Desalination advocates will have no doubt jumped for joy this week upon hearing a final report from the Independent Scientific Technical Advisory Panel (ISTAP) on the Huntington Beach desalination plant in California.
The planned 227,300 m3/day plant from Poseidon Water has undergone scrutiny regarding which type of intake it will use for seawater.
This follows a move in May this year from the California State Water Resources Control Board to implement guidelines for seawater desalination plants.
The rules specify that the State has authority over desalination intake and discharges. More specifically, subsurface, or seafloor infiltration gallery (SIG), has been deemed as the preferred intake structure and must be evaluated for new projects.
Critics suggested at the time that this move could potentially add hundreds of millions of dollars to the cost of new desalination plants in the State (read WWi article).
After releasing a public review draft in August, this week ISTAP published its final report assessing the feasibility of alternative subsurface intake technologies for Huntington Beach.
The report concluded that “The SIG option is not economically viable at the Huntington Beach location within a reasonable time frame, due to high capital costs and only modest reduction in annual operating costs compared to the open ocean intake option.”
The capital cost of the open intake facility is estimated to range from $850-$899 million, compared to £1.94-$2.35 billion for the subsurface intake based on a four to seven year construction time for the latter, according to the report.
Subsurface intake structures have been used on small scale desalination plants under 22,000 m3/day. As the seawater can be very clean, with a silt density index (SDI) of below 1.0, it means less pre-treatment, membrane fouling and maintenance are required, resulting in lower operating costs.
However, despite these advantages open intakes have been preferred as many locations do not have the geology to support an economic subsurface intake.
As a result of the public review in August and final report this week, Poseidon Water has resubmitted its application specifying that existing pipeline infrastructure will be used at Huntington.
Scott Maloni, vice president of Poseidon, said: “The ISTAP process has confirmed the conclusions previously reached by the City of Huntington Beach and the Santa Ana Regional Water Quality Control Board that subsurface intake technologies are technically infeasible and environmentally inferior, and that the seawater intake system Poseidon has proposed for the Huntington Beach desalination project is the only economically viable and most environmentally sensitive for that site.”
Randy Truby, comptroller of the International Desalination Association (IDA), told WWi magazine: “The authors of the report cautioned readers that the conclusions are specific to the location and it should not be assumed the result would be the same in other parts of the world. This is of course correct. However, many seawater desalination plants are operating worldwide almost all with open intake and many of them considered subsurface intake to reduce the cost of pre-treatment and lower operating costs. In all these cases the open intake was the optimum solution.”
Truby added: “The next step is to see if the State of California will accept this report and allow an open intake, and then what will this intake cost with the new criteria the State has defined to reduce entrainment/impingement.”
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