Remedial Plan Consulting
Using treatability / microcosm test results, Drs Fogel and Findlay provide practical recommendations to engineering clients for in situ and ex situ field bioremediations, including the types and amounts of microbial amendments, methods of application, and estimations of cost. They each have worked in the field of bioremediaiton for more than 20 years.
Chlorinated Solvents: How to Base Remedial Strategy on Microcosm Tests and Lab Data
Microcosm test results, together with an understanding of your site’s hydrogeology and geochemistry, can provide the basis for a remedial strategy.
Understand your site
To indicate the presence of dechlorinating bacteria, have groundwater analyzed for dechlorination products such as VC and ethene from PCE and TCE, and chloroethane from 1,1,1-TCA. Look for strong reducing conditions by analyzing for methane, as well as presence of ammonia rather than nitrate. Evaluate potential for natural attenuation by analyzing for food (‘donor’) for microbes such as volatile fatty acids and degradable contaminants such as methanol. Also measure constituents which compete with dechlorination for donor, such as sulfate.
Use Microcosms to Test Remediation Scenarios
Armed with your site data, work with BCI to plan a microcosm test using site groundwater to provide conclusive evidence for presence and capabilities of native dechlorinators, demonstrate the need for bioaugmentation, determine the optimal donor for your site, as well as the need for minerals required by microbes. If needed, BCI will grow the selected BCI culture in your site water.
Getting Started on Site
Work with BCI to plan an amendment strategy, including pH control (D.ethenogenes prefer pH above 6.5), and prepare a monitoring plan to track donor use, pH and treatment progress. Design a sealed amendment tank in which the concentrated amendments can be anaerobically mixed with water and metered into the injection wells. Initiate the injection process and verify that amendments can be detected in down-gradient wells. The ORP is low enough for dechlorinators (-180 milivolts) when sulfate is being reduced. Transfer culture to the anaerobic amendment tank or inject it into wells below the water table.