Using bioremediation to treat ground impacted by chlorinated hydrocarbons (CHCs) essentially requires building a bioreactor below the ground; therefore, direct observation of results is not possible. Rather, the process must be scientifically monitored through specialised tests to serve as the integral lines of evidence needed to assess the health and performance of the biobarrier.
The monitoring of this biobarrier, which is a living system, is clone using specific in situ and laboratory tests. These tests will give insight into the key prevailing conditions that are required to maintain the biobarrier's health and achieve the expected results in terms of CHC degradation. The characterisation of the affected ground will determine which geochemical conditions are most relevant to be included in the ongoing project assessment.
In situ monitoring of redox and pH
For instance. certain microbes responsible for the degradation of the dense non-aqueous phase liquids (DNAPLs) will only thrive in an anaerobic environment - in which case a ’vital aspect of monitoring will be focused on checking for oxidation-reduction (redox) conditions.
Acidity in the groundwater must also be carefully checked, as the microbes require a pH level In a range from five to seven. As they break down CHCs, the microbes generate volatile fatty acids that reduce the pH level of the groundwater and could undermine their effectiveness. Where pH levels are found to be too low, a ‘buffer' can be added to raise them to within the optimal range.
Inorganic indicators
It is also necessary to check other geochemical parameters such as the levels of nitrates and sulfates. This helps to identify and understand the complex geochemical dynamics in the aquifer and possible presence of other microbes in the aquifer that could influence remediation reactions; these other microbes can compete for the injected food source. Information on these factors enables the practitioner to adjust the food supply to ensure that the dehalorespirators are still well supplied.
SRK Contributors:
Michelle Roux, Sathisha Barath
