15 July 2009

Fresh idea with water desalination system

Clean water is not just a problem in developing countries; just take a look out West in the U.S.

Water supplies in major reservoirs and many groundwater basins are well below average, according to California’s state Department of Water Resources. Court-ordered restrictions on water deliveries have reduced supplies from the two largest water systems, and an outdated statewide water system cannot keep up with population growth.

With these critical issues looming, there may soon be a way to alleviate the state’s water deficit with their new mini-mobile-modular (M3) “smart” water desalination and filtration system, according to researchers at the UCLA Henry Samueli School of Engineering and Applied Science.

In designing and constructing new desalination plants, creating and testing pilot facilities is one of the most expensive and time-consuming steps. Traditionally, small yet very expensive stationary pilot plants go up to determine the feasibility of using available water as a source for a large-scale desalination plant. The M3 system helps cut costs and time.

“Our M3 water desalination system provides an all-in-one mobile testing plant that can be used to test almost any water source,” said Alex Bartman, a graduate student on the M3 team who helped to design the sensor networks and data acquisition computer hardware in the system. “The advantages of this type of system are that it can cut costs, and because it is mobile, only one M3 system needs to be built to test multiple sources. Also, it will give an extensive amount of information that can be used to design the larger-scale desalination plant.”

The M3 demonstrated its effectiveness in a field study in the San Joaquin Valley in which it desalted agricultural drainage water that was nearly saturated with calcium sulfate salts, accomplishing this with just one reverse osmosis (RO) stage.

“In this specific field study by our team, in the first part of the reverse osmosis process, 65% of the water that was fed in was recovered as drinking water, or potable water,” said Yoram Cohen, professor of chemical and biomolecular engineering and lead investigator on the team. “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.”

The approach taken by the group is “a significant leap” from the standard practice in the industry of constructing different pilot plants, often from scratch, in order to evaluate and demonstrate the feasibility of water production from different source waters, said Andi Rahardianto, a postdoctoral researcher on the team.

“We believe systems such as the M3 can help accelerate not only water technology development but also its adoption,” he said.

In addition to its use as a pilot-scale testing unit, the M3 could also deploy to various locations and produce fresh water in emergency situations, Bartman said.

“The M3’s ‘smart’ nature means it can autonomously adapt to almost any variation in source water, allowing the M3 system to operate in situations where traditional RO desalination systems would fail almost immediately,” he said.

Though the system is compact enough to be transported anywhere in the back of a van, it can generate 6,000 gallons of drinking water per day from the sea or 8,000 to 9,000 gallons per day from brackish groundwater. By Cohen’s estimate, that means producing enough drinking water daily for up to 6,000 to 12,000 people.

“The system measures in real-time water pH, temperature, turbidity, and salinity,” said Cohen, who is also the director of UCLA’s Water Technology Research Center, which is overseeing this project. “It can control a variety of process variables, including the precise measure of chemical additives to condition the water. All the valves are computer-controlled, so the system can adjust itself automatically. We can also see how much energy we’re using; and in the software, we’ve also included various techniques for optimizing the system so that it can run with minimum energy consumption.”

Rahardianto said the highly saline agricultural drainage wastewater in the San Joaquin Valley is one of the most difficult source waters to desalt.

“It has been a persistent issue for communities in the valley, one of California’s most productive agricultural regions,” he said. “While numerous attempts have been made to develop and test various desalting technologies since the 1960s, a practical, cost-effective solution has not yet been adopted, increasingly affecting the ability to sustain agricultural productivity in the region.”

Cohen’s team is working with water agencies and industries across the U.S., as well as with the international community, and collaborates with research institutions such as Ben Gurion University in Israel, Victoria University in Australia, and Tarragona University in Spain.

For related information, go to www.isa.org/manufacturing_automation.