Biomedical Engineering Reference
In-Depth Information
6.3 DEVELOPINGAMONITORINGSTRATEGY
Sampling aquifers for microbial and geochemical analyses in support of bioremediation
applications faces several constraints and the ideal sampling regime with regard to sampling
locations, sampling frequency and sample type is rarely achieved. For example, site access
limitations, obstruction by existing infrastructure, lack of sampling wells, and limitations on
well installation and sample collection may constrain sampling efforts. However, the impor-
tance of thoroughly considering monitoring strategies at the pre-design phases of a project
cannot be overstated. A monitoring strategy for assessing geochemical and microbiological
conditions before, during and after bioaugmentation can help to improve treatment efficiency
and allow changes in site conditions to be better anticipated and contingencies implemented.
The following sections provide an overview of key considerations for developing and imple-
menting a monitoring strategy for bioaugmentation.
6.3.1 Defining Monitoring Objectives
Prior to sampling, the expected outcomes of the analysis should be clearly defined.
Some key questions to consider when defining monitoring objectives include:
What information should the analysis provide?
Are data objectives qualitative (i.e., Dhc presence) or quantitative (i.e., Dhc
abundance)?
At what frequency will samples be collected?
Will samples be collected from all monitoring wells or a subset?
6.3.2 Temporal Considerations
Dhc cell titer data are valuable throughout the remedial investigation and feasibility study
process, and samples for Dhc analysis should certainly be collected prior to the design of a
bioremediation system (Stroo et al., 2006 ). These data, in conjunction with chlorinated ethene
and geochemical information, are crucial in deciding whether to proceed with bioaugmentation.
A one-time sampling event is sufficient for pre-design purposes and this may serve as the
baseline data for subsequent sampling events. Following bioaugmentation, Dhc analyses should
be conducted for at least 12-18 months, or until the system performance has stabilized.
Temporal Dhc data from a treated aquifer zone are critical for evaluating and managing the
system's performance. Monitoring strategies for assessing Dhc populations following aquifer
treatment are dependent upon site-specific conditions; however, a flexible strategy that can be
adjusted based on the monitoring results (e.g., changes in geochemistry or Dhc populations), is
recommended. As a general rule of thumb, the period of time between monitoring events
should be relatively short immediately following bioaugmentation (a few weeks), but may
increase as changes in the geochemistry and microbial activity decrease.
6.3.3 Selection of Sampling Wells
For practical reasons, MBT sampling focuses on groundwater. Solid aquifer samples are
typically not included in routine analyses, due to the cost and heterogeneity of aquifer core
samples. The distribution between solid and aqueous phases in different aquifer matrices is
poorly understood for most microbial populations. Until further information is available
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