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(searched for: doi:10.1016/j.scitotenv.2017.09.087)
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Tao Zhong, Hong Tian, Jun Zheng, , Yachao Wang, Zhongyan Yang, Peng Li, Peng Xiao
Published: 22 December 2022
Journal of Water and Climate Change, Volume 14, pp 142-155; https://doi.org/10.2166/wcc.2022.342

Abstract:
While utilizing hydrothermal resources, it is necessary to reinject wastewater into the reservoir through reinjection wells to extract heat without mining groundwater. Chemical clogging is a serious problem in the process of reinjection. The precipitation of minerals can lead to reservoir clogging and the reduction of permeability. Therefore, to study the effect of chemical clogging on permeability, the weakly consolidated sandstone of the Neogene Guantao Formation geothermal reservoir in northern Shandong (Eastern China) was taken as the research object. A long-term thermal-hydro-mechanical-chemistry (THMC) coupling reinjection experiment was carried out. The results showed that when the temperature of wastewater was higher than 45 °C, there was a temporary phase of permeability enhancement in the first 10 min of reinjection. However, wastewater with higher temperatures would cause more chemical clogging eventually. XRD and ion analysis results showed that the precipitation of minerals was mainly potash feldspar, illite, calcite, and other carbonate minerals during reinjection. According to the characteristics of low-TDS wastewater in the Guantao Formation, it is recommended to adopt low-temperature wastewater reinjection and reduce the concentration of Ca2+ and Mg2+ in wastewater before reinjection.
Published: 29 October 2022
by MDPI
Journal: Water
Abstract:
In situ remediation is usually restricted by temperature, lack of substrate for reductive dechlorination (anaerobic respiration), the presence of dehalogenating microorganisms, and specific bedrock conditions. In this work, trichloroethene (TCE) degradation was studied by a number of methods, from physical–chemical analyses to molecular biological tools. The abundance changes in dechlorinating bacteria were monitored using real-time PCR. The functional genes vcrA and bvcA as well as the 16S rRNA specific for representatives of genera Dehalococcoides, Dehalobacter, and Desulfitobacterium were monitored. Furthermore, the sulfate-reducing bacteria and denitrifying bacteria were observed by amplifying the functional genes apsA and nirK. The elevated temperature and the substrate (whey) addition significantly affected TCE dechlorination. The chlorine index decreased after nine weeks from 2.5 to 0.1 at 22 °C, to 1.1 at 17 °C and 1.7 at 12 °C and complete dechlorination was achieved at 22 °C with whey addition. The achieved results of this work show the feasibility and effectiveness of biological dechlorination of TCE enhanced with elevated temperature and whey addition.
Jie Yang, Wei-Xin Ren, , Yuezan Tao
Published: 12 January 2022
Environmental Technology pp 1-17; https://doi.org/10.1080/09593330.2021.2024275

Abstract:
Groundwater heat pumps (GWHP) are an efficient utilisation of shallow geothermal energy technology and of great significance in terms of promoting energy conservation and reducing emissions. However, recharge clogging has been a key problem restricting the continuous operation of GWHP. In this study, a simulation test device for sand column was designed with the aim of addressing chemical clogging induced by heat pump reinjection in a porous saline aquifer in the Huaibei Plain, China. The trend in the variation of the permeability coefficient was studied based on the detection of the sand sample composition, recharge water quality, and sand layer temperature, and the cause of formation was analysed using the saturation index (SI) and ion ratio method. The results indicated that the permeability coefficient in the sand column decreased exponentially, with a maximum and minimum decrease of 8.14% and 71.65% of the original coefficient, respectively, found in sections P2–P3 and P8–P9. Therefore, the clogging effect of the aquifer at approximately 200–400 mm from the recharge well was significant. Water–rock interactions predominantly involved the dissolution of halite, albite, chlorite, anhydrite, and dolomite and the precipitation of calcite, as well as the exchange adsorption of Ca2+ and Mg2+ to Na+, which were the key sources of ions during the water chemical evolution process. Finally, quartz was formed by the weathering and dissolution of aluminosilicate minerals such as albite, and particle migration and precipitation during the hydrodynamic disturbance were the primary causes of the front-end blockage of the column. GRAPHICAL ABSTRACT
Boyan Meng, Yan Yang, , Olaf Kolditz,
Published: 13 December 2021
Frontiers in Earth Science, Volume 9; https://doi.org/10.3389/feart.2021.790315

Abstract:
Underground thermal energy storage is an efficient technique to boost the share of renewable energies. However, despite being well-established, their environmental impacts such as the interaction with hydrocarbon contaminants is not intensively investigated. This study uses OpenGeoSys software to simulate the heat and mass transport of a borehole thermal energy storage (BTES) system in a shallow unconfined aquifer. A high-temperature (70 C) heat storage scenario was considered which imposes long-term thermal impact on the subsurface. Moreover, the effect of temperature-dependent flow and mass transport in a two-phase system is examined for the contaminant trichloroethylene (TCE). In particular, as subsurface temperatures are raised due to BTES operation, volatilization will increase and redistribute the TCE in liquid and gas phases. These changes are inspected for different scenarios in a contaminant transport context. The results demonstrated the promising potential of BTES in facilitating the natural attenuation of hydrocarbon contaminants, particularly when buoyant flow is induced to accelerate TCE volatilization. For instance, over 70% of TCE mass was removed from a discontinuous contaminant plume after 5 years operation of a small BTES installation. The findings of this study are insightful for an increased application of subsurface heat storage facilities, especially in contaminated urban areas.
Published: 1 October 2021
Environmental Pollution, Volume 287; https://doi.org/10.1016/j.envpol.2021.117609

Abstract:
There has been a worldwide interest in renewable energy technologies, as a means of decreasing reliance on fossil fuels, minimizing climate change effects, and reducing greenhouse emissions. One such technology is geothermal heating where the constant subsurface temperature is used to cool or heat building interiors via heat pumps. In Canada, the use of geothermal heating has become a popular option for heating and cooling buildings, and it is anticipated that, in the near term, most large buildings will include geothermal heating as part of their climate control strategy. However, little is known about the environmental impacts of geothermal heating on the subsurface environment. The present review will examine the effect of geothermal heating on groundwater flow and remediation efforts, whereby the heat generated by geothermal systems may help with urban pollution. "Geothermal Remediation" could leverage the subsurface heating resulting from geothermal systems to accelerate biodegradation of certain petroleum-based pollutants at brown-field sites, while providing building(s) with sustainable heating and cooling. This idea coincides with the rising momentum towards sustainable and green remediation in Europe and the United States. To ensure that Geothermal Remediation is achievable, the effect of heat on bioremediation needs to be examined. This review provides an insight into what we know about heat effects on bioremediation activities and subsurface transport.
Kyungjin Han, SunHwa Park, Sooyoul Kwon,
Published: 14 May 2020
Journal of Environmental Management, Volume 268; https://doi.org/10.1016/j.jenvman.2020.110691

Abstract:
During in situ bioremediation, continuous injection of growth substrates such as carbon sources, electron donors, or electron acceptors inevitably results in microbial growth, resulting in biological clogging in an aquifer. Therefore, for successful bioremediation, development of a new injection method is needed to reduce or alleviate this clogging problem. In this study, we carried out field tracer tests using single-well push-pull tests (SWPPTs), single-well natural gradient drift tests (SWNGDTs), and long-term in situ well-to-well tests to develop and evaluate a new method of liquid/gas mixture spray injection. The effectiveness of the new method was evaluated by estimating the factors as follow: longitudinal dispersivity (αL), radius of influence (RI), shear stress on the surface of aquifer particles (σ), biofilm-shear-loss rate (Rs), and the ratio of volume occupied by cells grown to the original pore volume. At the tested site, the liquid/gas mixture spray injection method turned out to have several advantages compared to the traditional solution injection method: 1) transport of solute to a larger proportion of an aquifer by a factor of 1.3–1.7, 2) application of higher shear stress onto the surface of soil particles by a factor of 4.2–5.0, 3) faster biofilm sloughing rates by a factor of 2.3–2.6, 4) reduction in the ratio of the volume occupied by microorganisms to total pore volume (Volmicrobes/Volpore), and 5) efficient trichloroethylene (TCE) dechlorination for a period of 550 days without any injection problems. This new injection method showed positive effects on the hydrogeological and physical characteristics of the system, thus alleviating the biological clogging problem.
, Yue Wang, Yafei Wang, , Manxi Xie, Tim Grotenhuis,
Environmental Science & Technology, Volume 54, pp 3039-3049; https://doi.org/10.1021/acs.est.9b07020

Abstract:
Due to the increasing need for sustainable energy and environmental quality in urban areas, the combination of aquifer thermal energy storage (ATES) and in situ bioremediation (ISB) has drawn much attention as it can deliver an integrated contribution to fulfill both demands. Yet, little is known about the overall environmental impacts of ATES-ISB. Hence, we applied a life-cycle assessment (LCA) to evaluate the environmental performance of ATES-ISB, which is also compared with the conventional heating and cooling system plus ISB alone (CHC + ISB). Energy supply via electricity is revealed as the primary cause of the environmental impacts, contributing 61.26% impacts of ATES-ISB and 72.91% impacts of CHC + ISB. Specifically, electricity is responsible for over 95% of water use, global warming potential, acidification potential, and respiratory inorganics, whereas the production of the biological medium for bioremediation causes more than 85% of the eco- and human toxicity impacts in both cases. The overall environmental impact of ATES-ISB is two times smaller than that of CHC + ISB. Sensitivity analysis confirms the importance of electricity consumption and electron donor production to the environmental impacts in both energy supply and bioremediation. Thus, future studies and practical applications seeking possible optimization of the environmental performances of ATES-ISB are recommended to focus more on these two essential elements, e.g., electricity and electron donor, and their related parameters. With the comprehensive LCA, insight is obtained for better characterizing the crucial factors as well as the relevant direction for future optimization research of the ATES-ISB system.
, Zhongli Wang, Jiaxin Shi,
Published: 15 October 2019
Geochimica Et Cosmochimica Acta, Volume 268, pp 296-309; https://doi.org/10.1016/j.gca.2019.10.011

The publisher has not yet granted permission to display this abstract.
Published: 1 July 2019
Environmental Pollution, Volume 253, pp 449-463; https://doi.org/10.1016/j.envpol.2019.06.118

Abstract:
Sustainable remediation is a goal and an imperative in the remediation industry. Thermal treatment can remediate contaminated sites quickly and reliably, but its energy-intensive nature and potential to damage soil properties make it seemingly not sustainable. This review evaluates the potential for thermal treatment to become a sustainable remediation technology based on a comprehensive analysis of the scientific literature. The fundamentals, advantages, and limitations of single thermal treatment technologies are summarized. The compatibility and superiority of thermal treatment coupled with thermal, physicochemical, or biological technologies is reviewed. The results suggest that ingeniously designed coupled technologies can improve the availability and removal efficiency of contaminant, suppress the production of toxic byproduct, and reduce the required heating temperature and energy input. The sustainability of thermal treatment is then discussed from the view of energy efficiency and land reuse. Approaches for improving energy efficiency include applying solar energy-based technologies, smoldering-based technologies, and coupled technologies. For land reuse, heating below 250 °C has negligible adverse impacts on most soil properties, and can increase nutrient availability and release dissolved organic carbon to support the growth of microorganisms and plants. Heating above 250 °C can significantly reduce soil organic matter and clay content, which decreases the soil cation exchange capacity and water holding capacity, and consequently damages the soil fertility. Some restoration strategies are also proposed for the recovery of soil health. In addition, thermally remediated soil is considered to be a good candidate as an engineering medium for construction. This review concludes with an outlook of future research efforts that further shift thermal treatment toward sustainable remediation.
, Jie Zhuang, Frank E. Löffler, Yingyue Zhang, , , , Mark Radosevich
Published: 17 February 2019
Environmental Microbiology, Volume 21, pp 2043-2055; https://doi.org/10.1111/1462-2920.14566

The publisher has not yet granted permission to display this abstract.
Wenbing Wang,
Environmental Science and Pollution Research, Volume 25, pp 28628-28641; https://doi.org/10.1007/s11356-018-2908-z

Abstract:
Biological clogging in porous media was an important concern in the design of bio-augmented permeable reactive barriers (Bio-PRBs) that were used to remediate groundwater with dense non-aqueous phase liquids (DNAPLs). Here, we used laboratory sandbox experiments to develop and calibrate reactive transport models (C1 and C2) simulating 1,1,1-trichloroethane (1,1,1-TCA) change in heterogeneous saturated porous media. The routine (1,1,1-TCA chain kinetic reactions) and subroutine (the relationship between hydraulic conductivity (K) and time (t)) were included in the model computer code. The simulation results suggested that the model C1 had the applicability for simulating contaminant transport and fate in bio-augmented flow field. By using the model C1 which was suitable for constant K condition, the performance of different types of Bio-PRBs was evaluated, and the regularity of contaminants chain kinetic reactions in different heterogeneous saturated porous media was obtained. The results demonstrated that Bio-PRBs in immobilized microorganism (IM) protocol were more superior to Bio-PRBs in free microorganism (FM) protocol. In addition, by using the model C2 (updated model C1) which was suitable for decreasing K condition, the different and optimized regularity of contaminants transport and transformation was obtained. The results showed that microbial growth which further decreased K was beneficial to preventing the transport of contaminants and accelerating the transformation of contaminants. However, the negative effects of biological clogging on hydraulic conductivity and relative hydraulic conductivity ratio in FM Bio-PRBs were significantly stronger than that in IM Bio-PRBs. Deploying IM Bio-PRBs for groundwater remediation would be much more efficient and meet the design criteria. The research work had guiding significance to engineering and provided consultation for designing and optimizing Bio-PRBs system. To make the design and optimization of Bio-PRBs system convenient, it was very essential to choose the suitable mathematical model (C1 or C2).
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