How does DCL Biosolv work?
DCL Biosolv promotes the natural biodegradation of target contaminants by a process known as reductive dechlorination. DCL Biosolv essentially acts as nutrient source for cell growth and as an electron donor for energy generation. The end result is that chlorinated solvents, such as tetrachloroethene and trichloroethene, are biologically degraded into non-toxic end products.
When injected into the ground, DCL Biosolv is fermented to hydrogen and low-molecular weight fatty acids. These short-chain molecules (such as acetate, butyrate and propionate) in turn provide carbon and energy to the microorganisms, which facilitate reductive dechlorination. In the reductive dechlorination process, microorganisms sequentially replace chlorine atoms with hydrogen forming more reduced dechlorination products. For example, chlorinated solvents are transformed sequentially from tetrachloroethene to ethene via the intermediate compounds trichloroethene, dichloroethene and vinyl chloride.
How do you use DCL Biosolv?
DCL Biosolv is a low-viscosity liquid that is easy to handle and non-toxic. It is very easy to mix with water and should be diluted before use by typically adding one part DCL Biosolv to nine parts water to produce a white liquid with the appearance and viscosity similar to milk. A powdered activator and buffering agent is then added to the diluted product before injection into the ground.
DCL Biosolv is usually introduced into the ground using injection rods installed by small tracked direct push drilling rigs. A mixing / injection unit is then connected to the rods and the remediation product injected into single or multiple locations. As the remediation product is injected, the rods are withdrawn so that distribution is achieved across the required vertical treatment zone. Multiple injection points can be fed simultaneously to speed up the process. Where small localised plumes are present it is also possible to gravity feed DCL Biosolv to existing boreholes.
What happens in the ground after injection of DCL Biosolv?
DCL Biosolv typically begins to take effect 3 to 4 weeks after injection. The injection zone becomes strongly anaerobic with dissolved oxygen levels usually falling below 0.5 mg/l and the oxidation-reduction potential (ORP) becoming negative. As the dissolved oxygen is removed other electron acceptors such as nitrate and sulphate are reduced. This is followed by rapid degradation of the more highly chlorinated contaminants such as PCE and TCE and the appearance of degradation intermediates including DCE and vinyl chloride. These intermediate compounds are subsequently degraded.
How long will DCL Biosolv remain active?
The length of time that DCL Biosolv remains active in an aquifer depends on the dosing level and site specific factors such as the hydrogen demand resulting from naturally occurring electron acceptors including oxygen, nitrate, sulphate, ferric iron and manganese. The product will continue to remain active for typically 12 months and potentially up to five years.
How do I test for the presence of DCL Biosolv in an aquifer?
The presence of DCL Biosolv in an aquifer can be determined by monitoring physical parameters and by chemical analysis. In-situ testing within monitoring boreholes can be used to determine dissolved oxygen (DO) and oxidation-reduction potential (ORP). Under the required conditions the DO concentration should be at or near zero and the ORP also be zero or less.
Total organic carbon (TOC) is a chemical test that measures the level of carbon present in groundwater and from this the presence of remediation product can be inferred. Analysis for fatty acids such as ethanoic acid and butyric acid also indicate the presence of DCL Biosolv.
How do you prevent migration of DCL Biosolv away from the intended remediation area?
Tests have shown that DCL Biosolv does not migrate a significant distance away from the point of injection. The emulsified vegetable oil droplets are initially retained by adsorption onto soil particles, and once microbial degradation begins to affect the stability of the emulsion, oil films or larger droplets appear to be strongly retained in the soils with no further migration.
What groundwater parameters should we monitor after injection?
In-situ field testing for ORP, pH, conductivity and dissolved oxygen are recommended. Additional detailed monitoring could include chemical tests for iron, manganese, total organic carbon and volatile fatty acids. Gaseous phase monitoring for volatile organic compounds (VOCs), oxygen, carbon dioxide and methane is also useful. Laboratory analysis should be undertaken to determine concentrations of contaminants of concern and their intermediate degradation products.
What happens to the remediation product after the contaminant has been degraded?
By its very nature, DCL Biosolv is biodegradable and is gradually removed from the aquifer by natural processes. Groundwater geochemistry will ultimately revert to a condition similar to that observed prior to injection of the remediation product.
Do you provide technical support?
Telluric Land Remediation can provide a full contracting service for the design, injection, monitoring and validation of remediation works. However, we are happy to supply the product to other contractors and consultants together with full technical support.