The Benefits of Bacteria in Environmental Remediation

15 Mar The Benefits of Bacteria in Environmental Remediation

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Readers of ESA’s articles know that our goal is to lessen the amount and degree of environmental services needed to effect compliance. Our recent three-part series addressing soil, groundwater, and PFAS remediation highlights ESA’s commitment to that objective. In some cases, however, contaminant concentrations are so great that active remediation is unavoidable. When this occurs, ESA prefers to employ an environmentally friendly solution involving bacteria known as bioremediation.

Bacteria are ubiquitous; we can only guess at their true abundance and numbers of species. And, because of their sheer numbers and voracious appetite for organic matter, bacteria create a formidable natural defense against non-chlorinated organic chemical spills. The most familiar example of human-directed bioremediation is found in sewage treatment plants. But bioremediation has actually been happening naturally since bacteria first appeared.

The Bioremediation Process

Bioremediation of chemical spills requires that the use of the technology be calculated and focused. For non-chlorinated organic spills, the following steps must be taken to develop an appropriate remediation strategy. ESA will address chlorinated organic spills in our next article.

1. Identify the chemical that spilled and determine its chemical structure. Short straight-chain chemicals (aliphatics) are the easiest to bioremediate. Longer chain chemicals and simple one-ring compounds (aromatics) are next easiest to bioremediate. Poly-nuclear aromatic compounds (multi-ring chemicals) are far more difficult, but not impossible.
2. Identify the breakdown products during the bioremedial process. Sometimes when running quality assurance analyses during a bioremedial project, never-before-encountered chemicals are found. Where did they come from? Bacteria tend to cleave the organic contaminant (i.e., create smaller compounds by “eating” the original compound in the same way every time). By doing so, the daughter compounds increase in concentration until the original compound has been reduced. In this way, the daughter compounds now become the preferred food target.
3. Isolate indigenous bacteria and culture them to increase their numbers or purchase bacteria specifically known and cultured that will do the job.
4. Confirm where the chemical is located, then determine its horizontal and vertical extent and whether it has contaminated the soil, groundwater, or both.
5. Determine the amount of the chemical at the site.
6. Determine the optimum ratio of bacteria and nutrients (i.e., fertilizer) to optimize the bioremedial process. Then determine the best means to deliver oxygen to the bioremedial system.
7. Lastly, design a system to deliver the liquid slurry containing bacteria, fertilizer, and oxygen. The bioremedial slurry must make direct contact with the chemical contaminant in both the soil and the groundwater.

Benefits of Bioremediation

Once it is decided to use bioremediation, there are several benefits to be aware of. The first is that, once the process is set up, operations and maintenance costs are relatively low. Bioremediation requires time.

Several variables determine project duration: good and efficient system design, the total mass of organic chemical to be eaten by the bacteria, and the full extent (vertically and horizontally) of the mass of material to be treated. Groundwater contamination that has penetrated bedrock will require more time due to the difficulty bedrock poses when trying to contact the contaminant. Sometimes bedrock contamination can be a hit-or-miss proposition.

Second are the health and safety benefits. Bioremediation reagents avoid the chemical hazard associated with strong oxidizing agents typically used with In-Situ Chemical Oxidation (ISCO).  The lowest level of personal protective equipment is usually sufficient, as there are negligible chemical hazards to the workers and bystanders. Also, and most importantly, there is no production of heat or fugitive gases that may impact adjacent structures.

If your site has non-chlorinated contamination that cannot be addressed by fast and simpler means, bioremediation should be considered. Some of the more easily bioremediated compounds include gasoline (with or without MTBE), No. 2 heating oil, and diesel fuel. Ask ESA to learn more about this time-proven remedial solution.