In today’s revenue-starved, account-for-every-dollar
economy, any means of reducing expenditures is warmly welcomed. This is especially true in California, where state budget shortfalls are impacting funding for local special districts. A discount of 15%, 20%, even 25% on a product or service would be considered exceptional. A savings of nearly 90% would be breathtaking.
Ninety percent is the savings in capital cost that HDR, Inc., has been able to provide to the Oro Loma (Calif.) Sanitary District on a wastewater-related project. The Oro Loma Sanitary District serves 150,000 people who reside in San Francisco’s East Bay area.
The Oro Loma Sanitary District was in the process of increasing its treatment capacity from 15 mgd to 20 mgd. Following submission of an RFP, HDR was hired in March 2002 to design the new facilities and to certify that the wastewater plant would meet secondary treatment criteria for 20 mgd.
Fixing activated sludge process
“The most significant issue was the need to increase the plant’s activated sludge process peak wet weather capacity from 30 mgd to 50 mgd at minimal cost,” said Hany Gerges, a national director at HDR.
The capacity of the existing facilities was limited by the oxygen transfer capacity of the existing surface aerators.
The HDR team identified three alternative solutions for Oro Loma’s consideration. One involved increasing the aeration system capacity by enlarging the size of the surface aerators at a cost of $2.3 million.
The second called for replacing the surface aeration system with a fine-bubble aeration system at a cost of $5 million. The third alternative was to reduce the load on the aeration system by improving the performance of the primary clarifiers by adding chemicals—ferric chloride and polymer—to the plant’s primary clarifiers. This final alternative came in at a cost of $600,000.
“Naturally, we were intrigued by the less expensive solution, but our principal concern is its efficiency and its ability to reliably meet secondary treatment standards,” said Mike Cortez, district treatment manager for Oro Loma. “We visited other plants that are using CEPT (chemically enhanced primary treatment) and soon became convinced that this really was the way to go.”
Client customization
HDR’s field testing team conducted tests and provided the results to Cortez.
“While CEPT is not a new technique, it’s one that we can easily customize for each client so they can make the best use of the equipment that is already in place,” Gerges stated. “We do this by implementing new field testing techniques to identify which specific design features are needed for a particular project. Particular attention is given to finding the most cost-effective measures.”
The overall industry trend is moving toward the use of chemicals in much the same way that Oro Loma uses them, Gerges continued.
“We believe we are at the onset of a trend that will help clients use their existing equipment to its full potential. This results in meaningful cost savings for clients and, we hope, additional opportunities to work with those clients.”
Oro Loma Sanitary District has increased the scope of HDR’s wastewater plant design responsibilities.
“Our initial scope of work was to design one new secondary clarifier. Now we are tasked with upgrading the entire treatment plant,” said John Larson, project manager.
Oro Loma is understandably pleased with the cost-
saving solution.
“The savings are phenomenal,” said Cortez.
For further information, phone 402/399-1289.
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