Oct 07, 2019

Paso Robles, Calif., Completes Tertiary Treatment Facility

Fulfilling the first part of the city’s Recycled Water Master Plan, Paso Robles finally completed its Tertiary Treatment Facility. 

Irrigation sprinklers

Paso Robles, Calif., has finally completed the city’s Tertiary Treatment Facility, one of the largest infrastructure projects in its history. Tertiary treatment is the third and final phase of the city’s wastewater treatment process, which fulfills the first part of the Pabo Robles’ Recycled Water Master Plan. The tertiary water will be used for irrigation of landscaping and agriculture. 

“The city has a master plan to capture wastewater it has disposed to the Salinas River for many decades and turn it into a new supplemental source of water we call recycled water,” said Wastewater Division Manager Matt Thompson. 

A notable addition to the plant included the use of ultraviolet light as a disinfectant, which is cheaper than using the chemical purification process that adds salt to the water. The plant also added a harvesting system that collects nutrients, including ammonia, phosphorus and nitrate, from the water and creates a commercial-grade fertilizer in the form of crystals called struvite. Struvite typically crystallizes inside the pipe walls, so collecting the nutrients keeps the pipes clean and extends their lifespan. 

“Not only are we recycling water but we are also recycling the nutrients that are coming in with the water,” Thompson said.

The fertilizer is being marketed to offset the cost of building the facility, which costs about $14.4 million. The city repurposed the existing infrastructure instead of constructing new buildings, which saved $2.8 million, according to Paso Robles Press. The facility utilizes gravity to move water through its system instead of pumps to reduce operating costs and will run off of natural gas instead of electricity.

The next phase of the plan is the Recycled Water Distribution System, which involves creating infrastructure to sell and deliver water to designated areas. The water will continue to flow into the Salinas River until completed.

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