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Assessing Microbes in Ground Water—A Highlight at the Sixth Annual Aquifer Storage and Recovery Meeting in Orlando, Florida

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microbiologists Ron Harvey and John Lisle
Above: USGS microbiologists Ron Harvey (right) and John Lisle compare two styles of diffusion chambers designed and built by the USGS. The diffusion chambers have been used to conduct in situ studies of microbes in ground water. [larger version]

three different designs of diffusion chambers designed to meet specific research needs
Above: Three different designs of diffusion chambers designed to meet specific research needs. The basic design includes a central plate that retains the sample, two outside plates that bolt to the central plate, and a silicone gasket that sits between the central and two outside plates between which a semipermeable membrane is secured. Samples are loaded and removed through syringe fittings. The membranes retain the bacterial cells within the central chamber while allowing chemical and nutrient constituents in the water to diffuse into and out of the chamber but preventing native bacteria from contaminating the internal volume. [larger version]

Representative collection of photographs showing bacteria that have been isolated from ground water
Above: Representative collection of photographs showing bacteria (bright spots) that have been isolated from ground water. All cells have been labeled with fluorescent stains. [larger version]

The Sixth Annual Aquifer Storage and Recovery meeting convened local and international experts in Orlando, Fla., on October 16-17, 2006. The meeting was organized by the American Ground Water Trust and cosponsored by the U.S. Geological Survey (USGS), along with many environmental consultants and other Federal and State agencies. Technical experts shared experience and discussed issues regarding the practice of using aquifers to temporarily store water, known as aquifer storage and recovery (ASR), during periods of high water availability so that it can be withdrawn for use during dry periods. The technique is part of Florida's comprehensive water-management plan to develop alternative sources of drinking water in order to meet future projected water-use demands; it is also an integral part of the Greater Everglades Ecosystem Restoration (GEER) plan. If effective, the practice will allow water managers to reduce impacts on both surface-water and ground-water resources by reducing withdrawals and the need to construct large reservoirs.

Technical issues that affect the feasibility of aquifer storage and recovery include potentially adverse geochemical changes in the aquifer, efficient recovery of the injected water, and availability and timing of water-supply diversions. From a regulatory perspective, the Florida Department of Environmental Protection (FDEP) is primarily focused on the mobilization of arsenic, which in several operating aquifer-storage-and-recovery systems has exceeded the new drinking-water standard of 10 µg/L. Arsenic mobilization in ground water is a complex geochemical problem that can be substantively affected by the activities of indigenous microbial populations. USGS research in characterizing microbial populations in ground water and monitoring accompanying geochemical changes associated with ground-water contamination and ASR techniques suggests that microbial populations can shift in response to changes in ambient ground-water quality such as pH, redox state, or availability of specific ions or metals.

USGS scientists were featured in the Aquifer Storage and Recovery meeting session titled, "How Mighty are the Microbes and Minerals?" The session was moderated by USGS hydrologist Ann Tihansky and featured USGS microbiologists Ron Harvey and John Lisle. Harvey discussed the USGS national perspective on new technology, innovative methods, and future directions for understanding microbial communities in ground water. Lisle presented results from his cooperative work with the FDEP and utilities in the Tampa Bay area, comparing microbial communities in recharge and native ground water associated with an operating ASR system in Tampa.

After the meeting, Harvey visited the USGS center in St. Petersburg, Fla., to work with Lisle on the latest designs of in situ (downwell) filter chambers designed to sequester specific nonindigenous and indigenous microbial populations in order to quantify population dynamics under ambient and altered ground-water conditions. According to Lisle: "We want to be able to demonstrate that we can safely contain known microbial communities in aquifers without letting them loose into the ground-water system. These chambers are designed to keep the bugs in and yet allow them to interact with the ground-water chemistry as they normally would. The idea is that we would deploy them for a period of time, allowing them to interact with the chemistry in the native or altered ground-water system; then we would quantitatively recover them and analyze for any changes. This will give us a much more realistic idea of what these populations are capable of doing and what their role is in mediating the biogeochemical changes in ions of interest as the ground-water environment changes."

The USGS is leading the way in developing new technologies that will ultimately help manage ground-water resources more effectively. According to Harvey: "Work done in aquifers throughout the country suggests that microbes play important roles in remediating aquifers contaminated by specific compounds. However, they also can mobilize other undesirable constituents, such as arsenic, depending upon the geochemistry of the aquifer." By better understanding these processes, the USGS will be able to advise resource managers about aquifer-remediation techniques and also help regulators determine guidelines for effective ASR practices.

The agenda for the Aquifer Storage and Recovery meeting can be downloaded from URL http://www.agwt.org/events/2006/ASR6Program.pdf (1.2 MB PDF). For more information about the group that organized the meeting, visit the American Ground Water Trust Web site.

Related Web Sites
SOFIA - Greater Everglades Ecosystem Restoration (GEER) Conference
U.S. Geological Survey (USGS)
American Ground Water Trust
non-profit education organization

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Surveying Faults and Sediment Outside San Francisco Bay

Submarine Ground-Water Discharge at Dor Beach, Israel

Outreach Middle-School Students Envision a Future City

Meetings Assessing Microbes in Ground Water

Chinese Delegation Briefed on USGS Science

Restore America's Estuaries Conference

Awards Scuba Scouts Recognize USGS Employees

Publications Estuaries and Coasts Special Issue

March Publications List

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