LA Water agency protects regional groundwater
The Water Replenishment District of Southern California, or WRD, is tasked with protecting groundwater sources for 43 cities, including Los Angeles. One of their new projects is the Regional Brackish Water Reclamation Program, which will take water that is too salty to drink and turn it into drinking water.
“This brackish groundwater has much less salt than ocean water making it less expensive and more environmentally sound to desalinate,” said Director Rob Katherman, a WRD board member who represents the City of Torrance and other beach cities.
In the 1900s, the over-pumping of groundwater made seawater from the ocean flow into groundwater aquifers, according to the WRD. Most of the water that Californians drink is groundwater, which is water underneath the ground. The groundwater and seawater mixed, creating brackish water, which is too salty to drink, but not as salty as seawater. Wells in the West Coast Basin and the southeastern tip of the Central Basin were affected by this. Instead of abandoning the wells, Los Angeles County started pumping in freshwater in the 1960s, creating an artificial barrier between the groundwater and seawater. It used more than 100 injection wells.
However, in the process of creating the barrier, the county trapped a plume of brackish water in aquifers in lower San Pedro, Gage, Silverado and Lynwood. A plume is a vertical body of fluid moving through another, in this case brackish water in freshwater. This plume consists of 20 billion gallons and prevents the county from pumping groundwater in some West Coast Basin areas.
The WRD first started treating brackish water at the Goldsworthy Desalter in Torrance, starting in 2002 and doubling its capacity in 2017.
“This treatment facility is jointly operated by WRD and the city of Torrance and currently purifies 5 million gallons per day of salty groundwater and sends that water directly into the city’s drinking water system,” Katherman said.
The WRD will apply this on a much larger scale with the Regional Brackish Water Reclamation Program.
The WRD initiated a study with seven stakeholders, according to its feasibility report published in March 2021. These included three cities, Torrance, Lomita, Manhattan Beach, and four water companies, the Los Angeles Department of Water and Power (LADWP), the Golden State Water Company, the California Water Service Company and the West Basin Municipal Water District.
The WRD is still planning the program, but it will be completed in phases, and the organization estimates finishing it in 2026, Katherman said. It will potentially have the capacity to treat 18 million gallons of water per day. Depending on which project plan the WRD decides to take, the program’s cost and maintenance could range from $8.5 million to $13.5 million, according to the feasibility report.
The project is expected to last 20 years, Katherman said.
“The benefits of the project will outlast the treatment process,” Katherman said. “As water is treated and used, it creates space in drinking water aquifers to store fresh water and purified recycled water. This water can be used as reserves for times of severe drought.”
It will treat the water using a process called reverse osmosis, which has the water go through a membrane which the salt can’t go through. Afterwards, the WRD will disinfect the water and adjust its pH level to make it suitable for drinking.
The program is targeting 375,000 acre-feet of brackish water, of which 240,000 acre-feet are in an aquifer in lower San Pedro, according to the feasibility report. The rest is an aquifer in Silverado, which has 113,000 acre-feet, and an aquifer in Gage, which has 13,000 acre-feet.
The program has multiple facets to it, including wells to extract the water, a desalination plant, and wells to inject water back into the aquifers, Katherman said.
The WRD is considering using 20-inch-diameter, 316 stainless steel, vertical wells at up to 10 different locations, the feasibility report says. Each of these wells should be able to extract 2,000 acre-feet of water per year, but the San Pedro aquifer might not be able to extract as much as the Silverado aquifer. The WRD is considering using a larger number of wells that are smaller sizes instead.
The WRD will likely use the Elm and Faysmith site in Torrance for the centralized treatment facility, according to the feasibility report. The site, which is also called the Old City Yard, was suggested by the City of Torrance. This site had wells that were previously demolished, and because of this it is adjacent to the city’s water main and has access to its distribution system. In addition, it is on the edge of the plume of brackish water.
The extracted salt from the water is called brine, and the WRD will most likely dispose of it in the Los Angeles County Sanitation Districts’ Joint Water Pollution Control Plant. The program could potentially have a direct sewer line to the plant. This would cost the WRD about $12.6 million per year in capital expenditure, but it’s their cheapest option for brine disposal.
Removing Toxic Substances
Another project the WRD is working on is the PFAS Remediation Program. PFAS stands for polyfluoroalkyl substances, which include perflourooctanic acid, or PFOA, and perfluorooctanesulfonate, or PFOS. These are man-made compounds that can be harmful to humans and the environment because they break down very slowly. According to the U.S. Environmental Protection Agency, or EPA, research is underway to study what the effects are on people. The potential negative effects include increased risk of cancer, decreased fertility, developmental effects or delays in children, weakening of immune systems, increased cholesterol levels and risk of obesity.
In October 2021, California became the seventh state to ban its use in food packaging. But they can still be found in drinking water, firefighting foam, fish, and household products.
According to the WRD’s website, some PFAS have been found in some active wells in LA County, but they are below the health advisory level established by the EPA. The WRD Board of Directors approved a $34 million grant program to treat these wells.
The WRD tested two pilots to decide on how to treat the water with PFAS. Both treated the water with ion exchange resins and granular activated carbon. The resins used were one time use, they were removed and disposed of afterwards. The carbon used was made of coal. The pilot tested four different types of resins and four types of carbon, and ultimately found that one of the resins was the most cost-effective method. It’s called Resinex PFCR-2, and is specifically designed to remove PFAS from water. It removes the most PFOA, and lasts longer than the other resins.
Other challenges
Katherman said that more than 200 water providers, including cities and water districts, have rights to pump from two basins that the WRD controls. A superior court allocated these rights decades ago, and they can’t be altered. They all have one thing in common, they all need drinkable water.
“Although cities may have varying water needs and differing allocations, the health of the groundwater basins is important for everyone,” Katherman said. “If an unwanted substance, such as brackish water, were to migrate throughout the groundwater basins it could affect multiple water providers.”
He said that the amount of groundwater each community can access was determined decades ago. However, water equity is still important to the WRD.
“Water providers that serve low-income communities may be under-resourced and in need of additional support to treat groundwater affected by unwanted substances,” Katherman said. “These substances can cause water to be discolored, malodorous or bitter tasting.”
The WRD has addressed this by starting a Safe Drinking Water Program and Disadvantaged Communities Program. Katherman said it has helped 13 cities address contamination issues.