CALIFORNIA DESALINATION STRATEGIES: AN INTERVIEW WITH RANDY TRUBY
BY STAS MARGARONIS
Randy Truby, California-based desalination consultant and comptroller for the International Desalination Association, told RBTUS in an interview that he believes states experiencing long-term drought conditions, such as California, may need to consider new investments in desalination plants in order to provide insurance against long term drought and to become “drought-proof.”
For example: “In Australia, the long drought there spawned construction of a number of desalination plants, some of which had to be mothballed when normal rainfalls returned. However, there has been a recent reduction in rainfall, so some desalination plants that had been mothballed have been reactivated. The long term solution is to build a sufficient number of desalination plants so that sea water treatment can be held in reserve for periods of low rainfall, and deactivated or mothballed when normal rainfall returns.”
Truby noted applications for agriculture that might be relevant to California: “The use of desalination technology has been used in several countries to support agriculture, including in the Canary Islands and Israel. The precedent has been established in case water is needed for agricultural producers in California.”
Truby notes that waste water treatment can be a major generator of new water supply: “Conservation, waste water treatment and treatment of brackish water are all means to improve the supply of water for drinking. About 85% of waste water, such as sewage water, can be transformed into potable water. However in the United States, there are concerns about putting treated sewer water back into the water supply. So treated sewer water is pumped back into the ground and ultimately resuscitated as drinking water and for other uses via underground aquifers.”
He adds that “Governor Brown’s water conservation initiative helps reduce water usage and especially water waste. However, some California locations are beginning to plan for long term shortages by investing in desalination of brackish water, waste water and in some cases sea water. The desalination process for sea water is the same process that is used in the treatment of waste water and brackish water. It uses a reverse osmosis system whereby water is filtered through membranes. This filtration process uses pumps that require energy that increases the expense of the desalination process. However, if you do not have water, or are experiencing chronic droughts, then the expense justifies the investment.”
Truby says there may be ways to link desalination to renewable energy development: “There have been several projects that use renewable energy to support desalination: (1) In Perth, Australia, they built a wind farm that generated power into the grid that provided the additional energy needed to support the desalination plant. (2) In Saudi Arabia, a new photovoltaic (PV) solar plant will be linked to a desalination plant (that will transform salt water into drinking water). This desalination plant is in the planning stage and designed to generate many millions of gallons per day. It directly links renewable energy to desalination. There is a sizable capital cost for the PV capability, but a lower operational cost for the desalination plant.”
He notes that “a new technology employs a process called forward osmosis. It uses a batching process rather than the continuous process used in the reverse osmosis system. The continuous process is likely to support a more massive filtration of sea water than a batching process. But the new technology is still in the development stage.”
A major stumbling block for new desalination installations is time delays due to permitting: “Another problem for the deployment of all desalination technologies is that from the time contracts are let, construction requires 2 to 3 years. This does not account for permitting time which in the case of the Carlsbad facility in San Diego County, took 9 years due to California coastal commission reviews and legal challenges in the courts.”
The result is: “The Carlsbad desalination plant will soon be operational and will generate 85 million gallons of water per day. San Diego County is planning on sourcing 5%-10% of its water needs from sea water.
He says desalination technology generates water from waste water in 40% of current applications and from sea water in 60% of applications.