In the rapidly developing shale gas industry, managing produced water is a major challenge for maintaining the profitability of shale gas extraction while protecting public health and the environment. We review the current state of practice for produced water management across the United States and discuss the interrelated regulatory, infrastructure, and economic drivers for produced water reuse. Within this framework, we examine the Marcellus shale play, a region in the eastern United States where produced water is currently reused without desalination. In the Marcellus region, and in other shale plays worldwide with similar constraints, contraction of current reuse opportunities within the shale gas industry and growing restrictions on produced water disposal will provide strong incentives for produced water desalination for reuse outside the industry. The most challenging scenarios for the selection of desalination for reuse over other management strategies will be those involving high-salinity produced water, which must be desalinated with thermal separation processes. We explore desalination technologies for treatment of high-salinity shale gas produced water, and we critically review mechanical vapor compression (MVC), membrane distillation (MD), and forward osmosis (FO) as the technologies best suited for desalination of high-salinity produced water for reuse outside the shale gas industry. The advantages and challenges of applying MVC, MD, and FO technologies to produced water desalination are discussed, and directions for future research and development are identified. We find that desalination for reuse of produced water is technically feasible and can be economically relevant. However, because produced water management is primarily an economic decision, expanding desalination for reuse is dependent on process and material improvements to reduce capital and operating costs.

Biofouling is a major operational challenge in reverse osmosis (RO) desalination, motivating a search for improved biofouling control strategies. Copper, long known for its antibacterial activity and relatively low cost, is an attractive potential biocidal agent. In this paper, we present a method for loading copper nanoparticles (Cu-NPs) on the surface of a thin-film composite (TFC) polyamide RO membrane. Cu-NPs were synthesized using polyethyleneimine (PEI) as a capping agent, resulting in particles with an average radius of 34 nm and a copper content between 39 and 49 wt.%. The positive charge of the Cu-NPs imparted by the PEI allowed a simple electrostatic functionalization of the negatively charged RO membrane. We confirmed functionalization and irreversible binding of the Cu-NPs to the membrane surface with SEM and XPS after exposing the membrane to bath sonication. We also demonstrated that Cu-NP functionalization can be repeated after the Cu-NPs dissolve from the membrane surface. The Cu-NP functionalization had minimal impact on the intrinsic membrane transport parameters. Surface hydrophilicity and surface roughness were also maintained, and the membrane surface charge became positive after functionalization. The functionalized membrane exhibited significant antibacterial activity, leading to an 80-95% reduction in the number of attached live bacteria for three different model bacterial strains. Challenges associated with this functionalization method and its implementation in RO desalination are discussed.

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1Biofouling may lead to severe operational challenges that can significantly impair membrane 2 desalination processes. In recent years, copper-based nanoparticles (Cu-NPs) have gained 3 increased attention as a potentially viable anti-biofouling agent in membrane processes, due to 4 their strong antibacterial activity and relatively low cost. This study presents a novel and facile 5 method to attach biocidal Cu-NPs on the surface of a thin-film composite reverse osmosis 6 membrane. Herein, we suggest a method for membrane surface functionalization with Cu-NPs 7 that is performed without disassembling the membrane module, which highlights its practicality 8 and potential application for reverse osmosis desalination plants. The loading of Cu-NPs on the 9 membrane was confirmed both by scanning electron microscope imaging and X-ray 10 photoelectron spectroscopy analysis, indicating the deposited nanoparticles were composed of 11 either metallic copper or copper-oxide. The impact of the in situ Cu-NPs modification on 12 membrane transport properties was found to be minor, with only a slight increase of the water 13 and salt permeability. Furthermore, except for a slight increase in hydrophobicity, the modified 14 membrane exhibited surface properties comparable to those of the pristine membrane. Finally, 15 the in situ formed Cu-NPs imparted strong antibacterial activity to the membrane surface, 16 leading to 90 % reduction in the number of attached live E. coli bacteria on the modified 17 membrane compared to the pristine reverse osmosis membrane. This study demonstrates that in 18 situ grafting of Cu-NPs on reverse osmosis membranes is an alternative to reduce biofouling.19 20