The Oro Loma Sanitary District (OLSD) is dedicated to finding innovative ways to safeguard the San Francisco Bay. In collaboration with industry partners, the District focused on strategies to minimize nutrient discharge into the Bay, drawing on its well-established expertise in testing, research, and development. This collaborative effort resulted in the creation of the Nutrient Optimization Project (NOP).
“We started by taking an outside-the-box look at what we had in-house,” said Jimmy Dang, OLSD’s general manager and treasurer. “It was quickly determined that we didn’t require a new plant; we already possess most of what was necessary and just needed an upgrade.”
The NOP’s planning began in 2018 and was completed in August 2020. It involved a major upgrade to the District’s treatment plant converting the wastewater treatment process from its decades-old operation to a new process that removes half the nitrogen loading from the influent.
“With growing concerns about nutrient levels being discharged into San Francisco Bay, Oro Loma was among the first agencies to take action and improve its wastewater processes to benefit the environment,” Dang said. “Our NOP was one of the first to provide both nitrification and denitrification processes within the San Francisco Bay area.”
The NOP significantly lowers nitrogen loading to the Bay by transforming ammonia into nitrogen gas. Additionally, enhancing OLSD’s ability to reduce nitrogen in the Bay may lower the risk of algal blooms, a factor currently addressed in the new permit guidelines established by the San Francisco Bay Regional Water Quality Control Board last fall.
OLSD’s discharge permit during the construction of the NOP requires an annual ammonia removal rate of 70%. However, the biological nutrient removal capabilities of the treatment plant expansion far exceed that rate, and the facility currently removes nearly 98% of ammonia from the influent flow.
“The new treatment process will convert nearly all incoming ammonia, which is generated by people and what goes down the toilet and drains, and discharge its treated effluent to the SF bay with much less nitrogen loading. We have the ability to remove even more nutrients if needed,” Dang said.
The OLSD and Castro Valley Sanitary District jointly own the Oro Loma Sanitary District/Castro Valley Sanitary District Water Pollution Control Plant (WWTP) with a 75% (OLSD) to 25% (CV San) ownership split. OLSD operates the facility, which serves the East San Francisco Bay communities of San Lorenzo, Ashland, Cherryland, Fairview, parts of Castro Valley, and the cities of San Leandro and Hayward, totaling a population of approximately 190,000.
The NOP upgraded an existing 16 MGD plant. The scope of work included the construction of a new aeration basin, a new blower building, modifications to three existing basins with mechanical process upgrades, and a new fine bubble-diffusion aeration system in all four aeration basins.
The project also involved local outfall pumping and piping from the disinfection channels to the existing dual outfall pipe, including local outfall metering, a de-chlorination feed system, various mechanical modifications, and electrical and instrumentation adjustments. Additional work was necessary to create a complete and operational facility.
A unique aspect of the project was the tidal intrusion of groundwater, which necessitated building the entire project on Bay mud. This required the installation of over 360 driven concrete piles. Additional scope included demolishing several old tanks and structures and installing a new Magnesium Hydroxide chemical dosing system, which included a retrofitted containment structure, a new MgOH2 tank, and chemical metering pumps.
“It was very forward-thinking of both our Board and CV San’s Board to have the upgrades completed early on before the permit changes came into effect,” Dang said. “With the NOP up and running, we can now focus on improving other aspects of the District’s infrastructure and get ahead of any new future regulations.”
Photo credit: Ozan U.
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