INTRODUCTION TO ENGINEERING PROJECT ASSOCIATES 1 2 3

INTRODUCTION TO ENGINEERING PROJECT ASSOCIATES 1. 2. 3. 4. 5. 6. S. HARI CHANDAN M. RAJEEV P. SRINIVAS RAO SK. WAJEED CH. MAHESH A. SAI VIGNESH

WATER DESALINATION VIA ENERGY EFFICIENT CAPACITIVE DEIONIZATION TECHNOLOGY

GLOBAL PERSPECTIVE : WATER SCARCITY • Water is a precious resource, which is rapidly becoming scarce in many parts of the world • In addition to the physical water scarcity, there is also economic water scarcity • Brackish waters (lakes, lagoons, springs) in such areas can become a source of potable water IF a cheap, easy to manufacture and maintain system for brackish water desalination is developed

JUST A COUPLE OF EXAMPLES FOR WATER SCARCITY IN DIFFERENT PARTS OF THE WORLD • “Egypt imports more than half of its food because it does not have enough water to grow it domestically. • Australia is faced with major water scarcity in the Murray-Darling Basin as a result of diverting large quantities of water for use in agriculture. ” Australia, inland from Brisbane – landscape after a severe drough

DESALINATION : EMERGING NECESSITY • Currently, there are 18 countries classified as water scarce. The majority of these countries are in the Middle East and northern Africa, however, a few countries are found in Europe, Asia and the Caribbean. By 2025, approximately 29 countries in the world are expected to experience water scarcity… Desalination, along with wastewater reuse and water importation, can provide a means of increasing the supply of available fresh water in the regions of the world where water is scarce…”

DESALINATION: QUEST FOR ENERGY EFFICIENCY AND LOW-COST SOLUTIONS To reduce costs, many coastal desalination plants are designed to treat large volumes of water, often 50 mgd* or greater, and are co-located with coastal power plants to take advantage of common intake and outfall structures and less expensive power. These strategies enable coastal facilities, such as the Tampa Bay Desalination Facility, to maintain desalination costs as low as $2. 00 -$2. 50 per 1000 gallons of water produced. Similar facilities in inland areas may cost twice as much to operate because of smaller plant sizes, higher concentrate disposal costs, higher water pumping costs, and higher energy costs * mgd = million gallons a day, or approximately 3. 78 million liters a day

WHAT ARE POSSIBLE SOLUTIONS? Fresh Water For The World's Poorest Lack of water causes great distress among the population in large parts of Africa and Asia. Small decentralized water treatment plants with an autonomous power supply can help solve the problem: They transform salty seawater or brackish water into pure drinking water. More than one out of six people lack access to safe drinking water around the world. That’s roughly 1. 1 billion people. Analysts are increasingly raising concerns about possible water wars which may occur in the near future as water becomes more and more scarce. One possible solution for large parts of Africa and Asia is the creation of small decentralized water treatment plants with an autonomous power supply. These treatment centers can help transform salty seawater or brackish water into pure drinking water for the immediate population

THE FIRST QUESTION: WHAT MAKES WATER SALTY? - - + + Salt ions Na (sodium cations) Cl- (chloride anions) - + + - + Fresh water

SO, WE NEED TO GET RID OF THE SALT IONS… …and Charles-Augustin de Coulomb came up with a clue for the solution about 220 years ago: - Ch arg es of op p os ite pel es g r a Ch o e m a fs a pol re ir ty + po la riti + es att rac t …which is due to the electric fields associated with the charges

SO, WE NEED TO APPLY AN EXTERNAL ELECTRIC FIELD TO SALTY WATER! - - + + + + - + Fresh water No external electric field applied – the water is electrically neutral and salt ions are flowing freely within it + - - - ++ + - External positive negative charge Fresh water charge External electric field causes the salt ions to flow towards the opposite polarity of the field and away from the same polarity

AND IF ONLY WE HAD A WAY TO KEEP THE IONS AWAY! • We could use a lot of power and keep the ions “stuck” to the points of application of the electric field despite the water flow • …but that would violate our requirement of low power! • Instead, we can try to use some sort of an ion-absorbing material at the electric field application points… • So, the conceptual engineering design can be as shown in the next page…

THE IDEA

LET’S NAME IT! • Actually, the name for such a technology has been around since the 1960’s – Capacitive Deionization (CDI) – but the technology itself has not received much attention until fairly recently… 1950’s 1960’s 1980’s • The idea of using electricity to separate compounds was introduced. • Ideas to use CDI for water treatment developed. • The technology began to pick up popularity again. 1990’s • Testing was done in laboratory settings with the first industrial CDI prototype under development during the late 1990 s. Prese nt • Lawrence Livermore National Laboratory (LLNL) is currently using CDI technology for industrial waste, municipal waste, medical applications, and mineral extraction. Prese nt • Several research groups around the world are trying to bring CDI to commercial implementation.

SYSTEM CONCEPT

CDI CELL CONCEPT Attach the ‘ion sponge’ material to the electrode (or use it as an electrode) Provide for a constant separation between the electrodes – it defines the strength of the electric field inside + Attach power wires Make the electrodes – choose size, shape, material Choose your lowpower source …and then comes the water!

WATER FLOW • The cheapest option is to make gravity do the job – no motor/pump is necessary, thus – no extra power requirements; although the throughput may be small • Depending on water salinity and the ability of the ‘ion sponge’ to trap and retain the salt ions, timing requirements for desalination process will vary • We can adjust the flow/timing by dialing the flow valve in/out Cut out for a place to insert a CDI cell

SALINITY TESTING • We need a device that can measure the levels of salinity from about zero to a maximum of 30 ppt • The finer the resolution – the better Example: Koi. Medic Digital Salt Meter: Range: 0 to 10 ppt Inexpensive, very accurate, but range goes to 10 ppt only…

COMPLETE SOLUTION: SUMMARY Prepare the brackish water solution with the known salinity level (use the salinity meter to verify) Assemble the CDI cell and put into the vessel Prepare the water vessel with a flow valve Run the test, while timing your measurements; plot the graph of salinity vs time