Traditionally contaminated soil has been treated as waste and therefore the most common method of achieving a clean site was to simply dig the contaminated soil up put them in a truck and haul it to the nearest landfill. In recent years the ability to create new landfills has become harder and harder with most citizens not wanting contaminated soil landfills near their place of residence.
This societal shift has created opportunities for on-site remediation technologies to flourish. The most common techniques used in on-site remediation include Chemical Remediation, Biological Remediation, and Thermal Remediation. Below is a brief description of each method and some of the basic pros and cons of each remediation process.
For all of the remediation techniques listed above, there are methods of completing both In-Situ (treating in place without excavation) or Ex-Situ (treating on site but excavation is required).
Thermal Remediation is a process that is most commonly performed through Ex Situ methods. Typically utilized on very large sites, the soils are excavated and moved to the thermal treatment unit for treatment. The treatment units consist of a number of belts, trommels, and shaker decks used to remove oversized material while increasing surface area and homogenizing the soils. Through the treatment process the soils are essentially cooked or heated with either energy from an external source or in some cases the contamination in the soils themselves can be extracted and burned to treat subsequent soils passing through the process.
The biggest advantage of thermal treatment is that because the systems are so robust in many cases the treatment can be “guaranteed”. Thermal treatment also has some downfalls including high cost and applicability for only large-scale projects. It is also debated in the environmental community how “usable” the soils are for both stability in construction and growing post-thermal treatment.
Chemical remediation methods most often refer to Chemical Oxidation or (“chemox”) which is the use of oxidants such as peroxide or permanganate which will have a chemical reaction when mixed with hydrocarbon and other organic contamination. While Chemical Oxidation can be done Ex-Situ it is most often done through injection galleries In-Situ. Typically the chemical reaction (remediation timeframe is in days or a week at most, meaning that results are usually quicker from chemical treatments than they are from biological or other natural attenuation methods.
Chemical remediation methods are effective from a time perspective but are typically very expensive when compared to alternative treatment methods such as bioaugmentation or bioremediation.
Bioremediation is in many ways, both the oldest and newest remediation strategy for effectively handling contamination. While that may sound strange it is absolutely true. Bioremediation is believed to have been utilized as far back in history as 600 BC. Back then and to this day bacteria are the primary mechanism for degrading wastewater and biosolids that are produced in both rural and urban environments from human waste.
Bioremediation was recognized scientifically in the 1940’s when scientists began working with bacterial strains to degrade different streams of organic waste including refined petroleum products such as diesel, as well as within rendering and poultry facilities to degrade fats, oils, and grease associated with meat and food production facilities. From the 1970’s to the early 2000’s dozens of bioremediation products and companies were born primarily around the use of bacteria that sporify or create an endospore. These types of bacterial species can stay in a sporified state for many years allowing companies to easily make batches that could be bottled and placed on a shelf for months or even years before being used for a remediation site. While this utilization was great from a transportation, distribution, and storage perspective, the efficacy of sporifying bacteria was limited due to the fact that the species would simply sporify again in the field prior to remediation goals being met.
While there was some scientific progression in the latter part of the 21st century, there were no major breakthroughs until bioremediation technology developers started working with non-sporifying species which were capable of degrading more complex mineral hydrocarbons as well as polyaromatic hydrocarbons. It was this scientific breakthrough of using new genus such as Pseudomonas that has allowed Bioremediation companies like Delta Remediation to create what is now recognized as “Bioremediation 2.0”
Although Bioremediation is the slowest remediation method mentioned in this article, It is also the most economical. Other advantages of bioremediation include scalability both up and down safety for applicators and the environment as well as versatility, being easily deployed through both In-Situ and Ex-Situ methods. Although Bioremeidaiton is not built for speed, it is highly effective to harness and utilize natural systems to clean up contaminated sites. It is for these reasons that Bioremediation is the most commonly used approach by remediation contractors such as Delta Remediation.