MICROCOSM STUDY + HYDRAULIC TEST = PILOT TEST
George Pon, Ph.D., Bioremediation & Treatability Center

Bioremediation pilot tests are becoming popular as a cautious remediation industry embraces bioremediation.  A properly conducted pilot test is invaluable and clearly demonstrates degradation/breakdown of the contaminant of concern under field conditions.  Due to the difficulty in accounting for contaminant mass loss in field demonstrations, however, bioremediation pilot studies are generally less than perfect and are qualitative in nature and only demonstrate technical feasibility. Microcosm testing procedures have evolved and improved dramatically over the past several years. Currently, microcosm studies are conducted using site soil and without "exotic" manipulation or additives to the groundwater.  They are truly representative of site conditions.

Microcosm tests (either batch or flow-through cell) offer a low cost alternative to generate a quantitative demonstration that site contaminants can be degraded.  A microcosm test can evaluate several electron donors, pH manipulation, inorganic nutrient addition for approximately $10,000 per location whereas a pilot study may cost up to $150,000 and only evaluate one set of conditions (electron donor, pH and nutrient content) in a qualitative manner. The major shortcoming of a microcosm study is that no site specific data for electron donor delivery is collected, and as such, full scale design data needs are not satisfied.

Combining microcosm studies with conventional hydraulic data collection methods such as short term pumping tests and tracer tests allows for the collection of data that is needed for designing an electron donor delivery system (10 days as a nominal average for soluble electron donors).  Sufficient data currently exists from numerous field studies for expected electron donor half lives in the subsurface.  An alternative to conducting a $150,000 pilot study is to conduct 3 microcosms and 3 hydraulic tests at different site locations for approximately $60,000.  One can collect significantly more information for full scale bioremediation system design if the formula: Microcosm Study + Hydraulic Test = Pilot Test is fully appreciated.

We have conducted over 60 microcosm studies and dozens of hydraulic tests leading to well designed and operational full scale bioremediation systems.  We have also conducted several enhanced anaerobic dechlorination pilot studies. We will contrast the costs and value of the collected information from our various projects.