California city ponders desalination revival

California's city of Morro Bay is poised to apply to the state Coastal Commission to operate continually its currently idle reverse osmosis desalination plant. The city let its operating permit expire in 2000, and the plant - built in 1992 - has not operated since then except for occasional emergency use.

Morro Bay has a 20-year contract to buy water from the state, paying about US$1.82 million annually. This year, that supply met 97% of the city's water demand with the rest coming from groundwater and reserves. According to Morrow city engineer, Rob Livick, the contract with the state expires in seven years and the city will not restart the desalination plant until it has renegotiated the contract to purchase less water. The city is obliged to pay for the contracted state supply whether it uses it or not said Livick.

Livick said the city expected to start planning for its future water supply within a year and those plans will include the desalination plant : "Even though it's years out, the planning for a transition like this needs to start happening well in advance," Livick said. He said the plant produces water at less than two thirds the cost of the rate charged by the state
Morro Bay's city council will ultimately decide how to structure its water supply portfolio. "In the long term, the permit is important to what will likely be part of our long- term water supply strategy," said city manager, Dave Buckingham.

In the long term, the city may not be able to use desalination as a primary supply because of complications with groundwater and seawater. The city has rights to draw groundwater in Morro Valley, to meet about half of its annual demand but he groundwater has a high nitrate content.

Seawater desalination has other problems, including high concentrations of naturally occurring iron in the water that clogs the desalination system. One of its five saltwater wells is especially impacted with iron. The city is looking into newer filtration devices for its seawater treatment component that require less maintenance and extensive backwashing.

Under current drought conditions in the region the plant provides a more reliable water source than the state contracted water. Last year, Morro Bay received 5% of its state water allocation, and this year it collected 15%.

The city stores reserve water in the San Luis Reservoir, which it has used during the current drought. "I envision at some point in the future, splitting up our water sourcing differently," Livick said. "One possibility might be one-third reclaimed water from our new water reclamation facility, one-third state water and one-third desalination."

Buckingham said he was optimistic that a water reclamation facility, planned as part of a new sewage treatment plant, will be available to recharge the Morro Creek well water.
He said the state water contract could be relegated to an emergency backup, given the possibilities for increased use of well water and desalination. The new reclamation facility could provide a significant supply should the use of treated wastewater for potable use become allowed under proposed legislation.

The sources of the water for desalination treatment are five saltwater wells along the Embarcadero and seven wells used to treat brackish water in the lower Morro Valley using reverse osmosis. Buckingham said the city was in the "very, very early stage" of exploring a partnership with private companies to build and operate a new desalination facility at the old Morro Bay power station site.

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