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Evaluation of Two Concentrate Disposal Alternatives for the Phoenix Metropolitan Area: Evaporation Ponds and Discharge to the Gulf of California

USBR; Denver, CO.
March 2000

Report #54 - Abstract -

The study was initiated due to concerns about the impact of wastewater effluent on the increasing salinity of the local groundwater. Curerntly, effluent from wastewater treatment is discharged to local surface waters which are hydraullically connected to the groundwater. Due to the closed basin hydrology of the metropolitan area, population growth, and climatic conditions, local municipalities will become more reliant on desalting technologies (e.g. RO) in order to treat and reuse wastewater. The concentrated waste streams that are generated by these technologies, however, carry high concentrations of dissolved salts which could have negative impacts if discharged to local surface waters.

This study evaluated two alternatives for the disposal of saline waste streams that would be generated by future desalting treatment of wastewater in the Phoenix metropolitan area: (1) evaporation of concentrate flows at evaporation ponds to be constructed about 25 miles southwest of Phoenix; and (2) conveyance of concentrate flows via pipeline across the international border with Mexico for discharge into the Gulf of California.

The City of Tucson is also considering the construction of a pipeline to convey RO concentrate to the Gulf of California to meet their desalting needs. Therefore, the pipeline alternative was evaluated as a cost-shared joint venture. Under this scenario, the report concludes that a regional pipeline to the Gulf of California would be about 2/3 the cost of evaporation ponds for disposal of concentrate.


For more information about the DWPR program, contact Kevin Price at: Bureau of Reclamation, 86-69000, PO Box 25007, Denver CO 80225; phone (303) 445-2260; or e-mail a message to MPrice@usbr.gov.