by Shannon Julius
Since 2008, the Marcellus shale formation has become the most productive region for extracting shale gas in the US. Managing wastewater for these operations is a challenge not only due to their size and distribution, but also because of the different types of contaminants that are present in various types of wastewater. Rahm et al. (2013) retrieved data from the Pennsylvania Department of Environmental Protection (PADEP) Oil and Gas Reporting website from 2008 to 2011 to look for the trends and drivers of Marcellus shale wastewater management. After analysis using internet resources and Geographic Information Systems (GIS), the authors found that there was a statewide shift towards wastewater reuse and injection disposal treatment methods and away from publicly owned treatment works (POTW) use. These wastewater management trends are likely due to new regulations and policies, media and public scrutiny, and natural gas prices. Research also shows that Marcellus shale development has influenced conventional gas wastewater practices and led to more efficient wastewater transportation.
Rahm et al. retrieved data from the publicly accessible PADEP Oil and Gas Reporting Website for the years 2008 through 2011. Information was submitted to this website by industry operators, so there is definitely potential for human error. Wastewater disposal methods reported to the website included industrial waste treatment plants, municipal sewage treatment plants, injection disposal wells, reuse (which involves some industrial treatment), and other or not determined. The authors also gathered information about conventional wastewater management for 2004–2006 and 2010–2011, which approximately represent the pre- and post- Marcellus shale development years. Information from the database was used to look up and geographically locate disposal facilities in order to calculate wastewater transportation miles. The shortest driving distance from wastewater generation site to wastewater destination was calculated using Google Earth. The authors made different analyses for statewide water disposal in Pennsylvania and for two regions of the Marcellus Shale.
The most significant trend was the increased reuse of wastewater and the decreased utilization of POTWs. New regulations and public pressure in large part drove this change. In 2009, PADEP required the submittal of a formal discharge strategy for wastewater high in total dissolved solids (TDS). This requirement limited the options for wastewater disposal, as POTWs usually cannot treat high-TDS waste. Public concern towards shale gas development and opposition to the use of public facilities for wastewater led to the state of Pennsylvania taking further action. Act 15, passed by the state legislature in 2010, made rules for tracking residual waste, required operators submit a report on gas production and wastewater management every six months, and established a database so the public could access this information. In response to continuing public pressure, PADEP requested in 2011 that operators completely cease the use of POTWs for wastewater management.
Natural gas prices influenced the trend of increased of injection well usage. When gas prices decreased between late 2011 and early 2012, fewer new wells were drilled and there was less of a demand for recycled water. Though reuse was by far the largest “disposal” method for wastewater, injection well usage increased substantially throughout the test period.
Conventional gas wastewater had additional disposal options and a relatively larger use of POTWs before major Marcellus shale development. After 2010, however, wastewater disposal methods for conventional and unconventional gas came to resemble each other. This is likely due to public scrutiny of Marcellus development, which pressured regulators to monitor disposal and limit treatment options for both conventional and unconventional gas producers. New regulations after 2010 affected conventional gas wastewater reporting, treatment, and discharge, and called for information related to wastewater to be publicly accessible. Another driver for the shift in conventional gas wastewater management practices was the infrastructural development in response to the Marcellus boom that led to increased industrial treatment capacity for all natural gas producers.
The final trends were related to wastewater transport. Marcellus shale infrastructure is currently quite spread out, evidenced by wastewater shipments to various areas throughout Pennsylvania, Ohio, West Virginia and Maryland. Infrastructure tends to develop regionally so that large wastewater exporters are near wastewater importers. An example of this is the southwest region of Pennsylvania, which had a high rate of injection disposal relative to other Marcellus drilling regions due to its proximity to the wastewater importing areas of Ohio and West Virginia. The presence of nearby infrastructure led to faster shale gas development in the southwest region, even in times of low natural gas prices. The northeast region did not have as much infrastructure before the Marcellus boom, so their wastewater travelled farther at first. As infrastructure developed across the state, wastewater travelled on average 30% less distance in 2011 than in 2008.
Rahm, B., Bates, J., Bertoia, L., Galford, A. Yoxtheimer, D., Riha, S., 2013. Wastewater management and Marcellus shale gas development: Trends, drivers, and planning implications. Journal of Environmental Management 120, 105–113. Abstract at: http://bit.ly/1CKv0Xj