PALMDALE – Recycled water that has been treated by an advanced treatment system can serve as a reliable and cost-effective water source in the future, increasing ground and surface water supplies.
The Palmdale Recycled Water Authority, a joint authority between the City of Palmdale and the Palmdale Water District, is investigating the possibility of adding an advanced treatment step to the recycled water in order to inject it underground, to be easily used in the water system.
“What it does is it gives us a local water supply that we can control and that is drought tolerant. We will always have this (recycled) water available, ”said Scott Rogers, Technical Director of the Palmdale Water District.
He detailed the process on 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 Palmdale water recovery plant in the Los Angeles County Health Districts.
One acre-foot equals 325,851 gallons, roughly the amount of water a typical Antelope Valley household used in a year, before the most recent drought reduction use.
Some of this treated water is currently used for irrigation at McAdam Park, passing through separate “purple pipes”. The Authority had planned to extend these pipelines to other parks and potentially to schools, but was unable to finance the necessary infrastructure to do so.
This is one of the downsides to this type of recycled water use, Rogers said.
Another method of use is to pour the recycled water into basins, where it will slowly seep through the ground to the aquifer below and recharge the groundwater supply. However, this recharging method requires mixing the recycled water with water imported from the State Water Project, with 80% of the total recharged water being imported.
Since the State Water Project’s deliveries are likely to be low during drought years, water for recharge may not always be available.
However, output from the water recovery plant is stable, Rogers said.
The advanced treatment method would bring the already treated water to a tertiary level at the recovery plant and subject it to an additional process.
In this treatment system, water first passes through a thin membrane to remove particles and pathogens, then undergoes reverse osmosis to remove dissolved solids, organic matter and additional pathogens, before passing through to further treatment with ultraviolet light and advanced oxidation process to destroy traces. organic products such as pharmaceuticals, disinfecting water. The last step is chlorination.
The advanced treatment would also remove contaminants such as drugs that end up in wastewater, Rogers said.
The treated water is then injected into the ground up to the aquifer.
“It’s basically an upside down well,” he said.
Several state water providers are already using this type of groundwater augmentation.
“We already have this roadmap so that we can easily use it to track the licensing process and the state approval process,” Rogers said.
The increase in advanced groundwater treatment offers cost savings over other ways of using recycled water and allows the full amount purchased to be used, said Dennis LaMoreaux, general manager of the Palmdale Water District .
This method costs about $ 1,710 per acre-foot per year for 5,325 acre-feet, while purple pipe systems cost $ 2,600 per acre-foot per year for 1,725 acre-feet. Charging systems cost $ 3,160 per acre-foot per year for 4,000 acre-feet.
“This appears to be the most cost effective way to use tertiary (treated) water,” LaMoreaux said.
Since the district’s groundwater use is regulated by judicial regulation, any water injected into the aquifer by the district is credited to it for future withdrawal, he said.
“It sets the stage for the future. This gives us the availability of water for the future, ”said Austin Bishop, director of PRWA. “It gives us the most bang for our buck. “