City of Oxnard Wastewater Treatment Plant Unit Processes Optimization Study

Westland Water District, CA

The City of Oxnard Wastewater Treatment Plant (OWTP) has a nominal dry weather capacity of 31.7 million gallons per day (MGD) and discharges treated effluent through an ocean outfall. The OWTP is a secondary treatment facility comprised of primary sedimentation tanks, biotowers, activated sludge treatment, secondary sedimentation tanks, flow equalization basins, chlorine contact basins, dechlorination, primary sludge treatment, dissolved air flotation, gravity thickeners, anaerobic digesters, and belt filter presses. Some of these plant structures are over 50 years old and in need of repair or replacement.

As a subconsultant to Stantec, MKN provided a comprehensive review of the existing wastewater treatment facility processes and equipment. MKN’s work included a condition assessment and a review of unit process alternatives based on criteria including energy requirements, operational complexity, risk, water quality, and capital and operating costs. MKN developed a spreadsheet model of the existing activated sludge basins to determine improvements required for future nitrification and denitrification, and also performed a process evaluation of pressate treatment alternatives.


MKN determined the existing biotowers were failing but could be removed from service without impacting water quality.

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