Paso Robles, California, recently celebrated the completion of the new Tertiary Treatment Facilities at its wastewater treatment plant (WWTP), augmenting the roughly 30,000-resident city’s water stewardship in a state dealing with water scarcity.
Black & Veatch served as designer and engineer of record for both the secondary treatment project and the tertiary treatment project heralded as one of the largest, most complex infrastructure projects in the history of the 130-year-old city known for its hot springs.
The Paso Robles WWTP project comes amidst California’s growing focus on sustainable, resilient and reliable water solutions. Like many other cities in California, water is at a premium, and Paso Robles has a master plan that involves producing quality recycled water to irrigate public areas such as city parks and golf courses. By reducing the need to pump groundwater from the Paso Robles Groundwater Basin, the WWTP project helps build sustainability while strengthening the city’s water supply.
The project builds upon Black & Veatch’s history of providing water and wastewater services to Paso Robles. In 2008, the company was selected to upgrade the original WWTP, which had a peak capacity of 4.9 million gallons per day (mgd). These improvements were driven by the need to update aging equipment and comply with new discharge permits. That project was completed in 2015.
When the time came to move onto the master plan’s next phase, the city again turned to Black & Veatch – this time to perform the preliminary and detailed design and construction on the Tertiary Treatment Facilities. This new assignment produces Title 22-compliant recycled water for beneficial reuse.
The Tertiary Treatment Facilities project involved multiple components, including an Aqua-Aerobic cloth disc filtration process and in-channel Trojan ultraviolet (UV) light disinfection. UV disinfection was selected in lieu of the more cost-effective chemical disinfection to remove potential for formation of disinfection by-products to the recycled water distribution system. The existing secondary clarifiers were repurposed and converted to an equalisation basin upstream of the new filtration process. The project also entailed converting one of the onsite ponds to store the recycled water.
The facilities also feature an advanced nutrient harvesting system that removes ammonia, nitrate and phosphorus from the filtrate that comes from the digested sludge dewatering system. The filtrate, without being treated, was causing build-up of struvite in the pipes and inhibiting treatment processes. The nutrient harvesting system is used to remove the nuisance struvite and to create commercial-grade fertiliser. In addition to plant maintenance purposes, the city is marketing the fertiliser to offset the cost of building the facility. This nutrient harvesting system is the first of its kind in the State of California.
“Black & Veatch has a long track record of solving challenging water needs by delivering innovative wastewater recycling and reuse solutions, particularly in areas of water scarcity,” said Ashutosh Shirolkar, Black & Veatch project manager. “Recycling and reuse strategies continue to evolve. What was once viewed as a creative solution to dispose of wastewater effluent has now become an important tool to help ensure a reliable and resilient water supply.”
“Our team has an unprecedented ability to tackle these large-scale wastewater treatment projects – navigating complicated regulatory environments, aligning disparate stakeholders, and addressing funding – to complete projects that deliver as promised.”