The selection of a specific substrate should take into consideration a number of factors such as the goals of the project, hydrogeology, contaminant profile, geochemistry, plume characteristics, and remedial resources.
Our approach to substrate dosing is based on site conditions. JRW Bioremediation L.L.C. provides 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 micro-emulsion, and ChitoRem® chitin complex.
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The selection of a specific substrate should take into consideration several factors such as the goals of the project, hydrogeology, contaminant profile, geochemistry, plume characteristics, and remedial resources. As part of the available resources, the experience of the practitioner as well as the injection crew need to be considered as injection of slurried solids like ChitoRem® under pressure in a low permeability soil can be significantly different than the injection of a miscible liquid like WILCLEAR® into a sandy matrix. Materials handling also can play a role in substrate selection as some substrates promote growth so vigorously that they need to be injected within a few days after being diluted to prevent biomass from growing in the mix tanks, while others have special storage requirements.
Substrates such as JRW’s WILCLEAR®, WILCLEAR Plus®, SoluLac®, and LactOil® are very soluble in water. These materials readily mix reducing substrate preparation costs and move well through groundwater advection.
This characteristic can be beneficial when designing a system to manage groundwater flow through recirculation systems or groundwater pump and treatment systems. Readily soluble substrates are also of significant value when multiple injections are planned. This can be done through either injection or through permanent injection points.
LactOil® soy microemulsion is a unique substrate that combines the solubility characteristics of highly soluble materials like lactates with the dissolution properties of vegetable oil. This allows the material to be injected like a readily soluble substrate for superior distribution in situations where a slowly soluble substrate is desired.
Substrates such as JRW’s LactOil® and ChitoRem® are slowly soluble in water but at the same time provide carbon for extended periods depending on advective velocity and microbial activity.
LactOil® is a soy microemulsion that provides carbon for at least as long as standard vegetable oil emulsions. LactOil® contains ethyl lactate as part of the microemulsion to slowly provide highly efficient lactate to the aquifer over extended periods of time.
ChitoRem® is a solid complex containing chitin, calcium carbonate, and protein. The chitin acts as a slow release substrate while the protein drives an aquifer anaerobic very quickly. Both also contain the essential nutrient nitrogen to rapidly promote and maintain microbial growth. The calcium carbonate is in a form that slowly releases into the system without armouring to provide a long-term buffering agent.
The selection of a substrate is site and project specific and should be conducted with the goals of the project in mind. Contact JRW for suggested uses based on your site-specific needs.
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.
