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SUMMARYThe primary objective of this study was to evaluate the potential environmental effects (both adverse and beneficial) of aquifer thermal energy storage (ATES) technology pertaining to microbial communities indigenous to subsurface environments (i .e., aquifers) and the propagation, movement, and potential release of pathogenic microorganisms (specifical ly, Legionel la) within ATES systems. Seasonal storage of thermal energy in aquifers shows great promise to reduce peak demand; reduce electric utility load problems; contribute to establishing favorable economics for district heating and cooling systems; and reduce pol 1 ution from extraction, refining, and combustion of fossi 1 fuels. However, concerns that the widespread implementation of this technology may have adverse effects on biological systems indigenous to aquifers, as well as he1 p to propagate and re1 ease pathogenic organisms that enter these envi ronments need to be resolved.Groundwaters are habitat to an abundant and diverse microbial population. The activities of these organisms are important to the removal of a variety of hazardous wastes. However, these organisms have only recently been studied, and their full importance is not known at this time. The growth and activity of microorganisms indigenous to aquifers are governed by a variety of environmental factors including: the porosity of the aquifer nutrient avai 1 abi 1 i ty oxidation-reduction conditions PH temperature the adsorption of microorganisms to subsurface particles. Perturbations, due to the implementation of ATES technology, can locally alter these physicochemical factors which can, to an unknown degree, affect the growth and activities of microorganisms inhabiting aquifers.Of the environmental factors 1 isted above, groundwater temperature a1 terations caused by injection of heated or cooled waters during the operation of ATES systems have the greatest potential for altering the types and activities of native microbial communities. Microorganisms, depending on the species, have specific temperature ranges that allow for their growth. If the use of ATES systems alters the temperature of an aquifer beyond the range that supports growth, microbial activity will become dormant or cease. Other ATES-related alterations that can cause changes in the microbial ecology of aquifers include groundwater chemistry (e.g., pH, Eh, solubi 1 ity of minerals) and changes in physical characteristics (e.g., adsorptive to subsurface particles, hydraul ic conductivity). However, the true impact of such changes in the microbial ecology and activity can not yet be assessed. Experience with ATES in other countries, as well as in the U.S., has not indicated major impacts; however, intensive monitoring programs have not been conducted in conjunction with the operation of most systems.In addition to indigenous microbial populations, allochthonous organisms (i .e., organisms foreign to that environment) can survive and grow in aquifers. A1 lochthonous microorganisms detrimental to human health (i .e., ...

The objective of this study by Pacific Northwest Laboratory was to assess the impact that past and potential future discharges of ammoniated water to the 216-A-36B crib have on groundwater and river concentrations of hazardous chemical constituents. Until August 1987, the 216-A-36B crib, located in the 200-East Area of the Hanford Site, accepted ammoniated water discharges. Although this study addresses known hazardous chemical constituents associated with such discharges, the primary concern is the discharge of NH»0H because of its microbiological conversion to NOZ and NOZ. As a result of fuel decladding operations, material balance calculations indicate that NH.OH has been discharged to the 216-A-36B crib in amounts that exceed reportable quantities under the Comprehensive Environmental Response, Compensation and Liability Act of 1980. Although flow to the crib is relatively constant, the estimated NH.OH discharge varies from negligible to a maximum of 10,000 g-moles/h. Because these discharges are intermittent, the concentration delivered to the groundwater is a function of soil sorption, microbiological conversion rates of NH-to N0Z and H0Z, and groundwater dispersion. This report provides results based on the assumptions of maximum, nominal, and discontinued NH,0H discharges to the crib. Consequently, the results + show maximum and realistic estimates of NH-, N0« and NO., concentrations in the groundwater. Because this study shows NH. conversions to N0Z and H0Z to be rapid and complete, predicted concentrations of N0Z in the groundwater caused by NH. discharges to the crib are noticeable. The calculated groundwater concentrations beneath the crib would be 430 mg/L N0Z under maximum yearly average operations and 320 mg/L under conditions representing past operations during fiscal years 1984 through 1987. (For comparison purposes, drinking water standards, although they do not apply because there are no community water systems on the Hanford Site, are 45 mg/L.) These predicted concentrations compare favorably with measured groundwater N0^ concentrations in the vicinity of the crib. Therefore, we conclude that ammoniated water discharges to the 216-A-36B crib have a significant effect on observed N0^ concentrations in the ACKNOWLEDGMENTS The authors wish to express their gratitude to all contributors of this report. Westinghouse Hanford Company provided much of the technical information on decladding and crib operations. Significant contributors from Pacific Northwest Laboratory included Frank Hara and Kris McFadden-analytical support; Kathy Cramer-review of regulations; Barb Denovan-NH.OH conversion studies; Wayne Martin, Clark Lindenmeier, and Stephanie McLaurineadsorption/desorption laboratory work; Virgina LeGore-radionuclide counting; and Paula Heller-sediment physical property measurements.

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