Frequently Asked Questions
These frequently asked questions (FAQs) are a culmination of select product-oriented questions and answers that our Sales, R&D, Technical Services and or Marketing Departments have received over time. Note: You must “left click” on the question to see the answer appear below it. You can “left click on the question again to hide the answer for easier viewing of entire list
- Knowledge of the existing aquifer redox state and geochemical parameters (redox potential (ORP), dissolved oxygen, nitrate, iron, sulfate, methane, and total organic carbon concentrations)
- Ease of shifting redox conditions to improve the rate of biodegradation. Is it easier to make the aquifer aerobic or anaerobic?
Software Related FAQs:
Additional oxygen demand factors are given for four categories:
- Individual species like BTEX components, MTBE, reduced inorganics, etc.
- Total Petroleum Hydrocarbons (TPH)
- Biological Oxygen Demand (BOD)
- Chemical Oxygen Demand (COD)
The user chooses the category on which to base the ORC design cost using the radio buttons in the table. The demand factors for each category are based on the degree to which each category provides a reasonable estimate of oxygen demand. For example, individual species like BTEX, MTBE, reduced inorganics, etc. (Category 1) are the most specific, least conservative measurement of oxygen demand, and COD (Category 4) is the most general, most conservative measurement of oxygen demand. The default additional demand factors for the each category are given in the following table. Although the default values summarized here have led to the design of many successful ORC applications, they can be modified based on the user's knowledge of the site characteristics and contaminant measurements.
|Individual species like BTEX components, MTBE, reduced inorganics, etc.||
|Measurements of individual species or sets of species will often underestimate the oxygen demand to a significant degree, so this category is given a high additional demand factor.|
|Total Petroleum Hydrocarbons (TPH)||
|TPH is given an additional demand factor of 2, because TPH is a more thorough measurement that will account for the background hydrocarbon contamination not considered in the individual species measurements. However, TPH does not include chemical reactions that consume oxygen (such as the oxidation of ferrous iron), so a safety factor must be used.|
|Biological Oxygen Demand (BOD)||
|BOD accounts for oxygen demand that is available to microorganisms and does not account for chemical reactions that consume oxygen. Thus, BOD is assigned a demand factor of 2.|
|Chemical Oxygen Demand (COD)||
|COD accounts for chemical and biological oxygen demand and is assigned a demand factor of 1 because it typically over represents the oxygen demand placed on ORC.|
The microbial demand factor accounts for non-targeted microbial demand for lactic acid and H2 for processes that are not directly involved with either reduction of the chemical species included in the software (iron, sulfate, etc.) or in reductive dechlorination of VOCs. It includes microbial inefficiencies associated with lactate and/or H2 metabolism and lactate use to grow biomass.
ORC Related FAQs:
ORC application in the vadose zone consists of a series of closely spaced injection points to which a dilute slurry of ORC and water is delivered. The dilute ORC/water mixture is used to mound and spread the ORC and provide moisture to the vadose zone.
If ORC application was within the previous 6-9 months, TPH/BTEX remains low, and little or no DO is present, ORC is most likely releasing oxygen, and it is being consumed in contaminant biodegradation. However, if TPH/BTEX has increased to the original, baseline levels or has reach a plateau that lasts for several months, and it is beyond the 6-9 month release period, ORC has probably been exhausted and new contaminant influx or desorption has occurred. As with all contaminants a careful review of groundwater elevation changes should be factored into any of the above issues. A significant change in groundwater elevation typically affects the concentration of contaminants in groundwater.
HRC Related FAQs:
HRC's radius of influence after injection is driven either by advection (groundwater velocity) or chemical diffusion. The faster groundwater is moving the larger the influence HRC and its derivatives will have. If groundwater is moving slow (less than ten feet per year) the main river will be chemical diffusion. Under slow moving groundwater conditions Regenesis believes that the HRC and its derivatives can move at a rate of approximately one-foot per month.
The qualitative measurements used for detecting HRC in an aquifer are Total Organic Carbon (TOC) and metabolic acids which includes acetic, butyric, lactic, propionic, and pyruvic acid. The TOC test simply measures the levels of carbon present in a groundwater sample (aquifer). HRC is a polylactate ester which by definition is a high molecular weight carbon source. Therefore the injection of HRC into an aquifer will increase the overall mass and concentration of TOC.
HRC is used to accelerate in situ biodegradation rates of chlorinated hydrocarbons via anaerobic reductive dechlorination processes. Reductive dechlorination is one of the primary attenuation mechanisms by which chlorinated solvent groundwater plumes can be remediated. During reductive dechlorination the lactic acid (CH3CHOHCOOH), a primary component of HRC, present in the compound provides electrons (Hydrogen) to facilitate the process. During this process other acids such as acetic, butyric, propionic, and pyruvic can be created. Hence, testing for metabolic acids can show the presence of HRC and its derivatives in an aquifer.
RegenOx Related FAQs:
- PCE, TCE, DCE, VC
- #2 Heating Oil
In order to document the effectiveness of a RegenOx treatment, Regenesis recommends the following performance monitoring program. Prior to injection of the chemical oxidant, a baseline round of sampling should be performed to identify the groundwater quality/conditions and soil concentrations at the site. The following table outlines the parameters and methods that should be used to monitor the performance of the RegenOx project as well as the recommended monitoring schedule (shown below).
|Analyte||Method||Baseline||~2 wks after
|4 wks after|
|In Field||pH, dissolved oxygen (DO), oxidation/reduction potential (ORP), conductivity||Meter reading taken in flow-through cell (DO can also be measured with a Hach field test kit)||GW||GW||GW|
|Contaminant of conern||Appropriate EPA method|| GW