Water Shortage Relief: Analyzing New Chemically Driven Processes for Desalination

by

Julie Perez

Conor Puckett

Submitted to

Professor Moore

and

Mark Provence

ME 333T

Fall 2013

1

Executive Summary

Water shortage is a large scale issue that the news, organizations, and other media have

played up in recent years. Unfortunately, it is as dangerous a problem as explained by these

outlets, if not more so. Jonathan Chenoweth from the New Zealand Scientist reports that

“According to the UN World Water Assessment Programme, by 2050, 7 billion people in 60

countries may have to cope with water scarcity” (Chenoweth, 2008, url). This critical point

looms near in our future, and the effects of severe water shortages can be observed and are

already felt today all around the world.

Currently, reverse osmosis (RO) water desalination is the primary way to “harvest” fresh

water from saturated salt water sources to be able to provide drinkable water. Reverse osmosis

requires a large amount of energy, time, and capital to run and maintain facilities. Forward

osmosis (FO) and electrochemically mediated saltwater desalination (EMSD) chips are two

unique solutions to these and other problems discussed in the paper.

Three criteria for investigation include production potential, efficiency, and cost. When

comparing the existing RO process with FO and EMSD, the researched technologies may apply

to large or small scale uses, respectively. Currently, as both the FO and EMSD systems exist in

research and development phases, comparing the final output in terms of overall production

capabilities is difficult to determine. Scientific tests are the primary grounds for production

potential claims. Both show signs of efficient desalination, ranging from 25% to 85%, but still

leave room for improvement. And though the initial costs for both are higher, investors are likely

to save in energy expenses.

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Both FO and EMSD have great potential to grow into the forefront of water desalination

techniques. Needing a stable energy infrastructure, FO is poised to replace RO in large,

economically stable areas such as Coastal Australia, India, and the Mediterranean. EMSD chips

are unique among all other desalination techniques in being small enough to work as a personal

unit while retaining the ability to combine with other chips to function for villages, cities, etc.

There is still a large amount of headway that can be made through investment in research,

especially with the EMSD chips. The company or companies that fund the research will be

known as facilitators of freshwater for the world, and will essentially play a major role in ending

the problem of water scarcity that these solutions seek to address.

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Introduction

Global freshwater sources are currently unable to sustain the world population because

existing techniques fail to meet the demands for clean drinking water. However, new technology

shows the potential to supply drinkable water to those who need it most. Presently used to treat

saltwater, Reverse Osmosis (RO) forces water through a semi-permeable membrane which

allows the smaller water molecules to pass though while the larger contaminants are held on the

other side ("How reverse osmosis," 2013, url). Forward Osmosis (FO), similar to RO, utilizes

two liquids of different concentrations to create a pressure difference across a semi-permeable

membrane with “low or no hydraulic pressures” introduced (Cath, Childress & Elimelech, 2006).

Electrochemically Mediated Seawater Desalination (EMSD) uses a microchip to support a

branched channel system where an induced electric field allows partially desalinated water to

travel through one channel and the concentrated salt solution to flow down the second channel

(R. Crooks, personal communication, November 12, 2013). Both of these technologies improve

upon RO techniques by reducing associated costs or necessary energy requirements in order to

produce clean water in a more efficient and cost effective way.

This white paper analyzes two potential solutions to the global water crisis: forward

osmosis desalination plants and electrochemical desalination microchips. After discussing the

present issues surrounding water availability and the pitfalls to reverse osmosis desalination

techniques, we will describe the two new technologies in greater detail. We will then compare

these two technologies across important criteria of evaluation in order to present an accurate

picture of where each technology stands with regards to their respective implementation. Finally,

we present our own recommendations on how to proceed with these developments in order to

prevent future water shortages from plaguing our global community.

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Statement of the Problem

Water scarcity is rapidly becoming an alarming issue. Access to fresh, clean drinking

water is limited in developing countries. The severity of this shortage can be seen through its

effects, including chronic illnesses, devastated local economies, and even death. In the past

decade, a study by the World Health Organization estimates Diarrhea contributes to nearly nine

million annual deaths of children under the age of 5, with a major factor being the consumption

of contaminated water (Alexander, 2013, p 13). This shows that access to clean water is an

integral part of maintain the health and safety of communities across the globe.

In the United States, growing population densities have created an unmet demand for

clean water. According to a journalist for the Saturday Evening Post, “Of the 47 states that

responded to a U.S. General Accounting Office, 36 states predicted shortages by 2013 under

normal conditions, 46 under drought conditions” (Yeoman, 2013, url). Factors such as

population growth, unbalanced economic distribution, and the effects of climate change all

reduce the usable freshwater in circulation. Water shortage has become a looming problem on a

global scale. To sustain itself, the public needs improved water purification techniques that will

allow for the treatment of current water sources that are not possible to drink.

Innovation has been halted in the past for a multitude of reasons. Though it is a well-

known fact that developing countries are economically depressed, research shows water scarcity

keeps them at this state. For example, pertaining to India’s water crisis, “Extremely poor

management, unclear laws, government corruption, and industrial and human waste have caused

a water supply crunch and rendered what water is available practically useless due to the huge

quantity of pollution” (Mehta, 2012, url). Because these countries lack the government setup or

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economic capital to regulate water usage, clean water supplies have all but disappeared in many

areas. Analysts predict this depletion rate of fresh water may affect a staggering portion of the

global population. Scientific journalist Jonathon Chenoweth from New Scientist magazine

reported that, “According to the UN World Water Assessment Programme, by 2050, 7 billion

people in 60 countries may have to cope with water scarcity” (Chenoweth, 2008, url). The scope

of water scarcity, as we can see, is certainly not solely a problem of dense, urban centers or that

of developing communities. It is a problem present across the world.

In addition to economic strife, government involvement and lax regulations have helped

cause the water scarcity problem that we face today. In nations like the United States, when

water levels get to drought conditions, water restrictions are typically put in place. However,

many homeowners circumvent this law by drilling their own wells to tap directly in to

groundwater beneath their property, not understanding their action’s effect on the current water

table. Sarah Courts, a well owner in Atlanta, defends herself and other well owners stating that

“We’re not draining Lake Lanier here” (Abkowitz, 2008). Evidence however shows conflicting

points. Georgia’s state geologist, Jim Kennedy, says that these wells “can lower the amount of

groundwater if there are a lot of wells in one area… [and] can actually cause land to sink”

(Abkowitz, 2008). Elsewhere, residents such as Jason Cooper from North Carolina are appalled

“that people would circumvent water restrictions in order to keep their lawns green” (Abkowitz,

2008). Issues like this prompt the submission of bills before state legislators urging for the same

restrictions to be placed on private wells, but because of the backlash from drilling companies

and wealthy residents, the issue of private wells was removed from further government

consideration (Abkowitz, 2008). Without a strong government influence, many public water

tables could be severely depleted if private drilling is left unchecked. This unchecked private

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drilling causes the available amount of water to decrease as a whole, perpetuates the problem

rather than alleviating it, and “could [even] deplete or dry up a creek” (Abkowitz, 2008).

New innovations into freshwater solutions are integral to the continued providing of a

global source of clean water. Without clean water, developing nations will continue to struggle to

overcome economic hardships. The health of these nations will also continue to suffer as we

have seen without access to fresh water. We will investigate cutting edge techniques to solve this

global water shortage.

Global Water Shortage Solutions

Before researching potential solutions, this section will give an overview of clean water

production, both in a general sense of the operation and in the effectiveness of current, factory

driven procedures utilizing reverse osmosis techniques. We will focus on two types of

technological advancements and discuss their functionality in reducing the amount of salt present

in water sources.

Conventional Technology

Desalination plants make up a good portion of the current technology associated with

large scale water filtration. That being said, they also have large draw backs that must be

evaluated before implementation of a system. Currently, most plants work under Reverse

osmosis (RO), Multi-Stage Flash (MSF), Electro-dialysis (ED) or some combination of RO and a

thermal process (Kim, Park & Yeh, 2013). The crux of RO desalination techniques lies in

membranes within the filtration housing. Published in the Journal of Membrane Science, Tzahi

Cath explains the methodology of RO, stating that “RO uses hydraulic pressure to oppose, and

exceed, the pressure of the saltwater in order to produce purified water by forcing the aqueous

7

feed through a membrane” (Cath, Childress & Elimelech, 2006). This, however, has a large

energy cost associated with production. Many of the areas that lack the most amount of clean

water do not have the economic or electrical power to support the “old-style” of RO desalination

plants (Chaudhary, 2013;Scott, 2013; Yeoman, 2013). A further analysis of cost will be

presented later.

Proposed Innovations

New technologies and paradigm shifts have caused a large potential for lessening the

current costs of desalination processes. Forward Osmosis (FO) techniques are rendering a more

efficient way to process seawater. The Electrochemically Mediated Seawater Desalination

(EMSD) process removes the need for a semi-permeable membrane and simplifies the

desalination procedure.

Large scale solution: forward osmosis. Professor Menachem Elimelech of Yale’s Mason

Laboratory states that “[t]he main advantages of using FO are that it operates at low or no

hydraulic pressures…” (Elimelech, 2007). Without the expense of maintaining hydraulic

pressures as in RO, the cost to run the facility will

decrease. The FO process is described to the right

with Figure 1 showing the different components to

the system. A concentrated solution called a draw

solution causes the water to move from the salt

water, across the semi-permeable membrane and

into the draw solution (Cath, Childress & Elimelech,

2006). A draw solution containing dissolved

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Figure 1- Schematic of Forward Osmosis Process (Elimelech, 2007)

ammonia and carbon dioxide gases effectively extract water from the salt water solution. From

the draw solution, applied thermal energy causes the ammonia and carbon dioxide to return to

their gaseous state, allowing for “efficient and complete removal and reuse” of the draw solution

components (Elimelech, 2007). This process takes place in a separate storage tank from the

holding draw solution. As the draw solution is heated and the solutes are removed, the fresh

water is piped to its own storage tank and is now free of both salt and the draw solution

components. The leftover brine solution is piped away and disposed (Cath, Childress &

Elimelech, 2006).

Small scale solution: electrochemically mediated seawater desalination. In contrast to

FO, the EDMS microchip operates at a microscopic level and incorporates a low power voltage

source instead of a semi-permeable membrane to drive desalination. The EDMS process is

demonstrated to the right in Figure 2. Scientific journalist Alex Scott from Chemical and

Engineering News explains, “as water is forced through two channels, which are electrically

connected through a bipolar electrode, the electrode creates an electric field that forces positive

ions into a branching channel, and the resulting charge imbalance forces negative ions to

follow”(Scott, 2013, url). The University of

Texas provides a more detailed chemical

interpretation: “An embedded electrode

neutralizes some of the chloride ions in

seawater to create an ‘ion depletion zone’ that

increases the local electric field compared

with the rest of the channel. This change in

the electric field is sufficient to redirect salts”

9

Figure 2. EMSD Microchip Operational Diagram (Scott, 2013).

(“Chemists work to,” 2013, url). The output has water flowing through the branch taking up

dissolved salt while the water continuing through the main channel is partially desalinated.

Cost Benefit Analysis

Established criteria for evaluation include production potential, efficiency, and monetary

expenses. We present the topics in a ranked order of significance. Because the two methods are

new concepts, with the EMSD chip barely at prototyping stages, we focused on the potentials

associated with each for future consumption. Declaration of the production potential is crucial as

it establishes the differences in the intended applications for each technology and compares them

with current production capabilities. The next key point was the desalination efficiency of each

device. Finally, we considered the ease of which each technology could be implemented by

determining the monetary costs.

Production Potential

Forward osmosis is a good desalination technique in that it can be applied in a variety of

intake sources including both brackish water and seawater. For countries, like Australia, that

have an infrastructure capable of supporting a desalination plant, a forward osmosis plant would

be a beneficial addition rather than continuing to create plants using reverse osmosis or thermal

techniques ("Perth seawater desalination," 2012,url). India’s government set aside roughly $18

billion for water projects in the hopes of attracting private groups to come up with the most

effective way to provide clean water (Chaudhary , 2013,url). Such support from the national

governments would allow for a larger interest in constructing cost effective, efficient

desalination facilities utilizing forward osmosis.

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Currently, forward osmosis has only been tested in a scaled environment. Yale professor

Menachem Elimelech states that “[t]he most important measure to be taken in order to advance

the field of forward osmosis is the development of new membranes” (Elimelech, 2007). Another

pivotal aspect of forward osmosis that can be improved upon is the composition of the draw

solution. It has been determined that using ammonium bicarbonate as a solute allowed for the

most cost-efficient process as it “required no electricity, thereby drastically reducing the cost per

ton of product water” (Kim, 2013). Should the membranes and draw solutions be scaled up,

forward osmosis systems have the ability to improve and reach a production scale comparable to

that of RO systems today. Currently the “average capacity and corresponding cost for [RO] was

6000m3/day and .70$/m3 (Karagiannis & Soldatos, 2007).

Considering EMSD technology, in order for the microchip to operate in the developing

countries or water stressed communities which require its assistance the most, the chip must

filter enough water to meet average consumption rates. The prototype of the microchip is

depicted in Figure 3 to better understand the scale

of its process. The research team, consisting of

Knust, Hlushkour, Anand, Tallarek, and Crooks,

clarifies that the device’s design only allows water

to flow through two micro-channels, each at a

diameter of about 22 µm (Knust et al., 2013,url).

At micro-channels comparable to the size of a

human hair, “operating a single micro-

desalination unit at a time produces 40 nano-liters of desalted water per minute. To prove

practicality for global usage, the chip requires the development of faster flow rates, on the order

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Figure 3- Microchip Prototype (“Chemists work to,” 2013)

of liters per day” (Knust et. al., 2013, url). Developers admit that adjusting the scale of achieved

desalinated water in a timely manner challenges the potential of a singular chip. According to

Morgan Anderson, Project Manager for Okeanos Technologies which helps sponsor the research,

“Right now, we are trying to build a unit capable of integrating 20,000 to channel larger

quantities of water for practical applications” (M. Anderson, personal communication,

November 12, 2013). Parallel arrangements of many micro-channel systems should allow for

increased water flow rates for varying applications.

While sponsoring companies debate over which communities the EMSD product should be

distributed to, researchers take a particular interest in two particular regions of the globe.

Countries within the Middle East and water stressed coastal regions in the U.S. can provide the

components to power this simple chip and benefit from its portability (R. Crooks, personal

communication, November 12, 2013). The amount of people each unit can sustain remains

uncertain at this early stage of development. Crooks states the long run goal, saying, “We are

running simulations to test methods which improve the water quality and increase volumetric

output of the device. We want the microchip to produce enough water for individual and

household usage” (R. Crooks, personal communication, November 12, 2013). Unlike reverse

osmosis and forward osmosis, the electrochemically mediated seawater desalination technology

gives an innovative perspective on future desalination methods by offering its users the

convenience of personal usage.

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Efficiency

As it stands now, forward osmosis is very close to having the same recovery amount as

standard desalination techniques. Elimelech states that within the last 6 years “Lab tests show an

effective 85% recovery from a sea water source…[and] the capability of FO to produce very

high recoveries is unmatched by existing desalination techniques” (Elimelech, 2007). This high

recovery is due, in part, to some of the slightly different components from that of RO. The

membranes used in FO techniques allow for a higher water transport as well as a larger salt

rejection (Mamisaheby, Phuntsho, Shon, Lotfi & Kim, 2012). This allows for FO plants to keep

more of the salt solution out of the freshwater making the membranes a key part in retaining a

higher efficiency than current processes.

If forward osmosis is used as the desalination process, “approximately 24-45% of the

thermal energy needed by multi-effect distillation (MED)” (Elimelech, 2007) will be used and

only about “21% of the electrical consumption of MED or 9% of the reverse osmosis techniques

is required” (Elimelech, 2007). This allows the thermal energy costs to remain closer to that of

steam condensers in current electrical power plants (Elimelech, 2007). Due to the efficiencies

described above, it requires less energy for the forward osmosis process to function because it

can work at lower temperatures than reverse osmosis processes. This allows for the operating

cost to actually be less than that of a typical reverse osmosis style plant.

Each solution must present proof of effective desalination to support our initial claim,

which considers optimized desalination techniques as the solution to drinking water shortages.

For the EMSD chip, Crooks explains, “To date, this electrochemically mediated desalination

provides up to 25% desalination. Health standards require drinking water to be at 99%

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desalination” (R.Crooks, personal communication, November 12, 2013). He reveals that a newer

model within the simulation stage of prototyping “adds a secondary voltage source, which can

reach upwards of 50% desalination” (personal communication, November 12, 2013). However,

according to Kyle Knust, the graduate student in the research team at the University of Texas

who is accredited for inventing the EMSD chip, creating the chip in the first place “was proof of

principle” (“Chemists work to,” 2013, url). Knust continues, “We’ve made comparable

performance improvements while developing other applications based on the formation of an ion

depletion zone, suggesting that 99 percent desalination is not beyond our reach” (“Chemists

work to,” 2013, url). Though the device is not yet able to perform to the necessary standards for

implementation, scientists remain optimistic on finding ways to improve the process to meet

demands.

Though previously mentioned aspects, such as processing time and desalination

percentage, require modifications, one key characteristic does not. The EMSD chip reduces

energy costs, intriguing most researchers. As large energy storage and generation run

desalination plants, the microchip requires nothing more than a single, standard variety, store-

bought battery with an output of 3 Volts to function. The only preceding step before desalination

is to remove sand and sediment by letting the grains settle naturally, with no further treatment,

chemical additives, or energy applications (“Chemists work to,” 2013, url). This breakthrough

therefore establishes notable energy efficiency through a low battery power input, making it an

ideal alternative to current methods as far as energy is concerned.

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Monetary Cost/Ease of Implementation

In bringing desalination facilities to places in need of water, a major factor is economic

cost. Tae-woo Kim from the Korea Advanced Institute of Science and Technology comments on

the economic cost posed by desalination facilities, “Construction costs are the largest portion of

the capital costs, ranging between 50-85%”(Kim, 2008). These construction costs can cripple a

project before it is able to launch and develop. If the project is given a green light, there are still

maintenance costs to consider, as well the energy costs to run the plant. One of the biggest

drawbacks with any mode of desalination plant is that in poor, rural communities, there is simply

not enough capital nor existing energy infrastructure in place to currently support a desalination

plant (Kim, 2008; Mehta, 2012).

As we saw earlier, the feasibility of implementation is quite good. In countries where the

infrastructure can support an updated desalination plant, government funding seems to be

available for private companies (Chaudhary , 2013, url). This allows for a sense of competition

that can drive the initial cost down as companies compete to receive the funding. Finally, the

longevity of forward osmosis seems to be guaranteed with huge potential for growth and

development. With companies vying for the ability to create the new plants, a need to research

even more efficient membranes and draw solutions will be created. In the future, these new

advances could lead to the potential for declining operating costs.

In starting at a microscopic scale and working up to both personalized and large scale

usage, EMSD allows for a range of price options. To evaluate the cost, we must understand the

investment and the potential profits long run successes bring. From Anderson’s experience with

Okeanos Technologis, he comments that only one fifth of total costs come from acquiring the

15

water supply, adding that the remaining operational cost for the EMSD chip, thought above RO

at the moment, will in the long run pay for themselves through the energy saved (M. Anderson,

personal communication, November 12, 2013). With the primary focus of aiding water stressed

regions, Richard Crooks voices the scope of savings associated with this research.

“Seawater desalination is one way to address this need, but most current

methods for desalinating water rely on expensive and easily contaminated

membranes. The membrane-free method we’ve developed still

needs to be refined and scaled up, but if we can succeed at that, then one day it

might be possible to provide fresh water on a massive scale using a simple,

even portable, system” (“Chemists work to,” 2013, url).

Although no dollar amount has been tagged to the technology, researchers aim for an overall

price that will be less than current desalination factories.

Recommendations

The fresh water shortage we are currently facing is a global problem that will require

many solutions in order to truly be remedied. We believe forward osmosis desalination to be at

the forefront of those solutions, followed by the encouraging developments achieved through

electrochemically mediated seawater desalination. Because FO plants would only be possible in

large countries with stable infrastructure, the FO plants would be focused on providing fresh

water to the densely populated coastal areas in countries like Australia, India, and nations in the

Mediterranean region. Poorer countries, as well as inland locations without groundwater,

generally do not benefit from this new form of desalination. In light of all the previously

presented information, we believe forward osmosis desalination to be a good solution towards

16

mitigating current water shortages in some densely populated regions around the globe. We

recommend that further research be done into making for effective draw solutions that will

require less energy to maintain. In addition to draw solutions, more effective membranes will

also allow for a cheaper desalination facility in the long run. That being said, we also recognize

the need for more comprehensive solutions for developing nations and those areas away from the

sea and without adequate amounts of groundwater.

For communities where desalination facilities are not a feasible option, including those

lacking the infrastructure to support them, electrochemically mediated seawater desalination

techniques provide for a practical alternative for producing clean water. Because the design of

the EMSD chip only requires the addition of a common variety battery source, coastal regions of

both the U.S. and developing countries are likely to carry the minimal resources needed for its

usage (“Chemists work to,” 2013, url). Similar to forward osmosis plants, the location of salt

water sources restricts the desalination application to these areas. After researching the creation

of the EMSD chip, we conclude that further development is necessary. Before the technology

can be distributed for public usage, the percentage of desalination must match that of safe

drinking levels. Additionally, the product needs to operate at a faster flow rate to produce the

volumetric output required to sustain its target audience. Overall, we commend this innovative

approach of a portable, individual water desalination system as it holds a promising future.

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