ECONOMICS AND VALUATION OF BIOAUGMENTATION - Bioaugmentation for Groundwater Remediation - page 309

The cost of qPCR analysis ranges between $250-300 1 for a single target, including DNA
extraction from groundwater; additional targets on the same sample adds approximately $100
per target. qPCR analysis provides information on the number of gene copies in a sample and
allows tracking microbial population growth during treatment. The results of qPCR analysis
can answer questions such as whether the indigenous or bioaugmented microbial populations
are growing after addition of electron donor, or if the bioaugmentation cultures are growing
and spreading through the treatment area. However, the results provide limited information on
the rate of microbial activity under various conditions.
In contrast, simple microcosm (bottle) studies can be conducted to evaluate the nutrient
and microbial requirements for biodegradation of target compounds in soil and groundwater
from a particular site. The tests typically consist of a number of treatments designed to
evaluate the effect of electron donor amendments with and without bioaugmentation relative
to controls. A small microcosm study might include three treatments (sterile control, biosti-
mulation, and biostimulation and bioaugmentation), each run in triplicate and cost in the range
of $10,000. Microcosm studies also allow for the collection of data pertaining to the nature of
specific microbial activities (e.g., sulfate reduction, methanogenesis, reductive dechlorination),
the effect of different electron donors and donor loading rates, nutrient requirements, reaction
rates, and the factors that inhibit reductive dechlorination. More complex studies will usually
require additional microcosms. Statistical methods (fractional factorial experimental designs)
can be used to reduce the number of bottles required to evaluate multiple variables. However,
these expanded studies typically cost from $20,000 to $30,000.
If dechlorination is not achieved or is slow to occur in microcosms without bioaugmenta-
tion, but occurs quickly with bioaugmentation, then it is likely that bioaugmentation will be of
benefit in the field. Microcosm studies also are quite effective at determining relative degra-
dation rates with different amendments and are therefore useful for designing the EISB
system. However, since microcosm tests represent ideal conditions of mixing and amendment
distribution, caution should be used when using the results to predict the rate that biodegrada-
tion will occur under field conditions.
In situ microcosms and samplers also may be used to evaluate the potential benefits of
bioaugmentation. Since these tests are still considered innovative, they are not covered in this
chapter, but are discussed in Chapter 4 .
It should be noted that variations in contaminant concentrations and geochemical or
hydrogeological characteristics across the site would affect the ability to transfer laboratory
results to the field. Therefore, the location and number of sampling locations should be
carefully considered in the decision-making process, regardless of the method used to assess
the need for bioaugmentation.
11.2.2 Amount and Distribution of Active Organisms
In most cases, the goal of bioaugmentation is to reduce the time needed for effective
treatment. The effectiveness of bioaugmentation in meeting this goal is dictated by three
primary factors: (1) the volume of culture required; (2) the distribution of the culture during
injection; and (3) the growth rate of the culture subsequent to its injection. These factors are
discussed in the following subsections.
1 All costs presented in this chapter are in U.S. dollars.