Enzyme Enhanced Bioremediation with Remtech's HC-2000
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General
To ìenhanceî the bioremediation process in soil and groundwater, Remtech Engineers has developed a propriety delivery system and mix of enzymes, micro-nutrients, biodegradable wetting agents, and other native microbial stimulants (HC-2000) to catalyze or speed up biochemical reactions. Native microorganisms are frequently acclimated, albeit are often dormant or degrading substrate slowly.
Biologic reactions are driven by enzymes, which serve as catalysts. Every living organism has enzymes. External enzymes break down substrate (pollutants) and transport food to the microbe. Internal enzymes continue the process converting food to energy. By introducing a rich source of external enzymes and micronutrients, the rate of metabolism of microorganisms in the soil and groundwater is accelerated.
Bio-surfactants or wetting agents assist in delivering nutrients and enzymes to native organisms and assist in desorbing waste products from soil to make the substrate more available to native microbes. Since enzymes are specific to the substrate they are breaking down or bonds they are breaking, a mixture of enzymes are added to degrade a variety of materials including chlorinated and non-chlorinated petroleum compounds co-metabolically.
Enzymatic reaction rates are governed by the quantity of enzymes, pH, temperature, and enzymatic catalysts called ìcofactorsî which include salts. The addition of excess external enzymes appears to be the rate-limiting step in biochemical reactions when pH (4 ñ 9) and temperature (50 ñ 90 degrees F) are held within allowable limits. Elevated temperatures, i.e. greater than 120 degrees F inactivates enzymes.
The bioremediation process of Remtechís HC-2000 is three fold ñ(1) direct enzyme breakdown of contaminates (2) acceleration of metabolization rates of native microbe colonies (3) and biosurfactants which assist in mass transport and mobility of contaminants.
During the bioremediation process (as longer chain hydrocarbons are broken down into more numerous and degradable hydrocarbons) a bouncing ball affect generally is observed when tracking total petroleum (TPH) concentrations. Degradation will exhibit an initial decline in TPH followed by an increase and subsequent decreases until concentrations approach their final values.
Since mass transfer governs insitu technologies, Remtech has also developed enzyme delivery systems to maximize the delivery of HC-2000 to the environment. Remtech manufactures a complete line of enzyme, moisture, and air delivery/treatment systems.
Technical:
The primary parameters employed to demonstrate the effectiveness of Remtechís HC-2000 is total heterotrophic plate counts. The micronutrients in HC-2000 are generally sufficient to prevent nutrient deficiencies. Secondary objectives are to control moisture and oxygen levels.
To stimulate native microorganisms, you need existing microbes, i.e.; soils can not be sterile. Baseline soil and groundwater samples are collected to determine total heterotrophic plate counts. Generally speaking, native soils have plate counts in the range of several million CFUs/gm. Groundwater frequently has plate counts in the range of several thousand to several hundred thousand CFUs/ml.
HC-2000 addition rates are adjusted to increase plate counts in soil to the tens of millions to billion CFU/gm levels; and groundwater to millions of CFU/ml from background levels. The objective is to maintain an elevated and sustained level of total heterotrophs throughout the treatment period.
Soil Dosage Rates:
HC-2000 application rates are contaminant, concentration, and site specific, and should be determined by pilot tests and under the direction of Remtech Engineers.
General rules of thumb application rates for soil are:
One gallon of HC-2000 treats 3 to 10 cubic yards of soil. Weekly pulsed applications are made by adding one gallon of concentrate to 16 gallons of water. It may be desirable to dechlorinate water prior to the dilution process to avoid oxidizing enzymes. Treatment periods range from 3 to 16 weeks to complete the bioremediation process.
To jump start the bioremediation process; two applications may be made 1 or 2 days apart followed by weekly treatment applications.
Soil moisture rates should be maintained at 70 to 80% of field holding capacity or enough water to maintain elevated plate counts.
For soil depths of 2 feet, HC-2000 may be applied topically. It is generally desirable to pressure spray HC-2000 to ensure proper broadcasting of HC-2000. For greater depths, infiltration galleries, injection wells or Remtechís Underground Mist application system may be employed.
Air may be delivered to soil via tilling or insitu Bioventing systems. Contact Remtech Engineers for site specific delivery systems.
Groundwater Dosage Rates:
One gallon of HC-2000 treats 3 to 7 cubic yards of groundwater. A rough estimate may be calculated by projecting the contamination foot print through the saturated zone, i.e., treatment depth x area = volume.
Weekly pulsed applications are made diluting the concentrate with water at a 1:30 to 1:50 ratio. Weekly application durations range from 12 to 20 weeks+ to complete the bioremediation process.
It is frequently desirable to exercise hydraulic controls or barriers for groundwater applications to ensure adequate reaction retention times and to prevent migration of leachates out of the treatment zone.
Air may be delivered to soil via tilling or to groundwater employing insitu BioSparging systems. Contact Remtech Engineers for site specific delivery systems.
Soil:
It is generally desirable to conduct a field pilot test to determine site specific mass transfer limitations. For insitu soil applications, generally radius of influence tests with low or medium pressure blowers are conducted. Larger radius of influences generally occur when air is injected into the ground rather than extracted. Pressure deflections are measured with magnehelic gauges on nested response wells spaced at appropriate distances and depths from the stimulant well.
Air injection pressures and rates should be minimized to avoid channelization and allow appropriate respiration residence times. Respiration gases may be measured, albeit, total plate counts are a direct measure of biological activity and should be used whenever possible.
The pilot test should be designed by Remtech Engineers to accommodate site specific conditions.
Groundwater:
Groundwater biosparge radius of influence pilot tests should be conducted with low, medium, or high-pressure blowers and compressors. Pressure gradients and fluctuations in the water table are one way of defining the treatment zone. Bubble formation may also be observed in the response well.
The pilot test should be designed by Remtech Engineers to accommodate site specific conditions.
Performance
Remtech initially started with Bactozyme (aka HCZyme) and now manufactures HC-2000 which out performs HCZyme and Bactozyme. Performance information is summarized in the attached information.
Environmental Regulatory
HC-2000 contains no CERCLA, RCRA, other hazardous materials, or bacterial constituents. HC-2000 application rates do not exceed Floridaís Primary and Secondary Drinking Water Standards with the exception of pH and foaming. The pH of HC-2000 ranges from 3.1 to 6.0 depending on the amount of preservative added to increase the shelf life. Biosurfactants foam under aeration, albeit do not persist. The perimeter of the treatment area should be monitored to insure that foam levels dissipate.
Safety
HC-2000 is non-toxic, non-allergenic, and biodegradable mixture of proteins, enzymes, micronutrients, and biodegradable emulsifiers. There are no bacteria in HC-2000. No special handling instructions are recommended for HC-2000. Remtech recommends that good hygienic practices be followed when handling, i.e. wash hands and area that comes in contact with the material. Ingestion of the material may cause a laxative affect.
Limitations
Mass transfer limits all insitu soil and groundwater technologies. In order to complete bioóoxidization reactions, HC-2000 needs to come in contact with the contaminant substrate of concern. Aerobic conditions should be maintained.
Wherever possible, free product should be removed from soil or groundwater to accelerate reaction kinetics. HC-2000 has been demonstrated to be effective in the bioremediation of diesel, gasoline, Jet A, JP-8, lubricants, and other petroleum hydrocarbons.
Limited data exists indicating that HC-2000 may also degrade TCE, MTBE, and other chlorinated compounds. Bench scale tests should be conducted on other materials to confirm the applicability of HC-2000.
Sterilants can not exist in concentrations that would inhibit microbial activity. Native bacteria need to exist.
Remtech EngineersTM