The Process and Water Quality Specialists

Recycled Water
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Filter Loading Evaluation for Water Reuse

1. Monterey Regional Water Pollution Control Agency (MRWPCA)
2. Delta Diablo Sanitation District (DDSD)
3. City of Santa Rosa

Phase I: Due to an inadequate understanding of the effect loading rate has on tertiary filter performance, California’s Water Recycling Criteria (Title-22) limit the maximum allowable filter loading rate to 5 gpm/ft2. Because filtration is often the limiting process in terms of treatment capacity, increasing the allowable loading rate would free many California water reclamation facilities to maximize their production of recycled water, without the need of costly capital additions. This pilot-study developed a better understanding of the role loading rate plays on tertiary filter performance and identified the factors necessary to achieve equivalent treatment at higher rates. As part of his doctoral research, Williams was integral to the success of this project by designing the pilot facility, overseeing pilot construction and operation, analyzing all results, and participating in discussions with the California Department of Public Health.

Phase II: Based on the findings from FLEWR Phase I, the California Department of Public Health (CDPH) allowed several full-scale granular-media tertiary filtration plants to test loading rates above the Title-22 allowable limit of 5 gpm/ft2. This study established a CDPH approved procedure for treatment facilities to obtain permanent exception to the Title-22 limit through demonstration of equivalent filter performance at higher loading rates. Currently, four agencies have successfully shown equivalency at higher rates: Monterey Regional Water Pollution Control Agency (MRWPCA), the San Jose/Santa Clara Water Pollution Control Agency, the Delta Diablo Sanitation District, and the City of Santa Rosa. Williams has played a key role in this multi-plant study by designing all study protocols, analyzing all results, preparing final reports for facilities as they complete testing, and working with California regulators to obtain approvals long-term facility operation at loading rates up 7.5 gpm/ft2.