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High-efficiency RO delivers zero liquid discharge solution for power plant in California
The Magnolia Power Project is a state-of-the-art, combined-cycle electric generation facility built on four acres of Burbank Water and Power (BWP) generation station complex adjacent to Magnolia Boulevard in Burbank, Calif. On June 10, 2003, the mayors and utility officials of the six participating cities joined together with Southern California Public Power Authority officials for a Magnolia Power Project groundbreaking ceremony to commemorate the start of the on-site work. In June 2005, the same group celebrated the plant’s dedication and most recently, enjoyed the award of 2005 Power Plant of the Year by Platt’s Power Magazine. The 310-megawatt power plant will serve as a locally controlled generating plant for the cities of Burbank, Anaheim, Glendale, Pasadena, Cerritos and Colton.
In order to expedite the California Energy Commission licensing process and ensure electric generation availability by mid-2005, the Magnolia Power Project selected a “zero liquid discharge” option for the power plant’s reclaimed cooling water system. The zero liquid discharge (ZLD) equipment allows the city to recycle/reuse the wastewater and adopt a policy of water conservation.
The Magnolia Power Project started the ZLD system evaluation process by reviewing traditional ZLD methods that use brine concentrators that consume electrical energy to evaporate the wastewater. The evaporated wastewater is recovered and recycled back for power plant operation. The solids left behind in the process are converted to sludge and disposed offsite as landfill. The brine concentrators, however, consume huge amounts of electrical energy, even while they are in standby mode—not generating any output.
After reviewing the available technologies, the Magnolia project selected HERO™, high-efficiency RO process technology supplied by Aquatech International Corp., followed by Crystallizer process on the following basis:
Significant reduction in power consumption. The HERO process replaces the brine concentrator and recovers the water using RO membranes. By avoiding the need to evaporate the water in this stage of the treatment process, the HERO process significantly reduces power consumption. For the city of Burbank, power thus saved is power generated.
Start-and-stop operation. The operating profile of the Magnolia Power Project causes the ZLD equipment to operate in a start-and-stop mode. Traditional brine concentrators operate on a heat cycle and achieve best efficiency when operating continuously. Short-term operation of the ZLD system requires these units to be maintained in hot standby condition, which consumes valuable electrical power while generating little or no output. In comparison, a HERO-based system has start-and-stop capability and can be operated only when required. Besides easing operation, this further helps reduce power consumption.
Visual impairment. The project is located within the city limits and hence, visual impact was a big consideration. Traditional ZLD methods using brine concentrators would have required tall structures more than 100 ft high to be installed at the site. The Magnolia project gave a lot of consideration to minimizing the visual impact to the city, and by using the HERO process, lowered the overall height of the system to less than 50 ft.
Space constraints and equipment delivery. Being located within the city limits, the project faced additional constraints of limited available space. To further lessen the visual impact, the ZLD equipment was located at the back of the power plant. This, coupled with limited laydown area for equipment as it arrived from the manufacturers, required that the equipment be delivered on expedited schedule.
The HERO system, compared to a brine concentrator, saved the project approximately 12 weeks on the overall delivery. This helped the project lower its installation costs by setting the equipment in place as it arrived from Aquatech Intl. Corp.
HERO is a proprietary process in which RO membranes are operated in a high pH environment and hence, in a “continuous cleaning mode,” eliminating the potential foulants, resulting in a substantially improved overall performance. Aquatech has an exclusive license for the proprietary HERO process technology for power industry in North America.
Besides having technical advantage over conventional RO, the HERO process offers significant economic advantages as well. These include:
Higher recovery. Because the HERO system allows users to recover more water (90%+), the cost per gallon for pure water production is reduced.
No SDI limitation. HERO is not limited by silt density index (SDI), which is a contributor to conventional RO fouling. Since SDI is not a limiting factor, up-stream systems such as microfiltration or ultra- filtration are not necessary.
Reduced cleaning frequency. HERO substantially reduces the number of times the system must go off-line for membrane cleaning. Operating installation data show a frequency requirement of less than once a year for HERO vs. once a quarter for conventional RO.
No proprietary chemicals. HERO runs on common chemical feed requirements. No expensive antiscalants or cleaning chemicals are required. mf