A big upgrade to San Luis Obispo’s 100-year-old wastewater plant is nearly complete. Officials say it’s a major step towards securing the City’s water supply.
On a sunny afternoon at the plant, sounds of whirring construction machinery and clanging metal fill the air.
The SLO Water Resource Recovery Facility has been cleaning wastewater for irrigation for a century, but now it’s going through a multi-million dollar update– the biggest one since it was built.
The SLO Water Plus project has been underway since 2015, and it’s finally set to be finished by the end of this year.
“Well, I'm thrilled,” SLO Mayor Erica Stewart said at a tour of the construction site earlier this month.
“This is helping us to have another hundred years of safe water recovery,” Stewart added.
The project is a joint effort between the City and PCL Construction; they’re replacing the plant’s old equipment with newer, more sustainable technology.
One key upgrade is a new Membrane Bioreactor, or MBR.
Project Manager for PCL Project Manager Jon Merryman said the MBR uses microfiltration to treat wastewater more effectively than the old design.
“Switching over to an MBR treatment has a smaller footprint than the traditional conventional treatment, a lot less moving parts and really enhances the treatment flow,” Merryman said.
The decision to upgrade the facility started when the California State Water Resources Control Board issued a permit expressing concerns about the plant releasing nitrates and other chemicals into the San Luis Obispo Creek.
Merryman said the new MBR treatment process not only discharges higher quality water, but also releases fewer harmful chemicals.
“It's gonna reduce chemical demand by about 80 percent,” Merryman said.
Before the water is discharged into the creek, it goes through a rigorous disinfection process that can take up to 45 days. This ensures the water’s clean and safe for aquatic ecosystems in the creek.
Merryman said this approach also addresses the pressing issue of water scarcity in California.
"Using higher quality discharge gives us the ability to reuse, repurpose some of that water and not have the water loss, right?" Merryman said. "Scarcity is our issue; we're dealing with every drop that we could get, we're utilizing it to the best of our capabilities."
The upgrades to the facility go beyond water conservation; they also include enhanced protection against floods and natural disasters.
Merryman said some of the upgrades already proved their resilience during this year’s heavy winter storms.
“We had two large rain events where we had significant water running through the job site,” Merryman said. “All the new gear stayed dry and clean, so that's a testament to preparing for the future.”
Another part of the upgrade project renews the facility’s digesters, which use special microorganisms to break down organic waste. Improved digesters may produce more biogas, a form of renewable energy that can power the plant and make it more environmentally friendly.
Water Resource Recovery Facility Supervisor Patrick McGrath said upgraded digesters can also solve another problem.
“At the end of the day, what the community really wants from us is to not smell bad,” McGrath said.
One of the plant’s digester tanks, which has been around since the 1940s, will be repurposed into an odor control facility.
The plant plays a key role in conserving the City of SLO’s drinking water reserves by making wastewater safe for irrigating farms, parks and lawns.
But– McGrath said the goal is to eventually make the plant capable of producing potable water on its own.
“Through engineering, construction and design, we can make that water potable,” McGrath said. “We can make that water drinkable.”
Morro Bay’s new Water Resources Center, which opened in February, is the most recent example of a local project with similar upgrades to this one.
However, the Morro Bay facility took things a step further by implementing reverse osmosis, an advanced treatment process capable of producing potable water.
McGrath said he hopes the current upgrades will be a stepping stone for the City of SLO to follow suit.
“This is setting the stage for that next level of advanced purification,” McGrath said
For more on the SLO Water Plus project, you can visit slowrrfproject.org.
