Forward osmosis treatment of drilling mud and fracturing wastewater from oil and gas operations Kerri L. Hickenbottom a , Nathan T. Hancock a , Nathan R. Hutchings b , Eric W. Appleton b , Edward G. Beaudry c , Pei Xu a , Tzahi Y. Cath a, ⁎ a Colorado School of Mines, Golden, CO, USA b Bear Creek Services, Shreveport, LA, USA c Hydration Technology Innovations, Albany, OR, USA abstract article info Article history: Received 14 January 2012 Received in revised form 5 May 2012 Accepted 31 May 2012 Available online 18 July 2012 Keywords: Forward osmosis Well fracturing Water reuse Wastewater treatment Produced water To produce large volumes of newly discovered unconventional gas, hydraulic fracturing of wells is commonly practiced in basins where shale gas and coal bed methane are extracted. Hydraulic fracturing of wells during oil and gas (O&G) exploration consumes large volumes of fresh water and generates larger volumes of con- taminated wastewater. In this study, a novel application of forward osmosis (FO) was tested for treatment and reclamation of water from drilling waste to facilitate beneficial water reuse. By using FO, two major benefits were achieved: both the volume of the waste stream and the need for a fresh water source were greatly reduced. Results indicate that FO can achieve high rejection of organic and inorganic contaminants, membrane fouling was reversible, and that the process was able to effectively recover more than 80% of the water from the drilling waste. Osmotic backwashing was demonstrated to be an effective membrane cleaning technique; successfully removing fouling and restoring water flux. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Environmental impacts of drilling and hydraulic fracturing of oil and gas (O&G) wells are becoming of greater concern in the United States and around the world. The main challenges include the influence of hy- draulic fracturing on groundwater quality and the management of dril- ling and fracturing wastes and produced water [1–4]. Consequently, state and federal governments are enforcing more stringent regulations and discharge limits on O&G companies [1]. Up to 5 million gallons of water are used during drilling and fracturing of a single well, and after drilling and fracturing, water flows back to the surface and becomes drilling and fracturing waste. Subsequently, pro- duced water flows out of the well together with the oil or gas through- out most of the productive lifetime of the well [1,3]. It is estimated that the water-intensive fracturing process is typically responsible for 25%– 30% of the cost of drilling a well in the Marcellus Shale play [5]. A fraction (up to 15%) of drilling and fracturing waste may constitute impurities and solids, minerals (including heavy metals) and organic matter from geologic formations, polymers and other chemical additives, and prop- pants, which are sand or high-strength ceramic particles/grains used during fracturing to keep shale fractures open and allow free flow of gas and oil to the well [1,6]. The water used for drilling and fracturing of O&G wells is often sourced from local water supplies and/or trucked to the site, thus creating competition for local water resources and supplies. If available, pro- duced water from nearby production wells is also used for develop- ment of new O&G wells. To decrease the consumption of regional fresh water, drilling and fracturing waste can be treated and reused on site. Thus, it is critical to explore and develop new technologies that can efficiently and sustainably treat O&G waste streams and facili- tate beneficial water reuse. Current management techniques for drilling and fracturing waste include treatment and discharge and deep-well injection [1,7]. Treat- ment methods typically involve settling solids and then decanting the fluid; yet, this method only allows for 50%–60% recovery of water, which can be reused, but is still contaminated [8]. Once drilling and fracturing operations are complete, the waste generated is usually injected into Class II deep wells [7]; however, the long-term implica- tions of underground injection of O&G waste are not well understood, and this method permanently removes water from the fresh water cycle [2]. 1.1. Forward osmosis for treatment of O&G exploration wastewater Forward osmosis (FO) is an osmotically driven membrane process in which the driving force for separation is the difference in chemical potential between a concentrated draw solution and a broad range of aqueous solutions, including contaminated wastewater [9]. The process involves the permeation of water from a feed solution of low osmotic Desalination 312 (2013) 60–66 ⁎ Corresponding author. Tel.: + 1 303 273 3402; fax: + 1 303 273 3413. E-mail address: tcath@mines.edu (T.Y. Cath). 0011-9164/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2012.05.037 Contents lists available at SciVerse ScienceDirect Desalination journal homepage: www.elsevier.com/locate/desal