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Hydraulic fracturing or “fracking” requires a vast amount of water, sand, and other chemical additives to be pumped underground at high pressures in order to free oil and natural gas trapped in tight shale rock formations deep below the earth’s surface. The chemicals added to the mixture of water and sand range in type (water, oil, and foam-based) and function (friction reducers, gelling agents, pH adjusters, sterilizers, etc.). One of the most common functional types of additives is biocides, which are used to prevent the growth of bacteria within the well. A single well can consume more than 1,000 gallons of biocide throughout the production process.
Excessive bacterial growth can lead to the presence of biofilms which can in turn clog the equipment used during hydraulic fracturing. Bacterial growth often originates in the tanks and pits holding the water and sand waiting to be pumped underground. In those tanks and pits, temperatures support the rapid growth of bacteria and microorganisms that can impede the fracking process.
Biocides employed by the industry are typically alcohol or ammonium-based and are used in many other settings including healthcare facilities and water treatment centers. The type and amount of biocide used in a well depends on the geology and biogeochemistry of a site. While mostly contained to the well itself, biocides can be released into the surrounding environment through accidental leaks and spills of hydraulic fracturing fluids (fracking fluids and produced waters).
In the case of a leak or spill, biocides used in hydraulic fracturing often exhibit a low toxicity for mammals. The primary impacts for humans include severe skin and eye irritation. However, biocides can prove deadly for aquatic life, even at low concentrations. Studies show that these chemicals are highly toxic for mollusks, which include oysters and clams.
As fracking continues, scientists are exploring alternative methods to prevent bacterial growth within the well. One particularly promising biocide is THPS. When used properly, THPS exhibits low toxicity, requires low treatment levels, and breaks down rapidly. Other methods avoid chemicals altogether. For example, the industry is evaluating the potential use of UV sterilization in wells. UV rays kill bacteria and sterilize the equipment.
Biocides employed by the industry are one of the many chemicals that local, state, and federal officials should be familiar with going forward as they can have an impact on the environment and human health.