Last update:
08/30/2006
Accelerated Mineral Salt Crystallization for Purification of High Salinity Water
Drinking water supplies are dwindling around the globe due to aggressive water consumption practices in both urban and agricultural areas. As a result, the salinity of groundwater and surface water supplies has been on the rise in many regions and even in California, salinity (i.e., mineral salt concentration) has been on the rise. The magnitude of this problem is alarming and has driven the U.S. Bureau of Reclamation and various states (including California) to invest hundreds of Millions of dollars in research to arrive at technical solutions to salinity reduction so as to ensure continued supply of quality water for both agricultural uses and for drinking water. Investments of billions of dollars are planned to retrofit water treatment facilities to treat water supplies with a variety of membrane processes. However, the efficiencies of membrane processes such as nanofiltration (NF) and reverse osmosis (RO) are limited due to potential surface scaling by mineral salts (i.e., due to precipitation, deposition and adhesion), the generation of a large volume of a concentration stream and low product water recovery. Therefore, in order to increase the economics of the process there is a need to treat the concentrate stream so as to remove a higher percentage of mineral salts and thereby increase product water recovery.
An approach to be investigated at UCLA involves the use of a crystallizer that utilizes a nano filtration/RO unit to concentrate the water stream and precipitate the mineral salts in a crystallizer from which the solids are removed using a submerged hollow fiber microfiltration system. Equipment for the study is currently being built by a UCLA partner in the project and will be installed at UCLA by the end of the 2001 Fall Quarter. The project at UCLA will consist of experimental studies to evaluate the variables that control the crystallization process and mineral salt removal, process optimization for maximum efficiency and longevity of membrane life. Part of the project will be devoted to membrane surface studies (AFM and SEM) in order to quantify interaction of colloids and mineral deposits on the membrane surface. It is expected that a theoretical model will be developed to predict the operation and performance of the membrane crystallizer system. Moreover, based on results from this and other ongoing studies at UCLA and by our collaborators, a theoretical model will be developed to describe the desalting process. It is also possible that the neural system model, developed as part of another on going project, could be used to assist and refine this specific desalination model development.
The results of the UCLA laboratory study will form the basis for the construction of a major pilot facility, by one of the major water utilities in Southern California, to demonstrate the large-scale feasibility of the process. It is expected that the UCLA research group will be involved in advising with respect to the design and construction of the pilot facility.
Fundamental areas: separation science, transport phenomena, process analysis, process thermodynamics, crystallization, membrane science and technology, nano-technology.
Schematics of the Membrane Crystallizer Apparatus
Fundamental areas: separation science, crystallization, water chemistry, process analysis, process thermodynamics, crystallization, membrane science and technology, nano-technology, process control..
For additional information on membrane desalination research check the web site of the UCLA Water Technology Research Center
References:
- Water Desalination in the San Joaquin Valley: membrane Process Diagnostics
- Cohen, Y., J. Glater, A. Tsao and R-W Lee, "Nanofiltration Membranes for Agricultural Drainage Water Reclamation," Paper published in the proceedings of the International Conference on Membrane Technology for Wastewater Reclamation and Reuse, September 9-13, 2001, Tel-Aviv, Israel.
- Check with Dr. Cohen for additional references.
