Black & Veatch’s nutrient removal project stands up to record California wet-weather event

New biological nutrient removal facilities in Sacramento handled epic rainfall, driving enhanced resilience in wastewater, wet-weather treatment.

When the combination of two weather phenomena – a bomb cyclone and atmospheric river – inundated Northern California with record-breaking rainfall in October, Sacramento’s recently completed biological nutrient removal (BNR) facility did more than just weather the storm; it flexed its muscle in keeping the Sacramento River, and subsequently the Sacrament-San Joaquin Delta, clean.

With a maximum capacity of 330 million gallons/day (MGD), the Sacramento Regional Wastewater Treatment Plant (SRWTP) is one of the largest BNR projects ever designed by Black & Veatch, and it incorporates some of the latest advancements in BNR technology.

The BNR facilities were placed fully into service just before the newly equipped SRWTP would face its first major test – when the cyclone and atmospheric river combined to dump a record 5.44 inches of rain on the capital city. This was the most rain Sacramento had been in one 24-hour period in more than 141 years, and put the strain on the region’s critical infrastructure, including wastewater conveyance and treatment facilities owned and operated by the Sacramento Regional County Sanitation District (Regional San).

Willian Yu, senior civil engineer with Regional San, commented: “This was a gigantic storm, one that far exceed the ‘100-year-storm’ event. At one point, there were more than 500 MGD coming into the wastewater treatment plant.

“We were able to run the maximum 330 MGD through the treatment plant while storing the remainder in equalisation basins for later treatment. The facilities performed well, demonstrating the necessary flexibility to handle such an extreme event while continuing to discharge cleaner effluent into local waterways.”

Black & Veatch provided planning, design, construction support and start-up and commissioning services for the new BNR facilities. The BNR system relies on microbial populations within aerobic and anoxic environments to remove nearly all ammonia and most nitrate from the effluent, addressing concerns of both local and downstream ecosystem impacts.

The BNR project is a cornerstone project in the Regional San EchoWater programme, initiated in 2010 to address stricter effluent discharge mandates issued by the State of California. The new BNR facility and additional tertiary treatment facilities, designed by others and currently in construction, will help Regional San to meet compliance and discharge cleaner water into the Sacramento River, driving enhanced environment water quality in the Sacramento-San Joaquin Delta. Regional San also provides recycled water for potential non-potable reuse.

Sean Goris, project manager for Black & Veatch, concluded: “Anticipating peak flows is always a critical design consideration when building these large-scale wastewater treatment facilities. We designed the SRWTP BNR facilities with significant flexibility that allow operators to bring additional treatment basins on-line rapidly. As illustrated by this last event, this flexibility helped fortify resilience for the utility, Regional San; the Sacramento community; and the local and downstream environment.”