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Salinity and TOC Removal Using Nanofiltration

University of Texas at El Paso; El Paso TX.
August 2002

Report #46 - Abstract -

El Paso, TX is located in the Chichuahuan desert and receives less than 8-inches of annual precipitation. Groundwater has been the main source of water since the early 1900's. Continued drawdown and salinization of the aquifers pose a serious threat to the El Paso and Ciudad Juarez, Mexico communities. The Rio Grande is a renewable resource and water rights are being transferred from agricultural to municipal use. Currently, the Rio Grande cannot be treated without desalination during the winter season, November through January, due to high salinity. Membrane treatment can reduce both salinity and total organic carbon (TOC) making winter season flows available for use.

A dual-membrane pilot system consisting of a microfiltration (MF) unit followed by a nonfiltration (NF) unit was evaluated for TOC removal and salinity reduction. This system was evaluated at the El Paso Water Utility's (EPWU) Robertson/Umbenhaumer, or Canal Street, Water Treatment Plant from May through October, 1998.

The pilot performance showed effective turbidity and suspended solids removal, greater than 99-percent, for the MF unit. The NF unit provided effective TOC removal to less than 1 mg/L in the permeate stream. The system also rejected 85-percent of total dissolved solids.

Sodium Adsorption Ratio (SAR) calculations were performed to evaluate impact on the Rio Grande from concentrate return to the river for a hypothetical 10-MGD water treatment plant. Use of selective ion rejection membranes would enable EPWU to maintain the same SAR while returning concentrate to the Rio Grande.


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.