Enhanced Water Treatment Means Better Creek Health



San Luis Obispo Creek runs southwest through the City before reaching the ocean at Avila beach. For residents and visitors to our community, the creek is often enjoyed via the downtown area’s scenic Creek Walk, where they can catch a glimpse of steelhead trout or myriad bird life from its banks.

Unfortunately, the creek has faced historic environmental challenges ranging from drought to urban development, resulting in impaired water quality. Construction kicks off at the Water Resource Recovery Facility (WRRF) this month on an enhanced water treatment technology, in part aimed at better protecting this valued waterway. 

The new membrane bioreactor (MBR) technology is the heart of a multi-year upgrade to the WRRF called SLO Water Plus. The MBR technology is designed to remove solids from the water and dramatically improve water quality.  The inclusion of the MBR in the SLO Water Plus Project is born from the City’s commitment to environmental and public health.

MBR technology is an advanced method of water treatment that will be used near the end of a multi-step wastewater treatment process to be employed at the WRRF in the future. The MBR system combines a biological treatment process with membrane filtration to produce high-quality effluent. Membrane filtration involves pulling water through a series of membranes with microscopic pore openings that are 1/300th the diameter of a human hair. The membranes help remove microorganisms, bacteria, pathogens and other suspended solids that remain from earlier treatment steps. 

The system will also facilitate nutrient removal to reduce the amount of nitrogen entering the creek by nearly 75 percent. This will help prevent excessive algae growth and maintain oxygen levels in the water to support sensitive and endangered species such as steelhead trout, California red-legged frogs and western pond turtles. 

The MBR system was selected by the City because of its ability to provide long-term environmental, economic and social benefits to the community. Overall, the SLO Water Plus upgrades will expand the treatment capacity of the WRRF from 5.1 million gallons per day to 5.4 million gallons. The resulting high-quality effluent will be discharged to San Luis Obispo Creek to enhance stream flows, and will be distributed within the City for beneficial uses such as landscape irrigation. 

Construction of the MBR system is expected to be completed in December 2021 with the entire SLO Water Plus upgrade scheduled to be finished in 2023. The MBR system is being constructed near the center of the facility and will replace several conventional treatment processes, resulting in as much as 80 percent fewer chemicals used during treatment. 

As the City’s largest capital investment to date, SLO Water Plus will provide both near- and long-term benefits to the environment and the community. The advancement of MBR technology prepares the City to meet critical water quality requirements and will continue to support species within the San Luis Obispo watershed. 

© City of San Luis Obispo 2019