Small Community Treatment Plant Expansion While in Operation Using Advanced Technology

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, the Viejas Reservation Tribal Government completed the infrastructure project to provide a new water supply distribution and wastewater collection system to serve the entire reservation in addition to the casino and outlet center. The added residential flows required additional capacity in the existing Membrane Bioreactor Treatment Plant.The treatment plant is the only facility serving the casino and outlet center and can not be taken off line for an extended period of time. The maximum duration for a plant shut down is 24 hours equivalent to the capacity of the existing equalization tanks. To keep the treatment plant on line and augment its treatment capacity, various options were evaluated for their reliability and capital cost including the following:Add a new treatment module in new separate tank.Maximize use of existing facilities and available tankage.Haul away wastewater flows for treatment off site.Based on the economical analysis Viejas Reservation selected to meet the challenge with the design consultant and expand the “Immersed Ultra-filtration Membrane Bioreactor” to meet their needs while it is in operation. This treatment facility is the first of its type to be in operation in California. It has been successfully operating since July 2000. A design/build project is underway to use plant effluent as recycled water for landscape irrigation at the casino, outlet mall and the reservation recreation center.