Key project staff include Mojtaba Farrokh Shad, Ariana Coracero, Matthew Robinette, and Joseph Delgado
The Dr. Jenkins Research Achievement award recognizes outstanding engineering research by an individual, group, or agency.
As nutrient limits emerge and the need for sustainable water resources in California increases, nitrogen management is a focus of many wastewater treatment facilities. As part of support for Pure Water Southern California (PWSC), a regional water recycling effort in collaboration with the Metropolitan Water District of Southern California, the Los Angeles County Sanitation Districts has been exploring novel technologies for nitrogen removal. One such technology is an Anoxic-Aerobic (AO) Tertiary Membrane Bioreactor (tMBR) with the Partial Denitrification-Anammox (PdNA) process, which leverages short-cut nitrogen removal to achieve energy and supplemental carbon savings.
Three major PdNA phases were tested: tMBR PdNA, tMBR PdNA at low dissolved oxygen (DO,< 1 mg/L) and higher return activated sludge (RAS) flow, and tMBR PdNA at low DO with lowered carbon dosing. All three phases were able to meet or exceed water quality targets. Low DO operation was realized, translating to decreased operational costs. Carbon dosing was reduced to achieve a C/N ratio of 2.2 g/g (g COD/g Nitrogen) for partial denitrification to meet the effluent target, representing a 67% reduction in carbon use compared to the 6.4 g/g reported in the literature.
This tMBR PdNA study successfully demonstrated the viability of a tMBR PdNA process for meeting water quality targets for future reuse applications. Furthermore, because the low DO and low C/N phases of the study were similarly able to meet the water quality targets, there is promise of energy and cost savings associated with the use of a PdNA process. Results indicated the potential to reduce carbon use by up to 66%, which could lead to substantial reductions in chemical use. Projected carbon costs for a 150 mgd full-scale facility are approximately $12 Million per year; a 66% reduction is projected to save approximately ~$8 Million per year. Further, the process operated at DO < 1 mg/L, half the 2 mg/L DO target for most activated sludge processes, resulting in half the energy and cost requirements. These results highlight the effectiveness of the tMBR PdNA process in achieving nitrogen removal and its suitability for long-term regulatory and sustainability objectives. Future work will consist of further process optimization and the use of primary effluent as a carbon source to reduce resource requirements for meeting water quality targets.
The knowledge gained from pilot testing of this novel technology has provided a range of benefits for PWSC, including future operational options for cost reduction, flexibility, and resource optimization. These benefits could contribute to PWSC’s overall success and sustainability and offer other utilities a successful case study to further advance the industry.
The Los Angeles County Sanitation Districts (LACSD) serve approximately 5.5 million residents in Los Angeles County, providing wastewater and solid waste management. LACSD’s Wastewater Research Section staff have constructed and operated a pilot-scale anoxic-aerobic tertiary MBR partial denitrification-anammox process, a novel approach to nitrogen management and to providing high-quality feedwater for advanced water treatment processes.
Innovative research has the power to move the wastewater profession forward. Nominate a deserving individual or team for CWEA’s Dr. Jenkins Research Achievement Award and recognize research that advances knowledge, addresses industry challenges, and contributes to the future of clean water.
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