High-Pressure Reverse Osmosis for Energy-Efficient Hypersaline

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High Pressure Reverse Osmosis for Energy-Efficient Hypersaline Brine Desalination: Current Status, Design Considerations, and Research Needs Douglas M Davenport, Akshay Deshmukh, Jay Ryan Werber, and Menachem Elimelech Environ. Sci. Technol. Lett., Just Accepted Manuscript • DOI: 10.1021/acs.estlett.8b00274 • Publication Date (Web): 29 Jun 2018 Downloaded from http://pubs.acs.org on July 4, 2018

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Environmental Science & Technology Letters

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High Pressure Reverse Osmosis for Energy-Efficient Hypersaline Brine Desalination: Current Status, Design Considerations, and Research Needs

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Douglas M. Davenport, Akshay Deshmukh, Jay R. Werber, and Menachem Elimelech*

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Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06520-8286, United States

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* Corresponding author: Menachem Elimelech, Email: [email protected], Phone: (203) 432-2789

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ABSTRACT

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Water scarcity, expected to become more widespread in the coming years, demands renewed

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attention to freshwater protection and management. Critical to this effort is the minimization of

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freshwater withdrawals and elimination of wastewater discharge, both which can be achieved via

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zero liquid discharge (ZLD), an aggressive wastewater management approach. Because of the

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high energetic cost of thermal desalination, ZLD is particularly challenging for high-salinity

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wastewaters. In this review, we discuss the potential of high pressure reverse osmosis (HPRO)

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(i.e., reverse osmosis operated at hydraulic pressure greater than ~100 bar) to efficiently

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desalinate hypersaline brines. We first discuss the inherent energy-efficiency of membrane

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processes as compared to conventional thermal processes for brine desalination. We then

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highlight the opportunity of HPRO to reduce energy requirements for desalination of key high-

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salinity industrial wastewaters. The current state of membrane materials and processes for

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hypersaline brine desalination is also discussed, emphasizing several process-design

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considerations unique to HPRO. Lastly, we discuss the most pressing research needs for the

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development of HPRO, notably the development of membranes and modules suitable for high

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pressures as well as fundamental studies of compaction and transport at HPRO conditions.

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INTRODUCTION

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Recent estimates suggest 1.2 billion people live in areas of physical water scarcity.1 Effective

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water resource management is critical to ensure the widespread availability of freshwater in the

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coming decades.2 Two specific concerns are the treatment and disposal of wastewater and the

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utilization of previously untapped water sources. Wastewater management from industrial

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sources is particularly challenging as it can be highly saline, vary temporally in volume and

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composition, and contain complex mixtures of contaminant species.3 The beneficial reuse of

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industrial wastewaters mitigates unsafe disposal by eliminating wastewater discharge, while

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simultaneously decreasing freshwater withdrawals.4, 5 A major challenge for the reuse of high-

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salinity wastewaters, however, is the high energetic cost of brine desalination.6 In the case of

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inland desalination, brine-disposal costs often render the desalination of brackish groundwater

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economically unfeasible.7 Low-cost brine management is critically needed to enable the

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utilization of inland brackish groundwater and prevent the unsafe discharge of saline industrial

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wastewaters.

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Due to the energy requirements for high-salinity wastewater desalination, the preferred brine

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management option  when it is both safe and effective to do so  is to dispose or reuse the

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waste stream without extensive treatment. For example, brine solutions (also called the retentate

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or reject) produced from seawater reverse osmosis (SWRO) processes can be safely discharged

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to the ocean without extensive treatment.8 In the oil and gas industry, produced water undergoes

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relatively moderate treatment such as dissolved air flotation, chemical precipitation, or advanced

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oxidation to remove oil and grease and reduce organic content.9 Produced water treated in this

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fashion is often discharged to the ocean at offshore locations, albeit with some environmental

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concerns.10 At inland sites, treated produced water can be reused in hydraulic fracturing fluid.9, 11

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When safe discharge or reuse are not possible, brines are commonly disposed of via deep-

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well injection or treated using evaporation ponds prior to solids disposal in landfills.9, 11-13 These

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processes, however, have serious environmental limitations. For instance, some geologic

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formations, such as those surrounding the Marcellus shale fields in the US, are unsuitable for

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wastewater disposal via deep-well injection due to a high potential to contaminate

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groundwater.14 Furthermore, deep-well injection has been linked to groundwater contamination

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in other areas as well as increased seismic activity.13 Volume minimization using evaporation



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ponds is similarly problematic as it poses a threat to groundwater and birdlife, requires large

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areas of land, and is only effective in warm, arid climates.15, 16 The challenges associated with

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brine management often result in exorbitant disposal costs, which can even lead to otherwise

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promising brackish water resources remaining untapped as sources for potable water.7 In order to

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avoid expensive brine disposal, increasing attention is being given to brine concentration and

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zero liquid discharge (ZLD) practices, in which waste is disposed of in solid form.17

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A critical step in the ZLD process chain is desalination, wherein water is recovered from a

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saline waste stream. Desalination can be achieved by membrane-based processes, such as reverse

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osmosis (RO) and electrodialysis, or phase-change-based (designated here as “thermal”)

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processes, including multi-effect distillation (MED), multi-stage flash (MSF), and mechanical

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vapor compression (MVC).18 RO utilizes hydraulic pressure, in excess of solution osmotic

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pressure, to drive the transport of water across a semi-permeable membrane while retaining most

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solutes.19 A combination of membrane and thermal processes are often used to achieve ZLD for

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saline wastewaters.20 First, RO concentrates wastewater to approximately 70,000 mg L-1 total

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dissolved solids (TDS), which has an osmotic pressure, π, of ~59 bar. At higher salinities,

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thermal technologies are used to concentrate brine streams to approximately 250,000 mg L-1 (π ≈

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290 bar), the typical inlet concentration for crystallizers in ZLD.17 Thermal-based brine

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crystallizers then concentrate the waste stream above its solubility limit (e.g., 357,000 mg L-1 for

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NaCl) to extract solid salts for disposal.17

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Because of its superior energy-efficiency, RO has displaced thermal processes in recent

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decades for the major applications of seawater and brackish water desalination for drinking water

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production.21 As such, membrane materials and processes have been optimized to treat

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feedwaters with salinities equal to or less than seawater (typically ~35,000 mg L-1, π ≈ 28 bar).

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Consequently, the maximum operating pressure for RO is typically around 80 bar,22 suitable to

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overcome the retentate osmotic pressure of seawater treated to 50% recovery (~70,000 mg L-1, π

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≈ 59 bar). Due to hydraulic pressure limitations of RO, hypersaline brines, here defined as

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solutions with a TDS concentration above 70,000 mg L-1, are primarily desalinated via thermal

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processes.17 These processes, however, are energy- and cost-intensive, which limits the

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implementation of brine wastewater desalination prior to disposal.


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In this article, we critically discuss the application of high-pressure RO (HPRO) — defined

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here as RO operating above ~100 bar — to the treatment of hypersaline brines. We start by

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considering the large volumes of industrial brines that could require desalination and the energy

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requirements of HPRO versus other processes. We largely consider two pressure limits for

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HPRO: (i) 150 bar as roughly double the current operating limit and (ii) 300 bar to enable

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retentate concentrations of 250,000 mg L-1, the inlet concentration for brine crystallizers. We

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then discuss the current state of HPRO and the process design requirements for its effective

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application. We conclude with discussion of the research needs that must be addressed to enable

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viable HPRO processes.

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ENERGY-EFFICIENCY OF MEMBRANE DESALINATION

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Desalinating highly saline waste streams is inherently energy intensive. The minimum specific

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energy consumption (SECmin) of desalination (i.e., the energy required by a thermodynamically

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reversible process per unit volume of product water) depends on the salinity of the feed stream,

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cF, and the water recovery ratio, R, the proportion of water recovered from the feed stream:23, 24

=

+ 1 − −

(1)

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where is the specific Gibbs free energy as a function of composition at fixed temperature and

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pressure, and cP and cR are the solute concentrations in the product and retentate streams,

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respectively. Assuming complete solute rejection, cP = 0 and = /1 − . Because of its

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salinity dependence, SECmin is high for hypersaline brines (5.3 kWh m-3 for 125,000 mg L-1 at

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50% recovery) as compared to more dilute solutions (1.1 kWh m-3 for 35,000 mg L-1 at 50%

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recovery). Further, the desalination energy efficiency, η, is defined as the useful specific

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desalination work performed by the system (i.e., SECmin) divided by its specific energy

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consumption (SEC): = /.

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Membrane-based desalination processes such as RO and electrodialysis, which do not

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require a phase change to separate water from dissolved solutes, are able to achieve energy

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efficiencies greater than 40%, particularly with multi-stage systems.24-26 In contrast, phase-

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change-based or thermal desalination processes, such as MED, MSF, and MVC, are inherently

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less efficient, with typical η values less than 20%.24,

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processes is strongly dependent on the recovery of the latent heat of vaporization, Δ . Given

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The energetic performance of thermal



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that Δ , greater than 630 kWh m-3 for saline waters, is two orders of magnitude larger than

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typical SECmin, imperfect heat recovery severely limits the energy efficiency of all thermal

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desalination processes.27

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To directly compare membrane- and thermal-based desalination (Figure 1A), we can

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quantitatively analyze the energetics of relevant processes. Typical SEC values and feed

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concentrations are shown in Figure 1B for conventional (largely thermal) desalination

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technologies,17,

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assuming a terminal hydraulic pressure (∆Pt) of 5 bar above the osmotic pressure of the retentate

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(πR).26, 28, 29 More detailed insights can be gained by modeling different processes for the same

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inlet and outlet streams. In particular, a feed solution of 70,000 mg L-1 NaCl is concentrated to

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250,000 mg L-1 via HPRO-based, MVC-based, and hybrid HPRO-MVC desalination systems

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(Figure 1A). MVC is chosen as a representative thermal process due to its highly effective heat

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recovery. Its SEC is calculated assuming isentropic (i.e., adiabatic and reversible) vapor

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compression with a terminal temperature difference (∆Tt) of 5 oC above the boiling point

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elevation of the retentate (δR).24, 30, 31 In the two-stage HPRO and MVC models, water recovery

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in each stage is optimized to minimize SEC. In the hybrid HPRO-MVC model, the HPRO stage

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is limited to a maximum hydraulic pressure of 150 bar. Further details on SEC calculations are

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given in the Supporting Information.

27

in addition to SEC calculated for HPRO. The SEC of HPRO is modelled

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FIGURE 1

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Figures 1C and 1D show the SEC and energy efficiency of each process, which illustrates

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the drastic three-fold energy savings made possible using HPRO rather than a thermal

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desalination process such as MVC. For example, concentration of 70,000 mg L-1 hypersaline

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feed to 250,000 mg L-1 would require 24 kWh m-3 with two-stage MVC (15% energy efficiency)

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and only 7.3 kWh m-3 (47% energy efficiency) with two-stage HPRO. For context, the RO stage

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in a typical SWRO process can operate as low as 1.8 kWh m-3 (59% energy efficiency).25

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Achieving a retentate concentration of 250,000 mg L-1 with HPRO would require approximately

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300 bar hydraulic pressure, a challenging target from membrane materials and module design

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perspectives. For this reason, a hybrid process is modeled where HPRO is limited to a maximum

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pressure of 150 bar, after which the retentate is further concentrated by MVC. At a retentate

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concentration of 250,000 mg L-1, the hybrid process SEC is 12 kWh m-3, representing a two-fold 6 ACS Paragon Plus Environment

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reduction compared to two-stage MVC. Below a retentate osmotic pressure of 150 bar, the SEC

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of the hybrid HPRO-MVC process is identical to the SEC of one-stage HPRO, as the optimal

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water recovery ratio of its first stage (HPRO) is almost equal to its final recovery. As the

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retentate osmotic pressure increases beyond 150 bar, the water recovery of the second stage

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(MVC) begins to increase, leading to an increase in SEC. It is important to note that the HPRO-

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MVC hybrid is a two-stage process and thus the brine flowrate entering the less-efficient MVC

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stage is significantly lower than the initial flow rate (approximately 50% lower for the conditions

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modeled). Consequently, the energetic performance of the hybrid HPRO-MVC process should

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be assessed relative to two-stage HPRO and two-stage MVC, rather than one-stage HPRO.

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POTENTIAL IMPACT OF HPRO

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A variety of industrial sources generate hypersaline brine wastewaters. Table 1 shows several

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brines of particular concern due to their large volume, concentration, or strict disposal

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regulations. In many circumstances, regulatory, financial, and environmental restrictions

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motivate brine concentration and volume reduction.17 The coal-to-chemicals industry in China,

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for example, requires ZLD for all new facilities.32 Additionally, the financial cost of brine

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disposal from inland desalination facilities motivates brine volume minimization.7 Further, strict

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disposal regulations for landfill leachate in the US and effluent from the textile industry in India

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necessitate brine volume reduction to minimize environmental impacts and health risks, despite

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the financial and energetic cost of brine desalination.33, 34

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TABLE 1

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Figure 2A shows the global desalination capacity which is currently installed or under

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construction for brine feedwaters with salinity ≥ 50,000 mg L-1 TDS.35 At present, these brine

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desalination processes utilize conventional thermal separation processes (e.g. MVC, MED, MSF)

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or conventional RO.35 Of the nearly 16,000 desalination plants online or under construction in

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the GWI/IDA Desalting Inventory, only 110 treat brine feedwaters.35 In practice, the high cost of

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brine desalination limits hypersaline wastewater desalination before disposal. Therefore, the total

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volume of hypersaline wastewater present in each industry is surely much greater. In the US, the

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Environmental Protection Agency cites the high financial cost of brine desalination as the reason

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it does not require evaporative brine concentration of flue gas desulfurization (FGD)



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wastewater.36 If cost-effective technologies were available, it is possible regulations would

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require brine desalination prior to disposal.

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FIGURE 2

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At present, thermal technologies account for 54% of the global brine desalination capacity.35

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The remaining 46% is treated using RO, but information is unavailable on water recoveries and

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operating pressures. To understand the energetic cost of treating these waste streams, we

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estimated the energy (Figure 2B) needed to concentrate the total quantity of brine wastewaters

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currently desalinated in each industry to 250,000 mg L-1 (initial volumes and concentrations are

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provided in Table S1 of Supporting Information). In these calculations, two-stage RO

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concentrates wastewater up to 70,000 mg L-1 followed by two-stage HPRO or two-stage MVC.

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The energy required to desalinate each stream is shown alongside the proportion this represents

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of the average daily US national electricity generation (NEG).37 In each scenario, MVC would

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require approximately two to three times more energy than HPRO. In the power industry, for

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example, approximately one million kWh day-1 (the equivalent of ~34,000 US homes)37 would

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be saved using HPRO as compared to MVC.

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Because of the lack of widespread brine desalination, a hypothetical scenario (Figure 2B) is

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imagined to estimate the potential energy savings of HPRO compared to MVC for each

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wastewater in Table 1. In this scenario, regulations require all saline wastewaters to be

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concentrated to 250,000 mg L-1 prior to disposal (i.e., approaching ZLD). The potential energy

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savings are most notable for large-volume applications like produced water, where MVC would

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require 130 million kWh day-1, representing 1.2% of the daily US NEG.37 In contrast, HPRO

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would utilize 85 million kWh day-1 less than MVC, albeit still requiring 0.4% of the daily US

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NEG.37 Consequently, despite being two- to three-fold more efficient than MVC, the high

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thermodynamic minimum energy of desalination will mean considerable quantities of energy

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would be required for HPRO. As such, work should be done to model the financial costs and

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human health and environmental impacts of hypersaline wastewater management38 to identify

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applications best suited for HPRO.


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CURRENT STATE OF MEMBRANE BRINE DESALINATION

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A few commercially available membranes rated above 80 bar currently exist. Most notable is the

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Pall Disc TubeTM (DT) Module System, which has been used for landfill leachate treatment.39

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DT modules are plate-and-frame configuration with large feed channels designed to reduce

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fouling from highly contaminated leachate streams. As a result, they have a low active

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membrane area (9 m2 per element)40 compared to high-pressure membranes with a spiral wound

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module design (27 m2 per element).41 Several DT module configurations are available ranging in

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maximum pressure during filtration from 70 bar to 150 bar.40 Average water output, however, is

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fairly low at 3 m3 day-1 per module for the treatment of landfill leachate or other wastewaters.40

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Membranes were also designed by Toray in the early 2000s for operation up to 100 bar to

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achieve 60% recovery SWRO.42 Nonetheless, at present, the maximum operating pressure for

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currently available Toray RO membranes is 83 bar.43 Additionally, Dow recently started

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manufacturing a specialty line of RO elements rated at operating pressures up to 120 bar.41, 44

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The largest of these spiral wound elements (8-inch diameter) is rated to generate permeate flow

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rates of 24.2 m3 day-1, albeit when treating 32,000 mg L-1 NaCl to 8% recovery at 55 bar

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(standard SWRO test conditions).41 The achievable permeate flowrate during high-pressure

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operation is unclear.

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To circumvent the need for high hydraulic pressures, alternative “osmotically-assisted” RO

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process configurations have recently been proposed that theoretically could use conventional

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(~70 bar) pressures.45,

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membrane permeate-side to reduce the osmotic pressure difference across the membrane and

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thus the required applied hydraulic pressure.45, 46 Several stages would be used to sequentially

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decrease the feed and permeate osmotic pressures, until finally conventional RO can be used to

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produce pure water. While these osmotically-assisted RO processes could theoretically avoid

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high pressure operation, their performance is inherently limited by internal concentration

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polarization (ICP) in the membrane support layer. As previous studies on forward osmosis have

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shown, ICP reduces the solute concentration at the permeate-side membrane-solution interface,

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drastically reducing the transmembrane driving force for water permeation and thus limiting

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water flux.47, 48

46

These hypothetical processes would use a saline solution at the



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Designing membranes for osmotically-assisted RO to mitigate ICP will be very challenging.

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An intrinsic tradeoff exists between ICP reduction and mechanical integrity: the membrane

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properties that decrease ICP (low support layer thickness and high porosity) will decrease the

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pressure tolerance of the membrane. The use of pressure retarded osmosis (PRO) membranes has

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been proposed in order to balance these contradictory needs;45 however, recent work has shown

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dramatic deformation of PRO membranes to take place at 55 bar applied pressure, the maximum

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pressure achieved prior to failure.49 In addition to ICP, increased capital costs from staging and

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high frictional pressure drops in the permeate channels49 would also hinder the proposed

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processes.

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HPRO PROCESS DESIGN CONSIDERATIONS

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The design and operation of conventional RO processes is well-established for brackish water

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RO and SWRO. However, at high pressure and salinity, HPRO will likely require unique design

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considerations. In this section, we discuss several aspects of HPRO process design which must

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be addressed for the development of membrane-based hypersaline brine desalination.

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Concentration polarization (CP) in the feed channel during RO increases the osmotic

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pressure at the membrane surface, πm, thus increasing the pressure needed to effect flux. Using

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film theory and the van’t Hoff approximation, CP modulus can be defined as 19

262

%

= exp $ & ( '

(2)

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where πb and πp are the osmotic pressures in the bulk feed and permeate solutions, respectively,

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Jw is the water flux, and k is the mass transfer coefficient. Neglecting the permeate osmotic

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pressure (πp = 0 assuming complete solute rejection) and changes in mass transfer coefficient,

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which will be affected to some extent by salinity (Figure S1), the ratio πm/πb is constant for a

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given water flux, meaning that the relative increase in osmotic pressure should be similar for

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different feed solutions. Conversely, the absolute increase in osmotic pressure from CP is

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correspondingly greater for high-salinity feeds. For example, a modest CP modulus of 1.15

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increases the feed osmotic pressure of flowback water (modeled as 157,000 mg L-1 TDS)50 by 26

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bar, approximately the osmotic pressure of seawater.


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We performed module-scale modeling to assess the impact of CP for one- and two-stage

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HPRO processes (Figure 3A). Comparing 35,000 mg L-1, 70,000 mg L-1, and 125,000 mg L-1

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feeds (each at 50% recovery), water fluxes are surprisingly similar. This result is partially a

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function of conventional direct-pass RO operation where the hydraulic pressure driving force is

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roughly the same throughout the module: the increased driving force at the head of the module

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for hypersaline feeds roughly balances the impact of increased CP. To improve process

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efficiency, inter-stage design (i.e., placing higher-rejection, low-flux membrane elements at the

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head of the module) may be useful to balance water flux along the module length (Figure S2).51

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While this analysis only considers a few cases, it appears that SWRO-like water fluxes (10−15 L

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m-2 h-1) should theoretically be attainable for HPRO, despite the increased CP stemming from the

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high feed osmotic pressures.

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FIGURE 3

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Although CP is expected to impact water flux relatively little in HPRO, it may critically

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influence inorganic scaling. In RO, sparingly soluble salts near their solubility limit can

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precipitate due to CP or increased retentate concentrations as water recovery increases.52 Scaling

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could be a performance-limiting phenomenon in HPRO processes, particularly at high water

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recovery (e.g., ZLD). Common scale forming species, including Ca2+, Mg2+, CO32-, SO42-, Ba2+,

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Sr2+, and silica,53,

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example, has average concentrations of gypsum precursors Ca2+ and SO42- of 2,000 mg L-1 and

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13,000 mg L-1, respectively.36 If FGD effluent (33,000 mg L-1 TDS)36 was concentrated to

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250,000 mg L-1 TDS (87% recovery), Ca2+ and SO42- concentrations would be 15,000 mg L-1 and

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100,000 mg L-1, respectively, far above the 2,400 mg L-1 solubility limit of gypsum.55 Further,

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antiscalants which are commonly used to prevent scaling in conventional RO53 have been

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ineffective at high ionic strength.56 Pretreatment processes are commonly employed to remove

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foulants in conventional RO desalination processes.22 Similarly, pretreatment to remove scale-

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forming species may be necessary to achieve high water recoveries in HPRO.

54

are present in many hypersaline brine wastewaters. FGD effluent, for

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An important consideration for HPRO is the large volumes of hypersaline brines which exist

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globally. To meet this need, HPRO technologies should have a high specific membrane area (i.e.,

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membrane surface area per unit volume of membrane module) in order to desalinate large-

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volume brines in compact facilities. Figure 3B shows the specific membrane surface area for 11 ACS Paragon Plus Environment


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several common module design configurations. While hollow fibers would provide the greatest

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specific areas, their employment in RO is affected by high bore-side pressure drops and poorly-

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defined shell-side fluid flow.19 In contrast, spiral wound modules are commonly used for

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conventional RO and, because SWRO-like water fluxes are expected for HPRO (Figure 3A),

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they are potentially an optimal HPRO module design. The design of modules and pressure

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vessels suitable for HPRO should be relatively simple using high-strength materials or more

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robust designs. Costs may increase for auxiliary system components and piping which must

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withstand high pressure and resist corrosion when exposed to hypersaline brines. The most

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challenging module design consideration is likely gluing membrane sheets together to form an

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envelope which can withstand high pressure, although this can likely be achieved using high-

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strength adhesives. Permeate spacers should also be designed for HPRO to minimize membrane

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deformation into spacer voids without large increases in frictional pressure losses.

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From a process design standpoint, high salinities in HPRO will incentivize unconventional

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configurations to decrease energy consumption. Conventional RO process designs (e.g., one-

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stage RO) are likely the best options to concentrate feed waters up to 70,000 mg L-1 due to

317

capital cost concerns. At higher concentrations (i.e., HPRO), energy costs would likely

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incentivize two-stage processes, which would substantially reduce energy requirements

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compared to a one-stage process, as shown in Figure 1C. Additional configurations are also

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possible such as batch and semi-batch RO (also called closed-circuit RO), which use retentate

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recycle streams.26 Energetic modeling has shown these processes could achieve similar energy

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consumption as two- or three-stage RO, without physical staging.26

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RESEARCH NEEDS FOR HPRO

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Conventional RO is a mature technology with high-performing materials, well-understood

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transport phenomena, and robust process designs.25 However, much is unknown about the

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behavior of membrane materials and processes at HPRO conditions. In this section, we highlight

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the primary research needs for the development and large-scale implementation of HPRO.

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One of the greatest unknown aspects of HPRO is the fundamental effect of membrane

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compaction (i.e., physical deformation) on membrane performance at high pressure. At present,

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only a few studies have assessed RO above 100 bar, with maximum tested pressures of 200

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bar.57, 58 These studies observed decreased water permeability at high pressure and attributed it to 12 ACS Paragon Plus Environment

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compaction, although compaction was not directly observed. Indeed, even at conventional RO

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pressures, much remains unknown about the nature of compaction. Laboratory-scale studies

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commonly attribute declining water permeability to compaction; however, recent work indicates

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fouling may be the primary cause.59 Compaction is best studied in ultrafiltration (UF) processes,

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where it has a strong dependence on membrane composition and morphology.60-63 Decreased

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water permeability has been correlated to changes in overall thickness63 and some results

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speculate it is primarily a result of compaction in the uppermost skin layer of UF membranes.62

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The compaction behavior of UF membranes may contribute to developing an understanding of

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RO compaction as the support layer of state-of-the-art thin-film composite (TFC) membranes is

341

typically a polysulfone (PSf) UF membrane. However, the polyamide selective layer dominates

342

resistance in TFC membranes, which complicates direct translation from study of UF

343

membranes. In TFC membranes, compaction is typically considered to occur in the support

344

layer;64 however, a recent study speculated that compaction can occur in the dense selective layer

345

as well.65 A much greater understanding of the location and impact of compaction is critically

346

needed for the development of deformation-resistant HPRO membranes.

347

Once the mechanisms of compaction are understood, high-strength membranes must be

348

fabricated with high water permeability and salt rejection at HPRO conditions. At high pressures,

349

membranes may follow two possible modes of failure: severe compaction, resulting in no

350

permeability, or rupture, resulting in no salt rejection. In the case of severe compaction, polymer

351

networks may deform to the extent they form a dense, impermeable film. Above a certain

352

pressure limit, however, membranes are likely to rupture, causing a catastrophic loss of solute

353

rejection. In spiral wound membranes, rupture is likely to occur within the voids of the permeate-

354

side spacer. Alternatively, in hollow fibers with a shell-side feed, membranes are likely to

355

collapse under pressure.

356

To gain an understanding of membrane mechanical strength, Figure 3C estimates the

357

compression pressure for non-porous hollow fibers fabricated from different polymers, with steel

358

and Kevlar shown for reference. This analysis focuses on hollow fiber membranes because their

359

cylindrical shape is more well-defined than flat sheet membranes supported by permeate spacers,

360

as in spiral wound modules. The von Mises criterion estimates the first point of fiber

361

compression as a function of applied pressure, material compressive yield strength, and fiber 13 ACS Paragon Plus Environment


362

radii ratio (details in Supporting Information).66, 67 The results in Figure 3C, calculated for non-

363

porous polymer materials, suggest high pressures may be achievable; however, material strength

364

will decrease considerably for porous materials. A critical research need is to identify porous

365

membrane morphologies that exhibit high compressive yield strength without compromising

366

membrane performance. It can be seen that polysulfone (PSf), the typical TFC RO support layer

367

material, has a relatively large pressure tolerance in comparison to the other polymers shown. As

368

such, it may be necessary to develop novel high-strength support layer materials to provide the

369

pressure resistance needed for HPRO. Figure 3C also shows a plateau in compression pressure

370

may be reached at a certain fiber radii ratio, indicating that increased support layer thickness may

371

not significantly increase pressure resistance and high-strength materials may be needed.

372

In addition to the unknown behavior of compaction, transport mechanisms in HPRO are

373

poorly understood. Water and solute transport in RO is traditionally characterized by the

374

solution-diffusion model.19 While this model is widely accepted and adequate for conventional

375

RO, it has not been tested at salinities and pressures relevant to HPRO. In the solution-diffusion

376

model, salt flux, Js, is typically defined as )* = +∆, where ∆C is the difference in salt

377

concentration between the feed- and permeate-side interfaces of the selective layer and B is the

378

salt permeability coefficient, typically assumed constant for a given membrane.19 However,

379

recent work has found B to increase substantially with salt concentration, possibly due to

380

decreased impacts of electrostatic repulsion to reject ions at higher salinities.49 To understand

381

this behavior, the mechanisms and assumptions of the solution-diffusion model must be studied

382

at HPRO conditions.

383

OUTLOOK FOR HPRO

384

The development of HPRO has the potential to enable energy-efficient and cost-effective

385

hypersaline brine desalination, although, due to the high thermodynamic minimum energy of

386

desalination, the quantity of energy required by HPRO remains relatively large. Therefore,

387

HPRO may be best-suited for applications where strict regulations or operational circumstances

388

preclude direct reuse or safe disposal of saline brines. Nevertheless, saline wastewater discharge

389

to the environment is undesirable. If the development of HPRO enables energy-efficient brine

390

desalination, future regulations may further restrict brine discharge practices, motivating greater

391

need for ZLD. 14 ACS Paragon Plus Environment

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Page 15 of 28


392

Decades of work improving conventional RO will provide a foundational knowledge from

393

which HPRO can be developed. It is possible many aspects of conventional RO membrane and

394

process design will directly translate to HPRO. Even so, significant work will be needed where

395

knowledge gaps exist, notably the fundamental nature of compaction. Similarly, inorganic

396

scaling, a performance-limiting phenomenon in conventional RO, may limit the achievable

397

recoveries of HPRO and necessitates the development of effective and efficient pretreatment to

398

remove scale-forming species.

399

Current brine management practices are expensive and environmentally unsustainable. At

400

present, saline waste streams are discharged to the environment, evaporated in large ponds, or

401

injected into the ground. Where ZLD is required, inefficient thermal separation processes must

402

be used. These costly and environmentally unsound disposal practices prevent the use of inland

403

brackish groundwater, often abundant in water scarce regions, and inhibit beneficial reuse of

404

saline industrial wastewater. In order to help increase the utilization of these waters, HPRO

405

offers great promise as an energy-efficient and cost-effective brine desalination technology.

406

ASSOCIATED CONTENT

407

Supporting Information

408

Derivation of energy-consumption equations, methodology of module-scale water flux analysis,

409

methodology for specific area calculations of various module designs, calculation of nonporous

410

hollow fiber compression pressure, industrial wastewater data (Table S1), CP modulus

411

dependence on Re and Sc (Figure S1), water flux as a function of module position (Figure S2),

412

and pressure drop for various feed concentrations (Figure S3). This information is available free

413

of charge on the ACS Publications website.

414

ACKNOWLEDGMENTS

415

We acknowledge the support received from the National Science Foundation under Grant CBET-

416

1701658 and Graduate Research Fellowship DGE-1122492 awarded to J.R.W.

417 418



419

REFERENCES

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22. Fritzmann, C.; Löwenberg, J.; Wintgens, T.; Melin, T., State-of-the-art of reverse osmosis desalination. Desalination 2007, 216, 1-76. 23. Mistry, K.; Lienhard, J., Generalized Least Energy of Separation for Desalination and Other Chemical Separation Processes. Entropy 2013, 15, 2046. 24. Mistry, K. H.; McGovern, R. K.; Thiel, G. P.; Summers, E. K.; Zubair, S. M.; Lienhard, J. H., Entropy Generation Analysis of Desalination Technologies. Entropy 2011, 13, 1829. 25. Elimelech, M.; Phillip, W. A., The Future of Seawater Desalination: Energy, Technology, and the Environment. Science 2011, 333, 712-717. 26. Werber, J. R.; Deshmukh, A.; Elimelech, M., Can batch or semi-batch processes save energy in reverse-osmosis desalination? Desalination 2017, 402, 109-122. 27. Deshmukh, A.; Boo, C.; Karanikola, V.; Lin, S.; Straub, A. P.; Tong, T.; Warsinger, D. M.; Elimelech, M., Membrane distillation at the water-energy nexus: limits, opportunities, and challenges. Energy Environ. Sci. 2018, 11, 1177-1196. 28. Sharqawy, M. H.; Lienhard, J. H.; Zubair, S. M., Thermophysical properties of seawater: a review of existing correlations and data. Desalin. Water Treat. 2010, 16, 354-380. 29. Nayar, K. G.; Sharqawy, M. H.; Banchik, L. D.; Lienhard V, J. H., Thermophysical properties of seawater: A review and new correlations that include pressure dependence. Desalination 2016, 390, 124. 30. Thiel, G. P.; Tow, E. W.; Banchik, L. D.; Chung, H. W.; Lienhard V, J. H., Energy consumption in desalinating produced water from shale oil and gas extraction. Desalination 2015, 366, 94-112. 31. Stoughton, R. W.; Lietzke, M. H., Thermodynamic properties of sea salt solutions. J. Chem. Eng. Data 1967, 12, 101-104. 32. Xiong, R.; Wei, C., Current status and technology trends of zero liquid discharge at coal chemical industry in China. Journal of Water Process Engineering 2017, 19, 346-351. 33. Effluent Limitations Guidelines, Pretreatment Standards, and New Source Performance Standards for the Landfills Point Source Category; Final Rule; United States Environmental Protection Agency: Washington DC, 2000. 34. Environment (Protection) Fifth Amendment Rules, 2016. In India Ministry of Environment, F. a. C. C., Ed. The Gazette of India: New Delhi, India, 2016; Vol. G.S.R. 978(E). 35. GWI/IDA Desalting Inventory. http://www.desaldata.com (February 26, 2018). 36. Technical Development Document for the Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category; United States Environmental Protection Agency Washington DC, 2015.

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37. Electric Power Annual 2016; United States Energy Information Administration: Washington DC, 2017. 38. Bartholomew, T. V.; Mauter, M. S., Multiobjective Optimization Model for Minimizing Cost and Environmental Impact in Shale Gas Water and Wastewater Management. ACS Sustainable Chem. Eng. 2016, 4, 3728-3735. 39. Renou, S.; Givaudan, J. G.; Poulain, S.; Dirassouyan, F.; Moulin, P., Landfill leachate treatment: Review and opportunity. J. Hazard. Mater. 2008, 150, 468-493. 40. Disc Tube Module System Datasheet; Pall Corporation: Port Washington, NY, 2010. 41. DOW™ XUS180808 Reverse Osmosis Element Product Data Sheet; The Dow Chemical Company: Midland, MI, 2016. 42. Taniguchi, M.; Kurihara, M.; Kimura, S., Behavior of a reverse osmosis plant adopting a brine conversion two-stage process and its computer simulation. J. Membr. Sci. 2001, 183, 249-257. 43. Standard SWRO: TM800M; Toray Industries, Inc.: Tokyo, Japan, 2014.



512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558

44. DOW™ Specialty Membrane XUS180804 and XUS180802 Reverse Osmosis Elements Product Data Sheet; The Dow Chemical Company: Midland, MI, 2017. 45. Bartholomew, T. V.; Mey, L.; Arena, J. T.; Siefert, N. S.; Mauter, M. S., Osmotically assisted reverse osmosis for high salinity brine treatment. Desalination 2017, 421, 3-11. 46. Chen, X.; Yip, N. Y., Unlocking High-Salinity Desalination with Cascading Osmotically Mediated Reverse Osmosis: Energy and Operating Pressure Analysis. Environ. Sci. Technol. 2018, 52, 2242-2250. 47. McCutcheon, J. R.; Elimelech, M., Influence of concentrative and dilutive internal concentration polarization on flux behavior in forward osmosis. J. Membr. Sci. 2006, 284, 237-247. 48. Deshmukh, A.; Yip, N. Y.; Lin, S.; Elimelech, M., Desalination by forward osmosis: Identifying performance limiting parameters through module-scale modeling. J. of Membr. Sci. 2015, 491, 159-167. 49. Straub, A. P.; Osuji, C. O.; Cath, T. Y.; Elimelech, M., Selectivity and Mass Transfer Limitations in Pressure-Retarded Osmosis at High Concentrations and Increased Operating Pressures. Environ. Sci. Technol. 2015, 49, 12551-12559. 50. Haluszczak, L. O.; Rose, A. W.; Kump, L. R., Geochemical evaluation of flowback brine from Marcellus gas wells in Pennsylvania, USA. Appl. Geochem. 2013, 28, 55-61. 51. Peñate, B.; García-Rodríguez, L., Reverse osmosis hybrid membrane inter-stage design: A comparative performance assessment. Desalination 2011, 281, 354-363. 52. Shirazi, S.; Lin, C.-J.; Chen, D., Inorganic fouling of pressure-driven membrane processes — A critical review. Desalination 2010, 250, 236-248. 53. Antony, A.; Low, J. H.; Gray, S.; Childress, A. E.; Le-Clech, P.; Leslie, G., Scale formation and control in high pressure membrane water treatment systems: A review. J. Membr. Sci. 2011, 383, 1-16. 54. Fakhru’l-Razi, A.; Pendashteh, A.; Abdullah, L. C.; Biak, D. R. A.; Madaeni, S. S.; Abidin, Z. Z., Review of technologies for oil and gas produced water treatment. J. Hazard. Mater. 2009, 170, 530-551. 55. Deng, M.; Liu, Q.; Xu, Z., Impact of gypsum supersaturated water on the uptake of copper and xanthate on sphalerite. Miner. Eng. 2013, 49, 165-171. 56. Greenlee, L. F.; Lawler, D. F.; Freeman, B. D.; Marrot, B.; Moulin, P., Reverse osmosis desalination: Water sources, technology, and today's challenges. Water Res. 2009, 43, 2317-2348. 57. Rautenbach, R.; Linn, T., High-pressure reverse osmosis and nanofiltration, a “zero discharge” process combination for the treatment of waste water with severe fouling/scaling potential. Desalination 1996, 105, 63-70. 58. Rautenbach, R.; Linn, T.; Eilers, L., Treatment of severely contaminated waste water by a combination of RO, high-pressure RO and NF — potential and limits of the process. J. Membr. Sci. 2000, 174, 231-241. 59. Van Wagner, E. M.; Sagle, A. C.; Sharma, M. M.; Freeman, B. D., Effect of crossflow testing conditions, including feed pH and continuous feed filtration, on commercial reverse osmosis membrane performance. J. Membr. Sci. 2009, 345, 97-109. 60. Brinkert, L.; Abidine, N.; Aptel, P., On the relation between compaction and mechanical properties for ultrafiltration hollow fibers. J. Membr. Sci. 1993, 77, 123-131. 61. Persson, K. M.; Gekas, V.; Trägårdh, G., Study of membrane compaction and its influence on ultrafiltration water permeability. J. Membr. Sci. 1995, 100, 155-162. 62. Stade, S.; Kallioinen, M.; Mikkola, A.; Tuuva, T.; Mänttäri, M., Reversible and irreversible compaction of ultrafiltration membranes. Sep. Purif. Technol. 2013, 118, 127-134. 63. Aghajani, M.; Maruf, S. H.; Wang, M.; Yoshimura, J.; Pichorim, G.; Greenberg, A.; Ding, Y., Relationship between permeation and deformation for porous membranes. J. Membr. Sci. 2017, 526, 293-300. 64. Jonsson, G., Methods for determining the selectivity of reverse osmosis membranes. Desalination 1977, 24, 19-37.


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65. Pendergast, M. T. M.; Nygaard, J. M.; Ghosh, A. K.; Hoek, E. M. V., Using nanocomposite materials technology to understand and control reverse osmosis membrane compaction. Desalination 2010, 261, 255-263. 66. Ekiner, O. M.; Vassilatos, G., Polyaramide hollow fibers for hydrogen/methane separation — spinning and properties. J. Membr. Sci. 1990, 53, 259-273. 67. Koh, D.-Y.; McCool, B. A.; Deckman, H. W.; Lively, R. P., Reverse osmosis molecular differentiation of organic liquids using carbon molecular sieve membranes. Science 2016, 353, 804-807. 68. Schock, G.; Miquel, A., Mass transfer and pressure loss in spiral wound modules. Desalination 1987, 64, 339-352. 69. Balster, J.; Pünt, I.; Stamatialis, D. F.; Wessling, M., Multi-layer spacer geometries with improved mass transport. J. Membr. Sci. 2006, 282, 351-361. 70. Inoue, N., Polymers. In Hydrostatic Extrusion: Theory and Applications, Inoue, N.; Nishihara, M., Eds. Springer Netherlands: Dordrecht, 1985; pp 333-362. 71. Raddon, B. J. Biaxial restraint of axially loaded steel cores. M.S., The University of Utah, Ann Arbor, 2010. 72. Deteresa, S. J.; Allen, S. R.; Farris, R. J.; Porter, R. S., Compressive and torsional behaviour of Kevlar 49 fibre. J. Mater. Sci. 1984, 19, 57-72. 73. Renner, R., Pennsylvania to regulate salt discharges. Environ. Sci. Technol. 2009, 43, 6120-6120. 74. Mickley, M. C. Membrane Concentrate Disposal: Practices and Regulation; U.S. Department of the Interior Bureau of Reclamation: Washington DC, 2006. 75. Huang, Y. H.; Peddi, P. K.; Tang, C.; Zeng, H.; Teng, X., Hybrid zero-valent iron process for removing heavy metals and nitrate from flue-gas-desulfurization wastewater. Sep. Purif. Technol. 2013, 118, 690-698. 76. Gingerich, D. B.; Grol, E.; Mauter, M. S., Fundamental challenges and engineering opportunities in flue gas desulfurization wastewater treatment at coal fired power plants. Environ. Sci.: Water Res. Technol. 2018, 4, 909-925. 77. Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category; Final Rule United States Environmental Protection Agency: Washington DC, 2015. 78. Postponement of Certain Compliance Dates for the Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category; United States Environmental Protection Agency: Washington DC, 2017. 79. Browner, C. M.; Fox, J. C.; Grubbs, G. H.; Frace, S. E.; Forsht, E. H.; Ebner, M. C. Development Document for Final Effluent Limitations Guidelines and Standards for the Landfills Point Source Category; United States Environmental Protection Agency: Washington DC, 2000. 80. Dasgupta, J.; Sikder, J.; Chakraborty, S.; Curcio, S.; Drioli, E., Remediation of textile effluents by membrane based treatment techniques: A state of the art review. J. Environ. Manage. 2015, 147, 55-72. 81. Vishnu, G.; Palanisamy, S.; Joseph, K., Assessment of fieldscale zero liquid discharge treatment systems for recovery of water and salt from textile effluents. J. Cleaner Prod. 2008, 16, 1081-1089. 82. Verma, A. K.; Dash, R. R.; Bhunia, P., A review on chemical coagulation/flocculation technologies for removal of colour from textile wastewaters. J. Environ. Manage. 2012, 93, 154-168.

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FIGURE 1. (A) Brine desalination process schematics. Three different process configurations are shown for the concentration of a 70 g L-1 NaCl solution to 250 g L-1. (B) Specific energy consumption (SEC) of various desalination processes. The typical feed concentration range and energy consumption are shown for conventional RO and thermal brine concentrators.17, 27 The expected SEC calculated for high pressure reverse osmosis (HPRO), at pressures up to 150 bar and 300 bar, is also shown. (C) Specific energy consumption and (D) energy efficiency for HPRO and mechanical vapor compression (MVC) brine desalination processes. The energy consumption requirements of five membrane- and thermal-based process configurations are analyzed for the desalination of 70 g L-1 NaCl at increasing retentate concentration (i.e., water recovery). Energy efficiency, η, is the ratio of the minimum energy of desalination for a given brine salinity and recovery, SECmin, to the SEC for each process. Shown here are one- and twostage processes for both HPRO and MVC. A hybrid HPRO-MVC process is also shown where an HPRO stage is employed up to a maximum applied pressure of 150 bar followed by an MVC stage. The water recovery ratio of each stage is optimized to reduce specific energy consumption for each two-stage process. Further details about the calculations are provided in the Supporting Information.

621 21 ACS Paragon Plus Environment


622 623 624 625 626 627 628 629 630 631 632 633 634 635 636

FIGURE 2. (A) Global installed desalination capacity for brine feedwaters with TDS ≥ 50,000 mg L-1.35 For each industry, hollow bars represent the capacity desalinated by membrane-based processes and solid bars represent brine capacity desalinated by thermal processes. (B) Energy consumption of brine desalination. The left-most portion of the figure shows the daily energy consumption required to desalinate the total quantity of brine wastewaters currently treated in each industry. The right-most portion of the figure shows a hypothetical scenario where the total volume of each saline wastewater presented in Table 1 must be concentrated to 250,000 mg L-1 prior to disposal. In each case, the energy consumption shown is that to concentrate the saline wastewaters to 70,000 mg L-1 using a two-stage RO system followed by either a two-stage HPRO or two-stage MVC process to concentrate the brine to 250,000 mg L-1. Hollow bars represent the HPRO process scheme and solid bars represent MVC. The corresponding percentage of the daily US national electricity generation (NEG) is also shown.37 Additional calculation details are provided in the Supporting Information.

637


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638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659

FIGURE 3. (A) Average water flux calculated from module-scale membrane process modeling. The average water flux for one- and two-stage HPRO processes at 50% water recovery is shown for different terminal hydraulic pressures, ∆Pt (i.e., applied pressure in excess of the retentate osmotic pressure). Osmotic pressures of the exiting retentate solution are also shown. Mass transfer coefficients are calculated using Sherwood-Reynolds-Schmidt correlations and a water permeability coefficient, A, of 1 L m-2 h-1 bar-1 is assumed. (B) Specific membrane area for common module designs. The specific membrane area is shown as a function of characteristic length along with the permeate production rate for a typical 8-inch diameter, 40-inch long module operating at 10 L m-2 h-1. Characteristic length shown here is the feed channel height for typical spiral wound68 and plate-and-frame modules.69 For hollow fiber modules, the characteristic length is the average distance between fibers for typical module packing densities.19 Schematics are shown where dark blue regions are the feed stream, light blue is the permeate, black is the membrane active layer, gray is the membrane support layer, and the characteristic length, a, is shown in white. (C) Compression pressure for nonporous hollow fibers. The compression pressure is calculated using the von Mises criterion as a function of the fiber radius ratio.66 Shown here are dense, nonporous materials which will have a greater compressive yield strength than porous hollow fiber membranes. The materials shown are polytetrafluoroethylene (PTFE), cellulose acetate (CA), polyvinyl chloride (PVC), polysulfone (PSf), polyimide (PI), A36 Steel, and Kevlar 49. The compressive yield strength, σ, is listed for each material.70-72

660



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Table 1: Characteristics of Significant Brine Sources, Current Practices, and Disposal Regulations brine wastewater oil & gas produced water

representative flowrate United States11 8.7 million m3 day-1

typical TDS (mg L-1) 13,000 - 210,0009

current disposal practice offshore11 direct ocean discharge onshore9, 11 deep well injection, where possible

regulations regarding disposal United States9, 11 regulations vary regionally based on permits Pennsylvania:73 discharge monthly average TDS < 500 mg L-1

reuse for hydraulic fracturing evaporation ponds brackish groundwater desalination retentate

United States35, 56 1.6 million m3 day-1

flue gas desulfurization (FGD) wastewater

United States36 1.2 million m3 day-1

5,000 - 55,00056

surface or sewer discharge74 deep well injection, where possible74

16,000 - 50,00036, 75

settling ponds36, 76 chemical precipitation and surface discharge36, 76

United States74 regulations vary regionally based on permits United States77 monthly average TDS < 24 mg L-1 (effective starting November 2020)78

zero liquid discharge36, 76 landfill leachate

United States79 230,000 m3 day-1

0 - 50,00079

zero liquid discharge via land application or recirculation to the landfill79

United States33 strict discharge regulations on 9 to 14 parameters not including TDS

coal-tochemicals wastewater

China32 320,000 m3 day-1

2,000 - 16,00017

zero liquid discharge 32

China17, 32 zero liquid discharge required for new plants

textile industry wastewater

estimates not available

1,500 -30,00080

zero liquid discharge81

India34 TDS < 2,100 mg L-1 for inland discharge

chemical and biological treatment prior to surface discharge82

663


APage 25 of 28

-1

70 g L TDS

250 g L TDS water for reuse

Conventional RO ∆Pmax = 80 bar

Hybrid HPRO-MVC ∆Pmax = 150 bar

All-HPRO ∆Pmax = 300 bar

Specific Energy Consumption (kWh m-3)

C

30

40%

Recovery 60%

70% VC ge M 1-Sta VC 2-Stage M

20

-MVC HPRO id r b y H RO ge HP 1-Sta RO 2-Stage HP

10

0 100

150

D Energy Efficiency

-1

Specific Energy Consumption (kWh m -3)

All-Thermal Brine Concentration Environmental Science &BTechnology Letters

80 60 40

20 Conventional RO 0

60%

Retentate Concentration (g L )

HPRO

∆Pmax= 80 bar HPRO ∆Pmax= 300 bar ∆Pmax= 150 bar

0

50

100

150

200

250

-1

Feed Concentration (g L ) 40%

Recovery 60%

70%

2-Stage HPRO

40%

1-Sta ge H PRO Hybrid H PRO-MV C

20%

2-Stage MVC 1-Stage MVC

0% ACS Paragon Plus Environment 100 200 250 -1

Thermal Brine Concentrator

150

200

250

-1

Retentate Concentration (g L )

1 0

2

*

*

*

1 0

5

1 0

4

1 0

B F D L

P o w e r

R e fin in g & C h e m ic a ls

1 0

6

O il & G a s

1 0

7

F o o d & B e v e ra g e

8

M in in g

U n s p e c ifie d

P o w e r

R e fin in g & C h e m ic a ls

1 0

2 -S ta g e H P R O 2 -S ta g e M V C

E le c tr o n ic s

1 0

3

M e ta ls

E le c tr o n ic s

1 0

4

9

1 0

E n e r g y C o n s u m p tio n -1 (k W h d a y )

M in in g

1 0

5

O il & G a s

1 0

F o o d & B e v e ra g e

M e m b ra n e T h e rm a l 6

H y p o th e tic a l S c e n a r io

C

C

L

P ro d u c e d W a te r r a c k is h W a t e r D e s a l lu e G a s e s u lf u r iz a t io n a n d f ill e a c h a te o a l to h e m ic a ls

Page 26 of 28

1 0 % 1 % 0 .1 % 0 .0 1 % 0 .0 0 1 % 0 .0 0 0 1 %

ACS Paragon Plus Environment

3

0 .0 0 0 0 1 %

P e r c e n t D a ily U S E le c tr ic ity G e n e r a tio n

G lo b a l In s ta lle d B r in e 3 e s a lin a tio n C a p a c ity ( m d a y

-1

)

B

M e ta ls

A

C u r r e n t In s ta lle d C a p a c ity


= 1 b a r

∆P t

= 5 b a r t

= 1 0 b a r

H o llo w F ib e r

-3

)

t

a

3

1 0

2 -S ta g e

1 -S ta g e

2 -S ta g e

1 -S ta g e

2 -S ta g e

F e e d C o n c e n tr a tio n ( g L

-1

1 2

)

1 0

-4

1 0

-3

1 0

-2

C h a r a c te r is tic L e n g th , a ( m ) ACS Paragon Plus Environment

-1

1 2 5

a

-1

7 0

a

5 0 0

S t e e l σ= 3 1 0 M P P I K e v la r 7 0 0 M P a P S a

a P M 6 0 1 = σ P a M 0 1 1 = f σ

a P M 6 = 7 σ C P V

2 5 0

P a M 8 4 = σ C A

0

P T F E σ= 1 4 M P a

1 .0

2 .0

3 .0

)

3 5

1 0

S p ir a l W o u n d

1 0

d a y

1 -S ta g e

1 0

P la te a n d F ra m e

3

S p e c ific A r e a ( m

2

πr e t = 1 3 3 b a r πr e t = 5 9 b a r πr e t = 2 8 8 b a r

0

7 0

m

2 0

1 0

∆P ∆P

4

C

C o m p r e s s io n P r e s s u r e o f N o n p o r o u s F ib e r s ( b a r )

B

m o d u le

A v e r a g e W a te r F lu x a t 5 0 % -2 -1 W a te r R e c o v e ry (L m h )

A


P r o d u c tio n R a te ( m

Page 27 of 28

R a d ii R a tio , r

o u te r

/r

in n e r

TDS = 70,000 mg L-1

Energy Consumption

∆P

High-Pressure Reverse Osmosis for Energy-Efficient Hypersaline

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