Whitley Burchett

Filtration Challenges at the Dublin San Ramon Services District:
Pilot Testing of New Technologies for Tertiary Recycled Water

(Presented at the Annual WateReuse Association Symposium XVIII,
September 7, 2003 - San Antonio, Texas)

Paul Friedlander, Whitley, Burchett & Associates
Casey LeBlanc,Whitley Burchett & Associates
David Requa, Dublin San Ramon Services District
Larry Olson, Dublin San Ramon Services District
Jerry Cole, Parsons Technologies

ABSTRACT

The Dublin San Ramon Services District (District) is undertaking a recycled water project in conjunction with the East Bay Municipal Utility District to produce over 20 mgd of recycled water for irrigation in the San Ramon Valley. The recycled water treatment facilities will consist of filtration and ultraviolet disinfection facilities at the District treatment plant to meet Title 22 tertiary recycled water requirements.

As part of the filtration evaluation process, the District conducted bench-scale and pilot-scale testing of selected promising filtration technologies. Initial testing raised concerns that the District's secondary effluent could not be adequately treated by media filtration alone. Consequently, further pilot testing was conducted using treatment trains consisting of ballasted sand flocculation followed by media filtration. Media filtration technologies included the cloth disk filter and continuous backwash sand filtration. Both ballasted sand flocculation and the cloth disk filter have limited experience in recycled water treatment.

This paper presents the results of both bench-scale and pilot-scale testing, which was ultimately successful in consistently meeting Title 22 requirements. The results emphasize the importance of evaluating wastewater variability in implementing recycled water treatment schemes, and the value of pilot testing new and emerging technologies in moving recycled water forward as a cost-effective and dependable resource.