Water Online

December 2014

Water Online the Magazine gives Water & Wastewater Engineers and end-users a venue to find project solutions and source valuable product information. We aim to educate the engineering and operations community on important issues and trends.

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wateronline.com ■ Water Online The Magazine verify this claim. In addition, the natural geochemical processes allow the gas to be assimilated by the fresh water aquifer, which reacts and may liberate natural contaminants such as metals and hydrogen sulfide, leading to degradation in water quality 4 . This claim has not been substantiated, as there have not been any baseline monitoring and assessment of the assimilation capacity in potential shale gas regions to ascertain the release of these contaminants 4 . Other proposed possible mechanisms include: • Oxidation of fugitive methane through sulfate-reducing bacteria. This initiates the reductive dissolution of oxides in the aquifer, which may mobilize redox- sensitive elements (manganese, iron, or arsenic) and reduce the quality of groundwater 3 . • High concentration of halogens in saline waters could lead to the formation of toxic trihalomethanes (THM), though there is no data related to stray gas contamination from shale gas wells 3 . • There is evidence of cases of naturally occurring saline groundwater in areas of shale gas development in the Appalachian Basin, which makes the quantification of contamination from antropogenic sources of groundwater pollution difficult 3 . Possible Solutions 1. Previous studies show that stray gas contamination happens within less than 1 km (3,281 ft.) 12,13 of the well site. Based on this, enforcing a safe zone of 1 km between an existing drinking water well and proposed shale gas sites is reasonable. 2. The impact of natural gas irrespective of naturally occurring, or leakage from, shale gas could be addressed by mandatory baseline monitoring using modern modeling tools for the characterization of the chemical and isotopic compositions in areas of shale gas development 3 . 3. Full disclosure of the hydraulic fracturing chemicals used for open and scientific discussion and investigations 3 is recommended. 4. A zero discharge policy on untreated wastewater and developing adequate treatment technologies will prevent surface contamination 3 . In addition, developing remediation technologies for adequate treatment and safe disposal of wastewater will alleviate environmental issues associated with hydraulic fracturing processes 3 . 5. The water scarcity issue could be remedied using the highlighted means: • By good water management practices coupled with improved characterization and monitoring of the drainage basin in the region of shale gas development, the challenge of water use could be avoided 4 . • The use of saline, mineralized, and other forms of marginal water or other types of liquid-like gel for hydraulic fracturing will limit the use of fresh water resources for shale gas development 3 . For instance, in the Horn River Basin of British Columbia, Canada, saline groundwater of TDS (30,000 mg/L) is treated, which removes hydrogen sulfide and other gases, and the treated water is used for hydraulic fracturing 9 . • The use of acid mine drainage (AMD) for hydraulic fracturing could mitigate the AMD discharge, which could be blended with flow-back waters, leading to the formation of Sr-barite salts that neutralize some of the contaminants in both fluids 8 . • Withdrawing water during the peak period and storing until it is needed 4 . • Recycling of flow-back water. Conclusion With the debate on the negative impacts of hydraulic fracturing to environment and human health, there is need for further research on the behavioral activities of hydraulic fracturing chemicals/additives and the mechanism of contamination of source water. Such research would identify the potential risks associated with hydraulic fracturing processes and provide means of mitigating the contamination of source water. References 1. McBroom, M. (2013). Effects of induced hydraulic fracturing on the environment: commercial demands vs. water, wildlife, and human ecosystems. Oakwood, Canada: Apple Academic Press. Retrieved from http://www.ebrary.com on September 10, 2014. 2. U.S. Environmental Protection Agency (2011). Plan to study the potential impacts of hydraulic fracturing on drinking water resources; EPA/600/R-11/122/November; U.S. Environmental Protection Agency: White Paper 12 Figure 2. The hydraulic fracturing process (adapted from EPA , 2011 2 )

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