New Harquahala Generating Project, LLC Tonopah, AZ, U.S.A.

The Harquahala Generating Project serves as a power and electrical wholesaler in the southwestern United States to fill the need for growing energy consumption in the region.

The Harquahala Generating Project is a 1000 MW combined cycle power facility located in Maricopa County, Arizona. Commissioned in 2003, the plant was designed to utilize water resources from either the Colorado River via the Central Arizona Project (CAP) aqueduct or from a local groundwater source. This gas-fired plant would be a major supplier of wholesale energy to the region.

The project at Harquahala would require generation of high-quality water for re-use by the power plant and process remaining solid waste based on the chemistry of feed water to the plant. Zero Liquid Discharge regulations mandate that the resulting solid waste, in the form of wetcake, was to be generated with a nominal content of 10% moisture for proper landfill disposal.

HPD, with these objectives in mind, used decades of experience in process design and design-build project management to build the complete wastewater facility. HPD was instrumental in the design and the focal point for this project as a leader in evaporation and crystallization technology.

The HPD designed wastewater treatment facility consisted of the following critical elements:

• Precipitation softening system to remove calcium, silica andother scale forming materials from the cooling water circuit. The system includes two 50% solids contact clarifiers, a sludge thickener/storage tank, twin sludge presses and chemical storage/feed systems for softening.
• RO Pre-concentration system to recover a majority of water in the softened tower blowdown prior to evaporation and concentration in the ZLD system.
• Zero Liquid Discharge (ZLD) system consisting of two MVR (Mechanical Vapor Recompression) driven, 50% falling film evaporators to further concentrate the stream at a rate of 260 gpm and brine crystallizers with a flow rate of 26 gpm for reclamation of additional quality water while producing a solid wetcake for proper disposal.
• Entire infrastructure including site preparation, foundation with chemical, electrical and control buildings.

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