There is increasing interest in beneficial uses of large volumes of wastewater co-produced with oil and gas extraction (produced water, PW) because of water scarcity, potential subsurface disposal limitations, and regional linkages to induced seismicity. Here we quantified PW volumes relative to water demand in different sectors and PW quality relative to treatment and reuse options for the major U.S. shale oil and gas plays. PW volumes from these plays totaled ~600 billion liters (BL, 160 billion gallons, Bgal) in 2017. One year of PW is equal to ~60% of one day of freshwater use in the U.S. For these plays, the total irrigation demand exceeded PW volumes by ~5× whereas municipal demand exceeded PW by ~2×. If PW is reused for hydraulic fracturing (HF) within the energy sector, there would be no excess PW in about half of the plays because HF water demand exceeds PW volumes in those plays. PW quality can be highly saline with median total dissolved solids up to 255 g/L in the Bakken play, ~7× seawater. Intensive water treatment required for PW from most unconventional plays would further reduce PW volumes by at least 2×. Desalination would also result in large volumes of salt concentrates, equivalent to ~3000 Olympic swimming pools in the Permian Delaware Basin in 2017. While water demands outside the energy sector could accommodate PW volumes, much lower PW volumes relative to water demand in most regions would not substantially alleviate water scarcity. However, large projected PW volumes relative to HF water demand over the life of the play in the Permian Delaware Basin may provide a substantial new water source for beneficial use in the future. Large knowledge gaps in PW quality, lack of appropriate regulations, and economic factors currently preclude beneficial uses outside the energy sector in most regions.

Desalination of seawater, brackish water, and reclaimed water is increasingly utilized worldwide to augment and diversify fresh water sources. The lack of economically and ecologically feasible concentrate management options, however, is a major barrier to widespread implementation of desalination, in particular at inland sites. This paper critically reviews strategies and technologies for concentrate management, including disposal, treatment, and beneficial use. Development of energy-efficient, cost-effective, and environmentally benign concentrate management systems is critical if desalination is to become a major part of a sustainable water future. This paper examines the limitations and advantages of a range of concentrate management tools, including emerging and novel technologies for minimization of concentrate volume, enhancement of water recovery, removal of organic contaminants, and recovery of valuable products and energy.

Scale deposits in water systems often result in ample technical and economic problems. Conventional chemical treatments for scale control are expensive and may cause health concerns and ecological implications. Non-chemical water treatment technologies such as electromagnetic field (EMF) are attractive options so the use of scale inhibitors, anti-scalants, or other chemical involved processes can be avoided or minimized. Although there are demonstrated beneficial effects of EMF on scale control, the scientific basis for its purported effectiveness is not clear in the available literature, especially lack of quantitative assessment and systematic evaluation of the effectiveness of EMF technologies. This review aims to elucidate the factors pertaining to EMF water treatment and their anti-scaling effects. We have critically reviewed relevant literature on EMF scale control, in particular recent studies, in various water systems, including desalination membranes, heat exchangers (e.g., cooling towers), water pipes, and bulk solutions. We systematically studied the impacts of operational conditions on EMF efficacy, and quantitatively evaluated the EMF improvement on scaling control. The scaling prevention mechanisms, conventional and cutting-edge characterization methods, and potential real-time monitoring techniques are summarized and discussed. The economic benefits of EMF treatment in terms of chemicals, operation and maintenance costs are highlighted. This review provides guidelines for future EMF system design and points out the research needed to further enhance EMF treatment performance.