Pilot Testing of Zero Liquid Discharge Technologies for Inland Desert Brackish Ground Water Desalting

The Indian Wells Valley Water District (IWVWD) is located in the northern Mojave Desert east of the Sierra Nevada Mountains and south of the Owens Valley.  The IWVWD is the primary water purveyor for the City of Ridgecrest and serves a population of more than 27,000 through almost 12,000 service connections.  The only source of water available to the IWVWD is groundwater.  With increasing growth in the area, the IWVWD is searching for new alternative sources of water.

 The IWVWD obtained funding to evaluate the potential to desalt brackish groundwater in the northwest area of the Valley through the 2006 Water Desalination grant program (Chapter 6(a) of Proposition 50).  The piloting project was developed to focus on minimizing the volume of brine produced from desalination.  The minimization of brine is important because brine disposal options are limited due to the inland location of the District.  The project included pilot testing of iron and manganese pretreatment, reverse osmosis (RO), electrodialysis reversal (EDR) and an evaluation of ZLD technologies.  

 The key objectives of the study are to demonstrate the feasibility of RO primary desalting and EDR secondary desalting, show the primary RO process can operate on the groundwater with minimal membrane fouling, and evaluate a novel reversible RO configuration.  In phase one, the RO unit operates in forward mode and is set to achieve a recovery of 70 percent.  In phase two, the RO unit will operate in reversible mode, which will have the hydraulic capability of reversing the flow through the pressure vessels and piping.  In both phases, the EDR unit will operate on the RO concentrate stream to achieve a 60 percent recovery. The overall recovery of this treatment scheme is expected to be around 90 percent.