Media
Feb 6, 2012
Desalination for Meeting the Demand of Drinking Water
Robert C. Nowak
Street/Stormwater Manager
City of Largo, Florida
Member, APWA Water Resources Management Committee
As the State of Florida continues to grow in population, so does the need for increased potable drinking water. It is projected that the additional demand for water will be up by 25% by the year 2025, which will bring the state’s daily average use to 8.7 billion gallons per day. With climate changes and the effect of prolonged drought periods the state has experienced in recent years, this will severely impact the state rivers, lakes, streams and thousands of springs which all tie to the Florida aquifer that flows underground through most of the state.
The Florida aquifer is a large supplier for the state’s population for drinking, agriculture and bottled water suppliers. The state is logistically surrounded by water on three sides—the Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico. This is where desalination comes into play.
In its early process, desalination was called distillation. This old technology was used on the open sea where water was heated to boiling and the condensed water vapors went through a cooling tube. Distillation was first used on land in the 1920s and 1930s in the Caribbean and Mideast. The first U.S. distillation plant was built in Texas. Distillation still produces 43% of the world’s desalinated water.
A couple of decades ago, a new technology was developed that was called reverse osmosis. Reverse osmosis is a process that uses pressure on a salty source of water and pushes water through a membrane leaving a saltier residue behind for later disposal. There are 12,000 such plants worldwide today that use reverse osmosis and produce over 11 billion gallons of water per day.
In the State of Florida, there are more than 140 facilities that produce 515 million gallons of potable water using the desalination procedure, but they are all used with a combination of brackish groundwater and surface water. These facilities use one of three processes: distillation, electrodialysis or reverse osmosis.
Reverse osmosis is the most commonly used process in the United States which is a very costly method as are the other two processes. The industries are presently using a combination of processes and are developing better pumping and filtering systems to lower the cost. Another drawback of desalination is energy use to produce raised greenhouse emissions, such as solar and other heat-generated sources. Other cost reduction measures taken are to locate desalination facilities next to power plants, to use the intake cooling facilities and generated discharges which are used in the process to desalinate seawater into drinking water.
In January 2008, a new desalination plant began operation in the Tampa Bay area. It is capable of producing 25 million gallons a day of potable drinking water and can be expanded in the future to produce 35 million gallons. This will supply the Tampa Bay area with 10% of its daily use of drinking water. This plant is the largest plant in North America to use reverse osmosis and seawater from Tampa Bay waters. It is located next to Tampa Electric’s Big Bend Power Plant and receives raw saltwater intake from the plant’s four discharge tunnels which in turn goes into the desalination plant pretreatment facility. It is then chemically treated and run through a series of filters during which the PH is adjusted. Then it goes through the reverse osmosis process of passing through several filtering systems at high pressure. This pressure varies from 625 to 1050 psi.
The salinity by-product is then piped back to the power plant cooling tube, premeasured and discharged back into Tampa Bay waters. As the state’s freshwater supply dwindles and the level of the Florida aquifer reaches new lows, other states and large cities that have access to seawater such as Jacksonville are looking toward desalination as an alternative source of drinking water. Just as a side note, a report from the government accountability office in 2003 anticipated that by 2013 about 36 states will experience water shortages.
So besides having great beaches and great weather most of the year in Florida there is an ample supply of water, and future technology should decrease the cost of producing freshwater from seawater.
Robert Nowak can be reached at (727) 587-6718 or rnowak@largo.com.
Street/Stormwater Manager
City of Largo, Florida
Member, APWA Water Resources Management Committee
As the State of Florida continues to grow in population, so does the need for increased potable drinking water. It is projected that the additional demand for water will be up by 25% by the year 2025, which will bring the state’s daily average use to 8.7 billion gallons per day. With climate changes and the effect of prolonged drought periods the state has experienced in recent years, this will severely impact the state rivers, lakes, streams and thousands of springs which all tie to the Florida aquifer that flows underground through most of the state.
The Florida aquifer is a large supplier for the state’s population for drinking, agriculture and bottled water suppliers. The state is logistically surrounded by water on three sides—the Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico. This is where desalination comes into play.
In its early process, desalination was called distillation. This old technology was used on the open sea where water was heated to boiling and the condensed water vapors went through a cooling tube. Distillation was first used on land in the 1920s and 1930s in the Caribbean and Mideast. The first U.S. distillation plant was built in Texas. Distillation still produces 43% of the world’s desalinated water.
A couple of decades ago, a new technology was developed that was called reverse osmosis. Reverse osmosis is a process that uses pressure on a salty source of water and pushes water through a membrane leaving a saltier residue behind for later disposal. There are 12,000 such plants worldwide today that use reverse osmosis and produce over 11 billion gallons of water per day.
In the State of Florida, there are more than 140 facilities that produce 515 million gallons of potable water using the desalination procedure, but they are all used with a combination of brackish groundwater and surface water. These facilities use one of three processes: distillation, electrodialysis or reverse osmosis.
Reverse osmosis is the most commonly used process in the United States which is a very costly method as are the other two processes. The industries are presently using a combination of processes and are developing better pumping and filtering systems to lower the cost. Another drawback of desalination is energy use to produce raised greenhouse emissions, such as solar and other heat-generated sources. Other cost reduction measures taken are to locate desalination facilities next to power plants, to use the intake cooling facilities and generated discharges which are used in the process to desalinate seawater into drinking water.
In January 2008, a new desalination plant began operation in the Tampa Bay area. It is capable of producing 25 million gallons a day of potable drinking water and can be expanded in the future to produce 35 million gallons. This will supply the Tampa Bay area with 10% of its daily use of drinking water. This plant is the largest plant in North America to use reverse osmosis and seawater from Tampa Bay waters. It is located next to Tampa Electric’s Big Bend Power Plant and receives raw saltwater intake from the plant’s four discharge tunnels which in turn goes into the desalination plant pretreatment facility. It is then chemically treated and run through a series of filters during which the PH is adjusted. Then it goes through the reverse osmosis process of passing through several filtering systems at high pressure. This pressure varies from 625 to 1050 psi.
The salinity by-product is then piped back to the power plant cooling tube, premeasured and discharged back into Tampa Bay waters. As the state’s freshwater supply dwindles and the level of the Florida aquifer reaches new lows, other states and large cities that have access to seawater such as Jacksonville are looking toward desalination as an alternative source of drinking water. Just as a side note, a report from the government accountability office in 2003 anticipated that by 2013 about 36 states will experience water shortages.
So besides having great beaches and great weather most of the year in Florida there is an ample supply of water, and future technology should decrease the cost of producing freshwater from seawater.
Robert Nowak can be reached at (727) 587-6718 or rnowak@largo.com.
