ENHANCED BIOREMEDIATION
Enhanced in-situ bioremediation, or ISB, involves the injection or addition of microorganisms (e.g., fungi, bacteria, and other microbes) or nutrients (e.g. oxygen, nitrates) to stimulate microbial degradation. It can be accomplished through direct injection, blending methods, or permeable reactive barriers.
The process occurs through a transfer of electrons from one substance to another resulting in usable energy for the microorganisms. This transfer of electrons requires a “donor” material or “food source” and an “acceptor” material. In natural uncontaminated systems, food sources are limited which causes a competition among indigenous microbial populations for available electron donors. Enhanced bioremediation attempts to restore the balance in the natural system by adding nutrients and donor substrates for consumption by the microbes.
Petroleum products are commonly reduced aerobically. They typically act as electron donors and quickly degrade if an adequate supply of electron acceptors is introduced into an aquifer system. Thus, a “treatment train” is created using ISCO and aerobic bio-stimulation.
Chlorinated solvents, however, are poor electron donors but can act as electron acceptors and degrade under anaerobic conditions. Therefore, they are treated anaerobically. As the donor substrate is metabolized under anaerobic conditions, an electron (hydrogen ion) is released and used to replace a chlorine atom attached to the carbon chain for the chlorinated solvent. This process is known as reductive dechlorination and is deemed complete when the chlorinated hydrocarbon is reduced to ethene or ethane and chloride. Reductive dechlorination is accomplished with lactose, soybean oil, and other low-level microorganisms or nutrients.
Advantages of enhanced bioremediation often include lower cost, effectiveness on low concentrations, and ease of application. Limitations include limited effectiveness on sites with NAPL and elevated contaminant concentrations, slower reactions due to microbial processes, and ineffectiveness on some compounds.
AEROBICAL CASE STUDY
Thermal: Steam Enhanced Extraction
Steam Enhanced Extraction (SEE) was originally developed at the University of California in the late 90s to efficiently remove petroleum-based free product from the subsurface. Redox Tech has adapted this technology to introduce super-heated water containing SBC™ which flashes to steam in the aquifer allowing NAPL (non-aqueous phase liquid) to be extracted from a nearby recovery well. The sulfate in SBC™ remains in the aquifer to supply an electron acceptor for bioremediation after the SEE process is completed.
Combined remedial pathway – LNAPL extraction and in situ bioremediation. ➢ Increases solubility of petroleum compounds while decreasing surface tension accelerating removal from soil and groundwater. ➢ Addresses the “smear zone” by flushing the capillary fringe. ➢ Recovered fluids are separated and properly treated and disposed.
Thermal remediation technology is designed to effectively treat contaminated soil and groundwater using heat to accelerate the degradation of hazardous substances.
Principle of Operation:
Thermal remediation involves applying heat to the contaminated site, which enhances the volatility of contaminants and can also accelerate chemical reactions. This process can either vaporize the contaminants for extraction
or promote their breakdown into less harmful substances.
Types of Thermal Remediation:
-
In Situ Thermal Desorption (ISTD): This method involves heating the soil in place to vaporize volatile organic compounds (VOCs) and other contaminants. The vapor is then extracted and treated.
-
Steam Injection: Steam is injected into the ground to increase the temperature and mobilize contaminants, making them easier to extract.
-
Electrical Resistance Heating (ERH): This technique uses electrical currents to generate heat within the soil, effectively treating contaminants through thermal desorption and enhanced chemical reactions.
Applications:
ISOTEC’s thermal remediation technologies are particularly effective for treating sites contaminated with VOCs, semi-volatile organic compounds (SVOCs), and certain heavy metals. It is commonly used for former industrial sites, landfills, and other areas with significant soil and groundwater contamination.
Benefits:
-
Rapid Results: Thermal remediation can often achieve quicker cleanup times compared to other methods.
-
Comprehensive Treatment: It can treat a wide range of contaminants, including those that are difficult to remediate
using traditional methods. -
Minimal Disruption: Many thermal techniques can be conducted in situ, reducing the need for extensive excavation and minimizing site disturbance.
Sustainability:
ISOTEC emphasizes sustainable practices, and their thermal remediation technologies can be integrated with other methods to enhance overall effectiveness and reduce environmental impact.
Overall, thermal remediation is part of a comprehensive suite of technologies aimed at addressing a wide variety of contamination issues efficiently and effectively.