Seawater Desalination: An Environmental Impact Analysis, 2

Seawater Desalination: An Environmental Impact Analysis

Matthew Lewis

May 8, 2014

GSP 480C

Introduction

The global demand for safe potable water is at an all-time high. Populations are skyrocketing especially in developing nations with little environmental regulations and even smaller existing water resources. Presently, over one-third of the worlds population lives in water-stressed countries and by 2025 this figure is predicted to rise to nearly two-thirds (Philip et al 2011). Around the world, humans now use more than 50% of the total runoff water that is fresh and reasonably accessible, with about 70% of this use in agriculture. People have also extensively altered river systems through diversions and impoundments. In the United States only 2% of the rivers run unimpeded, and by the end of this century the flow of about two-thirds of all of Earth's rivers will be regulated (Vitousek 1997). There are many modern techniques for capturing fresh water for the region. Most include canals for irrigation, small scale filtration centers from fresh water streams and rivers, and tapping in to ground water. These methods which we have been using for decades have many environmental impacts. Hydroelectric power plants help supply power to surrounding areas by damming water which regulates fresh water for millions of people around the world. These plants have huge impacts on surrounding areas. The large Balbina hydroelectric plant built in Brazil, flooded 2,360 square kilometers, an area the size of Delaware, which only provides 250 MW of power generating capacity (Environmental Impacts of Hydroelectric Power 2013). There is also an issue with the dam itself which create changes in the supply of sand and flow rates have, altered the sedimentary processes that create and maintain sandbars and related habitats, resulting in smaller and coarser grained deposits throughout the ecosystem (Lovich et al 2005).Desalination plants can be a potential answer for a more sustainable water supply. This alternative method is a process by which seawater or water which is high in salts and other unwanted minerals are filtered out and converted into fresh drinking water. Large scale desalination began in 1965 (Lior 2013). Modern day desalination is much more advanced and energy efficient after over fifty years of tweaking and innovations. There are over 16,000 facilities worldwide as of 2012 with most which are located in the Middle-East and Mediterranean regions (Philip et al 2011). Currently the most efficient process in which most desalination plants use around the world is called membrane-based processes for filtering seawater (Chen et al 2008). However, such as any other development, desalination has both its benefits and challenges in regards to environmental sustainability. The greatest environmental and ecological impacts surrounding desalination have occurred around older multi-stage flash (MSF) plants discharging to water bodies with little flushing (Roberts et al 2010). With this fact widely known, this process called is still being used in Kuwait and consumes heavy oil and crude oil for generating the power (Al-Dousari et al 2012). Even the most widely used method of desalination has wastewater discharging effect on coastal water quality. This is mostly due to the highly saline brine that is emitted into the sea, which may be increased in temperature, contain residual chemicals from the pretreatment process, heavy metals from corrosion or intermittently used cleaning agents (Lattemann 2005). According to the World Health Organization (WHO 1984), total dissolved solids should be less than 1,000 mg/L in drinking water based on taste considerations, and the EPA has set a secondary standard for total dissolved solids of less than 500 mg/L ( EPA 2002). By comparison seawater has an average total dissolved solid of about 35,000 mg/L (National Academies Press 2004). Not only wastewater discharge bad for the environment the overall power usage also effects the environment. With the reverse osmosis process used around the world in the largest desalination plants the largest energy usage is where a standard pressure of 1200 PSI is reached in order to pump water through membranes (Watereuse Association 2011).There are many future processes desalination can take in order to achieve a more sustainable process. Many include renewable energy sources which provide the energy it takes to run the plant such as geothermal desalination. One such process is known as solar desalination. In the direct method, a solar collector is coupled with a distilling mechanism and the process is carried out in one simple cycle (Gomez-Comacho et al 2002). Another method which has been gaining a lot of attention within the past few years uses a single sheet of graphene. This method uses nanometer-scale pores in single-layer freestanding graphene can effectively filter NaCl salt from water (Cohen-Taguni et al 2012). These future uses will provide the world with a more sustainable solution for clean potable water for generations to come.Research Problem Statement

Researchers are trying to develop a way to increase the fresh water supply for the steadily increasing world population. Additionally, the general environment is also suffering from the lack of fresh, steadily flowing water. Desalination plants can be a potential answer for a more sustainable water supply, and have been touted as such. The purpose of this paper is to examine how one such development is currently being applied. However, first a few questions need to be asked regarding topic of environmental impacts relating to seawater desalination. Is desalination a potential answer for a sustainable future? What are the environmental benefits and challenges of seawater desalination? Are the environmental benefits of desalination enough to outweigh any of its environmental challenges? How can the Carlsbad Desalination Plants impacts alleviate concerns related to arid regions in particular?

Research Site

The case study site will focus on the Carlsbad Desalination Plant is in Carlsbad, San Diego County, California. The Carlsbad Desalination Plant is located of Interstate 5, just off the Agua Hadionda Lagoon and adjacent to the Encina Power Station. This plant has an expected completion date in 2016 and will provide 300,000 people around San Diego County with 50 million gallons of clean water per day. These 50 million gallons will be sent through a 10 mile 54 inch in diameter pipeline which will connect the plant to existing distribution network. The total cost of the project is anticipated to exceed $1 billion that is being built and funded by Poseidon Water. Poseidon Water as a part of a Water Purchase Agreement signed by Poseidon Water and The San Diego County Water Authority; which is good because the Colorado River is San Diego Countys current freshwater source.Secondary Research

San Diego County located in Southern California had a population of 3,095,313 in 2010. This large populous is currently facing a dire state of water scarcity. The county is full of microclimates, usually varying between temperate dry Mediterranean climates to semi-arid and arid environments depending on ocean proximity and topography. Not only does San Diego County receive small amounts of precipitation throughout the year over average, it has been in a drought. Over the past decade this region has experienced sub-average precipitation totals which have resulted in not only drought but wildfires. Wildfires not only threaten the indigenous wildlife of the affected areas but in order to keep properties, structures, and humans safe, supplemental water taken from reservoirs and used to combat these blazes. San Diego Water Authority has aimed to battle these conditions by enacting a Water Shortage and Drought Response Plan. This response strategy plans to decrease water usage from citizens of the county, which has worked by decreasing the gallons per day per capita by 25% over the past decade (San Diego County Water Authority, 2014). The other aspect of this response plan is find alternative sources of water which includes seawater desalination. This aspect of the plan is to counteract the current means for receiving water. San Diego County is currently utilizing the Colorado River for 63% of its total water via the San Diego Aqueduct, State Water Project accounts for 20%, with the local water supplies accounting for only 17% (Bureau of Reclamation, 2011). This coupled with the fact the county has a steadily growing population provides a great study site comparable to other arid regions with similar water scarcity issues.Methods

The purpose of this case study was to obtain information regarding environmental concerns and benefits surrounding this major desalination plant. Even though this plant was not finished by the time research was complete, there was still an abundance of information encompassing how this plant will affect the surrounding environment. Preliminary questions with reference to environmental impacts have been researched by Poseidon and additional agencies which include an environmental impact report entailing very detailed information regarding these concerns. One method used was a comparative analysis to answer the question of environmental impacts. This comparative analysis contains how this plant will alter the surrounding environment. This compare and contrast included both environmental concerns as well as environmental benefits of the Carlsbad Desalination Plant. This included answering these questions with the City of Carlsbad and Poseidon providing scientific data which back claims. Another method which has been conducted is a social map of the desalination plants plan. This map contains where the plant is located with various other points important to the functioning of the plant. This includes potential habitat areas in which will improve as a result of the plant. Included in the map are where the majority of the water currently in use is taken from and where the water is being imported. Lastly, I met with two people from Poseidon Water in order to ask a few underlying questions regarding the Carlsbad Desalination Plant. This will help answer any potential missing information which is not contained on their website. I interviewed Jessica Jones the Community Outreach Manager and Tabitha Whipple, both of whom work at the Poseidon Water. These interviews were to obtain answers about the construction details of the Carlsbad Desalination Plant as well as its potential environmental impacts and advantages. I asked the following questions: Where is the 66 acres of wilderness which will be conserved with a result of the desalination plant as stated on your website? Where within San Diego County is the 50 million gallons of water which is generated in this plant being provided? Will this plant help any fresh water wildlife areas which are currently threatened? Considering the sites proximity to the Encina Power Station, will there be any energy saving measures taking place? Findings

These three methods of collecting data provided a greater understanding on how one plant can alter the environment. It also shed light on how desalination plants actually operate. These interview questions also aided the relationship of the mapping research method to the comparative analysis. The findings from this micro case study can easily be applied to desalination on a macro scale as well as other regional sites.

Figure 1: Main Study SiteFigure 1 shows the main study site for this project which contains: the Carlsbad Desalination Plant, Encina Power Station, delivery pipeline, distribution network facility, and the Agua Hedionda Lagoon. The adjacent Encina Power Station will be providing most of the power to the plant which will utilize during the desalination process. The remaining power for the plant will be gathered from photovoltaic solar power cells located atop the plants main structure. The Carlsbad Desalination Plant will be using a total of 304 million gallons of seawater. This seawater will be gathered via intake pipe from the neighboring Agua Hedionda Lagoon. During the desalination process 254 out of the 304 million gallons will be used for the following: discharge, dilution, and cooling. The smaller dark blue area in the map is a minor inlet of the Agua Hedionda Lagoon important for the intake and discharge channels which feeds seawater into the major body of the lagoon and disperses the 254 million gallons of discharge water to the Pacific Ocean. Figure 1 also shows the pipeline in the blue dashed line which will deliver the 50 million gallons of fresh water to the existing distribution network.After using the interviews and environmental impact report I received the information regarding the environmental benefits and challenges. These two categories consist of two subcategories each. Negative environmental impacts of the Carlsbad Desalination Plant: hypothetical impacts and confirmed impacts. Positive environmental impacts of the Carlsbad Desalination Plant: Indirectly affected impacts and directly affected impacts.Confirmed negative environmental impacts are only partial at this point because the plant is not yet completed so only basic construction has taken place. This includes clearing the six acres of land the site will be located on and construction efforts regarding the ten mile pipeline. Air pollution is occurring because of this suspended particulates are adding to the greenhouse gas emissions in the atmosphere. There are also very minor issues in topology and geology related to the digging of ground sediment to make room for the pipeline. Hypothetical negative environmental impacts differ from confirmed because this project is not completed yet. These hypotheticals include the desalination processes, wastewater discharge, and equipment impacts. Hydrology and water qualities may be altered due to the desalination process which may change the waters: temperature, salinity, chemicals, and turbidity. These changes in ocean characteristics may harm the general areas ecology. Changes to the ecology may include: marine biological habitats, species diversity, and/or ecological distribution patterns.

Figure 2: Mitigation Plan Potential AreasThe indirect positive impacts are due to a mitigation plan which aims to minimize the probability of any potential risk should anything negative occur. The mitigation plan is directed towards the company building the structure, Poseidon Water, per request of the following agencies: California Department of Fish and Game, National Marine Fisheries Service, and the United States Fish and Wildlife Service. Together they have created the following plan details: Planting trees to hide highly visible pump stations. Restoration of 66 acres of coastal wetland in South San Diego Bay, create buffer zones surrounding wetland areas with planted indigenous vegetation of at least 300 feet wide, and re-vegetate wildfire areas which burned in 2007. The upper left map of Figure 2 indicates potential recovery areas which will take in South San Diego Bay area.The direct positive impacts are directly related to the opening of the Carlsbad Desalination Plant and the water independence this provides from the current sources. Riparian areas surrounding the Colorado River may flourish. These areas have been greatly affected by current means of receiving the Rivers fresh water. So, decreasing dependency on this source can help by: bringing landscapes which have been altered by reservoirs, canals, and aqueducts, regulate the rivers water temperatures because of these reservoirs, and even returning the natural water depths thus allowing proper sediment transport to take place.This plant is also taking measures for sustainability and impact reduction. They plan to re-use existing industrial infrastructure and land. The have designed an energy efficient process which utilizes Encina Power Stations once-through cooling system saving great amounts of energy. Energy conservation measures are also in effect with the addition of solar panels atop the desalination structure. They have also proposed using 2100 tons of carbon dioxide, leftover from the process, for the use of post-treatment of the water. Conclusion

Researchers are trying to develop a way to increase the fresh water supply for the steadily increasing world population. The goal of this project was to examine how one such development is currently being applied for this problem. Desalination has a bright future ahead full of unique energy efficient techniques which are currently being tested. These techniques include two different categories. The first category is renewable desalination processes. This is when the standard desalination process is used but powered by renewable energy sources. These renewable energy sources include: solar, geothermal, biomass, wind, tides, hydraulic, and waves. This provides a cleaner alternative to the conventional natural gas or crude oil, common in the Middle-East desalination plants. The other category for potential desalination processes is alternative processes. The major alternative process currently being studied is called Carbon Nanotube/ Graphene Filtration. This is a process by which nanometer-scale pores which can be single layer thick or multiple layers thick. These pores are large enough for H2O to permeate, however small enough to shield salts and other unwanted particulates (Cohen-Taguni et al 2012). These future methods need further testing to determine if they are in fact more sustainable and energy efficient than current methods. This was not accomplished in this paper as it would have provided a great compare-contrast section. Using the information containing desalinations environmental benefits and challenges results there is sufficient information needed to answer the research questions. Is desalination a potential answer for a sustainable future? Yes, desalination is a potential answer for sustainability. However, desalination will never be completely sustainable until new methods which rely solely on renewable energies are used. What are desalinations current environmental benefits and challenges? There are significant negative impacts to marine, terrestrial wildlife and physical geography as a result of desalination. There are also significant positive impacts to plants, animals, and physical geography. The negative and positive impacts are with desalination effect the same environmental categories but differ in severity, geographic location, and natural environments. This leads to the next research question. Are the environmental benefits of desalination enough to outweigh any of its environmental challenges? Yes, the overall benefit for the environment is enough to outweigh any environmental impact. This is because the direction in which desalination is heading. This technology is still relatively young and will continue to grow exponentially with more energy saving techniques in the near future. The final research question asked was how can the Carlsbad Desalination Plants impacts alleviate concerns related to arid regions in particular? Carlsbad has higher environmental regulations than perhaps anywhere outside of Europe and this project is still being hailed as a major step towards a more sustainable future. Not only that but this project can shed a light on how one region with no natural water source can regulate a large land area and high population.References

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