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Bromide: A Pressing Issue to Address in China’s Shale Gas Extraction Mei Shi,† Dongyan Huang,† Gaowen Zhao,‡ Ronghua Li,§ and Jianzhong Zheng*,† †
College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China Department of Architecture Engineering, Yulin University, Yulin, Shaanxi 719000, China § College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China water after treatment, processing by evaporation ponds, and beneficial reuse outside of the industry.1 China’s shale gas exploration is presently at the stage of demonstrations mainly in Sichuan basin, and large scale commercial production is expected to start soon. Because of this, many environmental regulations and standards regarding SGW management (e.g., deep well injection, wastewater treatment and disposal) are lacking. As for infrastructure development in Sichuan basin, it would be a great challenge to develop, in limited time, a sufficient number of deep injection wells (similar to U.S. Class II wells) suitable for SGW disposal, considering the basin’s complex geology and the expensive cost in well drilling. In addition, SGW treatment plants need to be installed to treat the SGW that cannot be handled by other management approaches, and technologies for effective treatment and reuse of SGW still await to be developed. Based on the current status, it is concerned that, were SGW not properly managed at commercial production, partial discharge of SGW to surface waters might be inevitable. Discharge of effluents from SGW treatment facility to surface water is of particular concern for the water quality of the receiving water body, as elevated concentration of bromide has hina is fighting to shift its coal-based energy system to a the risk to form DBPs (Figure 1). In the early stage of shale gas clean and sustainable one to alleviate its ever increasing extraction in Marcellus, low availability of deep wells has led to environmental pressures. Backed by the largest proven shale gas surface discharge of treated produced water, causing elevated reserve worldwide, China has set an ambitious goal to produce bromide concentrations in the receiving water body. In a study 60−100 billion cubic meters of shale gas annually by 2020 by examining the impact of bromide discharge from one Marcellus hydraulic cracking. Large amounts of shale gas wastewater wastewater treatment plant on the water quality of a receiving (SGW) are expected to be generated in association with an stream, Warner et al. found bromide was enriched almost by 40 average 700 gallons of brine produced per million cubic feet of folds even 1.78 km downstream from the discharge site, with gas produced, according to a recent analysis of data from the stream receiving as much as 136.6 tons of bromide annually Marcellus.1 Shale gas wastewater consists of flowback and from the treatment plant.2 In another study, elevated bromide produced water, a mixture of injected fluids for hydraulic concentrations in the Allegheny River has been linked to fracturing and pore water from shale formation. Because of this, increased concentrations of brominated trihalomethanes in the SGW often contains heavy metals, radioactive metals, high finished water of Pittsburgh Water and Sewer Authority’s 2 levels of total dissolved solids (TDS), and in some cases, drinking water plants which draw raw water from this river. 2 elevated concentrations of bromide. Compared with other ions Further study suggested that the Marcellus Shale wastewater in water (e.g., heavy metals and radioactive ions), bromide does treatment facility was one of the major contributors of bromide not readily adsorb on soils and sediments, and hence can in the raw water.3 migrate a long distance downstream once entering surface Shale gas in China is mainly stored in Sichuan, Tarim, waters. At the dawn of massive production of shale gas, China Junggar, and Songliao basins. Although the published bromide should pay particular attention to this contaminant. Poor data on SGW is not available, useful information can still be management of bromide-containing wastewater would potenextracted from the reported geochemical data of underground tially cause contamination of China’s already limited drinking brine samples collected from oil and gas fields. Take Sichuan water resources, and pose threats to the quality of the finished basin (holding china’s 40% shale gas reserve) for example, both water from drinking water plants using the Br-contaminated its Lower Cambrian and the Upper Permian formations are source water due to the formation of carcinogenic brominated disinfection byproducts (DBPs) (Figure 1). Management strategies for SGW include underground Received: June 11, 2014 injection, reuse in hydraulic fracturing, discharge to surface Published: August 13, 2014 ‡
C
© 2014 American Chemical Society
9971
dx.doi.org/10.1021/es502848p | Environ. Sci. Technol. 2014, 48, 9971−9972
Environmental Science & Technology
Viewpoint
Figure 1. A schematic showing the fate of bromide in wastewater generated by shale gas production, and the potential DBPs (disinfection byproducts) formed by chlorine and ozone disinfection in downstream drinking water plants using the bromide-contaminated raw water. DBPs, disinfection byproducts; NOM, natural organic matter; THMs, trihalomethanes; HAAs, haloacetic acids.
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considered to be favorable for shale gas reserve.4 Based on the 240 brine samples collected from 67 oil and gas fields in this basin, bromide concentrations in the brines were found to be 62−2640 mg/L.5 Further analysis showed that the bromide concentrations were about 1600 mg/L and 1000 mg/L in the Permian and Cambrian strata, respectively.5 These values are higher than the reported mean concentration of bromide (744 mg/L) in flowback and produced waters in Marcellus.2 If, in the future, bromide concentrations of SGW in China are on this magnitude, the produced wastewater should be properly managed to protect China’s limited drinking water resources. To address the complex bromide issue that might arise once China starts shale gas production, strategies to manage the high TDS, bromide-containing wastewater should be thoroughly investigated now. First, China should learn from America’s experiences in shale gas production, and expedite legislation of environmental laws and regulations regarding SGW management. Second, reliable infrastructures, such as deep injection wells and wastewater treatment plants, should be developed and in place prior to commercial production. In addition, both the quantity and quality of SGW at full scale production need to be accurately assessed and clearly understood. In management of SGW, priority should be given to water reuse and deep well injection to minimize its impact on surface waters and shallow groundwater aquifers. Overall, before shale gas extraction to alleviate its severe energy and environmental pressures, China should fully take into account all potential risks associated with SGW, not only its TDS and radioactive metals contents, but also bromide contained. Only by balancing shale gas economics and environmental quality, can China truly benefit from shale gas extraction.
AUTHOR INFORMATION
Corresponding Author
*Phone: +86-10-8825-6145; e-mail: [email protected]. Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS Funding for this research was provided by the State Key Laboratory of Pollution Control and Resource Reuse (PCRRF12002). We gratefully acknowledge Dr. Susan E. Powers of Clarkson University, Dr. Baolin Deng of University of Missouri, and Dr. Xin Yu of Chinese Academy of Sciences for their valuable comments.
■
REFERENCES
(1) Shaffer, D. L.; Arias Chavez, L. H.; Ben-Sasson, M.; RomeroVargas Castrillon, S.; Yip, N. Y.; Elimelech, M. Desalination and reuse of high salinity shale gas produced water: drivers, technologies, and future directions. Environ. Sci. Technol. 2013, 47, 9569−9583. (2) Warner, N. R.; Christie, C. A.; Jackson, R. B.; Vengosh, A. Impacts of shale gas wastewater disposal on water quality in Western Pennsylvania. Environ. Sci. Technol. 2013, 47 (20), 11849−11857, DOI: 10.1021/es402165b. (3) States, S.; Cyprych, G.; Stoner, M.; Wydra, F.; Kuchta, J.; Monnell, J.; Casson, L. Marcellus Shale drilling and brominated THMs in Pittsburgh, PA., drinking water. J. Am. Water Works Ass. 2013, 105 (8), 53−54, http://dx.doi.org/10.5942/jawwa.2013.105.0093. (4) Wang, S. B.; Song, Z. G.; Cao, T. T.; Xu, S. The methane sorption capacity of Paleozoic shales from the Sichuan Basin, China. Mar. Petrol. Geol. 2013, 44, 112−119, DOI: 10.1016/j.marpetgeo.2013.03.007. (5) Lin, Y. T. Bromine resource in brines and its exploitation prospect. J. Salt Lake Res. 2000, 8 (2), 59−66 in Chinese.
9972
dx.doi.org/10.1021/es502848p | Environ. Sci. Technol. 2014, 48, 9971−9972
Bromide: A Pressing Issue to Address in China’s Shale Gas Extraction Mei Shi,† Dongyan Huang,† Gaowen Zhao,‡ Ronghua Li,§ and Jianzhong Zheng*,† †
College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China Department of Architecture Engineering, Yulin University, Yulin, Shaanxi 719000, China § College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China water after treatment, processing by evaporation ponds, and beneficial reuse outside of the industry.1 China’s shale gas exploration is presently at the stage of demonstrations mainly in Sichuan basin, and large scale commercial production is expected to start soon. Because of this, many environmental regulations and standards regarding SGW management (e.g., deep well injection, wastewater treatment and disposal) are lacking. As for infrastructure development in Sichuan basin, it would be a great challenge to develop, in limited time, a sufficient number of deep injection wells (similar to U.S. Class II wells) suitable for SGW disposal, considering the basin’s complex geology and the expensive cost in well drilling. In addition, SGW treatment plants need to be installed to treat the SGW that cannot be handled by other management approaches, and technologies for effective treatment and reuse of SGW still await to be developed. Based on the current status, it is concerned that, were SGW not properly managed at commercial production, partial discharge of SGW to surface waters might be inevitable. Discharge of effluents from SGW treatment facility to surface water is of particular concern for the water quality of the receiving water body, as elevated concentration of bromide has hina is fighting to shift its coal-based energy system to a the risk to form DBPs (Figure 1). In the early stage of shale gas clean and sustainable one to alleviate its ever increasing extraction in Marcellus, low availability of deep wells has led to environmental pressures. Backed by the largest proven shale gas surface discharge of treated produced water, causing elevated reserve worldwide, China has set an ambitious goal to produce bromide concentrations in the receiving water body. In a study 60−100 billion cubic meters of shale gas annually by 2020 by examining the impact of bromide discharge from one Marcellus hydraulic cracking. Large amounts of shale gas wastewater wastewater treatment plant on the water quality of a receiving (SGW) are expected to be generated in association with an stream, Warner et al. found bromide was enriched almost by 40 average 700 gallons of brine produced per million cubic feet of folds even 1.78 km downstream from the discharge site, with gas produced, according to a recent analysis of data from the stream receiving as much as 136.6 tons of bromide annually Marcellus.1 Shale gas wastewater consists of flowback and from the treatment plant.2 In another study, elevated bromide produced water, a mixture of injected fluids for hydraulic concentrations in the Allegheny River has been linked to fracturing and pore water from shale formation. Because of this, increased concentrations of brominated trihalomethanes in the SGW often contains heavy metals, radioactive metals, high finished water of Pittsburgh Water and Sewer Authority’s 2 levels of total dissolved solids (TDS), and in some cases, drinking water plants which draw raw water from this river. 2 elevated concentrations of bromide. Compared with other ions Further study suggested that the Marcellus Shale wastewater in water (e.g., heavy metals and radioactive ions), bromide does treatment facility was one of the major contributors of bromide not readily adsorb on soils and sediments, and hence can in the raw water.3 migrate a long distance downstream once entering surface Shale gas in China is mainly stored in Sichuan, Tarim, waters. At the dawn of massive production of shale gas, China Junggar, and Songliao basins. Although the published bromide should pay particular attention to this contaminant. Poor data on SGW is not available, useful information can still be management of bromide-containing wastewater would potenextracted from the reported geochemical data of underground tially cause contamination of China’s already limited drinking brine samples collected from oil and gas fields. Take Sichuan water resources, and pose threats to the quality of the finished basin (holding china’s 40% shale gas reserve) for example, both water from drinking water plants using the Br-contaminated its Lower Cambrian and the Upper Permian formations are source water due to the formation of carcinogenic brominated disinfection byproducts (DBPs) (Figure 1). Management strategies for SGW include underground Received: June 11, 2014 injection, reuse in hydraulic fracturing, discharge to surface Published: August 13, 2014 ‡
C
© 2014 American Chemical Society
9971
dx.doi.org/10.1021/es502848p | Environ. Sci. Technol. 2014, 48, 9971−9972
Environmental Science & Technology
Viewpoint
Figure 1. A schematic showing the fate of bromide in wastewater generated by shale gas production, and the potential DBPs (disinfection byproducts) formed by chlorine and ozone disinfection in downstream drinking water plants using the bromide-contaminated raw water. DBPs, disinfection byproducts; NOM, natural organic matter; THMs, trihalomethanes; HAAs, haloacetic acids.
■
considered to be favorable for shale gas reserve.4 Based on the 240 brine samples collected from 67 oil and gas fields in this basin, bromide concentrations in the brines were found to be 62−2640 mg/L.5 Further analysis showed that the bromide concentrations were about 1600 mg/L and 1000 mg/L in the Permian and Cambrian strata, respectively.5 These values are higher than the reported mean concentration of bromide (744 mg/L) in flowback and produced waters in Marcellus.2 If, in the future, bromide concentrations of SGW in China are on this magnitude, the produced wastewater should be properly managed to protect China’s limited drinking water resources. To address the complex bromide issue that might arise once China starts shale gas production, strategies to manage the high TDS, bromide-containing wastewater should be thoroughly investigated now. First, China should learn from America’s experiences in shale gas production, and expedite legislation of environmental laws and regulations regarding SGW management. Second, reliable infrastructures, such as deep injection wells and wastewater treatment plants, should be developed and in place prior to commercial production. In addition, both the quantity and quality of SGW at full scale production need to be accurately assessed and clearly understood. In management of SGW, priority should be given to water reuse and deep well injection to minimize its impact on surface waters and shallow groundwater aquifers. Overall, before shale gas extraction to alleviate its severe energy and environmental pressures, China should fully take into account all potential risks associated with SGW, not only its TDS and radioactive metals contents, but also bromide contained. Only by balancing shale gas economics and environmental quality, can China truly benefit from shale gas extraction.
AUTHOR INFORMATION
Corresponding Author
*Phone: +86-10-8825-6145; e-mail: [email protected]. Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS Funding for this research was provided by the State Key Laboratory of Pollution Control and Resource Reuse (PCRRF12002). We gratefully acknowledge Dr. Susan E. Powers of Clarkson University, Dr. Baolin Deng of University of Missouri, and Dr. Xin Yu of Chinese Academy of Sciences for their valuable comments.
■
REFERENCES
(1) Shaffer, D. L.; Arias Chavez, L. H.; Ben-Sasson, M.; RomeroVargas Castrillon, S.; Yip, N. Y.; Elimelech, M. Desalination and reuse of high salinity shale gas produced water: drivers, technologies, and future directions. Environ. Sci. Technol. 2013, 47, 9569−9583. (2) Warner, N. R.; Christie, C. A.; Jackson, R. B.; Vengosh, A. Impacts of shale gas wastewater disposal on water quality in Western Pennsylvania. Environ. Sci. Technol. 2013, 47 (20), 11849−11857, DOI: 10.1021/es402165b. (3) States, S.; Cyprych, G.; Stoner, M.; Wydra, F.; Kuchta, J.; Monnell, J.; Casson, L. Marcellus Shale drilling and brominated THMs in Pittsburgh, PA., drinking water. J. Am. Water Works Ass. 2013, 105 (8), 53−54, http://dx.doi.org/10.5942/jawwa.2013.105.0093. (4) Wang, S. B.; Song, Z. G.; Cao, T. T.; Xu, S. The methane sorption capacity of Paleozoic shales from the Sichuan Basin, China. Mar. Petrol. Geol. 2013, 44, 112−119, DOI: 10.1016/j.marpetgeo.2013.03.007. (5) Lin, Y. T. Bromine resource in brines and its exploitation prospect. J. Salt Lake Res. 2000, 8 (2), 59−66 in Chinese.
9972
dx.doi.org/10.1021/es502848p | Environ. Sci. Technol. 2014, 48, 9971−9972
