What information do you need to make a decision that enhanced reductive dechlorination is applicable to your site and how can you tell that you are progressing towards your goals?
Analytical methods need to take into account the sample matrix in order to prevent unanticipated interferences. Samples with high levels of complex organics that include elements like sodium, potassium, calcium, chlorine, magnesium, or sulfur can increase the formation of polyatomic ions that can interfere with the analytical accuracy of metals analysis.
Acetone is not always a lab contaminant. Some metabolic pathways can result in the formation of acetone, butanone, and other “errant” fermentation products. Review your project thoroughly before you accuse your lab of spilling acetone in your samples!
Principles and Practices of Enhanced Anaerobic Bioremediation of Chlorinated Solvents, Air Force Center for Environmental Excellence, Brooks City-Base, Texas, August 2004. In Situ Bioremediation of Chlorinated Ethene: DNAPL Source Zones, ITRC, June 2008. Natural Attenuation of Fuels and Chlorinated Solvents in the Subsurface, T. Wiedemeier, C. Newell, J. Wilson, H. Fifai, 1999, Wiley & Sons, Inc.
Natural systems contaminated with organics are dynamic systems striving to reach equilibrium and recognizing both the temporal and spatial changes can help the practitioner better understand the and manipulate the natural system. The proper evaluation of the geochemistry and contaminant profile of a site prior to the injection of a substrate to enhance reductive dechlorination is critical in selecting the proper substrate and application method for that particular situation. Likewise, a proper evaluation is critical after substrate injection to determine if the site conceptual model is correct and if remediation is progressing as planned. There are four major types of analytical parameters that are usually monitored for the design and evaluation of an enhanced reductive dechlorination project. These can be divided into geochemical field and laboratory parameters, and contaminant profile. In addition, specialized analysis can be conducted for different substrates and processes. These may include specialized molecular screening techniques and carbon isotope chemistry. Combined with hydrogeological data and a historical understanding of the release, a practitioner can design a more effective system and predict future trends in the remedial process. As with the collection of all data, the project goals must be understood and taken into account throughout the sampling program.
Field Geochemistry: Field geochemical parameters can be considered to include data that can degrade quickly after the sample is collected. The most common field analysis conducted on enhanced reductive dechlorination sites includes the collection and analysis of groundwater for dissolved oxygen, pH, temperature, and oxidation-reduction potential (ORP). Since these parameters can change dramatically after sample collection these parameters are usuallycollected by field staff. Although a number of sampling methods can be employed, care should be taken to select a sampling method that will provide a sample that is representative of the formation water as reasonably possible. Sampling methods such as bailing or high-volume purging are generally not conducive to providing a representative sample of the formation water and should be avoided, if possible. Field geochemical parameters are most accurately collected through down-hole sensors or through in-line probes. Low flow sampling techniques as described by USEPA (Robert W. Puls and Michael J. Barcelona, EPA/540/S-95/504, April 1996 and updates) can also provide consistent and accurate results. In all cases, care should be exercised to follow the equipment manufactures instructions for care, maintenance, calibration, and operations of any analytical equipment used.
Geochemical Laboratory Analysis: Geochemical laboratory analysis can be viewed as including all parameters done by a laboratory other than the constituents of concern. These typically include at least an evaluation of the concentration of competing electron acceptors such as nitrates, iron, manganese, and sulfate, and biological indicators such as alkalinity and gases like methane, ethene, and ethane. Although not as sensitive to changes as many of the field geochemical analytes, attention to proper sampling, preservation, shipping, and laboratory quality assurance and quality control is essential to ensuring consistent, accurate data. In most cases, the sampling strategy employed for the collection of the field geochemical parameters is adequate for the laboratory geochemical analysis. It is therefore important to work closely with the analytical laboratory to prepare an adequate sampling and analysis plan prior to mobilization to the site.
Contaminant Profile: As with the samples collected for geochemical laboratory analysis, the contaminant profile samples must be c ollected and analyzed using proper methods. Most chlorinated solvents degrade following predictable pathways. The initial contaminant profile can be compared to post- substrate application profiles to help evaluate the progress of biological activity. Because compounds such as butanone and acetone can be biologically produced under certain conditions, data reporting should include all analytes detected by the laboratory. Attention should be given to determining the appropriate detection limits for each analyte to ensure that the data can be useful for both evaluation and regulatory purposes.
Biological Parameters: Advanced analytical methods have been developed to profile the type and number of microbial populations present at a site. These tools were initially generally used to help evaluate underperforming sites but have become an important part of the site characterization process. These methods typically require unique sampling procedures not generally employed by most practitioners therefore it is imperative that the practitioner carefully coordinate the collection and shipping of all samples for biological parameters with the respective laboratory.
JRW is committed to the health and safety of our employees and our clients during the COVID-19 health crisis. Although our core business is considered essential, JRW has taken the step of encouraging all non-essential personnel to work remotely whenever possible. Our communications program seamlessly integrates telephone and web contact with each individual within the organization as well as our clients allowing staff to limit personal face to face contact while maintaining a high degree of personal attention. Each staff member has real-time access to project files and order databases allowing us to work remotely to maintain up to date information about your project and the status of your order. Our technical, logistics and administrative professionals also remain available to assist in your project planning and execution.
We will continue to work to maintain a commitment to superior service throughout the current health situation and hope that you, your staff, and their families remain healthy.
JRW is committed to the health and safety of our employees and our clients during the COVID-19 health crisis. Although our core business is considered essential, JRW has taken the step of encouraging all non-essential personnel to work remotely whenever possible.
Our communications program seamlessly integrates telephone and web contact with each individual within the organization as well as our clients allowing staff to limit personal face to face contact while maintaining a high degree of personal attention. Each staff member has real-time access to project files and order databases allowing us to work remotely to maintain up to date information about your project and the status of your order. Our technical, logistics and administrative professionals also remain available to assist in your project planning and execution.
We will continue to work to maintain a commitment to superior service throughout the current health situation and hope that you, your staff, and their families remain healthy.
Our approach to substrate dosing is based on site conditions. We provide substrates and nutrients for anaerobic bioremediation. The substrates provided include highly soluble materials such as WILCLEAR® sodium and potassium lactate, SoluLac® ethyl lactate, and Wilke Whey® whey powder and slowly soluble substrates including LactOil® soy microemulsion, and ChitoRem® chitin complex.
Enhanced reductive dechlorination is based on attaining and maintaining control of an aquifer for a period of time sufficient to degrade all constituents of concern and their daughter products. Attaining and maintaining control of an aquifer is highly dependent on the hydrogeology and geochemistry of the site along with the microbial populations present. Since the hydrogeology and geochemistry is different for every site, a blanket cost can not be given for any specific site. In general, enhanced reductive dechlorination will cost less than $10 per cubic yard of media treated on most non-DNAPL sites. This compares with about $60 per cubic yard for excavation (without disposal) and about $90 per cubic yard for chemical oxidation.
Because freight is costed from a warehouse to a delivery point, freight costs are quoted separately. Unless otherwise stated, due to the volatility of the fuels market, freight costs are generally valid for 30 days. Consideration should be given to the receiving facility’s capacity to off load a truck. In situations where the product is delivered to a facility without the capacity to off-load a delivery vehicle, arrangements can be made (for an additional charge) for delivery on a vehicle with a lift gate and pallet jack.
Reinjection schedules should be based on the geochemistry of an aquifer and not on a calendar schedule. In many cases, multiple injections can be spaced further apart over time.
Since the main goal of adding a substrate to an aquifer is to attain and maintain anaerobic conditions for an extended period of time, because of the limited flows clay sites should be ideal for enhanced reductive dechlorination. In practice, clay sites with adequately spaced injection points usually show very rapid response to substrate addition.
Injection spacing should be sufficient to promote robust reductive dechlorination throughout the treatment zone for a time sufficient to attain complete reductive dechlorination. Injection spacing is dependent upon the dissolution rate of the substrate, the dosage, aquifer velocity, and competing electron acceptor and contaminant flux.
