Is Desalination an Economically Viable Approach to Address Water Scarcity in the San Francisco Bay Area?

By: Charles Fitzsimmons

ENVS 190a: Senior Thesis Dr. Jeffery Foran

5/14/14

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Table of Contents

01. Introduction- pg.3

02. Water Scarcity- pg.3

1. Climate Change and Water Scarcity- pg.4

2. California Water Scarcity- pg.5

03. Desalination Methods- pg.7

1. Reverse Osmosis- pg.7

2. Multi-Stage Flash Distillation- pg.9

3. Multi-effect Distillation- pg.11

04. Economics of Desalination

1. Comparison of Thermal and Membrane based Desalination- pg.12

2. Environmental Costs- pg.16

3. New Technologies for Desalination- pg.18

05. Proposed Desalination Plant- pg.19

06. Conclusions- pg.21

Work Cited- pg.23

Figure.1- Reverse osmosis (RO) desalination (pg.9) Figure 2- Schematic flow diagram of a simplified MSF system (pg.11) Figure 3- Schematic flow diagram of a low-temperature horizontal-tube MED plant (pg.12) Figure 4- Decreasing desalination costs (pg.14) Figure 5- Production Cost Overview for Multistage Flash Distillation and Reverse Osmosis (pg.15)

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1 Introduction

The use of desalination has increasing become a method of dealing with water scarcity

throughout the world (Bremere, Kennedy et al. 2001). The actual process of desalination has

been around at least since 1662 with records of seafaring voyagers using on board distillation to

provide freshwater to crew (CADT, 2008). However, it hasn’t been commercially viable since

the mid twentieth century. As of today, the world produces over 59.9 million m3/day of

desalinized water using commercial methods of desalination (Mezher, Fath et al. 2011). Most of

the commercial desalination plants are located in extremely water scarce countries such as those

in the Middle East where there are few options to provide secure sources of water (Bernat, Gibert

et al. 2010). As climate change and increases in populations stress water sources in other

historically water secure countries, such as North America and Europe, the viability of using

desalination as a means to provide water security is gaining more attention. Currently, the San

Francisco Bay Area is looking for methods to insulate the area from water scarcity and drought

conditions that are becoming more prevalent as well as estimates that place the San Francisco

Bay Area in a deficit of water supplies by 2035 (Camp Dresser and McKee Inc., 2010). In the

context of increasing water scarcity and climate change, this paper will attempt to answer the

question of whether desalination is a economically viable method of preventing water scarcity in

the San Francisco Bay Area.

2 Water Scarcity

Increasing water scarcity has lead to countries finding alternative methods of conserving

and producing water such as desalination (Berrittella, Hoekstra et al. 2007). The causes for water

scarcity may include a physical lack of access to water or a lack of economic resources to

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allocate it effectively (Watkins 2006). The water scarcity situation pertaining to California is one

of physical access as it has the infrastructure and economic power to obtain water. The primary

use of water at around 70% of the global usage is in agricultural practices, but there are still

concerns about being able to provide potable water to populations while still maintaining a

robust agricultural system (Berrittella, Hoekstra et al. 2007). In addition, creating a stable water

supply for urban populations would alleviate some of the strain on agricultural water supplies

during periods of water scarcity. In an evaluation of water scarcity in 10 countries with water

supply issues, a survey of 405 river systems throughout the world found that over 201 of the

river systems experienced a significant level of water scarcity for at least one month out of the

year between 1996 and 2005 (Hoekstra, Mekonnen et al. 2012). The evaluation used river

systems as an evaluation of the water scarcity of the country as a whole. The river systems that

were impacted the most were in areas that already had unfavorable climatic conditions but it

does exhibit a trend that water scarcity is becoming an issue throughout the world. The threat of

water scarcity is enough to motivate countries to adopt technologies such as desalination to

protect their water supply, the urgency of which has only become greater in the face of changing

hydrological regimes due to climate change.

2.1 Climate Change and Water Scarcity

Developed nations such as the United States of America may not be at risk of facing

climate change induced water scarcity as readily as developing countries with preexisting water

supply issues due to native climate and internal issues, but population growth within urban

settings in conjunction with climate change will severely stress the water supplies of that region

(McDonald, Green et al. 2011). The issue of water scarcity is based on economic and physical

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water scarcity that is generally due to inadequate resources to secure water in those countries. As

such more developed nations face less of an issue securing water supplies, albeit that there will

still be a need for development of water supplies in those regions (Seckler, Barker et al. 1999).

Developed nations may be more insulated from the effects of climate change but still face the

same issues as developed nations when considering water supplies in areas of large population

growth (Griffin, Montz et al. 2013). The issue of water scarcity in developed nations isn’t an

immediate issue but when considering climate change and the future of water supplies it

becomes important to create safety nets using methods of producing and conserving freshwater.

The securing of future water supplies may be difficult to plan for, as many variables such as

groundwater reserves, watershed regimes, changing social practices, and new technologies

influence the access to an adequate water supply (Vörösmarty, Green et al. 2000). Although, it

may be difficult to accurately predict future water supplies it is, estimated that even with low risk

assessments of global water supplies that between 39% and 42% of the world’s population

between 2070 and 2100 would be presented with water scarcity issues (Hanasaki, N et al. 2013).

This statistic is created with the assumption that governmental policy would not enact policies to

address shifting climates. This caveat may make this statistic an overrepresentation of the

severity of water scarcity in light of climate change but it still provides a workable model from

which it can be asserted that the world’s nations will need to use every resource available to

ensure water security. The use of a multifaceted approach to prevent water scarcity is evident

within California’s proposed actions to abate water scarcity in the future.

2.2 California Water Scarcity

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The Public Policy Institute of California states that climate change will affect California’s

water supply by creating fluctuations in mean surface water inputs, prevalence of drought

conditions, and increasing the potential for flooding (Hanak and Lund 2012). These effects of

climate change provide ample reason for California to secure potential sources of potable water.

It is difficult to attribute any particular weather occurrence with climate change but the 2010

California drought was an example of how detrimental water scarcity can be to urban water

supplies, fish stocks, wildlife conservation, agricultural production and other services that require

water to function (California Department of Water Resources 2010).

The myriad issues that water scarcity presents to state and countries puts pressure on finding

methods to alleviate as many of these problems as possible. The costs of water scarcity on urban

consumers of California after 2020 are estimated at $1.6 billion for operational costs of water

each year (Jenkins, Lund et al. 2003). The costs of water scarcity for California consumers may

prompt the development of desalination plants to alleviate some of these costs by in theory

having a point of increasing returns from building such a plant. The city of San Diego is

currently planning for water scarcity scenarios in the future by creating two desalination plants

by 2020 which are to provide the city with 20% of its water supply (Richter, Abell et al. 2013).

The use of desalination is the most expensive method for the city to secure a portion of their

future water supply but the ability to ensure the security of water sources seems to have trumped

the overall costs of the method.

The San Francisco Bay Area may have more secure supplies of water than that of San

Diego but the Sierra Nevada water regime that provides the San Francisco Bay area has had a

20% reduction of average yearly water runoff from historic averages.(Knowles and Cayan 2002)

A report by the Bay Area Water Supply and Conservation Agency predicts that the available

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water supply will be inadequate to provide water to the increasing population by 2018 (Camp

Dresser and McKee Inc., 2010). The report also noted that an additional 25 million gallons of

water per day would be needed by 2035 to meet water demands in the San Francisco Bay Area

while still factoring in current and future conservation policies. This deficit of water could be

satisfied in part by the creation of desalination plants in the San Francisco Bay Area.

3 Desalination Methods

The most common form of desalination for commercial use is membrane based. Reverse

osmosis is the most used form of membrane methods and it comprises 53% of all desalination

plants worldwide of both brackish and seawater (Mezher, Fath et al. 2011). The second largest

category of desalination plants uses thermal energy to produce desalted water. These thermal

methods include multistage flash, multiple effect distillation and mechanical vapor compression.

There are also more novel forms of desalination that use a mix of different desalination methods

and ion exchange processes, but this particular form of desalination is used for removal of small

amounts of minerals in water (CADT 2008). This section will only delve into the desalination

methods of reverse osmosis, multistage flash distillation, and multiple effect distillation, as these

methods comprise nearly 86% of the world’s desalination capacity (Mezher, Fath et al. 2011).

3.2 Reverse Osmosis

Reverse osmosis can be used for both brackish water and seawater desalination. The

method consists of moving the feed water through a semi-permeable membrane spiraled around

a water intake at high pressures. The solute of the water builds up on one side of the membrane

creating a highly saline solution, brine, which is subsequently disposed of. The brine in most of

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the newer reverse osmosis plants is pumped out of the system at high pressures, which is then

sent through a system that takes the energy from the pressurized brine and uses the energy to

pressurize the feed water for the plant (Mezher, Fath et al. 2011) (Fig.1). The brine is generally

disposed of by releasing it into the same body of water that the feed water originated from, which

can produce issues in the ecosystems near the disposal site as well as possibly fouling new feed

water if disposal area is near in proximity to the intake (Roberts, Johnston et al. 2010). The water

that moves through the membrane devoid of most of the solutes that was previously in the water

at low pressures (CADT 2008).

The feed and desalinized water also has to go through pre and post treatment processes,

respectively. The post-treatment of the desalinized seawater is generally increasing its hardness

or alkalinity and disinfecting it with bleaches. The minimal amount of post-treatment processes

is due to the more intensive pre-treatment (Greenlee, Lawler et al. 2009). The feed water from

seawater can contain contaminants that need to be removed chemically or physically before

entering the reverse osmosis system. The feed water generally contains organic material,

sediments, insoluble salts or hydrocarbons such as oil (Greenlee, Lawler et al. 2009). The use of

on-shore beach wells are used to obtain the seawater for desalination as the beach sediment acts

as a preliminary filter for the water. The pretreatment of feed water usually consists of adding

acids, clarifying agents, anti-scalents and coagulants to the feed water; this removes the

contaminants in the water and reduces the pH levels of the feed water to increase the solubility of

calcium carbonate, which is a common precipitate of saline water (Ibid). The feed water then

usually goes through ultra filtration to remove flocculated materials in the water (CADT 2008).

The pretreatment process removes most of the contaminants in the feed water but the membranes

used in reverse osmosis become contaminated leading to membrane fouling.

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Membrane fouling is a common occurrence in the process. Membranes used to desalinate

seawater tend to have a replacement rate of 20% per year (Ettouney, El-Dessouky et al. 2002).

The rates of replacement for membranes are generally attributed to inadequate pre-treatment

processes. In seawater desalination the main cause of membrane fouling is the presence of

precipitated calcium carbonate which can aggregate into blockages in the membrane that provide

a medium for biological growth in the membrane thereby decreasing the filtering potential for

the fouled membrane (Greenlee, Lawler et al. 2009). Membrane cleaning can alleviate the issue

of membrane replacement, which is generally done by passing both acids and alkaline solutions

through the membrane to remove the contaminants (Ibid). Membrane fouling is one of the

unique costs associated with reverse osmosis desalination as opposed to other methods of

desalination.

Figure.1 Reverse osmosis (RO) desalination  (Ettouney, El-Dessouky et al. 2002)  

3.3 Multi-Stage Flash Distillation

The method of desalination uses a heat and pressure gradient between multiple stages to

produce pure steam from portions of the feed water thereby removing the salts from them and

producing potable water (IAEA. 2000). The system works by sending feed water through a

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system of tubes that pass through containers of increasing temperatures and pressures. The feed

water is then brought to an even higher heat and pressure with a heater. The heated feed water is

fed into the last container it traveled through, while in the tubes, at a lower pressure so that a

portion of the feed water flashes into water vapor to be then collected by condensing on the

cooler tubes containing the feed water before it is steam heated, which then falls on to collection

trays (Fig. 2). The process continues by passing the feed water through lower temperatures and

pressures to extract more pure water from the feed water until it becomes brine and no more

water can be extracted from it. The containers that reduce in pressure and temperature are

referred to as stages in the process and most multi-stage flash desalination plants have anywhere

from 18 to 25 of these stages (Mezher, Fath et al. 2011). Unlike reverse osmosis multistage flash

requires little to no pretreatment of the feed water.

The treatment of the feed water is mostly comprised of adding anti-scalants to reduce the

buildup of corrosive material within the system (CADT, 2008). The pre-treatment of feed water

with acids or polymer-scale inhibitors tends to effectively prevent build up of precipitants such

as calcium bicarbonate. The efficiency of the method can be increased by further pre-treatment

of the water through nano-filtration but it isn’t necessary (Mezher, Fath et al. 2011). The post-

treatment of desalinized water is similar to that of reverse osmosis and brings it to a desired

alkalinity but doesn’t require disinfectants due to the high temperatures used to heat the water.

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Figure.2 Schematic flow diagram of a simplified MSF system (IAEA, 2000)

3.4 Multiple-Effect Distillation

Multi-effect distillation works on similar principles as that of multi-stage distillation in

that it uses heat and pressure to turn the feed water into potable water vapor. The process begins

with the feed water being sprayed over a pipe containing high heat steam causing evaporation of

the feed water into heated water vapor. The heated water vapor is then used in the next stage of

evaporation as a heating agent to brine water being sprayed on a pipe containing the previously

mentioned heated water vapor (Fig.3) The process, although similar to multistage flash

distillation, is more energy efficient as the latent heat of the water vapor is recycled in each stage

(Mezher, Fath et al. 2011). Each subsequent stage uses the water vapor from the previous stage

to continue the process albeit at lower pressures and temperatures in every stage (IAEA 2000).

The process ends at a final cooling vessel for the desalinized water which is ready for post-

treatment of the water. Pre and post treatment of feed and desalinated water, respectively, is

virtually the same as multistage flash distillation.

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Figure.3 Schematic flow diagram of a low-temperature horizontal-tube MED plant (IAEA,

2000)

4.1 Comparison of Thermal and Membrane Based Desalination Costs

The recovery rate for reverse osmosis can range from 35% to 50% of seawater to

desalinized water while multistage flash and multiple effect distillation range from 35% to 45%

(CADT, 2008). The water quality from reverse osmosis depends on each desalination plant’s

individual design; it generally takes a single pass of feed water through the system to remove

over 99% of the salts in the feed water although, certain reverse osmosis plants may require two

or more passes. The total dissolved salt content of the processed desalinized water can vary in

reverse osmosis with a range of 200 to 500 parts per million while multistage flash and multiple

effect distillation are usually below a few parts per million (CADT 2008, IAEA 2000). The price

of a cubic meter of water for reverse osmosis plants ranges from $0.45/m3 to $1.54/m3. The

multistage flash distillation method can cost between $0.80/m3 to 1.86/m3. The multiple effect

distillation method can range in price from $0.45/m3 to $1.49/m3 (Younos 2005). Although, the

methods of desalination many seem fairly similar in overall pricing, the more suitable methods

for desalination will need to have lower energy requirements as the price of energy increases in

the coming years (Bernat, Gibert et al. 2010).

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Although, the economic cost of each desalination method is contingent on several

variables the largest factor in determining costs is energy consumption (Bernat, Gibert et al.

2010). The cost of energy was 55.2% and 42.6% of total costs for desalinized water production

through multistage flash distillation and reverse osmosis, respectively. The electrical energy

consumption of seawater reverse osmosis plants ranged from 2.5 to 7 kWhs/m3. Consumption of

electrical energy by seawater multistage flash distillation plants ranged from 3 to 5 kWhs/m3.

Multiple effect distillation of seawater consumes 1.5 to 2.5 kWhs/m3 of electrical energy (CADT

2008). Electrical energy is only part of the full energy costs of thermal desalination methods.

Reverse osmosis uses no thermal energy to produce desalinated water where as thermal

processes require a fair amount. The amount of thermal energy that multistage flash distillation

uses can range from 15.83 to 23.5 kWhs/m3 of desalinized water. Multiple effect distillation

requires thermal energy in a range of 12.2 to 19.1 kWhs/m3 (Al-Karaghouli and Kazmerski

2013). When accounting for the use of thermal energy, thermal desalination methods become

increasingly more economically expensive. Although, there are still high-energy costs associated

with all forms of desalination, the pricing of both thermal and membrane based desalination

methods has dramatically decreased over the past decades (Bernat, Gibert et al. 2010) (Fig. 4).

Operational costs of desalination plants are a contributing factor to the overall costs but tend to

make up a smaller portion of the overall cost.

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Figure.4 Decreasing desalination costs. Left-Multistage Flash Distillation, Right-Reverse

Osmosis (Bernat, Gibert et al. 2010)

The operational costs include chemicals used in pre and post treatment of feed and

desalinized water, maintenance and repair, labor, and more specifically for reverse osmosis

membrane replacement (Fig. 5). The operational costs for multistage flash desalination and

reverse osmosis are only 9.9% and 25% of the total costs (Bernat, Gibert et al. 2010). The higher

portion of operational costs for reverse osmosis is due to the more stringent water treatment

processes, membrane replacement, and higher amounts of necessary labor. Membrane

replacement costs can be upwards of $1,900,000 per year for reverse osmosis plants producing

37,850 cubic meters of water per day (Ettouney, El-Dessouky et al. 2002). This is a significant

cost but membrane replacement costs have been reduced by 75% between 1990 and 2002

(CADT 2008). There is currently a fair amount of research on developing more efficient

membranes that prevent membrane fouling, the chief reason for membrane replacement, but the

research into prevention of membrane fouling is based on short term studies when long term

studies are necessary as well as having only a few of the new researched technologies ready for

commercial usage (Kang and Cao 2012). It should also be noted that membrane fouling will

always be a cost of reverse osmosis desalination regardless of technological advances as there is

no way to completely prevent it from happening. Although, membrane based desalination may

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have more operational costs, it would seem that reverse osmosis is better suited for desalination

as there is more room for improvement in overall efficiency than thermal based desalination.

Figure.5 Production Cost Overview for Multistage Flash Distillation and Reverse Osmosis.

(Bernat, Gibert et al. 2010)

Reverse osmosis desalination of seawater for use in the San Francisco Bay Area is

currently the one of the best methods economically to mitigate increasing water demands and

water scarcity as opposed to thermal methods of desalination. Desalination is viewed as a

contingency for water scarcity as conservation methods are generally more affordable

economically and less environmentally damaging than desalination (Meerganz von Medeazza

2004, Bernat, Gibert et al. 2010). The use conservation in lieu of desalination may better

economically but when considering the San Francisco Bay Area’s water scarcity issues are still

estimated to be unresolved even with conservation is used as a main component of its water

policy (Camp Dresser and McKee Inc., 2010). Desalination would also provide a reliable source

of water in the face of the uncertainty of water regimes due to climate change, which would

provide invaluable when facing droughts or sporadic water inflows from early snowmelt (Hanak

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and Lund 2012). Reverse osmosis desalination can be improved upon to be even more efficient

to further reduce costs such as the durability of the membranes to reduce replacement rates

(Busch and Mickols 2004).

4.2 Environmental Costs

The main environmental costs associated with the use of desalination methods are

greenhouse gas emissions, disposal of brine as well as of pre and post treatment chemicals, and

ecological impacts (Hoepner and Lattemann 2003, Bernat, Gibert et al. 2010, Al-Dousari, Ai-

Ghadban et al. 2012). These environmental costs are extrinsic costs that are generally not

included in the price of producing desalinized water. These costs must be considered to ensure

that the full price of desalination is realized.

Greenhouse gas emissions are for the most part intrinsic within the desalination process.

There are few large-scale desalination plants that use renewable energy as their main source of

energy (CADT 2008). The carbon emissions of desalination plants may vary due to size and

design efficiency, but there are estimates for energy usage to the amount of carbon dioxide

emitted from the desalination plants. Multistage flash distillation is estimated to release up to 24

kgs of CO2/m3 of desalinized water. Multiple effect distillation is estimated to emit up to 19.2

kgs of CO2/m3. Reverse osmosis is estimated to release up to 8.6 kgs of CO2/m3 of desalinized

water (Gude, Nirmalakhandan et al. 2010). Using these metrics, if a theoretical reverse osmosis

desalination plant powered by oil was used to make up for the 25 million gallons/day water

deficit in the San Francisco Bay Area it could produce up to an estimated 813,861 kgs of

CO2/day (Camp Dresser and McKee Inc., 2010). It is unlikely that the deficit of water would be

done with a single desalination plant for all future water needs but the use of fossil fuels would

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be counter-intuitive to mitigating water deficits, as it would contribute to climate change and

thereby further exacerbation the water scarcity problem. Desalination plants also emit potential

damaging substances into the environment through the disposal of brine.

The proper disposal of brine is necessary to ensure that highly saline water containing

potentially toxic chemicals is not released into the surround aquatic environment. The

concentration of salt in the brine discharge from desalination of seawater can be up to 2.5 times

that of the surrounding seawater (CADT 2008). The brine tends to affect organisms and

ecosystems at lower depths as the salinity of the brine makes it denser than the surrounding water

(Bernat, Gibert et al. 2010). The dispersal range of the brine into the surrounding seawater is

dependent on the design of the desalination plant and the currents near the disposal site, but a

review of literature on the effects of brine found that its dispersal range could be as small as only

meters or as large as kilometers (Roberts, Johnston et al. 2010). The effects of brine on an

ecosystem can vary greatly but a meta-analysis of literature on the subject found that surface

disposal has the potential to adversely affect ecosystems. The issues associated with brine

disposal are the levels of salinity, the temperature of brine, and the contaminants in the brine.

Although, the temperature of the brine is an issue for thermal desalination plants, this can be

easily mitigated using a reverse osmosis plant that has brine discharges at low temperatures

(Ibid.). However, contaminants can be an issue for both membrane and thermal desalination. The

same meta-analysis found that out 60% of the 28 plants that were sampled in the literature had

levels of copper that failed to meet the United States Environmental Protection Agency

standards. Other contaminants found were mercury, nickel, and cadmium in some of the sampled

plants. Most of the contaminants were attributed to the anti-scalants used at the plants. This issue

will be difficult to mitigate for, as anti-scalants are used for cleaning in most desalination plants.

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There are other methods of disposing of brine such as injection into non-potable aquifers, and the

use of evaporation ponds (Mezher, Fath et al. 2011). The state water board of California

regulates the disposal of brine through the National Pollutant Discharge Elimination System of

permitting; there are few objectives for water salinity of the surrounding area as well as methods

of regulation (State Water Resources Control Board, 2005). Although, there is policy that is

being drafted to mitigate brine disposal, it still remains an issue to both the eventual economic

costs of gaining permits to operate and the environmental costs of discharging brine.

New Technologies for Desalination

The efficiency and productivity of desalination plants has steadily increased over the past

decades, but there are still several processes that can be made to be more efficient (Bernat, Gibert

et al. 2010). One of the most promising improvements is the use of nanoporous membranes in

reverse osmosis desalination plants. The nanoporous membranes are made of graphene, which is

a honeycomb latticework of carbon only an atom thick, which can filter salts at a molecular level

(Cohen-Tanugi and Grossman 2012). The new membrane is capable of filtering salts out of

water at a rate that is 2 to 3 times greater than conventional membranes. The technology could

provide significant savings for the use of reverse osmosis methods but the technology has only

been tested using water that contained NaCl. It might prove difficult to adapt the technology to

brackish or seawater which can contain a multitude of different salts aside from NaCl due to

graphene’s variable pore size and difficulties in stability of the material when subjected to high

pressures (Ibid.). Although, these issues can be resolved further in the future. The scalability of

technology to commercials may be difficult, it still has potential to make reverse osmosis

desalination an even more feasible option for desalination.

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Forward osmosis in conjunction with reverse osmosis has the potential to decrease the

energy used by desalination plants and reduce the environmental impacts of the brine produced

by desalination plants. The processes uses a gradient of salinity with one side more saline than

the other, to draw water through a membrane using osmotic pressure alone (Hoover, Phillip et al.

2011). Using forward osmosis seawater could be initially diluted before going through the

reverse osmosis processes, by using wastewater from municipal or agricultural wastewater as

draw water, which would decrease the energy costs, as the feed water would be less saline than

direct seawater. Forward osmosis can also be applied to the brine from desalination to further

dilute it before it is released into the sea (Ibid.). Some of the largest concerns around desalination

are the energy and environmental costs but with a large-scale application of forward osmosis in

the intake and output process of desalination these issues could be substantially mitigated for.

These are only but a few new technologies that could further improve the efficiency and reduce

the impact of desalination plants.

5. Proposed Desalination Plant in San Francisco Bay Area

Currently the Contra Costa Water District, the East Bay Municipal Utility District, the

San Francisco Public Utilities Commission and the Santa Clara Valley Water District are

working together to assess the feasibility of creating a joint desalination plant which would

provide potable water for droughts, natural disasters, or when issues arise with pre-existing water

delivery infrastructure (URS 2007). They’ve completed studies on the feasibility of the site, a

pilot test, an institutional analysis, site-specific analysis and are currently working on a regional

reliability study. The reliability study is slated to finish in 2015 with at least 3 more phases

before actual construction of the plant, which means that the plant may not even begin

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construction before 2020. The proposed desalination project is slated to produce a 20 million

gallon per day seawater reverse osmosis desalination plant or a 65 million gallon per day

brackish water reverse osmosis desalination plant. The report concluded that commercial and

industrial consumers will not purchase water from a proposed desalination plant in wet years due

to costs with developing infrastructure, time for the plant to come online, quality control of water

for industrial purposes and large scale consumers may be creating their own smaller scale

desalination plants (Ibid.). Although, in dry years these larger consumers may be apt to purchase

water from the proposed desalination plant as supplies of water may be difficult to find. Urban

consumers are seen as more viable markets as they are generally more willing to purchase water

supplies for continual use or to create reserves for dry year protection. Other governmental

agencies such as CALFED Environmental Water Account, for protection of ecosystems that may

need excess water in light of climate change. There has also been an environmental consideration

of the disposal of brine water in the bay. The initial report found that the release of brine into the

surrounding area would only raise ambient salinity levels less than 0.23%. Several Native fish

populations such as Delta Smelt, and Longfin Smelt that may be vulnerable to being swept up by

intake pumps (Contra Costa Water District, 2014). The report suggests reducing intake speeds

during migration seasons, creating diversions away from intakes for the migrating fish and

installing a fish return system that could periodically remove fish stuck on the intake membrane.

The proposed desalination plant has also had analysis done on the projected amount of green

house gases the plant will theoretically emit. The average over 30 years in both wet and dry years

is estimated to be 9,240 Megatons of CO2/year (Ibid.). It is also worth noting that the greenhouse

gases are considered to be indirect sources, as the majority of the plant’s emissions will be based

on electricity consumption, which is produced off site. There are also proposed methods of

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abating the amount of greenhouse gases that are produced by the plant through renewable energy

sources, energy/water conservation at residential levels, purchases of greenhouse gas offsets,

wetland restoration, and carbon sequestration. There is still more research to be done for the

project but it is continually moving forward and will most likely be built sometime in the next

decade.

Conclusions

The use of desalination seems to be an economically viable method of combating water

scarcity in the San Francisco Bay Area. The San Francisco Bay Area is facing a large deficit of

water within the next two decades even with the use of conservation techniques. This deficit

needs to be filled by some means. Although, conservation of water should be the first priority

when considering this problem, the use of desalination will prove to be an invaluable resource in

creating reliable sources of water during droughts, natural disasters and general shortages. The

proposed desalination plant identified that the primarily consumers of the water will mostly

likely be urban consumers who generally purchase water based on water supply rather than the

actual price of the water (URS 2007). This could mean that regardless of the method of

procuring water, the purchase of water will always be based on the water supply not a function of

the price. This being the case as climate change makes water supplies more variable in nature,

the urban consumers will likely pay for more expensive methods of obtaining water for

security’s sake (Hanak and Lund 2012). It has also been found that the public tends to have an

adverse reaction to the source of the water as well which can make the use of waste water or

other reclamation methods of water difficult to use as an alternative (Dolnicar and Schäfer 2006).

The actual cost of desalination plants has steadily decreased over the past decades and as new

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technologies become available the costs will further be reduced (Bernat, Gibert et al. 2010).

Most of the technologies mentioned in previous sections of the paper could be applied to older

plants which means that even if the San Francisco Bay Area moves ahead with the production of

a desalination plant before these technologies become commercially viable that the plant in

theory could be retrofitted with these technologies to reduce the overall costs of the plant in the

long term. The use of reverse osmosis as the primary method of desalination seems to the best

option as opposed to thermal desalination methods. Comparatively reverse osmosis uses less

energy to produce the same amount of water as thermal desalination methods (Younos 2005).

The efficiency of reverse osmosis plants can still be further improved upon to make the method

more cost efficient (Greenlee, Lawler et al. 2009). As a result the environmental impact of

reverse osmosis will also be less than that of thermal methods, as reductions in energy usage will

reduce the amount of indirect greenhouse gases produced. There can also be further reductions of

potential emissions as renewable energies become more affordable and widespread which can be

used to power desalination plants. Other environmental impacts such as brine disposal along with

the contaminants in the brine still remain to be an unresolved problem in the San Francisco Bay

Area as sensitive aquatic ecosystems exist within the area, however there are methods to reduce

the impact of brine discharges by doing thorough site analysis for discharge locations (Roberts,

Johnston et al. 2010) (Contra Costa Water District, 2014). Overall, desalination may not be a

perfect solution to increasing water scarcity in California and the San Francisco Bay Area but

economically desalination will be a viable method of providing water with all considerations

taken into account.

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