The Viejas Indian Reservation in eastern San Diego County owns and operates a gaming casino and outlet shopping mall that recently underwent a large expansion. At the same time, their existing extended aeration wastewater treatment plant was unable to meet strict effluent water quality
standards mandated by the Viejas Reservation Tribal Council due to wide variations in flow rates and/or organic loadings, and the rapidly increasing flows generated by the commercial enterprise. In order to improve the performance and capacity of the existing treatment plant, various
treatment processes were evaluated for their ability to: 1) handle wide variations in flow and organic loading, 2) maximize use of existing facilities and available land, and 3) be designed and constructed under an accelerated schedule in time for expanded casino and outlet mall opening dates.
At the recommendation of their engineering consultants, the Viejas Reservation selected an “Immersed Ultrafiltration Membrane Bioreactor” to meet their needs. This process met objectives by using existing tankage to almost triple the existing treatment facility capacity. This process
also improved plant performance by adding nutrient removal and producing effluent with turbidities about one-tenth the limit set by California's Administrative Code Title 22 standards for recycled water. This treatment process, the first of its type to be used in California, has been
successfully operating since late July 2000. This paper summarizes the history of how the project evolved to the present state and most importantly the operating experience with the Immersed Ultrafiltration Membrane Reactor. Viejas Reservation is now expanding their treatment plant to accommodate
wastewater generated by the Reservation's residences, now on septic tanks. In addition, design is underway to use plant effluent for landscape irrigation at the casino and outlet mall.
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