental Concerns
In terms of environment, the major concerns associated with fracking are water and soil contamination which can result from the processes and handling of the fluid as well as the large quantities of induced water necessary to undertake fracking. Huge volumes of water are taken from surface or ground that are mixed with sand and chemical additives including biocides, borate salts, potassium chloride, surfactants, etc.
Hundreds of thousands of gallons of water are pumped and withdrawn at each site, and great volume of flow-back and produced water are generated. Flow-back water is that which return to the surface after the pressure is released. It consists of hydrolytic fracturing fluids, water from the natural formation, chemical additives that were injected and the recovered hydrocarbons from the deep formations.
Methods of Disposal
For successful fracking water treatment, the wastewater must be disposed. The methods of disposal vary at each nation or state depending on their regulations. In many countries, there are regulated wells, usually old drained gas or wells, where the frack water is pumped into. Usually, the only water treatment necessary is filtration, which can be as simple as sock filters or as extensive as clarifiers, depending on the load of solids present in the water.
Another method of disposal is reuse. The frack water can be blended with fresh water and used at another site. This is generally simple, unless makeup water is required. The requirements for each fracking company is different, but usually they want the following variables: low TSS, hardness, metals (particularly barium, strontium, and iron), TDS, and bacteria count.
Where there are a lot of new wells being drilled, the drilling companies dilute 20:1 with fresh water without worrying about chemistry. I ffresh water is not available, the water will have to be treated to meet the company’s specifications. The treatment process, however, varies, but generally include the basic methods like filtration, chemical precipitation, and softening.
When there is no chance for dilution, the first few days of wastewater flow can be treated and reused. However, if the total dissolved solids in the wastewater exceed 10,000 ppm, it can no longer be reused. The only options that are then possible shall be deep well pumping or zero liquid discharge by the usage of evaporators and crystallizers.
Conclusion
Hydraulic fracturing technology is a breakthrough work to prevent contamination of groundwater that might potentially put humans and animals at serious health risks, as well as billions of money on solving the problem. It is now heavily regulated among nations and will ensure proper environmental regulations. Hydraulic fracking technology has the potential to make huge amount of natural gas available that otherwise would remain trapped below the earth. The increasing use of hydraulic fracking by these industries is driving the growth of the fracking water treatment market, which is estimated to grow a rate of nearly 3% through 2030.