Microbiological Response to Well Pumping
Article first published online: 9 JAN 2008
2008 The Author(s)
Volume 46, Issue 2, pages 286–294, March–April 2008
How to Cite
Kwon, M. J., Sanford, R. A., Park, J., Kirk, M. F. and Bethke, C. M. (2008), Microbiological Response to Well Pumping. Groundwater, 46: 286–294. doi: 10.1111/j.1745-6584.2007.00401.x
- Issue published online: 9 JAN 2008
- Article first published online: 9 JAN 2008
- Received May 2007, accepted October 2007.
To better constrain sampling strategies for observing biologically sensitive parameters in ground water, we vigorously pumped for 120 h a lightly pumped well completed in a confined glacial aquifer while observing how various physical and chemical parameters evolve in the water produced. The parameters commonly monitored when sampling a well stabilized within about an hour, after 5 wellbore volumes were produced; these parameters include temperature, pH, dissolved oxygen, oxidation-reduction potential (Eh), and electrical conductivity. The concentrations of ferrous iron, sulfide, and sulfate and various biological or biologically sensitive parameters, including the concentrations of dissolved hydrogen and methane, direct cell counts, and the microbial community profile, in contrast, required more than 8 h or 36 well volumes to stabilize. We interpret this result to mean that the zone of influence of the wellbore on biologic processes in the aquifer extends beyond the commonly recognized zone where physical properties are affected. A second period of adjustment of these biologically sensitive parameters began after about 50 h of pumping, following displacement of 230 wellbore volumes, and continued to the end of the experiment. During this period, the cell density and the composition of the microbial community suspended in the water samples changed. This finding indicates that the microbial community in and near the wellbore changed in response to pumping and the changes affected aspects of the composition of water produced from the well. The study demonstrates the importance of allowing adequate pumping time when sampling ground water for the analysis of biologically sensitive parameters.