PALMDALE — Recycled water that has been processed through an advanced treatment system may serve as a reliable and cost effective water source in the future, augmenting ground and surface water supplies.
The Palmdale Recycled Water Authority, a joint powers authority between the City of Palmdale and Palmdale Water District, is looking at the possibility of adding an advanced treatment step to recycled water in order to inject it underground, to be readily used as part of the potable water system.
“What this does is, it gives us a local water supply that we can control and it’s drought resistant. We’re always going to have that (recycled) water available,” Palmdale Water District Engineering Manager Scott Rogers said.
He detailed the process, Monday evening, to the Authority’s Board of Directors.
The Authority has an agreement to purchase 5,325 acre-feet per year of tertiary treated water from the Los Angeles County Sanitation Districts’ Palmdale Water Reclamation Plant.
An acre-foot is 325,851 gallons, or approximately the amount of water a typical Antelope Valley household used in one year, before the most recent drought-reduced usage.
A portion of this treated water currently is used for irrigation at McAdam Park, traveling through separate “purple pipes.” The Authority had planned to extend these pipes to other parks and potentially schools, but has been unable to fund the infrastructure necessary to do so.
That is one of the drawbacks to this type of use of recycled water, Rogers said.
Another method of use is to spread the recycled water in basins, where it will slowly percolate through the ground to the aquifer below and recharge the groundwater supply. However, this recharge method requires blending the recycled water with imported water from the State Water Project, with 80% of the total water recharged being imported.
Because State Water Project deliveries are likely to be low during drought years, water for recharge may not always be available.
The output of the water reclamation plant, however, is stable, Rogers said.
The advanced treatment method would take the water already treated to a tertiary level at the reclamation plant and put it through an additional process.
In this treatment system, the water first passes through a fine membrane to remove particles and pathogens, then undergoes reverse osmosis to remove dissolved solids, organics and additional pathogens, before moving on to further treatment with ultraviolet light and an advanced oxidation process to destroy trace organics such as pharmaceuticals, disinfecting the water. The final step is chlorination.
The advanced treatment would also remove contaminants such as medications that make it into wastewater, Rogers said.
The treated water is then injected into the ground to the aquifer.
“That’s basically a well in reverse,” he said.
Several water providers in the state already use this type of groundwater augmentation.
“We already have this road map so we can readily use it to go through the permitting process and the approval process with the state,” Rogers said.
The advanced treatment groundwater augmentation offers cost savings over other means of utilizing recycled water and provides the ability to use the full amount purchased, Palmdale Water District General Manager Dennis LaMoreaux said.
This method costs an estimated $1,710 per acre-foot per year for 5,325 acre-feet, while the purple pipe systems cost $2,600 per acre-foot per year for 1,725 acre-feet. Recharge systems cost $3,160 per acre-foot per year for 4,000 acre-feet.
“This appears to be the most cost-effective way to put tertiary (treated) water to use,” LaMoreaux said.
Given that the District’s groundwater use is governed by a court settlement, any water injected into the aquifer by the District is credited to it for future removal, he said.
“It sets the stage for the future. It gives us the water availability for the future,” PRWA Director Austin Bishop said. “It gives us the most bang for the buck.”