Safety

Bioremediation offers solutions for plant site contamination

Microorganisms break down and consume pollutants in contaminated media

By Bilgen Yuncu, PhD, PE February 5, 2021
Courtesy: Draper Aden Assoc.

Among today’s top concerns for manufacturing plants, especially older and legacy sites, is their impact on the environment, particularly in terms of potential site contamination.

Managing and minimizing site contamination risk is a top priority for plant owners and operators. Reducing and addressing potential contamination isn’t just the right thing to do, it also offers important economic benefits. Creating and implementing a robust contamination program ensures plants meet regulatory requirements and reduce the likelihood of costly fees and fines. Furthermore, remediating contamination at legacy or closed plants allows that land to be redeveloped or reused, resulting in the potential for significant financial savings or an influx in revenue.

As a result of technology advances and heightened focus on contamination at plant sites, manufacturers have access to a wide array of treatment plans to address areas affected by hazardous contaminants. One option that is highly effective yet often overlooked is bioremediation.

Plant owners and operators would be wise to consider bioremediation strategies because they can produce highly efficient results at a comparatively low operational cost. Bioremediation can be used on a variety of contaminants, including chlorinated solvents, pharmaceutical compounds and petroleum hydrocarbons.

Bioremediation strategies

Bioremediation is the use of naturally occurring or genetically engineered microorganisms, most often microorganisms like bacteria or fungi, to consume and break down pollutants in contaminated media, including water (groundwater and surface water), soil and sediment.

The U.S. Environmental Protection Agency (EPA) defines bioremediation as “an engineered technology that modifies environmental conditions (physical, chemical, biochemical, or microbiological) to encourage microorganisms to destroy or detoxify organic and inorganic contaminants in the environment.”

Bioremediation has been widely studied in the environmental biotechnology field over the past three decades and it has been shown that microorganisms in various environments can completely or partially transform pollutants into environmentally acceptable chemicals or alter their mobility (thus, contain them). As an example, bioremediation can be used to transform non-biodegradable pollutants such as heavy metals and radionuclides into less mobile forms.

Manufacturing Facility, AR – Following the implementation of in situ bioremediation Trichloroethene (TCE) concentrations at different injection areas decreased and the groundwater plume shrunk significantly. Courtesy: Draper Aden Assoc.

Manufacturing Facility, AR – Following the implementation of in situ bioremediation Trichloroethene (TCE) concentrations at different injection areas decreased and the groundwater plume shrunk significantly. Courtesy: Draper Aden Assoc.

Bioremediation technologies can be applied in situ (in place) or ex situ (removed from place). The ex situ methods, such as bioreactors or composting, require the removal of the contaminated material and its transportation to another area for treatment. It’s important to note that ex situ bioremediation can trigger additional regulatory requirements due to the movement of hazardous materials.

In situ technologies, such as bioventing or biostimulation, involve treatment of contaminated media where it is located. Although dependent on the site and type of contamination that needs to be addressed, in situ approaches are more common for manufacturing and industrial plants.

In situ bioremediation can be accomplished through natural attenuation or by biostimulation and bioaugmentation in groundwater and soil. Natural attenuation leverages a number of natural processes including biological degradation that can reduce or “attenuate” contaminant concentrations in groundwater and soil. Biostimulation consists of adding nutrients to encourage indigenous microorganism growth and thus enhance the rate and extent of biodegradation of target contaminants.

Bioaugmentation is the inoculation of contaminated sites with strains or microbial consortia (a group of two or more different microbial species that work together) with biodegrading capacities when an appropriate population of microorganisms does not exist or is too slow to stimulate complete remedial of the existing contaminants.

An advantage of bioremediation is that it’s highly tailored to a specific site. The exact approach will depend upon a variety of conditions at the site and the type of contaminants that need to be eliminated. Bioremediation takes more time than other treatment alternatives such as excavation or incineration, but the highly customized approach can yield improved results and still be less expensive than other treatments.

That’s one reason that bioremediation is well suited for legacy sites, especially those no longer in use, and for manufacturers or site owners that are open to the longer timelines. In return for their patience, the results can yield a contained or remediated site that can be repurposed. Rather than wasted resources and a liability, the site is once again an asset.

Results across sectors

The impressive results that bioremediation delivers aren’t a fluke or happenstance; they’re consistent and impactful. As an example, a manufacturing facility in Arkansas contaminated with chlorinated solvents implemented in situ bioremediation through subsurface injection of emulsified vegetable oil (biostimulation) and reduced contamination by more than 99% in about four years. Similarly, in another former manufacturing site in North Carolina contaminated with chlorinated solvent contamination and low pH (~ 3) in groundwater, the contaminant concentrations were decreased approximately 90% in about seven years with the implementation of biostimulation, bioaugmentation, and pH buffer injection.

These results also translate across industrial sectors. In another example, bioremediation approaches have shown significant promise in addressing contamination from pharmaceutical compounds and waste. Understanding the biological transformation of pharmaceuticals and determining the biological mechanisms and degradation pathways that are responsible for removal is essential for accurately tracking their ultimate environmental fate and could lead to improved removal of these compounds.

Significant progress has been made in understanding the role of microbial metabolism in the transformation and removal of pharmaceuticals in wastewater treatment plants and other aquatic systems. Numerous studies in peer-reviewed journals, such as Environmental Science & Technology and Advances in Applied Microbiology, have documented the use of microorganisms to breakdown the pharmaceutical wastes in wastewater treatment plants and in the environment.

An example study by Raj et al. in 2005 evaluated the treatability of a bulk drug pharmaceutical wastewater using an activated sludge reactor with acclimatized microbial consortia by integrating with chemical coagulation as the pretreatment process. An 86.6% reduction of Chemical Oxidation Demand (COD) was achieved in pharmaceutical industrial wastewater with the help of the biodegradation process. In another study, published in Water Science and Technology by Rosen et. al in 1998, modified activated sludge and multi-stage biofilm processes with a microbial consortia involving fungal and bacterial cultures for treatment was found effective in removing toxicity in wastewater from a pharmaceutical company in Sweden.

Best practices for success

Whether working to remediate or contain pharmaceutical contamination, petrochemical hydrocarbons, chlorinated solvents or other complex chemicals, the most effective bioremediation strategies focus on three key best practices:

  • Understand the Contaminant: Study the contaminant(s) to ensure you have a clear understanding of their properties and challenges. Not all contaminants are biodegradable and sometimes the degradation products are more toxic or persistent than the parent compound. Site conditions and the specific contaminants involved will dictate the exact bioremediation strategy needed. An important benefit of bioremediation is that it’s tailored to the specifics of each site to ensure the microorganisms selected can attack and remediate the contamination.
  • Understand the Site Conditions: Bioremediation strategies allow you to design specific solutions for a contaminant and the specific environmental conditions. Tailoring your bioremediation method based on thorough assessment of site-specific conditions is crucial for success. For in situ applications, you must identify and develop a targeted delivery strategy to ensure the nutrients or microorganisms added to the site are in contact with the contaminant for efficient remediation.
  • Maximize Ongoing Controls: For active manufacturing and industrial sites, it’s crucial to develop ongoing bioremediation strategies that will monitor and continue to address contamination. Monitoring ensures that the contamination is well maintained, while alerting you to any potential challenges or problems. Yet another benefit of bioremediation strategies is that they can be modified to meet the changing conditions at a site.
Former Manufacturing Site, NC – The graph depicts contaminant concentrations over time in one of the monitoring wells at the site. The contaminant concentrations in this monitoring well were decreased approximately 99 percent in seven years following the subsurface injections. Courtesy: Draper Aden Assoc.

Former Manufacturing Site, NC – The graph depicts contaminant concentrations over time in one of the monitoring wells at the site. The contaminant concentrations in this monitoring well were decreased approximately 99 percent in seven years following the subsurface injections. Courtesy: Draper Aden Assoc.

Proactive strategies minimize risk

Contamination challenges at plant sites affect all industrial and manufacturing sectors. The EPA offered a glimpse of the extent of this challenge for manufacturers when the agency reported in 2017 that they and their state counterparts provided oversight to approximately 1.3 million facilities to minimize the release of environmental contaminants.

Treatment of contamination caused by hazardous chemicals at industrial and manufacturing sites can be difficult to manage, given their complex nature. A number of potential solutions are available to manage chemical releases at plant sites. In recent years, bioremediation has emerged as a leading option to reduce contaminants at operating facilities and even address long-shuttered legacy sites. Perhaps the most attractive aspect of bioremediation is that this strategy produces highly effective results at comparatively lower costs than other relevant treatment technologies.

Contamination and hazardous byproducts are a reality for many manufacturers. The versatility inherent in bioremediation strategies, as well as the success rate of these strategies, makes this approach ideal for industrial sites. Identifying solutions, like bioremediation, to manage and mitigate those complex challenges is an optimal approach for businesses to address their environmental challenges and liabilities in an efficient manner.


Bilgen Yuncu, PhD, PE
Author Bio: Bilgen Yuncu is an environmental engineer with Draper Aden Associates, a mid-Atlantic engineering, surveying and environmental services firm. Based in the firm’s Raleigh, NC office, she serves as an environmental engineer, project manager and remediation group program manager. Bilgen specializes in bioremediation strategies of hazardous compounds in soil and groundwater. She received her PhD from North Carolina State University, holds an NC professional engineer license, and is a project management professional. Bilgen can be contacted at byuncu@daa.com.