Challenge
A major power plant to be built on the west coast required water, wastewater and drinking water treatment systems - all in a single plant.  Specifically, the plant required:

• Water make-up to the cooling towers
• Wastewater treatment and zero liquid discharge (ZLD) on the cooling tower blowdown stream
• A system that would inject water that is better than drinking water quality into the local aquifer, thus allowing the aquifer to be used as a backup water source for the cooling tower.

Solution
Siemens Water Technologies, formerly USFilter, provided the process design, engineering, fabrication and supply of more than 10 integrated water treatment technologies, including:

• CenTROL® media filtration
• CDI-LX™ continuous electrodeionization systems
• Memtek® microfiltration systems
• HPD™ crystallizer
• J-Press® dewatering systems
• Chemical feed systems

Siemens provided all the water, wastewater and drinking water equipment, as well as an overall performance-based warranty.

To meet the power plant’s water, ZLD and aquifer requirements, Siemens supplied a complete water management system with five subsystems:

• Water pretreatment: after clarifying and filtering the plant’s 5,800-gpm of intake water, the pretreatment system makes the water suitable for cooling tower makeup, steam cycle makeup and use by the gas-turbine evaporative cooler and the aquifer banking system.
• Aquifer banking system: An ultrafiltration system treats all the water from the pretreatment system that is used to replenish the aquifer.
• A blowdown treatment system uses lime softening and filtration, followed by reverse osmosis.  The RO product water is returned to the cooling tower, while the reject water is recycled to the ZLD system.
• A ZLD system evaporates the RO reject into a dry, crystalline solid that is landfilled.  The distillate is used as makeup water for the HRSG’s, with the remainder returned to the cooling tower.  CDI-LX systems polish the evaporator distillate for boiler/steam cycle makeup.
• A demineralized water system provides makeup water for the plant’s three HRSGs.

Results
Siemens' ability to: provide a wide range of technologies; integrate the systems; meet a fast-track engineering schedule; help to streamline the permitting process; and offer a performance-based warranty was key to the project’s success.  Placed into commercial operation in April 2003, the plant performed according to specification during its first few months and was successful in meeting the needs of the state and local community, as well as meeting environmental regulations.