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Potential biogeochemical impacts of heat rejection in the Mullaloo aquifer, Western Australia
Abstract
A rapid biogeochemical assessment protocol has been developed to assess the potential effects of returning heated groundwater to the Mullaloo aquifer in Perth, Western Australia. A multi-disciplinary study encompassed geochemical analysis of the aquifer sediment, and microbiological, organic contaminant and major ion surveys of the groundwater. Geochemical modelling indicates few, if any adverse implications of a proposed 10◦C temperature increase. A potential exists for chemical and biological clogging but this will be minimised by a closed loop design to avoid the introduction of atmospheric oxygen. Nevertheless, the need for regular monitoring of scheme performance and environmental impacts remains.
... Although the impacts are largely undocumented, another increasing use for urban coastal groundwaters is the injection of waste heat derived from cooling systems (Becher et al., 2022 and references therein). Assessments in Australia have been carried out at biogeochemical level (Douglas et al., 2015) but are still in their infancy for stygofaunal communities (Bennelongia, 2015). ...
1. Coastal aquifers are vital water sources for humanity. Their quality and the ecosystem services they provide depend on the integrity of their subterranean biota. However, current anthropogenic impacts such as climate change effects and coastal population growth place enormous pressure on the sustainability of these environments.
2. Despite the significance of subterranean biota to ecosystem function and the delivery of ecosystem services, stygofauna-groundwater-dwelling aquatic animals-have until recently been largely ignored in aquifer monitoring and management. This issue is of importance in both coastal and inland zones. Common threats in inland and coastal areas are water extraction, reduced recharge caused by aridification, and pollution, while, in coastal zones, additional complications arise from sea-level change and salt water ingress.
3. This review examines stygofaunal diversity, impacts, and future conservation challenges in coastal aquifers. Focussing on Australia, we provide a summary of the available data on stygofaunal communities and distributions; identify and describe potential threats to these communities across the diverse coastal regions of the continent; and propose future research priorities with the goal of facilitating the long-term preservation of these ecosystems on the Australian continent. While we focus this review on Australia, the threats and management issues discussed are relevant globally.
4. Recent subterranean studies in Australia have been primarily undertaken in inland areas, and while coastal data exist, ecological assessment of coastal subterranean ecosystems is incomplete, compromising the efficacy of conservation plans. This review indicates that the Australian continent hosts five major coastal stygofaunal biodiversity areas characterised by heterogeneous community assemblages, involving a total of 17 taxonomic groups spanning microscopic.
... A elevação da temperatura de águas subterrâneas pode causar alteração em sua composição química, uma vez que desempenha papel importante na solubilidade de minerais, cinética de reações, oxidação da matéria orgânica, processos redox e sorção de adsorção de ânions e cátions (HOLM et al., 1987;BONTE et al., 2014;BUNDSCHUH & MAITY, 2015;LIE-NEN et al., 2017). Possimiers et al. (2014) e Douglas et al. (2015) verificaram que, para variações de temperatura inferiores a 10ºC, as alterações geoquímicas são negligenciáveis, embora a mistura com água termal possa alterar a qualidade da água subterrânea. Por outro lado, Griebler et al. (2016) e Lienen et al. (2017) demonstraram que elevações significati-Palavras-chave: Isótopos estáveis. ...
Danos no revestimento de um poço do Sistema Aquífero Guarani, localizado no munícipio de Presidente Epitácio (SP), está liberando água quente para o Aquífero Caiuá, aflorante na área. A temperatura da água medida na boca do poço é de 70°C, possuindo propriedades hidroquímicas e isotópicas características. Neste trabalho foram utilizados dados hidroquímicos e de isótopos estáveis, bem como modelos numéricos de fluxo e transporte para avaliar a influência da água termal no aquífero raso Caiuá. Os resultados indicam que as águas subterrâneas nas proximidades do poço de água termal são isotopica e hidroquimicamente similares à água termal do Sistema Aquífero Guarani, possuindo tem-peraturas e características físico-químicas anômalas para o Aquífero Caiuá. As simulações numéricas indicam que a vazão de água quente, a partir do seu local de vazamento, é de aproximadamente 900 m3/dia. Estes resultados indi-cam a existência de fluxo de água quente do poço jorrante de água termal para o Aquífero Caiuá e que a elevação da temperatura de suas águas se restringe a cerca de uma centena de metros em torno do ponto do vazamento.
... Fluorescent microscopy was performed as previously reported (Douglas et al., 2015;Puzon et al., 2009) on 100 mL of the filtrate sample stained with 4 mL of 1 mg/mL DAPI dye (4 0 ,6-Diamidine-2 0 -phenylindole dihydrochloride) (Sigma, USA). Amoebae were observed under fluorescence on a Zeiss Imager microscope (M1 AXIO, Germany), AxioVision Rel. ...
The amoeba Naegleria fowleri is the causative agent of the highly fatal disease, primary amoebic meningoencephalitis, and estimated to cause 16 deaths per year in the United States alone. Colonisation of drinking water distribution systems (DWDSs) by the N. fowleri is a significant public health issue. Understanding the factors which enable this pathogen to colonise and thrive in DWDSs is critical for proper management. The microbial ecology within DWDSs may influence the ability of N. fowleri to colonise DWDSs by facilitating the availability of an appropriate food source. Using biofilm samples obtained from operational DWDSs, 16S rRNA amplicon metabarcoding was combined with genus-specific PCR and Sanger sequencing of intracellular associated bacteria from isolated amoeba and their parental biofilms to identify Meiothermus chliarophilus as a potential food source for N. fowleri. Meiothermus was confirmed as a food source for N. fowleri following successful serial culturing of axenic N. fowleri with M. chliarophilus or M. ruber as the sole food source. The ability to identify environmental and ecological conditions favourable to N. fowleri colonisation, including the detection of appropriate food sources such as Meiothermus, could provide water utilities with a predictive tool for managing N. fowleri colonisation within the DWDS.
... As the operation of an SCW could also promote development of pathogen microorganisms in groundwater, such dual use of SCWs should be permitted only after proving the local drinking water standards are met all year round. Iron bacteria is another possible nuisance of SCW systems (Citernesi et al., 1985; Cahalan-Roach et al., 2010; Douglas et al., 2015) that can clog a well and affect its productivity. If groundwater has naturally low iron concentration, designers should be aware that using steel casing and steel pipes introduces a source of iron that can foster growth of iron bacteria and accumulation of ocherous precipitates. ...
Standing column well (SCW) systems present a strong potential for energy savings, especially in dense urban areas with suitable geological conditions where lack of space constitutes an impediment to the use of closed-loop systems. This chapter aims at presenting some design considerations and recent advancements relative to the thermal, hydraulic, and chemical simulation of SCWs and identifies specific research needs to foster their use. It is shown how a thermal resistance and capacity model can assess the performance of a hybrid system operated under different bleed ratios in a fractured aquifer. Additionally, this chapter shows how to perform coupled thermo-hydrogeochemical simulation to predict the dissolution and precipitation of calcite that occurs along the well as a function of operating conditions. The approach helps to foresee possible operation problems with the SCW and to select suitable mitigation measures to sustain long-term performance of SCW.
... Potential impacts of the GWC system on neighbouring ecosystems are not considered here, but have been assessed as part of regulatory compliance activities , whereas biogeochemical impacts have been addressed by Douglas et al. (2015). While the details of this study relate to a specific system and its corresponding hydrogeology, the findings are of broad interest because this type of GWC system has the potential to be widely applicable in similar urban environments. ...
Groundwater cooling (GWC) is a sustainable alternative to conventional cooling technologies for supercomputers. A GWC system has been implemented for the Pawsey Supercomputing Centre in Perth, Western Australia. Groundwater is extracted from the Mullaloo Aquifer at 20.8 °C and passes through a heat exchanger before returning to the same aquifer. Hydrogeological simulations of the GWC system were used to assess its performance and sustainability. Simulations were run with cooling capacities of 0.5 or 2.5 Mega Watts thermal (MWth), with scenarios representing various combinations of pumping rate, injection temperature and hydrogeological parameter values. The simulated system generates a thermal plume in the Mullaloo Aquifer and overlying Superficial Aquifer. Thermal breakthrough (transfer of heat from injection to production wells) occurred in 2.7–4.3 years for a 2.5 MWth system. Shielding (reinjection of cool groundwater between the injection and production wells) resulted in earlier thermal breakthrough but reduced the rate of temperature increase after breakthrough, such that shielding was beneficial after approximately 5 years pumping. Increasing injection temperature was preferable to increasing flow rate for maintaining cooling capacity after thermal breakthrough. Thermal impacts on existing wells were small, with up to 10 wells experiencing a temperature increase ≥0.1 °C (largest increase 6 °C).
... The absence of clear rules for threshold values is due to the current lack of knowledge concerning quantitative and qualitative impacts of thermal changes on groundwater resources. Therefore, further research is still needed to understand the main factors controlling microbial biodiversity in groundwater (Bonte et al., 2014;Brielmann et al., 2009a,b;Douglas et al., 2015;Ilieva et al., 2014). It has been suggested that the temporal dynamics of subsurface microbial communities may be attributed to anthropogenic temperature fluctuations, but this has not yet been quantified (Danielopol et al., 2003;Griebler and Lueders, 2009;Steube et al., 2009). ...
This study attempts to promote new groundwater thermal management policies for the shallow geothermal energy sector, which is currently at risk of stalling due to the existing uncertainty of its international legal status. The physical constraints affecting groundwater thermal management policies are described as a basis for a later proposal of an approval process protocol for new shallow geothermal installations. The policy proposed for this process is based on numerical modeling and a relaxation factor which reserves a fraction of shallow geothermal energy resources for possible third party installations thus preventing its monopolization. The policy is then applied to simulate a concession process in a real urban groundwater body highly affected by ground source heat pumps. A calibrated numerical groundwater flow and heat-transport model has been utilized for the evaluation of the thermal response of the aquifer to a new projected installation and the thermal interference risk associated. The results obtained from the protocol application have proven its practical value in the sustainable management of shallow geothermal energy resources and in ensuring stakeholders water rights. In addition, a specific policy impact indicator was derived that should be of interest for numerical water policy assessment initiatives.
Alleviating bacterial-induced clogging is of great importance to improve the efficiency of managed aquifer recharge (MAR). Enzymes (lysozyme and alkaline protease) and sodium hypochlorite (NaClO) are common biological and chemical reagents for inhibiting bacterial growth and activity. To investigate the applicability of these reagents to reduce bioclogging, percolation experiments were performed to simulate a weak alkaline recharge water infiltration through laboratory-scale sand columns, with adding 10 mg/L lysozyme, alkaline protease, and NaClO, respectively. The results showed that, with the addition of lysozyme, alkaline protease, and NaClO, the average clogging rates (the reduced percentages of relative saturated hydraulic conductivity of the sand columns per hour during the percolation experiments) were 0.53%/h, 0.32%/h and 0.06%/h, respectively, which were much lower than that in the control group (0.99%/h). This implied that bioclogging could be alleviated to some extent following the treatments. For further analyzing the mechanisms of the regents on alleviating bioclogging, the bacterial cell amount and extracellular polymeric substances (EPS) concentration were also measured to study the effects of lysozyme, alkaline protease, and NaClO on bacterial growth and EPS secretion. Lysozyme and alkaline protease could disintegrate bacterial EPS by hydrolyzing polysaccharides and proteins, respectively, while they had little effect on the bacterial cell amount. The addition of NaClO significantly decreased the bacterial cell amount (P < 0.05) and thus greatly alleviated bioclogging. Although the lowest average clogging rate was achieved in the NaClO group, it can generate disinfection by-products that are potentially harmful to the environment and human health. Therefore, the biological-based method, i.e., enzyme treatment, could be a promising option for bioclogging control. Our results provide insights for understanding the mechanisms of lysozyme, alkaline protease, and NaClO to alleviate bioclogging, which is of great importance for addressing the clogging problem during MAR activities and achieving groundwater resources sustainable utilization.
We present an overview of the risks that underground thermal energy storage (UTES) can impose on the groundwater system, drinking water production, and the subsurface environment in general. We describe existing policy and licensing arrangements for UTES in the Netherlands, as well as the capability of the current and future Dutch policy and legal framework to minimize or mitigate risks from UTES on groundwater resources. A survey at the European Union member state level indicates that regulation and research on the potential impacts of UTES on groundwater resources and the subsurface environment often lag behind the technological development of and ever-growing demand for this renewable energy source. The lack of a clear and scientifically underpinned risk management strategy implies that potentially unwanted risks might be taken at vulnerable locations such as near well fields used for drinking water production, whereas at other sites, the application of UTES is avoided without proper reasons. This means that the sustainability of UTES as a form of renewable energy is currently not fully understood, and the technology may be compromising the natural resilience of the subsurface environment. We recognize three main issues that should be addressed to secure sustainable application of UTES: Scientific research is required to further elucidate the impacts of UTES on groundwater; cross-sectoral subsurface planning is required to minimize negative conflicts between UTES and other subsurface interests; and EU-wide guidelines and standards are required for quality assurance and control when installing UTES systems.
The use of shallow geothermal energy (SGE) systems to acclimatize buildings has increased exponentially in the Netherlands and worldwide. In certain areas, SGE systems are constructed in aquifers also used for drinking water supply raising the question of potential groundwater quality impact. This PhD thesis investigated this question with field and laboratory experiments, and reactive transport models. The results showed SGE systems can influence groundwater quality in a number of ways. Most prominent in low temperature (<20°C) systems is the physical mixing of deep and shallow groundwater of different quality distorting the natural water quality stratification in aquifers. At temperature of 25°C and beyond certain trace elements were observed to mobilize in laboratory experiments, and beyond 40°C redox conditions changed significantly while the microbial community shifted towards a thermophilic community. Based on the results of this research, guidelines are presented for monitoring and permitting of SGE systems.
To determine the effects of land use on groundwater quality in Western Australia, a quantitative analysis is carried out using groundwater quality data supplied by the Department of Water from over 500 groundwater wells across the Perth metropolitan area. We analyzed four main groundwater quality indicators; nutrients, physical parameters, inorganic non metals and trace metals. We found that groundwater beneath agricultural land was found to be particularly susceptible to nutrient loading due to the application of fertilizers. Nutrient levels were found to be rising over time due to increasing agriculture and urban development. Industrial ar-eas were also found to have numerous contamination plumes that continue to migrate with the groundwater flow. According to Australian and New Zealand Environment and Conservation Council (ANZECC) guide-lines and the Australian Drinking Water Guidelines (ADWG), several areas including rural areas like Cara-booda lake, Gnangara and Jandakot Mounds, Cockburn Sound, Forrestdale, Joondalup, and Ellenbrook and high density urban areas like Balcatta and Neerabup, industrial areas like North Fremantle, Welshpool and Kwinana are indentified as the vulnerable areas for groundwater quality.
Two issues arise in the long-term use of groundwater for thermal purposes: (1) the sustainability of an individual system; and (2) the effect of neighbouring systems on each other. Both of these effects are observed in an area of the Carbonate Rock Aquifer beneath Winnipeg in Manitoba, Canada, where groundwater has been exploited in thermal applications since 1965. In this area, there are four systems that utilize groundwater for cooling purposes that are closely spaced. The current temperatures observed in this area of the Carbonate Rock Aquifer and the results of the numerical modeling conducted in this study confirm that in each system, temperatures at the production well have risen as a result of breakthrough of injected water. The results of numerical modeling also indicate that interference effects are present in three of the four systems examined in this study. The influence of these systems on each other implies that these systems have a spacing that is smaller than the optimum spacing for such systems, and indicates that there is a limit to the density of development that can occur in a given aquifer.
Groundwater in the Gwelup groundwater management area in Perth, Western Australia has been enriched in As due to the exposure of pyritic sediments caused by reduced rainfall, increased groundwater abstraction for irrigation and water supply, and prolonged dewatering carried out during urban construction activities. Groundwater near the watertable in a 25–60 m thick unconfined sandy aquifer has become acidic and has affected shallow wells used for garden irrigation. Arsenic concentrations up to 7000 μg/L were measured in shallow groundwater, triggering concerns about possible health effects if residents were to use water from household wells as a drinking water source. Deep production wells used for public water supply are not affected by acidity, but trends of progressively increasing concentrations of Fe, SO4 and Ca over a 30-a period indicate that pyrite oxidation products extend to the base of the unconfined aquifer. Falling Eh values are triggering the release of As from the reduction of Fe(III) oxyhydroxide minerals near the base of the unconfined aquifer, increasing the risk that groundwater used as a drinking water source will also become contaminated with high concentrations of As.
The deep (>10 km) Permian to present day Perth Basin in southwest Western Australia is composed of sedimentary successions of continental to shallow marine origin. This study examines the compositional variation, weathering and provenance of the early Cretaceous Leederville Formation within the Perth Basin. Over 200 sediment samples were retrieved from two deep boreholes of similar to 350 to 530 m in depth encompassing the Leederville Formation, and analysed for major and trace element geochemistry and mineralogy. The Leederville Formation is composed of subarkosic sands, predominantly composed of quartz (64%) and K-feldspars (27%); silts and clays composed of kaolinite (24-54%), K-feldspars (20-29%) and quartz (18-40%), with their compositional variation reflecting weathering, hydraulic sorting during transport, mostly subaqueous deposition and subsequent diagenesis. Most trace elements are associated with fine grained lithologies due to their occurrence within clays, sulphide or zircon. Major and trace element geochemistry suggests a typical passive margin origin with minimal intrabasinal sediment recycling. The regionally extensive Yilgarn Craton, appears to be the main sediment source for the Leederville Formation within the study area.
We used data from an aquifer thermal energy storage (ATES) system located 570 m from a public water supply well field in the south of The Netherlands to investigate the relation between production of renewable energy with an ATES system and the production of drinking water. The data show that the groundwater circulation by the ATES system can impact chemical groundwater quality by introducing shallow groundwater with a different chemical composition at greater depth. However, the observed concentration changes are sufficiently small to keep groundwater suitable for drinking water production. Microbiological results showed that the ATES system introduced faecal bacteria in the groundwater and stimulated the growth of heterotrophic micro-organisms. At the studied site this forms no hygienic risk because of the long distance between the ATES wells and the public supply well field A further degradation of either chemical or microbiological groundwater quality however may necessitate additional water treatment which raises the energy requirements. The additional energy requirements for drinking water treatment may be up the same order of magnitude as the harvested energy by the ATES system.
Eight strains of spore-forming, sulfate-reducing bacteria, isolated from groundwater contaminated with motor fuel [mostly benzene, toluene ethylbenzene and xylene (BTEX) compounds] in sandy soil near Perth, Australia, were closely related to Desulfosporosinus (previously Desulfotomaculum) orientis DSM 765T (95.3-97.3% 16S rDNA sequence similarity). Whole-cell fatty acids were dominated by even-carbon, straight-chain saturated and mono-unsaturated fatty acids, in particular 16:0, 16:1cis9, 14:0 and 18:1cis11. The strains grew at temperatures between 4 and 42 degrees C and in medium containing up to 4% NaCl. The eight strains clustered into two main groups based on phylogeny, randomly amplified polymorphic DNA (RAPD)-PCR patterns and nutritional characteristics. Representatives of the two groups, strain S5 (group A) and strain S10T (group B) had 81% DNA-DNA homology with each other and therefore should be accommodated in the same species. Strain S10T had less than 38% homology with Desulfosporosinus orientis DSM 765T, the most closely phylogenetically related type strain available. The new strains were distinguished from Desulfosporosinus orientis DSM 765T by different banding patterns in a RAPD-PCR, and phenotypically by their inability to utilize fumarate as a carbon and energy source with sulfate as the electron acceptor and by their lower tolerance to NaCl. The DNA G+C contents were 46.8 and 46.9 mol% for strains S5 and S10T, respectively (Desulfosporosinus orientis DSM 765T 45.9 mol%). It is proposed that these new strains be placed in a new species of the genus Desulfosporosinus. The name Desulfosporosinus meridiei is proposed, with strain S10T as the type strain (= DSM 13257T = NCIMB 13706T).
To investigate the biomass and phylogenetic diversity of the microbial community inhabiting the deep aquifer of the Great Artesian Basin (GAB), geothermal groundwater gushing out from the aquifer was sampled and analyzed. Microbial cells in the groundwater were stained with acridine orange and directly counted by epifluorescence microscopy. Microbial cells were present at a density of 10(8)-10(9) cells per liter of groundwater. Archaeal and bacterial small-subunit rRNA genes (rDNAs) were amplified by PCR with Archaea- and Bacteria-specific primer sets, and clone libraries were constructed separately. A total of 59 clones were analyzed in archaeal and bacterial 16S rDNA libraries, respectively. The archaeal 16S rDNA clones were divided into nine operated taxonomic units (OTUs) by restriction fragment length polymorphism. These OTUs were closely related to the methanogenic genera Methanospirillum and Methanosaeta, the heterotrophic genus Thermoplasma, or miscellaneous crenarchaeota group. More than one-half of the archaeal clones (59% of total 59 clones) were placed beside phylogenetic clusters of methanogens. The majority of the methanogen-related clones (83%) was closely related to a group of hydrogenotrophic methanogens (genus Methanospirillum). The bacterial OTUs branched into seven phylogenetic clusters related to hydrogen-oxidizing thermophiles in the genera Hydrogenobacter and Hydrogenophilus, a sulfate-reducing thermophile in the genus Thermodesulfovibrio, chemoheterotropic bacteria in the genera Thermus and Aquaspirillum, or the candidate division OP10. Clones closely related to the thermophilic hydrogen-oxidizers in the genera Hydrogenobacter and Hydrogenophilus were dominant in the bacterial clone library (37% of a total of 59 clones). The dominancy of hydrogen-users strongly suggested that H(2) plays an important role as a primary substrate in the microbial ecosystem of this deep geothermal aquifer.
A 3-D numerical model was developed to simulate the distribution characteristics and influencing factors on geo-temperature field of groundwater heat pump. Analyzing from different soil layers, different permeability, different porosity, different inter-well distances, and different aquifer thickness, temperature distribution characteristics and variations of pumping temperature were gotten. Base on those, permeability and different porosity produce little effect to the temperature of pumping, different inter-well distances and different aquifer thickness produce great effect to the temperature of pumping.
The changes in the concentrations of Ca, dissolved silica, and alkalinity of the recovery waters of four short-term aquifer thermal energy storage test cycles with respect to the injection waters and the correlation of these concentrations with recovery water temperatures indicate that quartz and calcite dissolved during hot water storage. This hypothesis was supported by chemical equilibrium modeling and mass balance calculations. Magnesium concentrations were lower in recovery waters than in injection waters. Chemical equilibrium modeling indicated that a Mg silicate (talc) could have precipitated. Potassium concentrations correlated well with temperatures, probably because of ion exchange involving potassium feldspars in the aquifer.
Heating of calcite-saturated groundwater induces no precipitation to thermodynamic equilibrium with respect to end-member Ca-carbonates. Column experiments, using native groundwater and aquifer sediment, were performed to study the controlling factors in the kinetics of carbonate precipitation for a natural system by injection of groundwater in a sediment core at 90°C. The temperature increase induced a fast precipitation of a CaFe-carbonate, containing Mn and phosphate, and a CaMgFe-carbonate, containing Mn, within at most 10 h. Both precipitates varied in composition and were partly amorphic, partly crystalline. Prolonged precipitation, after almost all Fe[II] had been removed, was extremely slow despite a twelve-fold supersaturation with respect to end-member calcite. The resulting supersaturation cannot be explained by either calcite precipitation kinetics, Mg-inhibition, Mg-calcite solubility control, or Ca-organic acid complexing, because these factors may explain a two-fold supersaturation at most. The maintenance of supersaturation is attributed to inhibition of precipitation by phosphate and/or organic acids. The influence of secondary reactions, as cation-exchange and silicate weathering, is of minor importance on the carbonate chemistry. Cation-exchange was observed in the initial stages of heated water injection. Potassium, NH4 and Fe become desorbed upon temperature increase. Related Ca-adsorption is insufficient to avoid Ca-carbonate precipitation. Weathering of silicates occurs continuously and leads to the release of Na, Ca and Mg.
Ground water chemistry was monitored during a test of the feasibility of long-term (180-day) aquifer thermal energy storage. From a source well 92,100 m/sup 3/ of ground water was pumped, heated (110/sup 0/C), and injected into the aquifer consisting primarily of quartz sandstone, with lesser amounts of dolomite, feldspar, and clay minerals. Softening the water prior to heating effectively prevented mineral precipitation in the heat exchanger and injection well. Recovered water was saturated with respect to quartz, dolomite, and calcite, which indicates that quartz, dolomite, and calcite dissolved during aquifer storage. Loss of sodium in the aquifer is thought to result from mixing of ambient ground water (up to 27%) with heated, injection water. Upon subsequent cycles, softening requirements are expected to decrease, and less mineral dissolution is expected to occur during aquifer storage, resulting in negligible changes in the hydraulic characteristics of the aquifer.
Storage of thermal energy in aquifers has obvious benefits of saving energy and decreasing the consumption of fossil fuels. However, aquifer thermal energy storage (ATES), which involves groundwater aquifers as the storage medium for heat or chill, impinges on the environment. A literature review of pertinent microbiology publications (Hicks and Stewart, 1988) identified the potential for the interaction of ATES systems and microbiological processes to create a source of infectious diseases and the potential for damage to the environment. In addition, the review identified a potential for microbiological processes to develop conditions that would interfere with the operation of an ATES system. As a result of this research effort, investigators from Finland, Germany, Switzerland, and the United States have examined several ATES systems in operation and have observed that the ATES systems studied do not contribute to infectious disease transmission, do not adversely affect the environment, and do not contribute significantly to biofouling or biocorrosion.
Aquifer Thermal Energy Storage (ATES) Systems are used to store thermal energy seasonally, mainly for the provision of room heat and cold in buildings. According to the underground temperature-hydrologic flow coupled processes (TH) and Canada BORDEN storage energy test data, Building a TOUGH numerical model verifies the coupled processes of the mechanism in ATES. Results of the simulations appear to match the observed data well within 1°C. Besides, a practical commercial building in Shenyang on Groundwater Source Heat Pump (GWHSP) is simulated. Some problems, such as the variation and heat through of aquifer's temperature field in 3 years and multi-wells interference and so on are analyzed and predicted. By combination of investigation data and the application of numerical models leads to a performance -enhancing design.
The five liquid-dominated geothermal fields under production in Japan (Otake, Onuma, Onikobe, Hatchobaru, and Kakkonda) represent more than half the liquid dominated fields now in production worldwide. All five have total liquid reinjection programs. and thus collectively represent a major fraction of all full-scale water reinjection operations in the world. The implications of the Japanese reinjection experience are therefore of extreme importance to future liquid-dominated geothermal development. The major impact of the experience in these fields is that, with the exception of Otake, the reinjection wells show a rapid interference with the production wells. In most cases, the reinjected water travels to the production zone within a very short time, and there is consequently a discernible thermal drawdown. Tracer tests in most of the fields indicate flow paths of very high permeability, probably along fractures. For this reason, resource estimates based on assessed total reservoir volume are likely to be gross overestimates of the producible energy. The Japanese industry has made considerable advances in the determination of this kind of behavior, and their results suggest that the current geothermal reservoir concepts need some rethinking.
Introduction
Reinjection of water into geothermal reservoirs during utilization is intended to serve the dual purposes of waste water disposal and improved resource recovery. To assess the relative importance of these two purposes accurately, note that reservoir maintenance by reinjection is a controversial subject, and, in actual field cases to date, water has been reinjected solely for disposal purposes. Currently reinjection is a method of water disposal, and consideration of reservoir maintenance by reinjection is restricted largely to avoiding detrimental effects.
Commercial-scale reinjection in geothermal power plants has been practiced at The Geysers, CA; Ahuachapan, El Salvador; Mak Ban, the Philippines; and in five Japanese fields-Otake, Onuma, Onikobe, Hatchobaru. and Kakkonda. With the exception of The Geysers, all these fields are liquid-dominated, with producing steam/water ratios between 1:2 and 1:6. Liquid dominated geothermal utilization represents the most difficult configuration for reinjection since the quantity of hot water to be disposed of is greater than those of steam-dominated geothermal or conventional thermal generation systems. Since almost all future geothermal utilizations will be of the liquid-dominated type, it is important to evaluate current reinjection experience in this type of system. For example, power stations under construction or planning with definite commitments to reinject waste water include East Mesa, Heber, and Brawley, CA; Raft River, ID, Tongonan, the Philippines; Broad lands, New Zealand; and Nigorikawa, Japan. In addition, reinjection has been suggested for existing power stations at Cerro Preto, Mexico; Tiwi, the Philippines; and Wairakei, New Zealand.
In terms of its principal role as a waste disposal mechanism, reinjection is clearly a greater problem when the quantity of water to be reinjected (relative to the useful steam produced) is larger. However, there are additional constraints on the physical characteristics of the injected water. Because of dissolved solid deposition effects, the temperature of the injected water is a critical parameter. Thus the evaluation of a reinjection scheme needs to consider the quality, temperature, and chemical nature of the water to be injected.
The supposed benefits of reinjection to the reservoir itself usually are attributed to the maintenance of reservoir pressure and mass of fluid in place. In theory, maintaining high reservoir pressures and mass in place should reduce the effects of loss of deliverability, and also those of subsidence or formation collapse.
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Multi-element analysis of ferruginous nodules and pisoliths from lateritic residuum, derived lag and ferruginous gravel, selected from locally derived colluvium (laterite) sampled at an approximate 9 km interval (triangular grid) over the western Yilgarn Craton, shows regional geochemical trends, major lithologies and dispersion halos around significant bedrock mineralization. The sample density (one sample per 60-100 km(2), depending on sample availability) and extent of the coverage (c. 400 000 km, including large unsampled areas in drainage) mean that the data are potentially valuable for both exploration and environmental purposes. More than 3100 samples have been analysed for 53 elements by XRF, ICP-AES and ICP-MS, with selected samples also analysed for PGE. Elevated Au abundances in the NE of the survey area not only cluster around known gold deposits but extend beyond them, indicating the likelihood of more widespread mineralization in these areas. A chalcophile element index illustrates potential for Au and base metal mineralization in the westernmost part of the Yilgarn Craton, whereas a pegmatophile index shows a regional NW trend parallel to regional structures. Abundant chromium in granite-dominated areas might indicate mafic-ultramafic remnants (some with anomalous Au) beyond known greenstone belts. A newly discovered regional Hg anomaly trends NW for more than 500 km. Anomalous As, Bi, Mo and Sb along the southern margin of the craton may be related to Au mineralization. The spatial and geochemical consistency of the dataset means that it is well suited to multivariate statistics.
Yellow sands in the near‐coastal parts of the Swan Coastal Plain of the Perth region are of residual origin, developed from the weathering of Tamala Limestone. An alternative hypothesis that they were emplaced from a vast extension of sand dunes from the Central Australian Desert, is not supported. Samples collected mainly from the upper B‐horizon of the yellow sands, along a series of east‐west transects, have been studied mineralogically. A ‘maturity index’ was devised to compare the combined percentages in the heavy‐mineral fraction of ilmenite plus leucoxene against the combined percentages of three minerals which weather away rapidly from the soils, namely garnet, amphibole and epidote. The results reveal a pronounced east‐west zonation, ranging from a distinctive ‘young’ assemblage on dune ridges near the coast to an ‘old’ assemblage depleted in the three silicate minerals in areas further inland. Used in conjunction with geomorphic features this zonation has facilitated a subdivision of the Spearwood Dune System into several dune subsystems, named herein as the Trigg, Karrinyup, Gwelup, Balcatta and Yokine Dunes, plus a dune subsystem along the western edge of the Bassendean Dune System defined herein as the Gnangara Dunes.
The use of geothermal energy for space heating and the production of electricity is currently limited to a small number of regions around the world with exceptionally high geothermal gradients [Kruger and Otte, 1973]. Geothermal space heating or air conditioning can also be used, however, in regions with normal temperature gradients if it is possible and economically feasible to drill a well deep enough to reach an aquifer with adequate water temperature. Aquifers at depths of the order of 2000 m have already been used for space heating [Maugis, 1971] and were found suitable with the current spaceheating technology. Other heating processes should permit the use of much shallower formations. Free surface aquifers can also be used for air cooling, or even for space heating, by means of heat pumps. With the energy crisis and increasing fuel prices, aquifers may thus become a very important source of heat energy. Disposal of the heat-depleted water, however, may often be a problem because of the mineral contents, the temperature, or the volumes involved, all of which would prevent the water from being wasted into sewage lines. One solution consists of reinjecting the water back into the aquifer. This procedure maintains the reservoir pressure, prevents subsidence, and insures an indefinite supply of water. It also permits the recovery of the heat contained in the rock, but as a result it creates a zone of injected water around each injection well at a different temperature from that of the native water. These zones will grow with time and will eventually reach the production wells. After breakthrough occurs, the water temperature is no longer constant at the production wells, and this may reduce drastically the efficiency of the whole operation. It is thus important to design such a system in order to prevent injected water breakthrough before a specified time and to maintain the temperature variations at the production wells after breakthrough within reasonable limits. Although a few authors have considered a similar problem for a single recharging-discharging well pair [Houpeurt et al., 1965; Lagarde and Maugis, 1966], no general theory has been published to date. It is the purpose of this paper to develop a mathematical model for investigating the non-steady state temperature behavior of production wells during the reinjection of heat-depleted water into aquifers with uniform regional flow. Results are presented in terms of dimensionless parameters and should be helpful for the design of such systems. Our discussion will be based on an analytical model. A rectilinear system is placed such that the x, y plane coincides with the midplane of the aquifer. A few simplifying assumptions that are usual in this type of problem are made. These are listed below and will be discussed later. 1. The aquifer is assumed to be horizontal and of uniform thickness h. The cap rock and the bedrock, above and below the aquifer, are impermeable to flow and of infinite extent in the vertical direction. The system is thus symmetrical with respect to the midplane of the aquifer. 2. Flow is assumed to be steady, since the duration of the transient flow period is short in comparison with the length of time required to reach thermal equilibrium. The total injection rate Q is constant and equal to the total production rate. All wells fully penetrate the aquifer. The flow field due to the recharging and discharging wells is superimposed on a natural system of areal parallel flow of Darcy velocity V0, whose orientation is at an angle a with the x axis, as measured counterclockwise from that axis. 3. Initially, the water and rock in the aquifer and the cap rock and bedrock are at the same temperature To. (Actually, the cap rock and bedrock temperatures are neither identical nor uniform initially, because of the geothermal gradient, but this fact can be neglected, since we only consider temperature perturbations.) At time t = 0 the temperature of the injected water is set equal to Tt and is maintained constant thereafter. Thermal equilibrium is supposed to take place instantaneously between the water and the rock in the aquifer, so that anywhere in the aquifer the rock has the same temperature as the
Equations are derived for predicting the chemical and thermodynamic consequences of irreversible reactions among minerals and aqueous solutions as a function of time and surface area, and interpreted in terms of transition-state theory. The general rate-law formulated is consistent with experimental data and is applicable both near and far from overall equilibrium.-M.S.
Numerous potassium-argon ages have been determined on a variety of rocks from the Altiplano of Bolivia with the intent of providing data on the three following problems: (a) ages of the batholiths that intrude early Paleozoic sedimentary rocks along the Cordillera Real and Quimza Cruz; (b) ages of ore mineralization from Sorata to Potosi; and (c) stratigraphic relations and ages within the thick, largely nonfossiliferous Tertiary deposits of the Altiplano Basin. It is shown that all batholithic masses north of Illimani are of Triassic-Jurassic age as is the tin mineralization found within the rocks. Illimani and all major intrusions to the south as far as the Kari Kari batholith have ages of 19 to 26 m.y. Ore mineralization as young as late Pliocene or early Pleistocene is shown to exist. Volcanic rocks within the Tertiary deposits, together with extensive field mapping by the Geologic Survey of Bolivia, are adequate to allow elucidation of the major features of, and stratigraphic correlations within, the Tertiary deposits.
Previous studies on the geochemistry of a shallow unconfined aquifer contaminated with hydrocarbons suggested that the degradation of some hydrocarbons was linked to bacterial sulphate reduction. There was attenuation of naphthalene, 1,3,5-trimethylbenzene (TMB), toluene, p-xylene and ethylbenzene in the groundwater with concomitant loss of sulphate. Here, the recovery of eight strains of sulphate-reducing bacteria (SRB) from the contaminated site is reported. All were straight or curved rod-shaped cells which formed endospores. Amplification and sequencing of the 16S rDNA indicated that the strains were all sulphate reducers of the Gram-positive line of descent, and were most closely related to Desulfosporosinus (previously Desulfotomaculum) orientis DSM 8344 (97–98·9% sequence similarity). The strains clustered in three phylogenetic groups based on 16S rRNA sequences. Whole cell fatty acid compositions were similar to those of D. orientis DSM 8344, and were consistent with previous studies of fatty acids in soil and groundwater from the site. Microcosms containing groundwater from this aquifer indicated a role for sulphate reduction in the degradation of [ring-UL-14C]toluene, but not for the degradation of [UL-14C]benzene which could also be degraded by the microcosms. Adding one of the strains that was isolated from the groundwater (strain T2) to sulphate-enriched microcosms increased the rate of toluene degradation four- to 10-fold but had no effect on the rate of benzene degradation. The addition of molybdate, an inhibitor of sulphate reduction, to the groundwater samples decreased the rate of toluene mineralization. There was no evidence to support the mineralization of [UL-14C]benzene, [ring-UL-14C]toluene or unlabelled m-xylene, p-xylene, ethylbenzene, TMB or naphthalene by any of the strains in pure culture. Growth of all the strains was completely inhibited by 100 mol l−1 TMB.
The familiar model for determining the optimal ordering strategy, given an announced price increase, assumes that the buyer has an opportunity to place an order at the end of the next economic order quantity cycle before the price increase takes effect. This paper extends the price increase model by relaxing the requirement on the timing of the price increase. Specifically, we develop optimal ordering strategies for situations where the price increase becomes effective at any future specified time. We also calculate savings for alternate ordering strategies.
Because of the current environmental requirements for zero discharge from power plants and scarcity of water, the cooling tower—a proven and industry-recognized conventional option for combined cycle application heat sinks—is being scrutinized by designers, developers, operators, and regulatory agencies. This paper is a guideline to selecting the most appropriate solution for the plant heat sink based on water availability, site location, and wastewater disposal requirements. The paper discusses wet as well as dry cooling systems and evaluates the impact of heat sink selection for cogeneration applications and merchant power plant cycling operation mode. For each proposed option, the performance, relative costs, and noise issues will be presented.
The impacts of re-injection of geothermal waste waters on the physico-chemical characteristics of the fluids of the Larderello vapour-dominated geothermal field in Tuscany (Italy) were monitored using deuterium and oxygen-18 as 'natural' tracers. The observed variations were due mainly to mixing between the re-injected and deep components. Large isotopic fractionations occur at depth during the evaporation of the re-injected water in the reservoir and may affect the evaluation of the recovered fluid using a simple mixing model. Stable isotope and gas/steam ratios are closely correlated in the fluid collected from the monitored wells. Maps showing the isotopic distribution of the steam and the distribution of the gas content have been generated for the whole Larderello geothermal field. Evaluation of data collected before and after re-injection reveals a good distinction between natural inflow induced by exploitation, and artificial recharge with waste fluid. Gases other than N 2 in the wells affected by injection are substantially diluted since condensates are formed by evaporation. Isotopic variations of H 2, CH 4, and CO 2 have been used to describe the disequilibrium conditions among gas components. This disequilibrium is induced by the settling of a liquid plume at the producing level in the reservoir.
The subsurface flow and hydrogeothermal simulation system SHEMAT (Bartels, J., Kuhn, M., Pape, H., Clauser, C., 2000. A new aquifer simulation tool for coupled flow, heat transfer, multi-species transport and chemical water-rock interactions. In: Proceedings World Geothermal Congress 2000, Kyushu – Tohuku, Japan, May 28 – June 10, pp. 3997–4002) is used to investigate a typical hydrothermal sandstone reservoir situated in the North German Basin. This study focuses on the prediction of long-term behavior of reservoir properties for the entire operation time with reinjection during heat exploitation for district heating. The Stralsund location in NE Germany and the Detfurth sandstone horizon (Buntsandstein) are chosen due to the combination of its already confirmed geothermal potential and the availability of a complete data set. An installation of two production wells and one well for reinjection implements heat exploitation. Reinjection is required due to high salinity of the water. In order to quantify injectivity changes and allow the separation of thermal from chemical effects, changes in the hydraulic parameters of the reservoir are at first studied without chemical reactions. Reinjection of cooled water of higher viscosity than the natural reservoir fluid leads to a continuous reduction of the injectivity. This effect is partially balanced by thermally induced mineral reactions. Dissolution of anhydrite in the vicinity of the injection well dominates the effect of anhydrite precipitation at the propagating thermal front leading to a net increase of injectivity. Observed calcite precipitation around the injection well and dissolution at the thermal front are too small to alter reservoir properties significantly. Coupled numerical simulation indicates that the injectivity of the reservoir is influenced primarily by the viscosity effect, but that mineral reactions weaken this negative trend. Operation of a geothermal heating plant at the Stralsund location would not be restricted by a long-term reduction in the injectivity of the reinjection well.
This book describes the composition of the present upper crust, and deals with possible compositions for the total crust and the inferred composition of the lower crust. The question of the uniformity of crustal composition throughout geological time is discussed. It describes the Archean crust and models for crustal evolution in Archean and Post-Archean time. The rate of growth of the crust through time is assessed, and the effects of the extraction of the crust on mantle compositions. The question of early pre-geological crusts on the Earth is discussed and comparisons are given with crusts on the Moon, Mercury, Mars, Venus and the Galilean Satellites.
Heavy minerals are mined from two Cainozoic fossil strandlines in the southern Perth Basin. These arcuate, sub-parallel shorelines are situated on the Swan Coastal Plain, and are remote from the modern coast. The Capel shoreline is located 7 km inland and the Yoganup shoreline, 15 km inland, is adjacent to the arcuate-northwest facing Whicher Scarp, at the southern boundary of the plain. In the Yoganup shoreline, high-energy beach environments have concentrated heavy minerals by reworking sand from the Lower Cretaceous Leederville Formation. Heavy minerals were deposited in thin, shallowing-upward sequences along wave-dominated, eroding shorelines cut into pre-Cainozoic sediments.
The following notes on the laterites of Western Australia are the outcome of a careful study of the series of articles contributed to the Geological Magazine during the latter part of 1911 by Dr. L. Leigh Fermor, entitled “What is Laterite?” These deal with the subject from the point of view of one having an intimate knowledge of Indian laterite, but not a first-hand acquaintance with those of other parts of the world. The present writer, during the last fifteen years, has devoted much time to the study of the laterite of extratropical Western Australia, both in the field and in the laboratory, and is therefore in a position to supplement some of the work of Dr. Fermor, whilst inclined to differ from him in some of his deductions.
We investigated microbial methanogenesis and community structure based on 16S rRNA gene sequences from a coal seam aquifer located 843–907 m below ground level in northern Japan; additionally, we studied the δ13C and δ2H (δD) of coal-bed gases and other physicochemical parameters. Although isotopic analysis suggested a thermocatalytic origin for the gases, the microbial activity and community structure strongly implied the existence of methanogenic microbial communities in situ. Methane was generated in the enrichment cultures of the hydrogenotrophic and methylotrophic microorganisms obtained from coal seam groundwater. Methanogen clones dominated the archaeal 16S rRNA gene libraries and were mostly related to the hydrogenotrophic genus Methanoculleus and the methylotrophic genus Methanolobus. Bacterial 16S rRNA gene libraries were dominated by the clones related to the genera Acetobacterium and Syntrophus which have a symbiotic association with methanogens. LIBSHUFF analysis revealed that N2 gas injected into the coal seam (for enhanced methane production) does not affect the coverage of archaeal and bacterial populations. However, amova analysis does provide evidence for a change in the genetic diversity of archaeal populations that are dominated by methanogens. Therefore, N2 injection into the coal seam might affect the cycling of matter by methanogens in situ.
In this study we deal with the methods and applications of describing, assessing and using thermal energy storage systems, as well as economical, energy conservation and environmental aspects of such systems. The energetic and environmental impacts of thermal energy storage (TES) systems are discussed and highlighted with a number of illustrative examples. The main emphasis is laid on sensible TES, since it is internationally accepted as the most economical and practical energy storage technique. An energy and exergy modelling is presented for TES systems as a key component in the above-mentioned aspects. Illustrative examples are also given to practically demonstrate how exergy analysis provides a more realistic and meaningful assessment than the conventional energy analysis of the efficiency and performance of a sensible heat storage system. It is believed that the results will be useful to engineers and designers seeking to improve and optimize TES systems. Copyright © 2002 John Wiley & Sons, Ltd.
The performance of the ATES (aquifer thermal energy storage) system primarily depends on the thermal interference between warm and cold thermal energy stored in an aquifer. Additionally the thermal interference is mainly affected by the borehole distance, the hydraulic conductivity, and the pumping/injection rate. Thermo-hydraulic modeling was performed to identify the thermal interference by three parameters and to estimate the system performance change by the thermal interference. Modeling results indicate that the thermal interference grows as the borehole distance decreases, as the hydraulic conductivity increases, and as the pumping/injection rate increases. The system performance analysis indicates that if η (the ratio of the length of the thermal front to the distance between two boreholes) is lower than unity, the system performance is not significantly affected, but if η is equal to unity, the system performance falls up to ∼22%. Long term modeling for a factory in Anseong was conducted to test the applicability of the ATES system. When the pumping/injection rate is 100 m3/day, system performances during the summer and winter after 3 years of operation are estimated to be ∼125 kW and ∼110 kW, respectively. Therefore, 100 m3/day of the pumping/injection rate satisfies the energy requirements (∼70 kW) for the factory.
This paper presents and reviews the processes responsible for the distribution and formation of regolith and associated landscapes of the Yilgarn Craton and highlights their implications for mineral exploration. It provides an analysis of regolith geology investigations that were conducted in many districts of contrasting contemporary geomorphic and climatic conditions. The Yilgarn Craton is composed of Archaean rocks, predominantly granitoids, that are crossed by north-northwest-trending belts of greenstones. It has an arid to humid climate at present. The gently undulating landsurface forms a partial etchplain and the topography is largely related to bedrock lithologies and a complex history of valley development and aggradation. Deep weathering has affected most lithologies and geological provinces across the craton. The depth of the weathered mantle may be as much as 150 m, but it varies considerably and rock outcrop may occur in any part of the landscape. The main factors influencing extent of weathering are rock type, mineralisation and deformation. Palaeomagnetic dating of deeply weathered regolith profiles suggest that they formed throughout the Phanerozoic. Many of the regolith types resulting from a complex array of processes of weathering, erosion and deposition have a distinctive pattern, and could be potential sampling media. However, a combination of a long weathering history and a variable degree of erosion have resulted in a landscape of highly variable and complex regolith. Thus, assessment of the nature and origin of the regolith, weathering history, geomorphological processes and regolith-landform relationships are essential in determining the optimum geochemical sampling medium applicable in a particular terrain. A regolith-landform framework and models of regolith evolution of the Yilgarn Craton provide a basis for exploration models and exploration strategy that, with appropriate modification, may be extended into similar terrain elsewhere.
Numerical simulation models of the simultaneous transport of water and heat in porous media offer a useful technical tool for the evaluation of aquifers for the storage of heat energy. During the past several years, such models have been developed in the U.S. Geological Survey and in other institutions and have been tested by comparing computed results with analytical solutions. To more completely assess the performance of these simulation models, the U.S. Geological Survey and the Energy Research and Development Agency co-funded Auburn University to conduct a field experiment of heat storage in an aquifer near Mobile, Alabama. The data collected during the experiment were analyzed, and a simulation model of the aquifer system was constructed. Simulation of the experiment history indicates that the model can satisfactorily reproduce the observed behavior of the system. Heat capacity of the aquifer matrix and anisotropy of the aquifer permeability were found to be significant system parameters. An extensive evaluation of parameter sensitivity was not possible because experimental problems resulted in some unreliable data, but the utility of numerical models for simulating thermal energy storage in aquifers was clearly demonstrated.
Use of well doublets for groundwater-sourced heating or cooling typically results in a "thermal plume" of cool or warm reinjected groundwater. Such a plume may be regarded either as a potential anthropogenic geothermal resource or as pollution, depending on downstream aquifer usage. A thermal plume may pose an external risk to downstream users and environmental receptors or an internal risk to the sustainability of the well doublet, due to the phenomenon of thermal feedback. A three-tier assessment of the risk of thermal feedback is proposed, based on: (1) consideration of well separation and yield; (2) analytical modelling of heat migration in a doublet to ascertain breakthrough time and post-breakthrough temperature evolution and (3) numerical modelling of complex scenarios.
Quartz dissolution rates have been measured as a function of pH and ionic strength at 25° and 60°C and can be modeled by a rate law which takes into account speciation at the quartz-solution interface. Dissolution rates far from equilibrium in basic solutions are directly proportional to negative silica surface charge, changing with ionic strength and pH as surface charge changes. At pH 7.5 at 25°C and pH 7.0 at 60°C the logarithm of quart dissolution rates are −16.1 and −15.2 mol cm−2 s−1, respectively. Dissolution rates decrease slightly from pH 7 as pH is lowered, to pH 3, where they begin to increase with decreasing pH. The calculated activation enthalpy changes as a function of pH, being ∼11 kcal. mol−1 at near-neutral pH but increasing from 13 kcal. mol−1 at pH 8 to 23 kcal. mol−1 at pH 11.
The mobilization of organic compounds and the release of CO2 was studied in aquifer material from a site chosen for thermal energy storage (ETS). These processes have been measured aerobically and anaerobically within a temperature range of 4–95°C in sediment samples consisting of either quartz-rich coarse sand or peaty clay. At temperatures above 45°C organic carbon compounds, including fulvic acids, were mobilized from both sediments resulting in an increased chemical oxygen demand of the water phase. Complexation of calcium and magnesium by fulvic acids resulted in the supersaturation of the water phase with regard to calcite and dolomite and thus prevented the precipitation of these carbonates. The highest rates of CO2 release were observed during the first 4 days. Aerobically, the maximum velocity for CO2 formation varied between 35 and 800 (sand) or 15 and 150 (peaty clay) μmol CO2 per gram volatile solids per day. Anaerobically, similar rates were observed, namely 25–500 (sand) and 10–110 (peaty clay) μmol CO2 per gram volatile solids. At temperatures above 55°C, CO2 was produced purely chemically.
The use of groundwater as a carrier of thermal energy is an important source of sustainable heating and cooling. However, the effects of thermal use on geochemical and biological aquifer characteristics are poorly understood. Here, we have assessed the impacts of heat discharge on an uncontaminated, shallow aquifer by monitoring the hydrogeochemical, bacterial and faunal parameters at an active thermal discharge facility. The observed variability between wells was considerable. Yet, no significant temperature impacts on bacterial or faunal abundance and on bacterial productivity were observed. Also, we did not observe an improved survival or growth of coliforms with temperature. In contrast, the diversity of bacterial terminal restriction fragment (T-RF) length polymorphism fingerprints and faunal populations was either positively or negatively affected by temperature, respectively, and the abundance of selected T-RFs was clearly temperature dependent. Canonical correspondence analysis indicated that both the impact of temperature and of surface water from a nearby river, were important drivers of aquifer biotic variability. These results demonstrate that aquifer thermal energy discharge can affect aquifer bacteria and fauna, while at the same time controlling only a minor part of the total seasonal and spatial variability and therefore posing no likely threat to ecosystem functioning and drinking water protection in uncontaminated, shallow aquifers.
Maintaining optimal conditions in catchments or distribution systems relies heavily on water authorities having access to rapid and accurate water quality data, including an indication of bacteriological quality. In this study, the BacLight bacterial viability kit and carboxyfluorescein diacetate (CFDA) were coupled with flow cytometry (FCM) for rapid detection of physiologically active bacteria from raw and potable waters taken from various locations around South Australia. Results were compared to the direct viable count (DVC) and quantitative DVC (qDVC), in addition to the culture-based methods of the heterotrophic plate count (HPC) and a commercial SimPlate technique. Raw and potable water analysis revealed that DVC and culture-based techniques reported significantly fewer viable bacteria compared to the number of physiologically active bacteria detected using the rapid FCM assays, where this difference appeared to be nonlinear across different samples. Inconclusive results were obtained using qDVC as a viability assay. In particular, HPC results were 2-4 log orders of magnitude below that reported by the FCM assays for raw waters. Few bacteria in potable waters examined were culturable by HPC, even though FCM assays reported between 5.56 x 10(2) and 3.94 x 10(4) active bacteria ml(-1). These differences may be attributed to the presence of nonheterotrophic bacteria, sublethal injury or the adoption of an active but nonculturable (ABNC) state.
Spring water of two alpine karst aquifers differing in hydrogeology but of nearby catchments were investigated for their bacterial population dynamics. Dolomite karst aquifer spring 1 (DKAS 1) represents a dolomitic-limestone karst aquifer spring showing high average water residence time and relative constant flow. Limestone karst aquifer spring 2 (LKAS 2) constitutes a typical limestone karst aquifer spring with a dynamic hydrological regime and discharge. Dolomite karst aquifer spring 1 yielded constantly lower cell counts and biomasses (median of 15 x 10(6) cells l(-1) and 0.22 microg C l(-1)) as the LKAS 2 (median of 63 x 10(6) cells l(-1) and 1.1 microg C l(-1)) and distribution of morphotypes and mean cell volumes was also different between the considered systems, indicating the influence of hydrogeology on microbial spring water quality. Molecular bacterial V3 16S-rDNA profiles revealed remarkable constancy within each spring water throughout the investigation period. Time course analysis of a flood event in LKAS 2 further supported the trend of the temporal constancy of the microbial community. Except for one case, retrieval of partial and full length 16S rDNA gene sequences from the relative constant DKAS 1 revealed similarities to presently known sequences between 80% to 96%, supporting the discreteness of the microbial populations. The gathered results provide first evidence for the presence of autochthonous microbial endokarst communities (AMEC). Recovery of AMEC may be considered of relevance for the understanding of alpine karst aquifer biogeochemistry and ecology, which is of interest as many alpine and mountainous karst springs are important water resources throughout the world.
We report here a new staining procedure which uses both the enzymatic dehydrogenation of 2-(p-iodophenyl)-3-p-(nitrophenyl)-5 phenyltetrazolium chloride to a pink intracellular formazan and the DNA-specific fluorochrome 4',6'-diamidino-2-phenylindole. Application of this staining procedure to cells concentrated on filters and then transferred to microscope slides by the filter-transfer-freeze technique has proven valuable for statistically accurate enumeration of the total viable and metabolically active cells in groundwaters.