The California drought is officially over, but the city of Santa Barbara is not forgetting. After the last drought about 25 years ago, the city idled its desalination plant only a year after it opened and later sold off equipment. That won’t happen again.
The Charles E. Meyer desalination plant reopened in May, and it’s back to stay because there are too many uncertainties facing this tourist city on the Pacific coast northwest of Los Angeles.
“At one point during the latest drought our main reservoir dropped to 7 percent of capacity,” says Joshua Haggmark, water resources manager for the city.
“It literally came down to one day: Feb. 17. On that day we had 10 inches of rain. It was considered a 25-year storm, and it was right in line with the predictions of climate change, and it turned our situation around,” Haggmark says.
Here's a shot of construciton crews laying some piping as part of Santa Barbara's desalination plant project. (Photo Courtesy of the city of Santa Barbara)
When the city council voted 7-0 in July 2015 to reactivate the plant, the drought was a factor, but there were others that won’t go away, Haggmark says. There is an expectation of more regulations to come on surface water, in particular a diversion to promote recovery of the steelhead trout population. There is uncertainty about the large aqueduct that draws water from the San Joaquin River delta, which empties into San Francisco Bay, and sends it south to the Greater Los Angeles area.
“That water travels 500 miles, and we never want to depend on it entirely. The delta is built on levees. One big earthquake in that quake-prone area could disrupt our supply,” Haggmark says.
The 30 percent solution
With a capacity of 3 mgd the desalination plant provides about 30 percent of the city’s demand for its 93,000 customers drawing through 24,000 service connections. In addition to the year-round population, Santa Barbara annually draws more than 5 million tourists.
These are the holding tanks for Santa Barbara's finished desalinated water. (Photo Courtesy of the city of Santa Barbara)
To provide all that water, the city draws on a variety of sources with varying costs, Haggmark says.
Typical surface water is about $300 per acre-foot. (All of these costs are operating expenses and do not include capital outlays.) Groundwater costs depend on the well. One requires only basic chlorination, and its water is about $150 per acre-foot. Several wells need remediation for manganese, hydrogen sulfide, and iron, and that water is about $800 per acre-foot.
Water from the California aqueduct is about $1,500 per acre-foot. In the late 1980s the city invested in a water recycling system that treats wastewater for secondary uses, mostly irrigation for parks and golf courses, and the cost of that water is about $1,200 per acre-foot.
Desalinated water is about $1,400 per acre-foot. Most of that cost lies in energy to push water through the membranes, and Santa Barbara is working to reduce its energy cost, Haggmark says. The city has adopted a goal of using 50 percent renewable energy by 2020 and 100 percent by 2030. To help reach that goal the city wants to create a local marketplace where people can buy and sell renewable energy. Current rules allow the installation of solar-electric systems only if the capacity does not exceed a building’s needs, Haggmark says.
Rebuilding with experience
Instead of rebuilding the desalination plant on its own, the city hired IDE Americas, the U.S. branch of IDE Technologies, based in Israel.
IDE retained only about 10 percent of the old plant, says Greg Paul of IDE, who manages the desalination plant for the city. A few large tanks stayed, as did the backwash clarifiers for filters, and the control and administration buildings. Everything else was new and came in modules that could be dropped into concrete pads and connected.
Water enters the plant through a 36-inch HDPE pipe that originates from an intake structure about a half of a mile offshore. The intake has 1 mm screens to keep out small aquatic organisms, and the flow of less than 0.5 feet per second is less than the ocean current that organisms swim against. The intake pumps, and other low-pressure pumps in the system are from Xylem.
Ferric chloride is introduced into the pipe for flocculation, and the long pipeline allows plenty of contact time. A set of charcoal and sand filters removes the flocculant and large debris. Next is a set of IDE micron filters that provide an extra layer of protection for the membranes. Then, water is pushed through the IDE membranes at 800 to 900 psi by high-pressure pumps from Energy Recovery.
Water runs through a UV system, not because the membranes are inefficient, but because of California regulations, Paul says.
Under its contract, IDE is expected to produce desalinated water with an energy use of no more than 4400 kWh per acre-foot, Haggmark says. If energy use exceeds that, IDE pays the difference. If energy use is less, IDE and the city split the savings.
Charging the cost
Money for the $70 million desalination project came from a state revolving loan fund at a 1.6 percent interest rate for 20 years, Haggmark says.
As the drought took hold a few years ago, water customers still experienced a significant number of rate increases, Haggmark says. In one year, rates increased about 30 percent, in another, 18 to 20 percent. Higher rates compensated for reduced demand because of increased conservation, for the additional cost of drilling new wells and for the cost of buying some water on the open market. Now, the average bill is about $120 a month, and with no surprises on the horizon, rates should need to increase by only about 1 percent for the next three years, he says.
Those higher costs also encouraged people to replace old fixtures and replace thirsty landscaping with plants suited to southern California’s arid climate. Grants helped people do that, Haggmark says.
Designed for growth
While the desalination plant is permitted for 3 mgd, it is designed for expansion to 10 mgd. The city won’t reach that demand on its own, but if regional water partners want some of the plant’s output the additional capacity could be available in about 12 months, Haggmark says.
The modularity of the plant plays a role in this and played a role in the city’s decision to pick IDE, he says. The modules that comprise the plant are built to shipping-container size, which means they can be produced by highly skilled technicians and then shipped anywhere to be connected by people with less skill, Haggmark said. That is an advantage should the plant need an expansion or an upgrade.
Delalination may help solve the city’s supply problem, but it introduces a problem: purity.
“We have really hard water here to begin with, so we have to go through a pretty complex remineralization process because the permeate is too pure — too pure for drinking, too,” Haggmark says. “A long-term goal is to have equipment so we can blend desalinated water with our other water.”
The present process involves adding lime and carbon dioxide to put more calcium in the water and prevent the permeate from stripping minerals from the inside of pipes.
Disposing of brine from the desalination process is not a problem. For each gallon of drinking water the plant generates a gallon of brine, but across the street from the desalination plant is the city’s wastewater plant. Brine is used there to dilute the treated water discharged into the ocean.
Because of different densities, fresh water naturally wants to rise in ocean water, and brine naturally wants to sink, Haggmark says. That would disturb the ocean ecosystem, in particular organisms that live near, on, or in the sea bottom. But mixing the two water streams, and pumping them out through jet diffusers, removes that density gradient.
Now that it’s up and running, Haggmark wants the public to tour the plant. It’s important, he says, for citizens to see how complex an issue water is, and how complex it is to protect the environment.