Paso Robles WWTP upgrade garners top wastewater project award for packing multifaceted sustainability into existing footprint

Packing long-term water resilience and other sustainable solutions into a small footprint earned the upgrade of the Paso Robles Wastewater Treatment Plant (WWTP) top honors as the Global Water Awards’ 2020 Wastewater Project of the Year.

The California city earned the award, announced in August, in recognition of its innovative optimization of its physical and environmental footprint. Completed in May 2019, the upgraded facilities yield Title 22-compliant recycled water for irrigation and struvite for beneficial reuse – all within existing space constraints. Paso Robles worked with designer and engineer-of-record Black & Veatch, a global leader in infrastructure solutions, to incorporate flexibility and savings.

New tertiary treatment facilities at the 4.9-mgd (million gallons per day) Paso Robles WWTP showcase a sustainable approach to water management, advanced wastewater treatment, and cost-effective solutions for communities of any size. Adding advanced reclamation and nutrient-harvesting technologies to an existing footprint enables Paso Robles to produce both high-quality recycled water and a struvite product that can be used as a fertilizer to supplement supplies. The upgrade optimizes the city’s water, nutrient, land and even financial resilience.  

Drought conditions and changing influent conditions necessitated WWTP upgrades, and the city’s 2014 master plan called for construction of tertiary treatment facilities to produce high-quality recycled water to irrigate public areas such as city parks and golf courses as well as private-sector vineyards. The upgraded WWTP converts wastewater into California Title 22-compliant recycled water for irrigation, a crucial move in supporting the city’s water resilience goals.

“The project is a milestone in our long-term plan to create a resilient and sustainable water supply,” Paso Robles Wastewater Resources Manager Matt Thompson said. “We now can produce high-quality recycled water without building a purification plant, and Black & Veatch helped us optimize existing assets and minimize capital and future operating costs in the process.”

The already-planned installation of a side stream nutrient harvesting system was accelerated when operators discovered during construction of the tertiary treatment facilities that the phosphorus-laden filtrate from the digested sludge dewatering system was causing buildup of struvite in the pipes and inhibiting treatment processes. Adding a system to effectively remove phosphorus and recover struvite essentially turned a nutrient nuisance into a future marketable fertilizer to help the city offset project and operating costs. 

With a total cost of $14.4 million, the new facilities feature sustainable solutions that save energy and minimize chemical use. The innovative environmental features of the upgrade helped Paso Robles secure a $4 million Green Project Reserve grant for environmentally innovative projects.

“Interest is rising in integrated solutions that meet the increasingly complex need for utility resilience,” said Cindy Wallis-Lage, president of Black & Veatch’s water business. “The Paso Robles project is an example of what’s possible. The upgrade serves the city’s long-term water quality and water supply needs while minimizing its capital and future operating costs.”

The flexibility of the design means that the plant can send water to the Salinas River when demand for recycled water is low. The tertiary treatment process train, which includes ultraviolet (UV) disinfection to eliminate the potential formation of disinfection byproducts, flows by gravity – eliminating the need for pumping and thereby saving equipment and energy expenses. Repurposed secondary sedimentation tanks that previously sat unused allow disinfection processes to operate continuously and at a more constant rate, and onsite ponds are used to store recycled water.

Each year, the coveted Global Water Awards are presented at the Global Water Summit, a major business conference for the water industry worldwide. The award program was established in 2006 to recognize the most important achievements in the international water industry in several categories and reward those initiatives in water, wastewater and desalination sectors that are moving the industry forward through improved operating performance, innovative technology adoption and sustainable financial models. The 2020 Global Water Summit was canceled due to the COVID-19 pandemic, and the awards are being presented weekly online between July 23 and Oct. 8.