In order to address needs and regulatory requirements, including nitrogen removal to 10 mg/L of total inorganic nitrogen for groundwater recharge, the city of Bakersfield, Calif., decided to upgrade and expand its Wastewater Treatment Plant (WWTP) No. 3 to treat 32 million gal per day (mgd). Before expansion, WWTP No. 3’s capacity was 16 mgd, and it was often in violation of its effluent discharge permit in Kern County.
The project’s major items of work to be performed included: 1) Approximately 3,900 ft of new 60-in. sewer on McCutchen Road from the McCutchen/Gosford Lift Station to the treatment plant to replace the existing 42-in. sewer; 2) A new headworks that includes mechanically cleaned bar screens, influent pumps and grit removal tanks; 3) Conversion of four existing secondary clarifiers into primary clarifiers; 4) A new activated sludge secondary treatment system that includes aeration basins, fine-bubble air diffusers, aeration blowers, blower building, secondary clarifiers, RAS/WAS pump station and plant process water pump station; 5) A 2-mgd tertiary treatment system that includes a rapid mixer, cloth media continuous backwash filter, chlorine contact tank and flocculation and disinfection chemical facilities; 6) Six new effluent disposal percolation basins; 7) Dissolved-air flotation sludge thickeners; 8) Replacement of existing digester heaters with new units in the six existing anaerobic sludge digesters; 9) Two new anaerobic sludge digesters and a sludge dewatering building 10) A new power cogeneration building; 11) Plantwide odor control systems that include foul air ducting, blowers and odor removal biofilters; 12) A new administration/operation building and new maintenance shop. This project was the single largest CIP project for the city. City of Bakersfield Wastewater Manager Louis Sun said: “One major challenge was to build and complete this project by a deadline set from the Regional Water Board, which is why the schedule for this project was so aggressive. Other challenges are to perform a biddability/constructability review of the documents. Some of the items identified helped make the new plant operate more efficiently, but also save $5.4 million. We looked at the project from a contractor’s point of view and how to avoid problems, conflicts, changes and claims.” The project was started in September 2007, and finish date was June 2010.