Biomedical Engineering Reference
In-Depth Information
of electron donor will be required to achieve remedial goals, and if bioaugmentation
will allow remedial goals to be achieved even 12 months sooner than they would be
without bioaugmentation, then the costs to purchase electron donor and operate the
bioremediation system could be reduced by 20% with bioaugmentation. This cost
saving also may be viewed as maximizing the value of the electron donor and system
operating costs during the first year of operation, when these activities would other-
wise not contribute effectively to the treatment of the target contaminants. As can be
seen in the examples presented later in this chapter, the cost of bioaugmentation is very
small (typically less than 3% of other costs) relative to a potential savings of 20% in
other costs. In the case of a biobarrier that may be operated for a much longer period
of time, the savings in electron donor and system operation actually may not be
realized until the end of the operating period sometime in the future, but the use of
bioaugmentation will still capture the value of the electron donor added and system
operation in the early period of operation.
2. Reducing the monitoring costs . Reducing the operating time for an EISB program
also reduces the costs for monitoring. As discussed in the example above, if bioaug-
mentation reduces the operating time by 20%, then a 20% reduction in associated
operational costs also may be achieved. Bioaugmentation also may result in further
reductions in monitoring costs (or avoid escalations in monitoring costs) relative to
situations where complete dechlorination is not achieved for some period of time (e.g.,
12-36 months). It is quite possible that responsible parties or regulators will have an
increased level of concern regarding the success of an EISB program until complete
dechlorination can be demonstrated. Further, delayed reductions in the concentrations
of intermediate degradation products such as VC may result in potential exposures
that need to be addressed. These factors may result in requirements for additional
monitoring that would not be required if bioaugmentation was implemented and
dechlorination was demonstrated sooner.
3. Reducing costs associated with reporting and discussions with stakeholders .
If bioaugmentation is implemented and dechlorination is achieved, it is likely that
costs associated with reporting and discussions with stakeholders (i.e., property own-
ers, regulators and neighbors) will be reduced relative to situations where remedial
objectives are not being achieved for some period of time. In more extreme cases, the
use of bioaugmentation may avoid the need to implement contingent remedies that
may be required if remedial objectives are not achieved within a time period expected
by stakeholders.
11.4 ECONOMICS OF ALTERNATIVE APPROACHES
11.4.1 Costs for Purchase and Injection of Concentrate Versus
In Situ Growth and Distribution
It may be possible at some sites to accomplish bioaugmentation by pumping groundwater
from specific areas of the site where elevated concentrations of Dhc are already established
either by bioaugmentation or by natural processes, and inoculating other areas where Dhc is
absent or less abundant. This approach can work, but consideration must be given to the time
and effort required relative to the costs to purchase culture. The concentrations of Dhc in
natural groundwater, even under optimal conditions, are typically in the range of 10 8 cells/L,
while a typical bioaugmentation culture contains 10 10 -10 11
cells/L. Thus, to establish active
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