By Savannah Volkoff
Just as in any field of expertise, those working in the field of contaminated site clean-up seem to speak a totally different language. This post will introduce you to a few words and technologies commonly used when discussing the remediation of a contaminated site to make it a little easier to keep track of what might be happening in your community. Check out this website to find a polluted site near you!
EPA defines remediation as a treatment that “permanently and significantly reduces the volume, toxicity, or mobility of hazardous substances, pollutants and contaminants as a principal element.” In other words, a remediation technology should not only reduce the amount of pollutants and contaminants at a certain location, but also reduce their ability to cause harm and move beyond the original polluted area.
Remediation can occur in two types of locations: in situ, meaning on site, or ex situ, meaning off site. In situ remediation treats the contaminated material (water, sediment, soil, etc.) at the polluted location. For ex situ remediation, the contaminated material is treated only after it’s been removed from the polluted site and transported elsewhere.
There are a wide variety of strategies and technologies that can be used to clean-up a contaminated site. Here are some of the most common:
Pump and Treat: Contaminated material is pumped out of the ground, treated, and returned to the ground. This technique is most commonly used for cleaning up groundwater polluted with chemicals such as industrial solvents, metals, and fuel oil.
Fracturing: This technology is usually used for creating pathways to access groundwater or soil needing remediation. Fracturing may create new cracks or enlarge existing ones in order to access contaminants.
Solidification and stabilization: These two methods are typically ex situ (off site) techniques that prevent contaminants from spreading and wreaking more havoc. Solidification is the process by which wastes are clumped together and trapped into solid material so they are secure and can’t spread, or so that they are easier to remove. With stabilization, contaminants are immobilized after substances such as cement or lime are added to the site.
Permeable reactive barriers: An underground wall is constructed at the contaminated site to create a barrier between the contaminated materials and a downstream water source. As water flows through the wall, contaminants are filtered out. This technique’s effectiveness decreases as the wall collects large quantities of contaminants. (Much like a household water filter gets full and stops being effective after a while!)
Activated carbon treatment: Usually placed in columns or tanks, contaminated water or air is pushed through the carbon system. This process can remove solvents, PCBs, dioxins, some types of metals, and industrial chemicals.
Monitored natural attenuation: Used for both soils and groundwater, this strategy simply allows natural processes (such as dilution, evaporation, chemical reactions with natural substances, and bioremediation) to lower the concentrations of contaminants. It’s a strategy commonly used at some point during remediation for most contaminated sites. EPA monitors the progress of natural processes to make sure they are still effectively working to remove contaminants.
Capping: Usually used for landfills or soils, caps are not used to destroy or remove contaminants, but rather secure them in place to prevent movement and further contamination.
Bioremediation: As a focus of Project 4’s work, bioremediation strategies will be the topic of future blogs. But for a quick overview, bioremediation relies on micro- and macroorganisms to degrade contaminants in soil, sediment, sludge, and groundwater. Utilizing this strategy depends on site characteristics such as pH, temperature, water content, and nutrient availability, as well as the concentrations and accessibility of contaminants.
What’s right for the site?
As mentioned earlier, the approach used to clean up a site depends on the type and concentration of contaminants, as well as the depth and span of contamination. Community concerns and needs may also cause one strategy to be chosen over another. But which strategies are best for which types of contaminants? For a quick run-down of the types of technologies and strategies (some of which I mentioned above) and how useful they are for particular contaminants and site conditions (light availability, temperatures, etc.), check out this cool factsheet: Treatment Technologies Screening Matrix.
Sounds good, but what’s the catch?
Some of the technologies and strategies mentioned above can wear out or become outdated, thereby becoming less effective. These drawbacks might require further remediation which can take even more time, money, and resources.
Especially in cases of polluted rivers and sediment, kicking up settled pollution is a major concern. During the cleanup of the Diamond Alkali Superfund site along the Passaic River in Newark, NJ, riverfront industries argued against dredging the river and removing contaminated sediment because the process would expose more pollution that would then be more accessible to organisms in the water. [googlemaps https://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=120+Lister+Avenue,+Newark,+NJ&aq=0&oq=120+Lister+&sll=40.782104,-74.27067&sspn=0.225908,0.528374&ie=UTF8&hq=&hnear=120+Lister+Ave,+Newark,+New+Jersey+07105&t=m&ll=40.741535,-74.130249&spn=0.045521,0.072956&z=13&output=embed&w=425&h=350]
You can read about concerns with cleaning up the Passaic River, in this NY Times article.
Nearby communities might also be affected by remediation. Such fancy techniques may bring a lot of traffic to a site once remediation has begun. Depending on the needs of the site and the selected plan, there could be a lot of truck and heavy equipment movement to and from the site
Despite the potential negative impacts of remediation, it usually does more good than harm. Remediating contaminated sites protects people and the environment from exposure to harmful chemicals. Now that you’re familiar with types of remediation and some of the jargon used by professionals, you may want to revisit our previous post and explore the types of remediation that have happened, are happening, or might happen in your own community! In our next blog, we’ll see which of these technologies is being used to remediate our Superfund study site along the Elizabeth River!