Field trials during April and May 2009 of a small modular membrane-based water supply system by researchers at the University of California, Los Angeles (UCLA), have proved that the plant can be used to test brackish water or seawater for use in a full-scale desalination plant.
It can also use a novel scale detection and mitigation technique.
The M3 unit (mini, mobile, modular) employs low-pressure reverse-osmosis (RO) membranes in variable configurations, usually with two or three membrane modules and one or two pumps.
The M3 demonstrated its effectiveness in the recent field study in the San Joaquin Valley in which it desalted agricultural drainage water that was nearly saturated with calcium sulphate salts, accomplishing this with just one RO stage. It can be manually loaded into a cargo van and deployed in about 3 hours. Disassembly takes about the same time.
Former IDA scholarship winner Michael Uchymiak, who works with Professor Yoram Cohen, head of the research at UCLA, explained the system to D&WR at the American Membrane Technology Association conference in Austin, Texas.
“The system is way more flexible than other methods,” said Uchymiak. “It can be used for flows up to about 8 gallons (30 liters) per minute.”
The M3 unit can also employ the system developed by Prof Cohen during the last 3-4 years at the UCLA Water Technology Research (WaTeR) Center for real-time monitoring of RO membranes. The innovation consists of a specially designed plate-and-frame high-pressure RO membrane cell with optical windows. The feed solution can be fed to the cell from any side-stream in the mobile (or any other) plant.
A unique optical imaging system provides real-time imaging of the membrane surface capable of detecting and characterizing the onset of surface mineral salt crystal formation. The data are collected by a computerized data-acquisition system and displayed in real-time as well as stored for off-line analysis.
Uchymiak explained that the system can detects a small crystal growth on the membrane long before it will have any effect on the flux across the membrane. The detector can be used without impeding flow through the system, which can also be used as a stand-alone system for rapid diagnostic evaluating the performance of scale mitigation strategies.
Announcing the M3’s successful trial, Prof Cohen said on 14 July 2009, “In this specific field study by our team, in the first part of the RO process, 65% of the water that was fed in was recovered as potable water. We can potentially go up to 95% recovery using an accelerated chemical demineralization process that was also developed here at UCLA.
“This first field study with the M3 was a major achievement and the first phase of our high-recovery RO process demonstration program,” he concluded.
Information about the crystal monitoring system can be found on the WaTeR website and a publicity video about the M3 system is available on YouTube.